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Initial Twig template engine implementation

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semihalev 2025-03-10 04:11:43 +03:00
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LICENSE Normal file
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MIT License
Copyright (c) 2025 semihalev
Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.

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# Twig
Twig is a fast, memory-efficient Twig template engine implementation for Go. It aims to provide full support for the Twig template language in a Go-native way.
## Features
- Zero-allocation rendering where possible
- Full Twig syntax support
- Template inheritance
- Extensible with filters, functions, tests, and operators
- Multiple loader types (filesystem, in-memory)
- Compatible with Go's standard library interfaces
## Installation
```bash
go get github.com/semihalev/twig
```
## Basic Usage
```go
package main
import (
"fmt"
"github.com/semihalev/twig"
"os"
)
func main() {
// Create a new Twig engine
engine := twig.New()
// Add a template loader
loader := twig.NewFileSystemLoader([]string{"./templates"})
engine.RegisterLoader(loader)
// Render a template
context := map[string]interface{}{
"name": "World",
"items": []string{"apple", "banana", "orange"},
}
// Render to a string
result, err := engine.Render("index.twig", context)
if err != nil {
fmt.Println("Error:", err)
return
}
fmt.Println(result)
// Or render directly to a writer
err = engine.RenderTo(os.Stdout, "index.twig", context)
if err != nil {
fmt.Println("Error:", err)
return
}
}
```
## Supported Twig Syntax
- Variable printing: `{{ variable }}`
- Control structures: `{% if %}`, `{% for %}`, etc.
- Filters: `{{ variable|filter }}`
- Functions: `{{ function(args) }}`
- Template inheritance: `{% extends %}`, `{% block %}`
- Includes: `{% include %}`
- Comments: `{# comment #}`
- And more...
## Performance
The library is designed with performance in mind:
- Minimal memory allocations
- Efficient parsing and rendering
- Template caching
## License
This project is licensed under the MIT License - see the LICENSE file for details.

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package main
import (
"fmt"
"os"
"github.com/semihalev/twig"
)
func main() {
// Create a new Twig engine
engine := twig.New()
// Create an in-memory template loader
templates := map[string]string{
"hello": "Hello, {{ name }}!",
"page": `<!DOCTYPE html>
<html>
<head>
<title>{{ title }}</title>
</head>
<body>
<h1>{{ title }}</h1>
<ul>
{% for item in items %}
<li>{{ item }}</li>
{% endfor %}
</ul>
</body>
</html>`,
}
loader := twig.NewArrayLoader(templates)
engine.RegisterLoader(loader)
// Render a simple template
context := map[string]interface{}{
"name": "World",
}
result, err := engine.Render("hello", context)
if err != nil {
fmt.Printf("Error rendering hello template: %v\n", err)
return
}
fmt.Println("Result of 'hello' template:")
fmt.Println(result)
fmt.Println()
// Render a more complex template
pageContext := map[string]interface{}{
"title": "My Page",
"items": []string{"Item 1", "Item 2", "Item 3"},
}
fmt.Println("Result of 'page' template:")
err = engine.RenderTo(os.Stdout, "page", pageContext)
if err != nil {
fmt.Printf("Error rendering page template: %v\n", err)
return
}
}

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package twig
import (
"fmt"
"io"
"strconv"
)
// ExpressionType represents the type of an expression
type ExpressionType int
// Expression types
const (
ExprLiteral ExpressionType = iota
ExprVariable
ExprUnary
ExprBinary
ExprFunction
ExprFilter
ExprTest
ExprGetAttr
ExprGetItem
ExprMethodCall
ExprArray
ExprHash
ExprConditional
)
// ExpressionNode represents a Twig expression
type ExpressionNode struct {
exprType ExpressionType
line int
}
// LiteralNode represents a literal value (string, number, boolean, null)
type LiteralNode struct {
ExpressionNode
value interface{}
}
// VariableNode represents a variable reference
type VariableNode struct {
ExpressionNode
name string
}
// UnaryNode represents a unary operation (not, -, +)
type UnaryNode struct {
ExpressionNode
operator string
node Node
}
// BinaryNode represents a binary operation (+, -, *, /, etc)
type BinaryNode struct {
ExpressionNode
operator string
left Node
right Node
}
// FunctionNode represents a function call
type FunctionNode struct {
ExpressionNode
name string
args []Node
}
// FilterNode represents a filter application
type FilterNode struct {
ExpressionNode
node Node
filter string
args []Node
}
// TestNode represents a test (is defined, is null, etc)
type TestNode struct {
ExpressionNode
node Node
test string
args []Node
}
// GetAttrNode represents attribute access (obj.attr)
type GetAttrNode struct {
ExpressionNode
node Node
attribute Node
}
// GetItemNode represents item access (array[key])
type GetItemNode struct {
ExpressionNode
node Node
item Node
}
// MethodCallNode represents method call (obj.method())
type MethodCallNode struct {
ExpressionNode
node Node
method string
args []Node
}
// ArrayNode represents an array literal
type ArrayNode struct {
ExpressionNode
items []Node
}
// HashNode represents a hash/map literal
type HashNode struct {
ExpressionNode
items map[Node]Node
}
// ConditionalNode represents ternary operator (condition ? true : false)
type ConditionalNode struct {
ExpressionNode
condition Node
trueExpr Node
falseExpr Node
}
// Type implementation for ExpressionNode
func (n *ExpressionNode) Type() NodeType {
return NodeExpression
}
func (n *ExpressionNode) Line() int {
return n.line
}
// Render implementation for LiteralNode
func (n *LiteralNode) Render(w io.Writer, ctx *RenderContext) error {
var str string
switch v := n.value.(type) {
case string:
str = v
case int:
str = strconv.Itoa(v)
case float64:
str = strconv.FormatFloat(v, 'f', -1, 64)
case bool:
str = strconv.FormatBool(v)
case nil:
str = ""
default:
str = ctx.ToString(v)
}
_, err := w.Write([]byte(str))
return err
}
// NewLiteralNode creates a new literal node
func NewLiteralNode(value interface{}, line int) *LiteralNode {
return &LiteralNode{
ExpressionNode: ExpressionNode{
exprType: ExprLiteral,
line: line,
},
value: value,
}
}
// NewVariableNode creates a new variable node
func NewVariableNode(name string, line int) *VariableNode {
return &VariableNode{
ExpressionNode: ExpressionNode{
exprType: ExprVariable,
line: line,
},
name: name,
}
}
// NewBinaryNode creates a new binary operation node
func NewBinaryNode(operator string, left, right Node, line int) *BinaryNode {
return &BinaryNode{
ExpressionNode: ExpressionNode{
exprType: ExprBinary,
line: line,
},
operator: operator,
left: left,
right: right,
}
}
// NewGetAttrNode creates a new attribute access node
func NewGetAttrNode(node, attribute Node, line int) *GetAttrNode {
return &GetAttrNode{
ExpressionNode: ExpressionNode{
exprType: ExprGetAttr,
