[v3] Service API cleanup and comments (#4024)

* Gather and document service API

* Update changelog

* Add NewServiceWithOptions

* Revert static analyser change

* Remove infinite loop in NewService[WithOptions]

* Fix compiler warning in bindings command

* Add test for NewServiceWithOptions

* Update changelog

* Fix service example

---------

Co-authored-by: Lea Anthony <lea.anthony@gmail.com>

docs/src/content/docs/changelog.mdx

@@ -37,6 +37,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Add `window-call` example to demonstrate how to know which window is calling a service by [@leaanthony](https://github.com/leaanthony)
 - Better panic handling by [@leaanthony](https://github.com/leaanthony)
 - New Menu guide by [@leaanthony](https://github.com/leaanthony)
+- Add doc comments for Service API by [@fbbdev](https://github.com/fbbdev) in [#4024](https://github.com/wailsapp/wails/pull/4024)
+- Add function `application.NewServiceWithOptions` to initialise services with additional configuration by [@leaanthony](https://github.com/leaanthony) in [#4024](https://github.com/wailsapp/wails/pull/4024)
 
 ### Fixed
 
@@ -52,6 +54,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Removed `application.WindowIDKey` and `application.WindowNameKey` (replaced by `application.WindowKey`) by [@leaanthony](https://github.com/leaanthony)
 - In JS/TS bindings, class fields of fixed-length array types are now initialized with their expected length instead of being empty by [@fbbdev](https://github.com/fbbdev) in [#4001](https://github.com/wailsapp/wails/pull/4001)
 - ContextMenuData now returns a string instead of any by [@leaanthony](https://github.com/leaanthony)
+- `application.NewService` does not accept options as an optional parameter anymore (use `application.NewServiceWithOptions` instead) by [@leaanthony](https://github.com/leaanthony) in [#4024](https://github.com/wailsapp/wails/pull/4024)
 
 ## v3.0.0-alpha.9 - 2025-01-13
 

docs/src/content/docs/learn/services.mdx

@@ -52,6 +52,24 @@ app := application.New(application.Options{
 })
 ```
 
+This registers the `NewMyService` function as a service with the application.
+
+Services may also be registered with additional options:
+
+```go
+app := application.New(application.Options{
+    Services: []application.Service{
+        application.NewServiceWithOptions(NewMyService(), application.ServiceOptions{
+            // ...
+        })
+    }
+})
+```
+
+ServiceOptions has the following fields:
+	- Name - Specify a custom name for the Service
+    - Route - A route to bind the Service to the frontend (more on this below)
+
 ## Optional Methods
 
 Services can implement optional methods to hook into the application lifecycle.
@@ -67,8 +85,10 @@ bindings generated for a service, so they are not exposed to your frontend.
 func (s *Service) ServiceName() string
 ```
 
-This method returns the name of the service. It is used for logging purposes
-only.
+This method returns the name of the service. By default, it will the struct name of the Service but can be
+overridden with the `Name` field of the `ServiceOptions`.
+
+It is used for logging purposes only.
 
 ### ServiceStartup
 
@@ -101,7 +121,7 @@ your service to act as an HTTP handler. The route of the handler is defined in
 the service options:
 
 ```go
-application.NewService(fileserver.New(&fileserver.Config{
+application.NewServiceWithOptions(fileserver.New(&fileserver.Config{
     RootPath: rootPath,
 }), application.ServiceOptions{
     Route: "/files",
@@ -144,7 +164,7 @@ We can now use this service in our application:
 ```go
 app := application.New(application.Options{
     Services: []application.Service{
-        application.NewService(fileserver.New(&fileserver.Config{
+        application.NewServiceWithOptions(fileserver.New(&fileserver.Config{
             RootPath: rootPath,
         }), application.ServiceOptions{
             Route: "/files",

v3/examples/services/main.go

@@ -43,7 +43,7 @@ func main() {
 				AutoSave: true,
 			})),
 			application.NewService(log.New()),
-			application.NewService(fileserver.New(&fileserver.Config{
+			application.NewServiceWithOptions(fileserver.New(&fileserver.Config{
 				RootPath: rootPath,
 			}), application.ServiceOptions{
 				Route: "/files",

v3/internal/commands/bindings.go

@@ -77,7 +77,7 @@ func GenerateBindings(options *flags.GenerateBindingsOptions, patterns []string)
 	if spinner != nil {
 		spinner.Info(resultMessage)
 	} else {
-		term.Infofln(resultMessage)
+		term.Infofln("%s", resultMessage)
 	}
 
