Allow passing nil as invoker to Invoke, InjectInto and Build. Add more functions with work with contexts

README.md

@@ -103,11 +103,15 @@ Pal provides several functions for registering services:
 
 Pal also provides functions for retrieving services:
 
-- `Invoke[T](ctx, invoker, args...)` - Retrieves or creates an instance of type `T` from the container, factory services may require argumens
+- `Invoke[T](ctx, invoker, args...)` - Retrieves or creates an instance of type `T` from the container, factory services may require argumens.
 - `InvokeAs[T, C](ctx, invoker, args...)` - A wrapper around `Inoke`, castes invoked service to specified `C`, returns an error if casging fails.
 - `Build[S](ctx, invoker)` - Creates an instance of S, resolves its dependencies, injects them into its fields.
 - `InjectInto[S](ctx, invoker, *S)` - Resolves S's dependencies and injects them into its fields.
 
+All these functions accept nil as invoker, in this case, a Pal instance will be extracted from the context.
+Pal automatilly adds itself into contexts paseed to `Init`, `Shutdown` and `Run` under `pal.CtxValue` key.
+You can extract it manually with `pal.FromContext`
+
 ## Service Types
 
 Pal supports several types of services, each designed for different use cases:

api.go

@@ -82,8 +82,17 @@ func ProvidePal(pal *Pal) *ServiceList {
 }
 
 // Invoke retrieves or creates an instance of type T from the given Pal container.
+// Invoker may be nil, in this case an instance of Pal will be extracted from the context,
+// if the context does not contain a Pal instance, an error will be returned.
 func Invoke[T any](ctx context.Context, invoker Invoker, args ...any) (T, error) {
 	name := typetostring.GetType[T]()
+	if invoker == nil {
+		var err error
+		invoker, err = FromContext(ctx)
+		if err != nil {
+			return empty[T](), err
+		}
+	}
 
 	a, err := invoker.Invoke(ctx, name, args...)
 	if err != nil {
@@ -105,6 +114,8 @@ func MustInvoke[T any](ctx context.Context, invoker Invoker, args ...any) T {
 
 // InvokeAs invokes a service and casts it to the expected type. It returns an error if the cast fails.
 // May be useful when invoking a service with an interface type and you want to cast it to a concrete type.
+// Invoker may be nil, in this case an instance of Pal will be extracted from the context,
+// if the context does not contain a Pal instance, an error will be returned.
 func InvokeAs[T any, C any](ctx context.Context, invoker Invoker, args ...any) (*C, error) {
 	service, err := Invoke[T](ctx, invoker, args...)
 	if err != nil {
@@ -128,6 +139,8 @@ func MustInvokeAs[T any, C any](ctx context.Context, invoker Invoker, args ...an
 // Build resolves dependencies for a struct of type T using the provided context and Invoker.
 // It initializes the struct's fields by injecting appropriate dependencies based on the field types.
 // Returns the fully initialized struct or an error if dependency resolution fails.
+// Invoker may be nil, in this case an instance of Pal will be extracted from the context,
+// if the context does not contain a Pal instance, an error will be returned.
 func Build[T any](ctx context.Context, invoker Invoker) (*T, error) {
 	s := new(T)
 
@@ -148,6 +161,13 @@ func MustBuild[T any](ctx context.Context, invoker Invoker) *T {
 // It only sets fields that are exported and match a resolvable dependency, skipping fields when ErrServiceNotFound occurs.
 // Returns an error if dependency invocation fails or other unrecoverable errors occur during injection.
 func InjectInto[T any](ctx context.Context, invoker Invoker, s *T) error {
+	if invoker == nil {
+		var err error
+		invoker, err = FromContext(ctx)
+		if err != nil {
+			return err
+		}
+	}
 	return invoker.InjectInto(ctx, s)
 }
 

errors.go

@@ -29,4 +29,7 @@ var (
 
 	// ErrServiceInvalidCast is returned when a service is cast to a different type.
 	ErrServiceInvalidCast = errors.New("failed to cast service to the expected type")
+
+	// ErrInvokerIsNotInContext is returned when a context passed to Invoke does not contain a Pal instance.
+	ErrInvokerIsNotInContext = errors.New("invoker is not in context")
 )

hook_priority_test.go

@@ -119,7 +119,7 @@ func TestHookPriority_ToHealthCheck(t *testing.T) {
 			})
 
 		p := newPal(palService)
-		ctx := context.WithValue(t.Context(), pal.CtxValue, p)
+		ctx := pal.WithPal(t.Context(), p)
 
 		// Initialize first
 		err := p.Init(t.Context())
@@ -280,7 +280,7 @@ func TestHookPriority_MultipleHooks(t *testing.T) {
 			})
 
 		p := newPal(palService)
-		ctx := context.WithValue(t.Context(), pal.CtxValue, p)
+		ctx := pal.WithPal(t.Context(), p)
 
 		// Initialize
 		err := p.Init(t.Context())

pal.go

@@ -58,9 +58,22 @@ func New(services ...ServiceDef) *Pal {
 }
 
 // FromContext retrieves a *Pal from the provided context, expecting it to be stored under the CtxValue key.
-// Panics if ctx misses the value.
-func FromContext(ctx context.Context) *Pal {
-	return ctx.Value(CtxValue).(*Pal)
+func FromContext(ctx context.Context) (*Pal, error) {
+	invoker, ok := ctx.Value(CtxValue).(*Pal)
+	if !ok {
+		return nil, ErrInvokerIsNotInContext
+	}
+
+	return invoker, nil
+}
+
+// MustFromContext is like FromContext but panics if an error occurs.
+func MustFromContext(ctx context.Context) *Pal {
+	return must(FromContext(ctx))
+}
+
+func WithPal(ctx context.Context, pal *Pal) context.Context {
+	return context.WithValue(ctx, CtxValue, pal)
 }
 