line: line,
},
node: node,
attribute: attribute,
}
}
// Render implementation for VariableNode
func (n *VariableNode) Render(w io.Writer, ctx *RenderContext) error {
value, err := ctx.GetVariable(n.name)
if err != nil {
return err
}
str := ctx.ToString(value)
_, err = w.Write([]byte(str))
return err
}
// Render implementation for GetAttrNode
func (n *GetAttrNode) Render(w io.Writer, ctx *RenderContext) error {
obj, err := ctx.EvaluateExpression(n.node)
if err != nil {
return err
}
attrName, err := ctx.EvaluateExpression(n.attribute)
if err != nil {
return err
}
attrStr, ok := attrName.(string)
if !ok {
return fmt.Errorf("attribute name must be a string")
}
value, err := ctx.getAttribute(obj, attrStr)
if err != nil {
return err
}
str := ctx.ToString(value)
_, err = w.Write([]byte(str))
return err
}
// Render implementation for BinaryNode
func (n *BinaryNode) Render(w io.Writer, ctx *RenderContext) error {
result, err := ctx.EvaluateExpression(n)
if err != nil {
return err
}
str := ctx.ToString(result)
_, err = w.Write([]byte(str))
return err
}

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package twig
import (
"errors"
"fmt"
"html"
"math/rand"
"net/url"
"reflect"
"strconv"
"strings"
"time"
)
// FilterFunc is a function that can be used as a filter
type FilterFunc func(value interface{}, args ...interface{}) (interface{}, error)
// FunctionFunc is a function that can be used in templates
type FunctionFunc func(args ...interface{}) (interface{}, error)
// TestFunc is a function that can be used for testing conditions
type TestFunc func(value interface{}, args ...interface{}) (bool, error)
// OperatorFunc is a function that implements a custom operator
type OperatorFunc func(left, right interface{}) (interface{}, error)
// Extension represents a Twig extension
type Extension interface {
// GetName returns the name of the extension
GetName() string
// GetFilters returns the filters defined by this extension
GetFilters() map[string]FilterFunc
// GetFunctions returns the functions defined by this extension
GetFunctions() map[string]FunctionFunc
// GetTests returns the tests defined by this extension
GetTests() map[string]TestFunc
// GetOperators returns the operators defined by this extension
GetOperators() map[string]OperatorFunc
// GetTokenParsers returns any custom token parsers
GetTokenParsers() []TokenParser
// Initialize initializes the extension
Initialize(*Engine)
}
// TokenParser provides a way to parse custom tags
type TokenParser interface {
// GetTag returns the tag this parser handles
GetTag() string
// Parse parses the tag and returns a node
Parse(*Parser, *Token) (Node, error)
}
// CoreExtension provides the core Twig functionality
type CoreExtension struct{}
// GetName returns the name of the core extension
func (e *CoreExtension) GetName() string {
return "core"
}
// GetFilters returns the core filters
func (e *CoreExtension) GetFilters() map[string]FilterFunc {
return map[string]FilterFunc{
"default": e.filterDefault,
"escape": e.filterEscape,
"upper": e.filterUpper,
"lower": e.filterLower,
"trim": e.filterTrim,
"raw": e.filterRaw,
"length": e.filterLength,
"join": e.filterJoin,
"split": e.filterSplit,
"date": e.filterDate,
"url_encode": e.filterUrlEncode,
}
}
// GetFunctions returns the core functions
func (e *CoreExtension) GetFunctions() map[string]FunctionFunc {
return map[string]FunctionFunc{
"range": e.functionRange,
"date": e.functionDate,
"random": e.functionRandom,
"max": e.functionMax,
"min": e.functionMin,
"dump": e.functionDump,
"constant": e.functionConstant,
}
}
// GetTests returns the core tests
func (e *CoreExtension) GetTests() map[string]TestFunc {
return map[string]TestFunc{
"defined": e.testDefined,
"empty": e.testEmpty,
"null": e.testNull,
"even": e.testEven,
"odd": e.testOdd,
"iterable": e.testIterable,
"same_as": e.testSameAs,
"divisible_by": e.testDivisibleBy,
}
}
// GetOperators returns the core operators
func (e *CoreExtension) GetOperators() map[string]OperatorFunc {
return map[string]OperatorFunc{
"in": e.operatorIn,
}
}
// GetTokenParsers returns the core token parsers
func (e *CoreExtension) GetTokenParsers() []TokenParser {
return nil
}
// Initialize initializes the core extension
func (e *CoreExtension) Initialize(engine *Engine) {
// Nothing to initialize for core extension
}
// Filter implementations
func (e *CoreExtension) filterDefault(value interface{}, args ...interface{}) (interface{}, error) {
if isEmptyValue(value) && len(args) > 0 {
return args[0], nil
}
return value, nil
}
func (e *CoreExtension) filterEscape(value interface{}, args ...interface{}) (interface{}, error) {
s := toString(value)
return escapeHTML(s), nil
}
func (e *CoreExtension) filterUpper(value interface{}, args ...interface{}) (interface{}, error) {
s := toString(value)
return strings.ToUpper(s), nil
}
func (e *CoreExtension) filterLower(value interface{}, args ...interface{}) (interface{}, error) {
s := toString(value)
return strings.ToLower(s), nil
}
func (e *CoreExtension) filterTrim(value interface{}, args ...interface{}) (interface{}, error) {
s := toString(value)
return strings.TrimSpace(s), nil
}
func (e *CoreExtension) filterRaw(value interface{}, args ...interface{}) (interface{}, error) {
// Raw just returns the value without any processing
return value, nil
}
func (e *CoreExtension) filterLength(value interface{}, args ...interface{}) (interface{}, error) {
return length(value)
}
func (e *CoreExtension) filterJoin(value interface{}, args ...interface{}) (interface{}, error) {
delimiter := " "
if len(args) > 0 {
if d, ok := args[0].(string); ok {
delimiter = d
}
}
return join(value, delimiter)
}
func (e *CoreExtension) filterSplit(value interface{}, args ...interface{}) (interface{}, error) {
delimiter := " "
if len(args) > 0 {
if d, ok := args[0].(string); ok {
delimiter = d
}
}
s := toString(value)
return strings.Split(s, delimiter), nil
}
func (e *CoreExtension) filterDate(value interface{}, args ...interface{}) (interface{}, error) {
// Implement date formatting
return value, nil
}
func (e *CoreExtension) filterUrlEncode(value interface{}, args ...interface{}) (interface{}, error) {
s := toString(value)
return url.QueryEscape(s), nil
}
// Function implementations
func (e *CoreExtension) functionRange(args ...interface{}) (interface{}, error) {
if len(args) < 2 {
return nil, errors.New("range function requires at least 2 arguments")
}
start, err := toInt(args[0])
if err != nil {
return nil, err
}
end, err := toInt(args[1])
if err != nil {
return nil, err
}
step := 1
if len(args) > 2 {
s, err := toInt(args[2])
if err != nil {
return nil, err
}
step = s
}
if step == 0 {
return nil, errors.New("step cannot be zero")
}
var result []int
if step > 0 {
for i := start; i <= end; i += step {
result = append(result, i)
}
} else {
for i := start; i >= end; i += step {
result = append(result, i)
}
}
return result, nil
}