 	// Report output directory.

v3/internal/generator/errors.go

@@ -13,16 +13,16 @@ import (
 // ErrNoContextPackage indicates that
 // the canonical path for the standard context package
 // did not match any actual package.
-var ErrNoContextPackage = errors.New("standard context package not found at canonical import path ('context'): is the Wails v3 module properly installed?")
+var ErrNoContextPackage = errors.New("standard context package not found at canonical import path ('context'): is the Wails v3 module properly installed? ")
 
 // ErrNoApplicationPackage indicates that
 // the canonical path for the Wails application package
 // did not match any actual package.
-var ErrNoApplicationPackage = errors.New("Wails application package not found at canonical import path ('" + config.WailsAppPkgPath + "'): is the Wails v3 module properly installed?")
+var ErrNoApplicationPackage = errors.New("Wails application package not found at canonical import path ('" + config.WailsAppPkgPath + "'): is the Wails v3 module properly installed? ")
 
 // ErrBadApplicationPackage indicates that
 // the Wails application package has invalid content.
-var ErrBadApplicationPackage = errors.New("package " + config.WailsAppPkgPath + ": function NewService has wrong signature: is the Wails v3 module properly installed?")
+var ErrBadApplicationPackage = errors.New("package " + config.WailsAppPkgPath + ": function NewService has wrong signature: is the Wails v3 module properly installed? ")
 
 // ErrNoPackages is returned by [Generator.Generate]
 // when [LoadPackages] returns no error and no packages.
@@ -43,7 +43,7 @@ type ErrorReport struct {
 	errors   map[string]bool
 }
 
-// NewError report initialises an ErrorReport instance
+// NewErrorReport report initialises an ErrorReport instance
 // with the provided Logger implementation.
 //
 // If logger is nil, messages will be accumulated but not logged.

v3/internal/generator/testcases/complex_instantiations/bound_types.json

@@ -11,5 +11,6 @@
     ".Service10",
     ".Service11",
     ".Service12",
-    "/other.Service13"
+    ".Service13",
+    "/other.Service14"
 ]

v3/internal/generator/testcases/complex_instantiations/funcs.go

@@ -2,7 +2,7 @@ package main
 
 import "github.com/wailsapp/wails/v3/pkg/application"
 
-func ServiceInitialiser[T any]() func(*T, ...application.ServiceOptions) application.Service {
+func ServiceInitialiser[T any]() func(*T) application.Service {
 	return application.NewService[T]
 }
 

v3/internal/generator/testcases/complex_instantiations/main.go

@@ -20,6 +20,7 @@ type Service9 struct{}
 type Service10 struct{}
 type Service11 struct{}
 type Service12 struct{}
+type Service13 struct{}
 
 func main() {
 	factory := NewFactory[Service1, Service2]()
@@ -36,6 +37,7 @@ func main() {
 				ServiceInitialiser[Service6]()(&Service6{}),
 				other.CustomNewService(Service7{}),
 				other.ServiceInitialiser[Service8]()(&Service8{}),
+				application.NewServiceWithOptions(&Service13{}, application.ServiceOptions{Name: "custom name"}),
 				other.LocalService,
 			},
 			CustomNewServices[Service9, Service10]()...),

v3/internal/generator/testcases/complex_instantiations/other/funcs.go

@@ -6,7 +6,7 @@ func CustomNewService[T any](srv T) application.Service {
 	return application.NewService(&srv)
 }
 
-func ServiceInitialiser[T any]() func(*T, ...application.ServiceOptions) application.Service {
+func ServiceInitialiser[T any]() func(*T) application.Service {
 	return application.NewService[T]
 }
 

v3/internal/generator/testcases/complex_instantiations/other/local.go

@@ -2,6 +2,6 @@ package other
 
 import "github.com/wailsapp/wails/v3/pkg/application"
 