 // InitTimeout sets the timeout for the initialization of the services.
@@ -124,7 +137,7 @@ func (p *Pal) Init(ctx context.Context) error {
 		return nil
 	}
 
-	ctx = context.WithValue(ctx, CtxValue, p)
+	ctx = WithPal(ctx, p)
 
 	if err := p.config.Validate(ctx); err != nil {
 		return err
@@ -155,7 +168,7 @@ func (p *Pal) Run(ctx context.Context, signals ...os.Signal) error {
 		signals = DefaultShutdownSignals
 	}
 
-	ctx = context.WithValue(ctx, CtxValue, p)
+	ctx = WithPal(ctx, p)
 
 	ctx, stop := signal.NotifyContext(ctx, signals...)
 	defer stop()
@@ -196,6 +209,7 @@ func (p *Pal) Run(ctx context.Context, signals ...os.Signal) error {
 	}()
 
 	shutdownCtx, cancel := context.WithTimeout(context.Background(), time.Duration(float64(p.config.ShutdownTimeout)*0.9))
+	shutdownCtx = WithPal(shutdownCtx, p)
 	defer cancel()
 
 	return errors.Join(runErr, p.container.Shutdown(shutdownCtx))
@@ -211,7 +225,7 @@ func (p *Pal) Services() map[string]ServiceDef {
 // It implements the Invoker interface.
 // The context is enriched with the Pal instance before being passed to the container.
 func (p *Pal) Invoke(ctx context.Context, name string, args ...any) (any, error) {
-	ctx = context.WithValue(ctx, CtxValue, p)
+	ctx = WithPal(ctx, p)
 
 	return p.container.Invoke(ctx, name, args...)
 }
@@ -220,7 +234,7 @@ func (p *Pal) Invoke(ctx context.Context, name string, args ...any) (any, error)
 // It implements the Invoker interface.
 // The context is enriched with the Pal instance before being passed to the container.
 func (p *Pal) InjectInto(ctx context.Context, target any) error {
-	ctx = context.WithValue(ctx, CtxValue, p)
+	ctx = WithPal(ctx, p)
 
 	return p.container.InjectInto(ctx, target)
 }

pal_test.go

@@ -70,9 +70,10 @@ func Test_FromContext(t *testing.T) {
 		t.Parallel()
 
 		p := newPal()
-		ctx := context.WithValue(t.Context(), pal.CtxValue, p)
+		ctx := pal.WithPal(t.Context(), p)
 
-		result := pal.FromContext(ctx)
+		result, err := pal.FromContext(ctx)
+		assert.NoError(t, err)
 
 		assert.Same(t, p, result)
 	})

service_const_test.go

@@ -32,7 +32,7 @@ func TestService_Instance(t *testing.T) {
 		service := pal.Provide(NewMockRunnerServiceStruct(t))
 		p := newPal(service)
 
-		ctx := context.WithValue(t.Context(), pal.CtxValue, p)
+		ctx := pal.WithPal(t.Context(), p)
 
 		err := p.Init(t.Context())
 		assert.NoError(t, err)
@@ -65,7 +65,7 @@ func TestService_ToInit(t *testing.T) {
 			})
 		p := newPal(service)
 
-		ctx := context.WithValue(t.Context(), pal.CtxValue, p)
+		ctx := pal.WithPal(t.Context(), p)
 
 		err := p.Init(t.Context())
 		assert.NoError(t, err)
@@ -86,7 +86,7 @@ func TestService_ToInit(t *testing.T) {
 		service := pal.Provide[any](s)
 		p := newPal(service)
 
-		ctx := context.WithValue(t.Context(), pal.CtxValue, p)
+		ctx := pal.WithPal(t.Context(), p)
 
 		err := p.Init(t.Context())
 		assert.NoError(t, err)

service_factory1_test.go

@@ -28,7 +28,7 @@ func TestServiceFactory1_Instance(t *testing.T) {
 		})
 		p := newPal(service)
 
-		ctx := context.WithValue(t.Context(), pal.CtxValue, p)
+		ctx := pal.WithPal(t.Context(), p)
 
 		err := p.Init(t.Context())
 		assert.NoError(t, err)
@@ -57,7 +57,7 @@ func TestServiceFactory1_Instance(t *testing.T) {
 		})
 		p := newPal(service)
 
-		ctx := context.WithValue(t.Context(), pal.CtxValue, p)
+		ctx := pal.WithPal(t.Context(), p)
 
 		err := p.Init(t.Context())
 		assert.NoError(t, err)
@@ -75,7 +75,7 @@ func TestServiceFactory1_Instance(t *testing.T) {
 		})
 		p := newPal(service)
 
-		ctx := context.WithValue(t.Context(), pal.CtxValue, p)
+		ctx := pal.WithPal(t.Context(), p)
 
 		err := p.Init(t.Context())
 		assert.NoError(t, err)
@@ -93,7 +93,7 @@ func TestServiceFactory1_Instance(t *testing.T) {
 		})
 		p := newPal(service)
 
-		ctx := context.WithValue(t.Context(), pal.CtxValue, p)
+		ctx := pal.WithPal(t.Context(), p)
 
 		err := p.Init(t.Context())
 		assert.NoError(t, err)