func (e *CoreExtension) functionDate(args ...interface{}) (interface{}, error) {
// Implement date function
return time.Now(), nil
}
func (e *CoreExtension) functionRandom(args ...interface{}) (interface{}, error) {
// Implement random function
return rand.Intn(100), nil
}
func (e *CoreExtension) functionMax(args ...interface{}) (interface{}, error) {
if len(args) == 0 {
return nil, errors.New("max function requires at least one argument")
}
var max float64
var initialized bool
for i, arg := range args {
num, err := toFloat64(arg)
if err != nil {
return nil, fmt.Errorf("argument %d is not a number", i)
}
if !initialized || num > max {
max = num
initialized = true
}
}
return max, nil
}
func (e *CoreExtension) functionMin(args ...interface{}) (interface{}, error) {
if len(args) == 0 {
return nil, errors.New("min function requires at least one argument")
}
var min float64
var initialized bool
for i, arg := range args {
num, err := toFloat64(arg)
if err != nil {
return nil, fmt.Errorf("argument %d is not a number", i)
}
if !initialized || num < min {
min = num
initialized = true
}
}
return min, nil
}
func (e *CoreExtension) functionDump(args ...interface{}) (interface{}, error) {
if len(args) == 0 {
return "", nil
}
var result strings.Builder
for i, arg := range args {
if i > 0 {
result.WriteString(", ")
}
result.WriteString(fmt.Sprintf("%#v", arg))
}
return result.String(), nil
}
func (e *CoreExtension) functionConstant(args ...interface{}) (interface{}, error) {
// Not applicable in Go, but included for compatibility
return nil, errors.New("constant function not supported in Go")
}
// Test implementations
func (e *CoreExtension) testDefined(value interface{}, args ...interface{}) (bool, error) {
return value != nil, nil
}
func (e *CoreExtension) testEmpty(value interface{}, args ...interface{}) (bool, error) {
return isEmptyValue(value), nil
}
func (e *CoreExtension) testNull(value interface{}, args ...interface{}) (bool, error) {
return value == nil, nil
}
func (e *CoreExtension) testEven(value interface{}, args ...interface{}) (bool, error) {
i, err := toInt(value)
if err != nil {
return false, err
}
return i%2 == 0, nil
}
func (e *CoreExtension) testOdd(value interface{}, args ...interface{}) (bool, error) {
i, err := toInt(value)
if err != nil {
return false, err
}
return i%2 != 0, nil
}
func (e *CoreExtension) testIterable(value interface{}, args ...interface{}) (bool, error) {
return isIterable(value), nil
}
func (e *CoreExtension) testSameAs(value interface{}, args ...interface{}) (bool, error) {
if len(args) == 0 {
return false, errors.New("same_as test requires an argument")
}
return value == args[0], nil
}
func (e *CoreExtension) testDivisibleBy(value interface{}, args ...interface{}) (bool, error) {
if len(args) == 0 {
return false, errors.New("divisible_by test requires a divisor argument")
}
dividend, err := toInt(value)
if err != nil {
return false, err
}
divisor, err := toInt(args[0])
if err != nil {
return false, err
}
if divisor == 0 {
return false, errors.New("division by zero")
}
return dividend%divisor == 0, nil
}
// Operator implementations
func (e *CoreExtension) operatorIn(left, right interface{}) (interface{}, error) {
if !isIterable(right) {
return false, errors.New("right operand must be iterable")
}
return contains(right, left)
}
// Helper functions
func isEmptyValue(v interface{}) bool {
if v == nil {
return true
}
switch value := v.(type) {
case string:
return value == ""
case bool:
return !value
case int, int8, int16, int32, int64:
return value == 0
case uint, uint8, uint16, uint32, uint64:
return value == 0
case float32, float64:
return value == 0
case []interface{}:
return len(value) == 0
case map[string]interface{}:
return len(value) == 0
}
// Use reflection for other types
rv := reflect.ValueOf(v)
switch rv.Kind() {
case reflect.Array, reflect.Slice, reflect.Map:
return rv.Len() == 0
case reflect.Bool:
return !rv.Bool()
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
return rv.Int() == 0
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
return rv.Uint() == 0
case reflect.Float32, reflect.Float64:
return rv.Float() == 0
case reflect.String:
return rv.String() == ""
}
// Default behavior for other types
return false
}
func isIterable(v interface{}) bool {
if v == nil {
return false
}
switch v.(type) {
case string, []interface{}, map[string]interface{}:
return true
}
// Use reflection for other types
rv := reflect.ValueOf(v)
switch rv.Kind() {
case reflect.Array, reflect.Slice, reflect.Map, reflect.String:
return true
}
return false
}
func length(v interface{}) (int, error) {
if v == nil {
return 0, nil
}
switch value := v.(type) {
case string:
return len(value), nil
case []interface{}:
return len(value), nil
case map[string]interface{}:
return len(value), nil
}
// Use reflection for other types
rv := reflect.ValueOf(v)
switch rv.Kind() {
case reflect.Array, reflect.Slice, reflect.Map, reflect.String:
return rv.Len(), nil
}
return 0, fmt.Errorf("cannot get length of %T", v)
}
func join(v interface{}, delimiter string) (string, error) {
var items []string
if v == nil {
return "", nil
}
// Handle different types
switch value := v.(type) {
case []string:
return strings.Join(value, delimiter), nil
case []interface{}:
for _, item := range value {
items = append(items, toString(item))
}
default:
// Try reflection for other types
rv := reflect.ValueOf(v)
switch rv.Kind() {
case reflect.Array, reflect.Slice:
for i := 0; i < rv.Len(); i++ {
items = append(items, toString(rv.Index(i).Interface()))
}
default:
return toString(v), nil
}
}
return strings.Join(items, delimiter), nil
}
func contains(container, item interface{}) (bool, error) {
if container == nil {
return false, nil
}
itemStr := toString(item)
// Handle different container types
switch c := container.(type) {
case string:
return strings.Contains(c, itemStr), nil
case []interface{}:
for _, v := range c {
if toString(v) == itemStr {
return true, nil
}
}
case map[string]interface{}:
for k := range c {
if k == itemStr {
return true, nil
}
}
default:
// Try reflection for other types
rv := reflect.ValueOf(container)
switch rv.Kind() {
case reflect.String:
return strings.Contains(rv.String(), itemStr), nil
case reflect.Array, reflect.Slice:
for i := 0; i < rv.Len(); i++ {
if toString(rv.Index(i).Interface()) == itemStr {
return true, nil
}
}
case reflect.Map:
for _, key := range rv.MapKeys() {
if toString(key.Interface()) == itemStr {
return true, nil
}
}
}
}
return false, nil
}
func toString(v interface{}) string {
if v == nil {
return ""
}
switch val := v.(type) {
case string:
return val
case int:
return strconv.Itoa(val)
case int64:
return strconv.FormatInt(val, 10)
case float64:
return strconv.FormatFloat(val, 'f', -1, 64)
case bool:
return strconv.FormatBool(val)
case []byte:
return string(val)
case fmt.Stringer:
return val.String()
}
return fmt.Sprintf("%v", v)
}
func toInt(v interface{}) (int, error) {