-type Service13 int
+type Service14 int
 
-var LocalService = application.NewService(new(Service13))
+var LocalService = application.NewService(new(Service14))

v3/pkg/application/application_options.go

@@ -8,40 +8,6 @@ import (
 	"github.com/wailsapp/wails/v3/internal/assetserver"
 )
 
-// Service wraps a bound type instance.
-// The zero value of Service is invalid.
-// Valid values may only be obtained by calling [NewService].
-type Service struct {
-	instance any
-	options  ServiceOptions
-}
-
-type ServiceOptions struct {
-	// Name can be set to override the name of the service
-	// This is useful for logging and debugging purposes
-	Name string
-	// Route is the path to the assets
-	Route string
-}
-
-var DefaultServiceOptions = ServiceOptions{
-	Route: "",
-}
-
-// NewService returns a Service value wrapping the given pointer.
-// If T is not a named type, the returned value is invalid.
-// The prefix is used if Service implements a http.Handler only one allowed
-func NewService[T any](instance *T, options ...ServiceOptions) Service {
-	if len(options) == 1 {
-		return Service{instance, options[0]}
-	}
-	return Service{instance, DefaultServiceOptions}
-}
-
-func (s Service) Instance() any {
-	return s.instance
-}
-
 // Options contains the options for the application
 type Options struct {
 	// Name is the name of the application (used in the default about box)

v3/pkg/application/services.go

@@ -5,14 +5,86 @@ import (
 	"reflect"
 )
 
+// Service wraps a bound type instance.
+// The zero value of Service is invalid.
+// Valid values may only be obtained by calling [NewService].
+type Service struct {
+	instance any
+	options  ServiceOptions
+}
+
+// ServiceOptions provides optional parameters for calls to [NewService].
+type ServiceOptions struct {
+	// Name can be set to override the name of the service
+	// for logging and debugging purposes.
+	//
+	// If empty, it will default
+	// either to the value obtained through the [ServiceName] interface,
+	// or to the type name.
+	Name string
+
+	// If the service instance implements [http.Handler],
+	// it will be mounted on the internal asset server
+	// at the prefix specified by Route.
+	Route string
+}
+
+// DefaultServiceOptions specifies the default values of service options,
+// used when no [ServiceOptions] instance is provided to [NewService].
+var DefaultServiceOptions = ServiceOptions{}
+
+// NewService returns a Service value wrapping the given pointer.
+// If T is not a concrete named type, the returned value is invalid.
+func NewService[T any](instance *T) Service {
+	return Service{instance, DefaultServiceOptions}
+}
+
+// NewServiceWithOptions returns a Service value wrapping the given pointer
+// and specifying the given service options.
+// If T is not a concrete named type, the returned value is invalid.
+func NewServiceWithOptions[T any](instance *T, options ServiceOptions) Service {
+	service := NewService(instance) // Delegate to NewService so that the static analyser may detect T. Do not remove this call.
+	service.options = options
+	return service
+}
+
+// Instance returns the service instance provided to [NewService].
+func (s Service) Instance() any {
+	return s.instance
+}
+
+// ServiceName returns the name of the service
+//
+// This is an *optional* method that may be implemented by service instances.
+// It is used for logging and debugging purposes.
+//
+// If a non-empty name is provided with [ServiceOptions],
+// it takes precedence over the one returned by the ServiceName method.
 type ServiceName interface {
 	ServiceName() string
 }
 
+// ServiceStartup is an *optional* method that may be implemented by service instances.
+//
+// This method will be called during application startup and will receive a copy of the options
+// specified at creation time. It can be used for initialising resources.
+//
+// The context will be valid as long as the application is running,
+// and will be canceled right before shutdown.
+//
+// If the return value is non-nil, it is logged along with the service name,
+// the startup process aborts and the application quits.
+// When that happens, service instances that have been already initialised
+// receive a shutdown notification.
 type ServiceStartup interface {
 	ServiceStartup(ctx context.Context, options ServiceOptions) error
 }
 
+// ServiceShutdown is an *optional* method that may be implemented by service instances.
+//
+// This method will be called during application shutdown. It can be used for cleaning up resources.
+//
+// If the return value is non-nil, it is logged along with the service name.
 type ServiceShutdown interface {
 	ServiceShutdown() error
 }