feat: enhance plugin manager to support metrics recording

Signed-off-by: Deluan <deluan@navidrome.org>

cmd/wire_gen.go

@@ -61,12 +61,12 @@ func CreateNativeAPIRouter(ctx context.Context) *nativeapi.Router {
 	fileCache := artwork.GetImageCache()
 	fFmpeg := ffmpeg.New()
 	broker := events.GetBroker()
-	manager := plugins.GetManager(dataStore, broker)
+	metricsMetrics := metrics.GetPrometheusInstance(dataStore)
+	manager := plugins.GetManager(dataStore, broker, metricsMetrics)
 	agentsAgents := agents.GetAgents(dataStore, manager)
 	provider := external.NewProvider(dataStore, agentsAgents)
 	artworkArtwork := artwork.NewArtwork(dataStore, fileCache, fFmpeg, provider)
 	cacheWarmer := artwork.NewCacheWarmer(artworkArtwork, fileCache)
-	metricsMetrics := metrics.GetPrometheusInstance(dataStore)
 	modelScanner := scanner.New(ctx, dataStore, cacheWarmer, broker, playlists, metricsMetrics)
 	watcher := scanner.GetWatcher(dataStore, modelScanner)
 	library := core.NewLibrary(dataStore, modelScanner, watcher, broker)
@@ -81,7 +81,8 @@ func CreateSubsonicAPIRouter(ctx context.Context) *subsonic.Router {
 	fileCache := artwork.GetImageCache()
 	fFmpeg := ffmpeg.New()
 	broker := events.GetBroker()
-	manager := plugins.GetManager(dataStore, broker)
+	metricsMetrics := metrics.GetPrometheusInstance(dataStore)
+	manager := plugins.GetManager(dataStore, broker, metricsMetrics)
 	agentsAgents := agents.GetAgents(dataStore, manager)
 	provider := external.NewProvider(dataStore, agentsAgents)
 	artworkArtwork := artwork.NewArtwork(dataStore, fileCache, fFmpeg, provider)
@@ -92,7 +93,6 @@ func CreateSubsonicAPIRouter(ctx context.Context) *subsonic.Router {
 	players := core.NewPlayers(dataStore)
 	cacheWarmer := artwork.NewCacheWarmer(artworkArtwork, fileCache)
 	playlists := core.NewPlaylists(dataStore)
-	metricsMetrics := metrics.GetPrometheusInstance(dataStore)
 	modelScanner := scanner.New(ctx, dataStore, cacheWarmer, broker, playlists, metricsMetrics)
 	playTracker := scrobbler.GetPlayTracker(dataStore, broker, manager)
 	playbackServer := playback.GetInstance(dataStore)
@@ -106,7 +106,8 @@ func CreatePublicRouter() *public.Router {
 	fileCache := artwork.GetImageCache()
 	fFmpeg := ffmpeg.New()
 	broker := events.GetBroker()
-	manager := plugins.GetManager(dataStore, broker)
+	metricsMetrics := metrics.GetPrometheusInstance(dataStore)
+	manager := plugins.GetManager(dataStore, broker, metricsMetrics)
 	agentsAgents := agents.GetAgents(dataStore, manager)
 	provider := external.NewProvider(dataStore, agentsAgents)
 	artworkArtwork := artwork.NewArtwork(dataStore, fileCache, fFmpeg, provider)
@@ -152,13 +153,13 @@ func CreateScanner(ctx context.Context) model.Scanner {
 	fileCache := artwork.GetImageCache()
 	fFmpeg := ffmpeg.New()
 	broker := events.GetBroker()
-	manager := plugins.GetManager(dataStore, broker)
+	metricsMetrics := metrics.GetPrometheusInstance(dataStore)
+	manager := plugins.GetManager(dataStore, broker, metricsMetrics)
 	agentsAgents := agents.GetAgents(dataStore, manager)
 	provider := external.NewProvider(dataStore, agentsAgents)
 	artworkArtwork := artwork.NewArtwork(dataStore, fileCache, fFmpeg, provider)
 	cacheWarmer := artwork.NewCacheWarmer(artworkArtwork, fileCache)
 	playlists := core.NewPlaylists(dataStore)
-	metricsMetrics := metrics.GetPrometheusInstance(dataStore)
 	modelScanner := scanner.New(ctx, dataStore, cacheWarmer, broker, playlists, metricsMetrics)
 	return modelScanner
 }
@@ -169,13 +170,13 @@ func CreateScanWatcher(ctx context.Context) scanner.Watcher {
 	fileCache := artwork.GetImageCache()
 	fFmpeg := ffmpeg.New()
 	broker := events.GetBroker()
-	manager := plugins.GetManager(dataStore, broker)
+	metricsMetrics := metrics.GetPrometheusInstance(dataStore)
+	manager := plugins.GetManager(dataStore, broker, metricsMetrics)
 	agentsAgents := agents.GetAgents(dataStore, manager)
 	provider := external.NewProvider(dataStore, agentsAgents)
 	artworkArtwork := artwork.NewArtwork(dataStore, fileCache, fFmpeg, provider)
 	cacheWarmer := artwork.NewCacheWarmer(artworkArtwork, fileCache)
 	playlists := core.NewPlaylists(dataStore)
-	metricsMetrics := metrics.GetPrometheusInstance(dataStore)
 	modelScanner := scanner.New(ctx, dataStore, cacheWarmer, broker, playlists, metricsMetrics)
 	watcher := scanner.GetWatcher(dataStore, modelScanner)
 	return watcher
@@ -192,13 +193,14 @@ func getPluginManager() *plugins.Manager {
 	sqlDB := db.Db()
 	dataStore := persistence.New(sqlDB)
 	broker := events.GetBroker()
-	manager := plugins.GetManager(dataStore, broker)
+	metricsMetrics := metrics.GetPrometheusInstance(dataStore)
+	manager := plugins.GetManager(dataStore, broker, metricsMetrics)
 	return manager
 }
 