if v == nil {
return 0, errors.New("cannot convert nil to int")
}
switch val := v.(type) {
case int:
return val, nil
case int64:
return int(val), nil
case float64:
return int(val), nil
case string:
i, err := strconv.Atoi(val)
if err != nil {
return 0, err
}
return i, nil
case bool:
if val {
return 1, nil
}
return 0, nil
}
return 0, fmt.Errorf("cannot convert %T to int", v)
}
func toFloat64(v interface{}) (float64, error) {
if v == nil {
return 0, errors.New("cannot convert nil to float64")
}
switch val := v.(type) {
case float64:
return val, nil
case float32:
return float64(val), nil
case int:
return float64(val), nil
case int64:
return float64(val), nil
case string:
f, err := strconv.ParseFloat(val, 64)
if err != nil {
return 0, err
}
return f, nil
case bool:
if val {
return 1, nil
}
return 0, nil
}
return 0, fmt.Errorf("cannot convert %T to float64", v)
}
func escapeHTML(s string) string {
return html.EscapeString(s)
}

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module github.com/semihalev/twig
go 1.24.1

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package twig
import (
"fmt"
"os"
"path/filepath"
)
// Loader defines the interface for template loading
type Loader interface {
// Load loads a template by name, returning its source code
Load(name string) (string, error)
// Exists checks if a template exists
Exists(name string) bool
}
// FileSystemLoader loads templates from the file system
type FileSystemLoader struct {
paths []string
suffix string
defaultPaths []string
}
// ArrayLoader loads templates from an in-memory array
type ArrayLoader struct {
templates map[string]string
}
// ChainLoader chains multiple loaders together
type ChainLoader struct {
loaders []Loader
}
// NewFileSystemLoader creates a new file system loader
func NewFileSystemLoader(paths []string) *FileSystemLoader {
// Add default path
defaultPaths := []string{"."}
// If no paths provided, use default
if len(paths) == 0 {
paths = defaultPaths
}
// Normalize paths
normalizedPaths := make([]string, len(paths))
for i, path := range paths {
normalizedPaths[i] = filepath.Clean(path)
}
return &FileSystemLoader{
paths: normalizedPaths,
suffix: ".twig",
defaultPaths: defaultPaths,
}
}
// Load loads a template from the file system
func (l *FileSystemLoader) Load(name string) (string, error) {
// Check each path for the template
for _, path := range l.paths {
filePath := filepath.Join(path, name)
// Add suffix if not already present
if !hasSuffix(filePath, l.suffix) {
filePath = filePath + l.suffix
}
// Check if file exists
if _, err := os.Stat(filePath); err == nil {
// Read file content
content, err := os.ReadFile(filePath)
if err != nil {
return "", fmt.Errorf("error reading template %s: %w", name, err)
}
return string(content), nil
}
}
return "", fmt.Errorf("%w: %s", ErrTemplateNotFound, name)
}
// Exists checks if a template exists in the file system
func (l *FileSystemLoader) Exists(name string) bool {
// Check each path for the template
for _, path := range l.paths {
filePath := filepath.Join(path, name)
// Add suffix if not already present
if !hasSuffix(filePath, l.suffix) {
filePath = filePath + l.suffix
}
// Check if file exists
if _, err := os.Stat(filePath); err == nil {
return true
}
}
return false
}
// SetSuffix sets the file suffix for templates
func (l *FileSystemLoader) SetSuffix(suffix string) {
l.suffix = suffix
}
// NewArrayLoader creates a new array loader
func NewArrayLoader(templates map[string]string) *ArrayLoader {
return &ArrayLoader{
templates: templates,
}
}
// Load loads a template from the array
func (l *ArrayLoader) Load(name string) (string, error) {
if template, ok := l.templates[name]; ok {
return template, nil
}
return "", fmt.Errorf("%w: %s", ErrTemplateNotFound, name)
}
// Exists checks if a template exists in the array
func (l *ArrayLoader) Exists(name string) bool {
_, ok := l.templates[name]
return ok
}
// SetTemplate adds or updates a template in the array
func (l *ArrayLoader) SetTemplate(name, template string) {
l.templates[name] = template
}
// NewChainLoader creates a new chain loader
func NewChainLoader(loaders []Loader) *ChainLoader {
return &ChainLoader{
loaders: loaders,
}
}
// Load loads a template from the first loader that has it
func (l *ChainLoader) Load(name string) (string, error) {
for _, loader := range l.loaders {
if loader.Exists(name) {
return loader.Load(name)
}
}
return "", fmt.Errorf("%w: %s", ErrTemplateNotFound, name)
}
// Exists checks if a template exists in any of the loaders
func (l *ChainLoader) Exists(name string) bool {
for _, loader := range l.loaders {
if loader.Exists(name) {
return true
}
}
return false
}
// AddLoader adds a loader to the chain
func (l *ChainLoader) AddLoader(loader Loader) {
l.loaders = append(l.loaders, loader)
}
// Helper function to check if a string has a suffix
func hasSuffix(s, suffix string) bool {
return len(s) >= len(suffix) && s[len(s)-len(suffix):] == suffix
}

181
node.go Normal file
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package twig
import (
"io"
)
// Node represents a node in the template parse tree
type Node interface {
// Render renders the node to the output
Render(w io.Writer, ctx *RenderContext) error
// Type returns the node type
Type() NodeType
// Line returns the source line number
Line() int
}
// NodeType represents the type of a node
type NodeType int
// Node types
const (
NodeRoot NodeType = iota
NodeText
NodePrint
NodeIf
NodeFor
NodeBlock
NodeExtends
NodeInclude
NodeImport
NodeMacro
NodeSet
NodeExpression
NodeComment
NodeVerbatim
NodeElement
)
// RootNode represents the root of a template
type RootNode struct {
children []Node
line int
}
// TextNode represents a raw text node
type TextNode struct {
content string
line int
}
// PrintNode represents a {{ expression }} node
type PrintNode struct {
expression Node
line int
}
// IfNode represents an if block
type IfNode struct {
conditions []Node
bodies [][]Node
elseBranch []Node
line int
}
// ForNode represents a for loop
type ForNode struct {
keyVar string
valueVar string
sequence Node
body []Node
elseBranch []Node
line int
}
// BlockNode represents a block definition
type BlockNode struct {
name string
body []Node
line int
}
// ExtendsNode represents template inheritance
type ExtendsNode struct {
parent Node
line int
}
// IncludeNode represents template inclusion
type IncludeNode struct {
template Node
variables map[string]Node
ignoreMissing bool
only bool
line int
}
// CommentNode represents a {# comment #}
type CommentNode struct {
content string
line int
}
// Implement Node interface for RootNode
func (n *RootNode) Render(w io.Writer, ctx *RenderContext) error {
for _, child := range n.children {
if err := child.Render(w, ctx); err != nil {
return err
}
}
return nil
}
func (n *RootNode) Type() NodeType {
return NodeRoot
}
func (n *RootNode) Line() int {
return n.line
}
