Make public options opaque

engine.go

@@ -52,7 +52,15 @@ type Config struct {
 }
 
 // Option customizes engine construction.
-type Option func(*engineOptions) error
+type Option interface {
+	apply(*engineOptions) error
+}
+
+type optionFunc func(*engineOptions) error
+
+func (f optionFunc) apply(options *engineOptions) error {
+	return f(options)
+}
 
 type engineOptions struct {
 	llmClient       llm.Client
@@ -68,17 +76,17 @@ type engineOptions struct {
 
 // WithLLMClient injects a custom LLM client for execution.
 func WithLLMClient(client LLMClient) Option {
-	return func(options *engineOptions) error {
+	return optionFunc(func(options *engineOptions) error {
 		if client == nil {
 			return ErrInvalidConfig
 		}
 		options.llmClient = publicLLMClientAdapter{client: client}
 		return nil
-	}
+	})
 }
 
 func WithPromptFS(fsys fs.FS, root string) Option {
-	return func(options *engineOptions) error {
+	return optionFunc(func(options *engineOptions) error {
 		if fsys == nil {
 			return ErrInvalidConfig
 		}
@@ -88,11 +96,11 @@ func WithPromptFS(fsys fs.FS, root string) Option {
 		options.promptDefs = promptdef.NewFSRepository(fsys, root)
 		options.promptSource = true
 		return nil
-	}
+	})
 }
 
 func WithPromptFile(path string) Option {
-	return func(options *engineOptions) error {
+	return optionFunc(func(options *engineOptions) error {
 		fsys, root, err := fileSource(path)
 		if err != nil {
 			return err
@@ -100,11 +108,11 @@ func WithPromptFile(path string) Option {
 		options.promptDefs = promptdef.NewFSRepository(fsys, root)
 		options.promptSource = true
 		return nil
-	}
+	})
 }
 
 func WithProfileFS(fsys fs.FS, root string) Option {
-	return func(options *engineOptions) error {
+	return optionFunc(func(options *engineOptions) error {
 		if fsys == nil {
 			return ErrInvalidConfig
 		}
@@ -114,11 +122,11 @@ func WithProfileFS(fsys fs.FS, root string) Option {
 		options.profiles = profile.NewFSRepository(fsys, root)
 		options.profileSource = true
 		return nil
-	}
+	})
 }
 
 func WithProfileFile(path string) Option {
-	return func(options *engineOptions) error {
+	return optionFunc(func(options *engineOptions) error {
 		fsys, root, err := fileSource(path)
 		if err != nil {
 			return err
@@ -126,13 +134,13 @@ func WithProfileFile(path string) Option {
 		options.profiles = profile.NewFSRepository(fsys, root)
 		options.profileSource = true
 		return nil
-	}
+	})
 }
 
 // WithProfiles configures in-memory profiles that take precedence over
 // configured profile files and built-in profiles.
 func WithProfiles(profiles ...Profile) Option {
-	return func(options *engineOptions) error {
+	return optionFunc(func(options *engineOptions) error {
 		repo, err := newMemoryProfileRepository(profiles)
 		if err != nil {
 			return err
@@ -140,11 +148,11 @@ func WithProfiles(profiles ...Profile) Option {
 		options.memoryProfiles = repo
 		options.memorySource = true
 		return nil
-	}
+	})
 }
 
 func WithSchemaFS(fsys fs.FS, root string) Option {
-	return func(options *engineOptions) error {
+	return optionFunc(func(options *engineOptions) error {
 		if fsys == nil {
 			return ErrInvalidConfig
 		}
@@ -154,11 +162,11 @@ func WithSchemaFS(fsys fs.FS, root string) Option {
 		options.validator = validate.NewFSValidator(fsys, root)
 		options.validatorSource = true
 		return nil
-	}
+	})
 }
 
 func WithSchemaFile(path string) Option {
-	return func(options *engineOptions) error {
+	return optionFunc(func(options *engineOptions) error {
 		fsys, root, err := fileSource(path)
 		if err != nil {
 			return err
@@ -166,7 +174,7 @@ func WithSchemaFile(path string) Option {
 		options.validator = validate.NewFSValidator(fsys, root)
 		options.validatorSource = true
 		return nil
-	}
+	})
 }
 
 // NewEngine constructs an Engine using the same default internal components as
@@ -177,7 +185,7 @@ func NewEngine(cfg Config, opts ...Option) (*Engine, error) {
 		if opt == nil {
 			continue
 		}
-		if err := opt(&options); err != nil {
+		if err := opt.apply(&options); err != nil {
 			return nil, fmt.Errorf("%w: %v", ErrInvalidConfig, err)
 		}
 	}

engine_test.go

@@ -1378,6 +1378,45 @@ func TestSourceOptionsRejectInvalidInputs(t *testing.T) {
 	}
 }
 
+func TestPackageOptionsComposeFromSlice(t *testing.T) {
+	fake := &fakeLLMClient{response: &scriptorium.GenerateResponse{Content: "ok"}}
+	options := []scriptorium.Option{
+		nil,
+		scriptorium.WithProfiles(scriptorium.Profile{
+			ID:       "slice-profile",
+			Endpoint: "http://slice/v1",
+			Model:    "slice-model",
+		}),
+		scriptorium.WithLLMClient(fake),
+	}
+
+	engine, err := scriptorium.NewEngine(scriptorium.Config{
+		PromptDir: "./examples/prompts",
+		SchemaDir: "./examples/schemas",
+	}, options...)
+	if err != nil {
+		t.Fatalf("expected package-provided options to compose, got %v", err)
+	}
+
+	_, err = engine.Run(context.Background(), scriptorium.RunRequest{
+		PromptID:  "generic.markdown_summary",
+		ProfileID: "slice-profile",
+		Inputs: map[string]scriptorium.ArtifactRef{
+			"transcript": scriptorium.Inline("Rin opens the gate."),
+			"glossary":   scriptorium.Inline("gate: A guarded passage."),
+		},
+	})
+	if err != nil {
+		t.Fatalf("expected run with composed options to succeed, got %v", err)
+	}
+	if len(fake.requests) != 1 {
+		t.Fatalf("expected one generate request, got %d", len(fake.requests))
+	}
+	if fake.requests[0].Target.Model != "slice-model" {
+		t.Fatalf("expected profile from composed options, got %q", fake.requests[0].Target.Model)
+	}
+}
+
 func TestExtraParamsTypedNestedValuesAreCopiedAcrossPublicBoundary(t *testing.T) {
 	fake := &fakeLLMClient{response: &scriptorium.GenerateResponse{Content: "ok"}}
 	engine := newExampleEngineWithOptions(t, "./examples/schemas", scriptorium.WithLLMClient(fake))