Add collection input helper

configuration_sources_test.go

@@ -1,6 +1,8 @@
 package promptkit_test
 
 import (
+	"context"
+	"errors"
 	"io/fs"
 	"os"
 	"path/filepath"
@@ -16,6 +18,78 @@ type sourceDocument struct {
 	Second string `yaml:"second"`
 }
 
+func TestCollectionInputValidatesWithoutReadingSource(t *testing.T) {
+	input, err := promptkit.CollectionInput("docs", configkit.File(filepath.Join(t.TempDir(), "not-read.yaml")))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if input.Destination.String() != "/collections/docs" || !input.Imports {
+		t.Fatalf("collection input = %+v, want destination /collections/docs with imports enabled", input)
+	}
+	for _, namespace := range []string{"", " ", "docs/api"} {
+		if _, err := promptkit.CollectionInput(namespace, configkit.NoSource()); !errors.Is(err, promptkit.ErrInvalidConfig) {
+			t.Errorf("namespace %q error = %v, want ErrInvalidConfig", namespace, err)
+		}
+	}
+}
+
+func TestCollectionInputLoadsNativeImportsAndLaterOverride(t *testing.T) {
+	directory := t.TempDir()
+	mainPath := filepath.Join(directory, "collection.yaml")
+	defaultsPath := filepath.Join(directory, "defaults.yaml")
+	if err := os.WriteFile(mainPath, []byte("configkit:\n  imports:\n    - path: defaults.yaml\n"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(defaultsPath, []byte("prompts:\n  greeting:\n    version: imported\n    messages:\n      - role: user\n        content: Hello\n    output:\n      format: text\n      validation_mode: none\n"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	input, err := promptkit.CollectionInput("docs", configkit.File(mainPath))
+	if err != nil {
+		t.Fatal(err)
+	}
+	engine, err := promptkit.NewEngine(promptkit.Config{Sources: promptkit.ConfigurationSources{
+		Underlays: []configkit.Underlay{{Inputs: []configkit.Input{input}}},
+		Main: &configkit.Input{
+			Source:      configkit.Mapping("later collection override", map[string]any{"prompts": map[string]any{"greeting": map[string]any{"version": "overridden"}}}),
+			Destination: configkit.Keys("collections", "docs"),
+		},
+	}})
+	if err != nil {
+		t.Fatalf("construct engine with native collection import: %v", err)
+	}
+	inspection, err := engine.InspectPrompt(context.Background(), "docs/greeting")
+	if err != nil || inspection.PromptVersion == nil || *inspection.PromptVersion != "overridden" {
+		t.Fatalf("inspect imported and overlaid prompt = (%+v, %v)", inspection, err)
+	}
+}
+
+func TestCollectionInputLoadsEmbeddedImportsAndLaterOverride(t *testing.T) {
+	files := fstest.MapFS{
+		"collection.yaml": {Data: []byte("configkit:\n  imports:\n    - path: defaults.yaml\n")},
+		"defaults.yaml":   {Data: []byte("prompts:\n  greeting:\n    version: imported\n    messages:\n      - role: user\n        content: Hello\n    output:\n      format: text\n      validation_mode: none\n")},
+	}
+	filesystem := configkit.NewFilesystem("embedded collection", files)
+	input, err := promptkit.CollectionInput("docs", filesystem.File("collection.yaml"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	input.Filesystem = &configkit.FilesystemContext{FS: &filesystem, Root: "."}
+	engine, err := promptkit.NewEngine(promptkit.Config{Sources: promptkit.ConfigurationSources{
+		Underlays: []configkit.Underlay{{Inputs: []configkit.Input{input}}},
+		Main: &configkit.Input{
+			Source:      configkit.Mapping("later collection override", map[string]any{"prompts": map[string]any{"greeting": map[string]any{"version": "overridden"}}}),
+			Destination: configkit.Keys("collections", "docs"),
+		},
+	}})
+	if err != nil {
+		t.Fatalf("construct engine with embedded collection import: %v", err)
+	}
+	inspection, err := engine.InspectPrompt(context.Background(), "docs/greeting")
+	if err != nil || inspection.PromptVersion == nil || *inspection.PromptVersion != "overridden" {
+		t.Fatalf("inspect imported and overlaid prompt = (%+v, %v)", inspection, err)
+	}
+}
+
 func TestDirectoryInputsSelectsSortedFilesWithRootContext(t *testing.T) {
 	root := t.TempDir()
 	if err := os.Mkdir(filepath.Join(root, "nested"), 0o755); err != nil {