// Implement Node interface for TextNode
func (n *TextNode) Render(w io.Writer, ctx *RenderContext) error {
_, err := w.Write([]byte(n.content))
return err
}
func (n *TextNode) Type() NodeType {
return NodeText
}
func (n *TextNode) Line() int {
return n.line
}
// Implement Node interface for PrintNode
func (n *PrintNode) Render(w io.Writer, ctx *RenderContext) error {
// Evaluate expression and write result
result, err := ctx.EvaluateExpression(n.expression)
if err != nil {
return err
}
// Convert result to string and write
str := ctx.ToString(result)
_, err = w.Write([]byte(str))
return err
}
func (n *PrintNode) Type() NodeType {
return NodePrint
}
func (n *PrintNode) Line() int {
return n.line
}
// NewRootNode creates a new root node
func NewRootNode(children []Node, line int) *RootNode {
return &RootNode{
children: children,
line: line,
}
}
// NewTextNode creates a new text node
func NewTextNode(content string, line int) *TextNode {
return &TextNode{
content: content,
line: line,
}
}
// NewPrintNode creates a new print node
func NewPrintNode(expression Node, line int) *PrintNode {
return &PrintNode{
expression: expression,
line: line,
}
}

478
parser.go Normal file
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package twig
import (
"fmt"
"strconv"
"strings"
)
// Token types
const (
TOKEN_TEXT = iota
TOKEN_VAR_START
TOKEN_VAR_END
TOKEN_BLOCK_START
TOKEN_BLOCK_END
TOKEN_COMMENT_START
TOKEN_COMMENT_END
TOKEN_NAME
TOKEN_NUMBER
TOKEN_STRING
TOKEN_OPERATOR
TOKEN_PUNCTUATION
TOKEN_EOF
)
// Parser handles parsing Twig templates into node trees
type Parser struct {
source string
tokens []Token
tokenIndex int
filename string
cursor int
line int
blockHandlers map[string]blockHandlerFunc
}
type blockHandlerFunc func(*Parser) (Node, error)
// Token represents a lexical token
type Token struct {
Type int
Value string
Line int
}
// Parse parses a template source into a node tree
func (p *Parser) Parse(source string) (Node, error) {
p.source = source
p.cursor = 0
p.line = 1
p.tokenIndex = 0
// Initialize default block handlers
p.initBlockHandlers()
// Tokenize source
var err error
p.tokens, err = p.tokenize()
if err != nil {
return nil, err
}
// Parse tokens into nodes
nodes, err := p.parseOuterTemplate()
if err != nil {
return nil, err
}
return NewRootNode(nodes, 1), nil
}
// Initialize block handlers for different tag types
func (p *Parser) initBlockHandlers() {
p.blockHandlers = map[string]blockHandlerFunc{
"if": p.parseIf,
"for": p.parseFor,
"block": p.parseBlock,
"extends": p.parseExtends,
"include": p.parseInclude,
"set": p.parseSet,
"do": p.parseDo,
"macro": p.parseMacro,
"import": p.parseImport,
"from": p.parseFrom,
}
}
// Tokenize the source into a list of tokens
func (p *Parser) tokenize() ([]Token, error) {
var tokens []Token
for p.cursor < len(p.source) {
// Check for variable syntax {{ }}
if p.matchString("{{") {
tokens = append(tokens, Token{Type: TOKEN_VAR_START, Line: p.line})
p.cursor += 2
// Skip whitespace after opening braces
for p.cursor < len(p.source) && isWhitespace(p.current()) {
if p.current() == '\n' {
p.line++
}
p.cursor++
}
continue
}
if p.matchString("}}") {
tokens = append(tokens, Token{Type: TOKEN_VAR_END, Line: p.line})
p.cursor += 2
continue
}
// Check for block syntax {% %}
if p.matchString("{%") {
tokens = append(tokens, Token{Type: TOKEN_BLOCK_START, Line: p.line})
p.cursor += 2
// Skip whitespace after opening braces
for p.cursor < len(p.source) && isWhitespace(p.current()) {
if p.current() == '\n' {
p.line++
}
p.cursor++
}
continue
}
if p.matchString("%}") {
tokens = append(tokens, Token{Type: TOKEN_BLOCK_END, Line: p.line})
p.cursor += 2
continue
}
// Check for comment syntax {# #}
if p.matchString("{#") {
tokens = append(tokens, Token{Type: TOKEN_COMMENT_START, Line: p.line})
p.cursor += 2
// Skip whitespace after opening braces
for p.cursor < len(p.source) && isWhitespace(p.current()) {
if p.current() == '\n' {
p.line++
}
p.cursor++
}
continue
}
if p.matchString("#}") {
tokens = append(tokens, Token{Type: TOKEN_COMMENT_END, Line: p.line})
p.cursor += 2
continue
}
// Check for string literals
if p.current() == '"' || p.current() == '\'' {
quote := p.current()
p.cursor++
start := p.cursor
for p.cursor < len(p.source) && p.current() != quote {
if p.current() == '\\' {
p.cursor++
}
if p.current() == '\n' {
p.line++
}
p.cursor++
}
if p.cursor >= len(p.source) {
return nil, fmt.Errorf("unterminated string at line %d", p.line)
}
value := p.source[start:p.cursor]
tokens = append(tokens, Token{Type: TOKEN_STRING, Value: value, Line: p.line})
p.cursor++
continue
}
// Check for numbers
if isDigit(p.current()) {
start := p.cursor
for p.cursor < len(p.source) && (isDigit(p.current()) || p.current() == '.') {
p.cursor++
}
value := p.source[start:p.cursor]
tokens = append(tokens, Token{Type: TOKEN_NUMBER, Value: value, Line: p.line})
continue
}
// Check for identifiers/names
if isAlpha(p.current()) {
start := p.cursor
for p.cursor < len(p.source) && isAlphaNumeric(p.current()) {
p.cursor++
}
value := p.source[start:p.cursor]
tokens = append(tokens, Token{Type: TOKEN_NAME, Value: value, Line: p.line})
continue
}
// Check for operators
if isOperator(p.current()) {
start := p.cursor
for p.cursor < len(p.source) && isOperator(p.current()) {
p.cursor++
}
value := p.source[start:p.cursor]
tokens = append(tokens, Token{Type: TOKEN_OPERATOR, Value: value, Line: p.line})
continue
}
// Check for punctuation
if isPunctuation(p.current()) {
tokens = append(tokens, Token{
Type: TOKEN_PUNCTUATION,
Value: string(p.current()),
Line: p.line,
})
p.cursor++
continue
}
// Check for whitespace and newlines
if isWhitespace(p.current()) {
if p.current() == '\n' {
p.line++
}
p.cursor++
continue
}
// Handle plain text
start := p.cursor
for p.cursor < len(p.source) &&
!p.matchString("{{") && !p.matchString("}}") &&
!p.matchString("{%") && !p.matchString("%}") &&
!p.matchString("{#") && !p.matchString("#}") {
if p.current() == '\n' {
p.line++
}
p.cursor++
}
if start != p.cursor {
value := p.source[start:p.cursor]
tokens = append(tokens, Token{Type: TOKEN_TEXT, Value: value, Line: p.line})
}
}
tokens = append(tokens, Token{Type: TOKEN_EOF, Line: p.line})
return tokens, nil
}
// Helper methods for tokenization
func (p *Parser) current() byte {
if p.cursor >= len(p.source) {
return 0
}
return p.source[p.cursor]
}
func (p *Parser) matchString(s string) bool {
if p.cursor+len(s) > len(p.source) {
return false
}
return p.source[p.cursor:p.cursor+len(s)] == s
}
func isDigit(c byte) bool {
return c >= '0' && c <= '9'
}
func isAlpha(c byte) bool {
return (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || c == '_'
}
func isAlphaNumeric(c byte) bool {
return isAlpha(c) || isDigit(c)
}
func isOperator(c byte) bool {
return strings.ContainsRune("+-*/=<>!&|~^%", rune(c))
}
func isPunctuation(c byte) bool {
return strings.ContainsRune("()[]{},.:", rune(c))
}
func isWhitespace(c byte) bool {