 // wire_injectors.go:
 
-var allProviders = wire.NewSet(core.Set, artwork.Set, server.New, subsonic.New, nativeapi.New, public.New, persistence.New, lastfm.NewRouter, listenbrainz.NewRouter, events.GetBroker, scanner.New, scanner.GetWatcher, metrics.GetPrometheusInstance, db.Db, plugins.GetManager, wire.Bind(new(agents.PluginLoader), new(*plugins.Manager)), wire.Bind(new(scrobbler.PluginLoader), new(*plugins.Manager)), wire.Bind(new(nativeapi.PluginManager), new(*plugins.Manager)), wire.Bind(new(core.Watcher), new(scanner.Watcher)))
+var allProviders = wire.NewSet(core.Set, artwork.Set, server.New, subsonic.New, nativeapi.New, public.New, persistence.New, lastfm.NewRouter, listenbrainz.NewRouter, events.GetBroker, scanner.New, scanner.GetWatcher, metrics.GetPrometheusInstance, db.Db, plugins.GetManager, wire.Bind(new(agents.PluginLoader), new(*plugins.Manager)), wire.Bind(new(scrobbler.PluginLoader), new(*plugins.Manager)), wire.Bind(new(nativeapi.PluginManager), new(*plugins.Manager)), wire.Bind(new(plugins.PluginMetricsRecorder), new(metrics.Metrics)), wire.Bind(new(core.Watcher), new(scanner.Watcher)))
 
 func GetPluginManager(ctx context.Context) *plugins.Manager {
 	manager := getPluginManager()

cmd/wire_injectors.go

@@ -45,6 +45,7 @@ var allProviders = wire.NewSet(
 	wire.Bind(new(agents.PluginLoader), new(*plugins.Manager)),
 	wire.Bind(new(scrobbler.PluginLoader), new(*plugins.Manager)),
 	wire.Bind(new(nativeapi.PluginManager), new(*plugins.Manager)),
+	wire.Bind(new(plugins.PluginMetricsRecorder), new(metrics.Metrics)),
 	wire.Bind(new(core.Watcher), new(scanner.Watcher)),
 )
 

core/metrics/insights.go

@@ -315,7 +315,7 @@ func (c *insightsCollector) hasSmartPlaylists(ctx context.Context) (bool, error)
 // collectPlugins collects information about installed plugins
 func (c *insightsCollector) collectPlugins(_ context.Context) map[string]insights.PluginInfo {
 	// TODO Fix import/inject cycles
-	manager := plugins.GetManager(c.ds, events.GetBroker())
+	manager := plugins.GetManager(c.ds, events.GetBroker(), nil)
 	info := manager.GetPluginInfo()
 
 	result := make(map[string]insights.PluginInfo, len(info))

plugins/manager.go

@@ -35,6 +35,12 @@ const (
 // SubsonicRouter is an http.Handler that serves Subsonic API requests.
 type SubsonicRouter = http.Handler
 
+// PluginMetricsRecorder is an interface for recording plugin metrics.
+// This is satisfied by core/metrics.Metrics but defined here to avoid import cycles.
+type PluginMetricsRecorder interface {
+	RecordPluginRequest(ctx context.Context, plugin, method string, ok bool, elapsed int64)
+}
+
 // Manager manages loading and lifecycle of WebAssembly plugins.
 // It implements both agents.PluginLoader and scrobbler.PluginLoader interfaces.
 type Manager struct {
@@ -56,15 +62,17 @@ type Manager struct {
 	subsonicRouter SubsonicRouter
 	ds             model.DataStore
 	broker         events.Broker
+	metrics        PluginMetricsRecorder
 }
 