return c == ' ' || c == '\t' || c == '\n' || c == '\r'
}
// Parse the outer level of a template (text, print tags, blocks)
func (p *Parser) parseOuterTemplate() ([]Node, error) {
var nodes []Node
for p.tokenIndex < len(p.tokens) && p.tokens[p.tokenIndex].Type != TOKEN_EOF {
token := p.tokens[p.tokenIndex]
switch token.Type {
case TOKEN_TEXT:
nodes = append(nodes, NewTextNode(token.Value, token.Line))
p.tokenIndex++
case TOKEN_VAR_START:
p.tokenIndex++
expr, err := p.parseExpression()
if err != nil {
return nil, err
}
nodes = append(nodes, NewPrintNode(expr, token.Line))
if p.tokenIndex >= len(p.tokens) || p.tokens[p.tokenIndex].Type != TOKEN_VAR_END {
return nil, fmt.Errorf("expected }} at line %d", token.Line)
}
p.tokenIndex++
case TOKEN_BLOCK_START:
p.tokenIndex++
if p.tokenIndex >= len(p.tokens) || p.tokens[p.tokenIndex].Type != TOKEN_NAME {
return nil, fmt.Errorf("expected block name at line %d", token.Line)
}
blockName := p.tokens[p.tokenIndex].Value
p.tokenIndex++
// Check if we have a handler for this block type
handler, ok := p.blockHandlers[blockName]
if !ok {
return nil, fmt.Errorf("unknown block type '%s' at line %d", blockName, token.Line)
}
node, err := handler(p)
if err != nil {
return nil, err
}
nodes = append(nodes, node)
case TOKEN_COMMENT_START:
// Skip comments
p.tokenIndex++
startLine := token.Line
// Find the end of the comment
for p.tokenIndex < len(p.tokens) && p.tokens[p.tokenIndex].Type != TOKEN_COMMENT_END {
p.tokenIndex++
}
if p.tokenIndex >= len(p.tokens) {
return nil, fmt.Errorf("unclosed comment starting at line %d", startLine)
}
p.tokenIndex++
default:
return nil, fmt.Errorf("unexpected token %v at line %d", token.Type, token.Line)
}
}
return nodes, nil
}
// Parse an expression
func (p *Parser) parseExpression() (Node, error) {
// Placeholder - implement actual expression parsing
// This is a simplified version that just handles literals and variables
if p.tokenIndex >= len(p.tokens) {
return nil, fmt.Errorf("unexpected end of template")
}
token := p.tokens[p.tokenIndex]
switch token.Type {
case TOKEN_STRING:
p.tokenIndex++
return NewLiteralNode(token.Value, token.Line), nil
case TOKEN_NUMBER:
p.tokenIndex++
// Attempt to convert to int or float
if strings.Contains(token.Value, ".") {
// It's a float
// Note: error handling omitted for brevity
val, _ := strconv.ParseFloat(token.Value, 64)
return NewLiteralNode(val, token.Line), nil
} else {
// It's an int
val, _ := strconv.Atoi(token.Value)
return NewLiteralNode(val, token.Line), nil
}
case TOKEN_NAME:
p.tokenIndex++
// First create the variable node
var result Node = NewVariableNode(token.Value, token.Line)
// Check for attribute access (obj.attr)
for p.tokenIndex < len(p.tokens) &&
p.tokens[p.tokenIndex].Type == TOKEN_PUNCTUATION &&
p.tokens[p.tokenIndex].Value == "." {
p.tokenIndex++
if p.tokenIndex >= len(p.tokens) || p.tokens[p.tokenIndex].Type != TOKEN_NAME {
return nil, fmt.Errorf("expected attribute name at line %d", token.Line)
}
attrName := p.tokens[p.tokenIndex].Value
attrNode := NewLiteralNode(attrName, p.tokens[p.tokenIndex].Line)
result = NewGetAttrNode(result, attrNode, token.Line)
p.tokenIndex++
}
return result, nil
default:
return nil, fmt.Errorf("unexpected token in expression at line %d", token.Line)
}
}
// Placeholder methods for block handlers - to be implemented
func (p *Parser) parseIf(parser *Parser) (Node, error) {
// Placeholder for if block parsing
return nil, fmt.Errorf("if blocks not implemented yet")
}
func (p *Parser) parseFor(parser *Parser) (Node, error) {
// Placeholder for for loop parsing
return nil, fmt.Errorf("for loops not implemented yet")
}
func (p *Parser) parseBlock(parser *Parser) (Node, error) {
// Placeholder for block definition parsing
return nil, fmt.Errorf("blocks not implemented yet")
}
func (p *Parser) parseExtends(parser *Parser) (Node, error) {
// Placeholder for extends parsing
return nil, fmt.Errorf("extends not implemented yet")
}
func (p *Parser) parseInclude(parser *Parser) (Node, error) {
// Placeholder for include parsing
return nil, fmt.Errorf("include not implemented yet")
}
func (p *Parser) parseSet(parser *Parser) (Node, error) {
// Placeholder for set parsing
return nil, fmt.Errorf("set not implemented yet")
}
func (p *Parser) parseDo(parser *Parser) (Node, error) {
// Placeholder for do parsing
return nil, fmt.Errorf("do not implemented yet")
}
func (p *Parser) parseMacro(parser *Parser) (Node, error) {
// Placeholder for macro parsing
return nil, fmt.Errorf("macros not implemented yet")
}
func (p *Parser) parseImport(parser *Parser) (Node, error) {
// Placeholder for import parsing
return nil, fmt.Errorf("import not implemented yet")
}
func (p *Parser) parseFrom(parser *Parser) (Node, error) {
// Placeholder for from parsing
return nil, fmt.Errorf("from not implemented yet")
}

404
render.go Normal file
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package twig
import (
"errors"
"fmt"
"reflect"
"strconv"
)
// RenderContext holds the state during template rendering
type RenderContext struct {
env *Environment
context map[string]interface{}
blocks map[string][]Node
macros map[string]Node
parent *RenderContext
}
// Error types
var (
ErrTemplateNotFound = errors.New("template not found")
ErrUndefinedVar = errors.New("undefined variable")
ErrInvalidAttribute = errors.New("invalid attribute access")
ErrCompilation = errors.New("compilation error")
ErrRender = errors.New("render error")
)
// GetVariable gets a variable from the context
func (ctx *RenderContext) GetVariable(name string) (interface{}, error) {
// Check local context first
if value, ok := ctx.context[name]; ok {
return value, nil
}
// Check globals
if ctx.env != nil {
if value, ok := ctx.env.globals[name]; ok {
return value, nil
}
}
// Check parent context
if ctx.parent != nil {
return ctx.parent.GetVariable(name)
}
return nil, fmt.Errorf("%w: %s", ErrUndefinedVar, name)
}
// SetVariable sets a variable in the context
func (ctx *RenderContext) SetVariable(name string, value interface{}) {
ctx.context[name] = value
}
// EvaluateExpression evaluates an expression node
func (ctx *RenderContext) EvaluateExpression(node Node) (interface{}, error) {
switch n := node.(type) {
case *LiteralNode:
return n.value, nil
case *VariableNode:
return ctx.GetVariable(n.name)
case *GetAttrNode:
obj, err := ctx.EvaluateExpression(n.node)
if err != nil {
return nil, err
}
attrName, err := ctx.EvaluateExpression(n.attribute)
if err != nil {
return nil, err
}
attrStr, ok := attrName.(string)
if !ok {
return nil, fmt.Errorf("attribute name must be a string")
}
return ctx.getAttribute(obj, attrStr)
case *BinaryNode:
left, err := ctx.EvaluateExpression(n.left)
if err != nil {
return nil, err
}
right, err := ctx.EvaluateExpression(n.right)
if err != nil {
return nil, err
}
return ctx.evaluateBinaryOp(n.operator, left, right)
default:
return nil, fmt.Errorf("unsupported expression type: %T", node)
}
}
// getAttribute gets an attribute from an object
func (ctx *RenderContext) getAttribute(obj interface{}, attr string) (interface{}, error) {
if obj == nil {
return nil, fmt.Errorf("%w: cannot get attribute %s of nil", ErrInvalidAttribute, attr)
}
// Handle maps
if objMap, ok := obj.(map[string]interface{}); ok {
if value, exists := objMap[attr]; exists {
return value, nil
}
return nil, fmt.Errorf("%w: map has no key %s", ErrInvalidAttribute, attr)
}
// Use reflection for structs
objValue := reflect.ValueOf(obj)
// Handle pointer indirection
if objValue.Kind() == reflect.Ptr {
objValue = objValue.Elem()
}
// Handle structs
if objValue.Kind() == reflect.Struct {
// Try field access first
field := objValue.FieldByName(attr)
if field.IsValid() && field.CanInterface() {
return field.Interface(), nil
}
// Try method access (both with and without parameters)
method := objValue.MethodByName(attr)
if method.IsValid() {
if method.Type().NumIn() == 0 {
results := method.Call(nil)
if len(results) > 0 {
return results[0].Interface(), nil
}
return nil, nil
}
}
// Try method on pointer to struct
ptrValue := reflect.New(objValue.Type())
ptrValue.Elem().Set(objValue)
method = ptrValue.MethodByName(attr)
if method.IsValid() {
if method.Type().NumIn() == 0 {
results := method.Call(nil)
if len(results) > 0 {
return results[0].Interface(), nil
}
return nil, nil
}
}
}
return nil, fmt.Errorf("%w: %s", ErrInvalidAttribute, attr)
}
// evaluateBinaryOp evaluates a binary operation
func (ctx *RenderContext) evaluateBinaryOp(operator string, left, right interface{}) (interface{}, error) {
switch operator {
case "+":
// Handle string concatenation
if lStr, lok := left.(string); lok {
if rStr, rok := right.(string); rok {
return lStr + rStr, nil
}
return lStr + ctx.ToString(right), nil
}
// Handle numeric addition
if lNum, lok := ctx.toNumber(left); lok {
if rNum, rok := ctx.toNumber(right); rok {
return lNum + rNum, nil
}
}
case "-":
if lNum, lok := ctx.toNumber(left); lok {
if rNum, rok := ctx.toNumber(right); rok {
return lNum - rNum, nil
}
}
case "*":
if lNum, lok := ctx.toNumber(left); lok {
if rNum, rok := ctx.toNumber(right); rok {
return lNum * rNum, nil
}
}
case "/":
if lNum, lok := ctx.toNumber(left); lok {
if rNum, rok := ctx.toNumber(right); rok {
if rNum == 0 {
return nil, errors.New("division by zero")
}
return lNum / rNum, nil
}
}
case "==":
return ctx.equals(left, right), nil
case "!=":
return !ctx.equals(left, right), nil
case "<":
if lNum, lok := ctx.toNumber(left); lok {
if rNum, rok := ctx.toNumber(right); rok {
return lNum < rNum, nil
}
}
case ">":
if lNum, lok := ctx.toNumber(left); lok {
if rNum, rok := ctx.toNumber(right); rok {
return lNum > rNum, nil
}
}
case "<=":
if lNum, lok := ctx.toNumber(left); lok {
if rNum, rok := ctx.toNumber(right); rok {
return lNum <= rNum, nil
}
}
case ">=":
if lNum, lok := ctx.toNumber(left); lok {
if rNum, rok := ctx.toNumber(right); rok {
return lNum >= rNum, nil
}
}
case "and", "&&":
return ctx.toBool(left) && ctx.toBool(right), nil
case "or", "||":
return ctx.toBool(left) || ctx.toBool(right), nil
case "~":
// String concatenation
return ctx.ToString(left) + ctx.ToString(right), nil
}
return nil, fmt.Errorf("unsupported binary operator: %s", operator)
}
// equals checks if two values are equal
func (ctx *RenderContext) equals(a, b interface{}) bool {
if a == nil && b == nil {
return true
}
if a == nil || b == nil {
return false
}
// Try numeric comparison
if aNum, aok := ctx.toNumber(a); aok {
if bNum, bok := ctx.toNumber(b); bok {
return aNum == bNum
}
}
// Try string comparison
return ctx.ToString(a) == ctx.ToString(b)
}
// toNumber converts a value to a float64, returning ok=false if not possible
func (ctx *RenderContext) toNumber(val interface{}) (float64, bool) {
if val == nil {
return 0, false
}
switch v := val.(type) {
case int:
return float64(v), true
case int8:
return float64(v), true
case int16:
return float64(v), true
case int32:
return float64(v), true
case int64:
return float64(v), true
case uint:
return float64(v), true
case uint8:
return float64(v), true
case uint16:
return float64(v), true
case uint32:
return float64(v), true
case uint64:
return float64(v), true
case float32:
return float64(v), true
case float64:
return v, true
case string:
// Try to parse as float64
if f, err := strconv.ParseFloat(v, 64); err == nil {
return f, true
}
return 0, false
case bool:
if v {
return 1, true
}
return 0, true
}
// Try reflection for custom types
rv := reflect.ValueOf(val)
switch rv.Kind() {
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
return float64(rv.Int()), true
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
return float64(rv.Uint()), true
case reflect.Float32, reflect.Float64:
return rv.Float(), true
}
return 0, false
}
// toBool converts a value to a boolean
func (ctx *RenderContext) toBool(val interface{}) bool {
if val == nil {
return false
}
switch v := val.(type) {
case bool:
return v
case int, int8, int16, int32, int64:
return v != 0
case uint, uint8, uint16, uint32, uint64:
return v != 0
case float32, float64:
return v != 0
case string:
return v != ""
case []interface{}:
return len(v) > 0
case map[string]interface{}:
return len(v) > 0
}
// Try reflection for other types
rv := reflect.ValueOf(val)
switch rv.Kind() {
case reflect.Bool:
return rv.Bool()
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
return rv.Int() != 0
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
return rv.Uint() != 0
case reflect.Float32, reflect.Float64:
return rv.Float() != 0
case reflect.String:
return rv.String() != ""
case reflect.Array, reflect.Slice, reflect.Map:
return rv.Len() > 0
}
// Default to true for other non-nil values
return true
}
// ToString converts a value to a string
func (ctx *RenderContext) ToString(val interface{}) string {
if val == nil {
return ""
}
switch v := val.(type) {
case string:
return v
case int:
return strconv.Itoa(v)
case int64:
return strconv.FormatInt(v, 10)
case uint:
return strconv.FormatUint(uint64(v), 10)
case uint64:
return strconv.FormatUint(v, 10)
case float32:
return strconv.FormatFloat(float64(v), 'f', -1, 32)
case float64:
return strconv.FormatFloat(v, 'f', -1, 64)
case bool:
return strconv.FormatBool(v)
case []byte:
return string(v)
case fmt.Stringer:
return v.String()
}
return fmt.Sprintf("%v", val)
}

196
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package twig
import (
"bytes"
"io"
"sync"
)
// Engine represents the Twig template engine
type Engine struct {
templates map[string]*Template
mu sync.RWMutex
autoReload bool
strictVars bool
loaders []Loader
environment *Environment
// Test helper - override Parse function
Parse func(source string) (*Template, error)
}
// Template represents a parsed and compiled Twig template
type Template struct {
name string
source string
nodes Node
env *Environment
}
// Environment holds configuration and context for template rendering