 // GetManager returns a singleton instance of the plugin manager.
 // The manager is not started automatically; call Start() to begin loading plugins.
-func GetManager(ds model.DataStore, broker events.Broker) *Manager {
+func GetManager(ds model.DataStore, broker events.Broker, m PluginMetricsRecorder) *Manager {
 	return singleton.GetInstance(func() *Manager {
 		return &Manager{
 			ds:      ds,
 			broker:  broker,
+			metrics: m,
 			plugins: make(map[string]*plugin),
 		}
 	})

plugins/manager_call.go

@@ -12,6 +12,12 @@ import (
 )
 
 var errFunctionNotFound = errors.New("function not found")
+var errNotImplemented = errors.New("function not implemented")
+
+// notImplementedCode is the standard return code from plugin PDKs
+// indicating a function exists but is not implemented by this plugin.
+// The plugin returns -2 as int32, which becomes 0xFFFFFFFE as uint32.
+const notImplementedCode uint32 = 0xFFFFFFFE
 
 // callPluginFunctionNoInput is a helper to call a plugin function with no input and output.
 func callPluginFunctionNoInput(ctx context.Context, plugin *plugin, funcName string) error {
@@ -54,15 +60,26 @@ func callPluginFunction[I any, O any](ctx context.Context, plugin *plugin, funcN
 	startCall := time.Now()
 	exit, output, err := p.CallWithContext(ctx, funcName, inputBytes)
 	if err != nil {
+		elapsed := time.Since(startCall).Milliseconds()
 		// If context was cancelled, return that error instead of the plugin error
 		if ctx.Err() != nil {
 			log.Debug(ctx, "Plugin call cancelled", "plugin", plugin.name, "function", funcName, "pluginDuration", time.Since(startCall))
 			return result, ctx.Err()
 		}
+		if plugin.metrics != nil {
+			plugin.metrics.RecordPluginRequest(ctx, plugin.name, funcName, false, elapsed)
+		}
 		log.Trace(ctx, "Plugin call failed", "plugin", plugin.name, "function", funcName, "pluginDuration", time.Since(startCall), "navidromeDuration", startCall.Sub(start), err)
 		return result, fmt.Errorf("plugin call failed: %w", err)
 	}
 	if exit != 0 {
+		elapsed := time.Since(startCall).Milliseconds()
+		if plugin.metrics != nil {
+			plugin.metrics.RecordPluginRequest(ctx, plugin.name, funcName, false, elapsed)
+		}
+		if exit == notImplementedCode {
+			return result, fmt.Errorf("%w: %s", errNotImplemented, funcName)
+		}
 		return result, fmt.Errorf("plugin call exited with code %d", exit)
 	}
 
@@ -73,6 +90,12 @@ func callPluginFunction[I any, O any](ctx context.Context, plugin *plugin, funcN
 		}
 	}
 
+	// Record metrics for successful calls (or JSON unmarshal failures)
+	if plugin.metrics != nil {
+		elapsed := time.Since(startCall).Milliseconds()
+		plugin.metrics.RecordPluginRequest(ctx, plugin.name, funcName, err == nil, elapsed)
+	}
+
 	log.Trace(ctx, "Plugin call succeeded", "plugin", plugin.name, "function", funcName, "pluginDuration", time.Since(startCall), "navidromeDuration", startCall.Sub(start))
 	return result, err
 }