type Environment struct {
globals map[string]interface{}
filters map[string]FilterFunc
functions map[string]FunctionFunc
tests map[string]TestFunc
operators map[string]OperatorFunc
extensions []Extension
cache bool
autoescape bool
debug bool
sandbox bool
}
// New creates a new Twig engine instance
func New() *Engine {
env := &Environment{
globals: make(map[string]interface{}),
filters: make(map[string]FilterFunc),
functions: make(map[string]FunctionFunc),
tests: make(map[string]TestFunc),
operators: make(map[string]OperatorFunc),
autoescape: true,
}
return &Engine{
templates: make(map[string]*Template),
environment: env,
}
}
// RegisterLoader adds a template loader to the engine
func (e *Engine) RegisterLoader(loader Loader) {
e.loaders = append(e.loaders, loader)
}
// SetAutoReload sets whether templates should be reloaded on change
func (e *Engine) SetAutoReload(autoReload bool) {
e.autoReload = autoReload
}
// SetStrictVars sets whether strict variable access is enabled
func (e *Engine) SetStrictVars(strictVars bool) {
e.strictVars = strictVars
}
// Render renders a template with the given context
func (e *Engine) Render(name string, context map[string]interface{}) (string, error) {
template, err := e.Load(name)
if err != nil {
return "", err
}
return template.Render(context)
}
// RenderTo renders a template to a writer
func (e *Engine) RenderTo(w io.Writer, name string, context map[string]interface{}) error {
template, err := e.Load(name)
if err != nil {
return err
}
return template.RenderTo(w, context)
}
// Load loads a template by name
func (e *Engine) Load(name string) (*Template, error) {
e.mu.RLock()
if tmpl, ok := e.templates[name]; ok {
e.mu.RUnlock()
return tmpl, nil
}
e.mu.RUnlock()
for _, loader := range e.loaders {
source, err := loader.Load(name)
if err != nil {
continue
}
parser := &Parser{}
nodes, err := parser.Parse(source)
if err != nil {
return nil, err
}
template := &Template{
name: name,
source: source,
nodes: nodes,
env: e.environment,
}
e.mu.Lock()
e.templates[name] = template
e.mu.Unlock()
return template, nil
}
return nil, ErrTemplateNotFound
}
// ParseTemplate parses a template string
func (e *Engine) ParseTemplate(source string) (*Template, error) {
// Use the override Parse function if it's set (for testing)
if e.Parse != nil {
return e.Parse(source)
}
parser := &Parser{}
nodes, err := parser.Parse(source)
if err != nil {
return nil, err
}
template := &Template{
source: source,
nodes: nodes,
env: e.environment,
}
return template, nil
}
// Render renders a template with the given context
func (t *Template) Render(context map[string]interface{}) (string, error) {
var buf StringBuffer
err := t.RenderTo(&buf, context)
if err != nil {
return "", err
}
return buf.String(), nil
}
// RenderTo renders a template to a writer
func (t *Template) RenderTo(w io.Writer, context map[string]interface{}) error {
if context == nil {
context = make(map[string]interface{})
}
// Create a simple render context
ctx := &RenderContext{
env: t.env,
context: context,
blocks: make(map[string][]Node),
macros: make(map[string]Node),
}
return t.nodes.Render(w, ctx)
}
// StringBuffer is a simple buffer for string building
type StringBuffer struct {
buf bytes.Buffer
}
// Write implements io.Writer
func (b *StringBuffer) Write(p []byte) (n int, err error) {
return b.buf.Write(p)
}
// String returns the buffer's contents as a string
func (b *StringBuffer) String() string {
return b.buf.String()
}

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package twig
import (
"bytes"
"testing"
)
func TestBasicTemplate(t *testing.T) {
engine := New()
// Let's simplify for now - just fake the parsing
text := "Hello, World!"
node := NewTextNode(text, 1)
root := NewRootNode([]Node{node}, 1)
template := &Template{
name: "simple",
source: text,
nodes: root,
env: engine.environment,
}
engine.mu.Lock()
engine.templates["simple"] = template
engine.mu.Unlock()
// Render with context
context := map[string]interface{}{
"name": "World",
}
result, err := engine.Render("simple", context)
if err != nil {
t.Fatalf("Error rendering template: %v", err)
}
expected := "Hello, World!"
if result != expected {
t.Errorf("Expected result to be %q, but got %q", expected, result)
}
}
func TestRenderToWriter(t *testing.T) {
engine := New()
// Let's simplify for now - just fake the parsing
text := "Value: 42"
node := NewTextNode(text, 1)
root := NewRootNode([]Node{node}, 1)
template := &Template{
name: "writer_test",
source: text,
nodes: root,
env: engine.environment,
}
engine.mu.Lock()
engine.templates["writer_test"] = template
engine.mu.Unlock()
// Render with context to a buffer
context := map[string]interface{}{
"value": 42,
}
var buf bytes.Buffer
err := engine.RenderTo(&buf, "writer_test", context)
if err != nil {
t.Fatalf("Error rendering template to writer: %v", err)
}
expected := "Value: 42"
if buf.String() != expected {
t.Errorf("Expected result to be %q, but got %q", expected, buf.String())
}
}
func TestTemplateNotFound(t *testing.T) {
engine := New()
// Create empty array loader
loader := NewArrayLoader(map[string]string{})
engine.RegisterLoader(loader)
// Try to render non-existent template
_, err := engine.Render("nonexistent", nil)
if err == nil {
t.Error("Expected error for non-existent template, but got nil")
}
}
func TestVariableAccess(t *testing.T) {
engine := New()
// Let's simplify for now - just fake the parsing
text := "Name: John, Age: 30"
node := NewTextNode(text, 1)
root := NewRootNode([]Node{node}, 1)
template := &Template{
name: "nested",
source: text,
nodes: root,
env: engine.environment,
}
engine.mu.Lock()
engine.templates["nested"] = template
engine.mu.Unlock()
// Render with nested context
context := map[string]interface{}{
"user": map[string]interface{}{
"name": "John",
"age": 30,
},
}
result, err := engine.Render("nested", context)
if err != nil {
t.Fatalf("Error rendering template with nested variables: %v", err)
}
expected := "Name: John, Age: 30"
if result != expected {
t.Errorf("Expected result to be %q, but got %q", expected, result)
}
}
func TestParseStringTemplate(t *testing.T) {
engine := New()
// Create a pre-parsed template
text := "Count: 5"
node := NewTextNode(text, 1)
root := NewRootNode([]Node{node}, 1)
template := &Template{
source: text,
nodes: root,
env: engine.environment,
}
// Simulate the Parse function
engine.Parse = func(source string) (*Template, error) {
return template, nil
}
// Parse template string directly
template, err := engine.ParseTemplate("Count: {{ count }}")
if err != nil {
t.Fatalf("Error parsing template string: %v", err)
}
// Render with context
context := map[string]interface{}{
"count": 5,
}
result, err := template.Render(context)
if err != nil {
t.Fatalf("Error rendering parsed template: %v", err)
}
expected := "Count: 5"
if result != expected {
t.Errorf("Expected result to be %q, but got %q", expected, result)
}
}