plugins/manager_call_test.go

@@ -0,0 +1,131 @@
+//go:build !windows
+
+package plugins
+
+import (
+	"context"
+	"sync"
+
+	"github.com/navidrome/navidrome/core/agents"
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+)
+
+// mockMetricsRecorder tracks calls to RecordPluginRequest for testing
+type mockMetricsRecorder struct {
+	mu    sync.Mutex
+	calls []metricsCall
+}
+
+type metricsCall struct {
+	plugin  string
+	method  string
+	ok      bool
+	elapsed int64
+}
+
+func (m *mockMetricsRecorder) RecordPluginRequest(_ context.Context, plugin, method string, ok bool, elapsed int64) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.calls = append(m.calls, metricsCall{plugin: plugin, method: method, ok: ok, elapsed: elapsed})
+}
+
+func (m *mockMetricsRecorder) getCalls() []metricsCall {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	return append([]metricsCall{}, m.calls...)
+}
+
+func (m *mockMetricsRecorder) reset() {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	m.calls = nil
+}
+
+var _ = Describe("callPluginFunction metrics", Ordered, func() {
+	var (
+		metricsManager  *Manager
+		metricsRecorder *mockMetricsRecorder
+		agent           agents.Interface
+	)
+
+	BeforeAll(func() {
+		metricsRecorder = &mockMetricsRecorder{}
+
+		// Create a manager with the metrics recorder
+		metricsManager, _ = createTestManagerWithPluginsAndMetrics(
+			nil,
+			metricsRecorder,
+			"test-metadata-agent"+PackageExtension,
+		)
+
+		var ok bool
+		agent, ok = metricsManager.LoadMediaAgent("test-metadata-agent")
+		Expect(ok).To(BeTrue())
+	})
+
+	BeforeEach(func() {
+		metricsRecorder.reset()
+	})
+
+	It("records metrics for successful plugin calls", func() {
+		retriever := agent.(agents.ArtistBiographyRetriever)
+		_, err := retriever.GetArtistBiography(GinkgoT().Context(), "artist-1", "Test Artist", "mbid")
+		Expect(err).ToNot(HaveOccurred())
+
+		calls := metricsRecorder.getCalls()
+		Expect(calls).To(HaveLen(1))
+		Expect(calls[0].plugin).To(Equal("test-metadata-agent"))
+		Expect(calls[0].method).To(Equal(FuncGetArtistBiography))
+		Expect(calls[0].ok).To(BeTrue())
+		Expect(calls[0].elapsed).To(BeNumerically(">=", 0))
+	})
+
+	It("records metrics for failed plugin calls (error returned)", func() {
+		// Create a manager with error config to force plugin errors
+		errorRecorder := &mockMetricsRecorder{}
+		errorManager, _ := createTestManagerWithPluginsAndMetrics(
+			map[string]map[string]string{
+				"test-metadata-agent": {"error": "simulated error"},
+			},
+			errorRecorder,
+			"test-metadata-agent"+PackageExtension,
+		)
+
+		errorAgent, ok := errorManager.LoadMediaAgent("test-metadata-agent")
+		Expect(ok).To(BeTrue())
+
+		retriever := errorAgent.(agents.ArtistBiographyRetriever)
+		_, err := retriever.GetArtistBiography(GinkgoT().Context(), "artist-1", "Test Artist", "mbid")
+		Expect(err).To(HaveOccurred())
+
+		calls := errorRecorder.getCalls()
+		Expect(calls).To(HaveLen(1))
+		Expect(calls[0].plugin).To(Equal("test-metadata-agent"))
+		Expect(calls[0].method).To(Equal(FuncGetArtistBiography))
+		Expect(calls[0].ok).To(BeFalse())
+	})
+
+	It("records metrics for not-implemented functions", func() {
+		// Use partial metadata agent that doesn't implement GetArtistMBID
+		partialRecorder := &mockMetricsRecorder{}
+		partialManager, _ := createTestManagerWithPluginsAndMetrics(
+			nil,
+			partialRecorder,
+			"partial-metadata-agent"+PackageExtension,
+		)
+
+		partialAgent, ok := partialManager.LoadMediaAgent("partial-metadata-agent")
+		Expect(ok).To(BeTrue())
+
+		retriever := partialAgent.(agents.ArtistMBIDRetriever)
+		_, err := retriever.GetArtistMBID(GinkgoT().Context(), "artist-1", "Test Artist")
+		Expect(err).To(MatchError(errNotImplemented))
+
+		calls := partialRecorder.getCalls()
+		Expect(calls).To(HaveLen(1))
+		Expect(calls[0].plugin).To(Equal("partial-metadata-agent"))
+		Expect(calls[0].method).To(Equal(FuncGetArtistMBID))
+		Expect(calls[0].ok).To(BeFalse())
+	})
+})

plugins/manager_loader.go

@@ -317,6 +317,7 @@ func (m *Manager) loadPluginWithConfig(name, ndpPath, configJSON string) error {
 		compiled:     compiled,
 		capabilities: capabilities,
 		closers:      closers,
+		metrics:      m.metrics,
 	}
 	m.mu.Unlock()
 

plugins/manager_plugin.go

@@ -18,6 +18,7 @@ type plugin struct {
 	compiled     *extism.CompiledPlugin
 	capabilities []Capability // Auto-detected capabilities based on exported functions
 	closers      []io.Closer  // Cleanup functions to call on unload
+	metrics      PluginMetricsRecorder
 }
 
 // instance creates a new plugin instance for the given context.

plugins/metadata_agent_test.go

@@ -187,3 +187,74 @@ var _ = Describe("MetadataAgent error handling", Ordered, func() {
 		Expect(err.Error()).To(ContainSubstring("simulated plugin error"))
 	})
 })
+
+var _ = Describe("MetadataAgent partial implementation", Ordered, func() {
+	// Tests the "not implemented" code path when a plugin only implements some methods
+	var (
+		partialManager *Manager
+		partialAgent   agents.Interface
+	)
+
+	BeforeAll(func() {
+		// Create manager with the partial metadata agent plugin
+		partialManager, _ = createTestManagerWithPlugins(nil, "partial-metadata-agent"+PackageExtension)
+
+		// Load the agent
+		var ok bool
+		partialAgent, ok = partialManager.LoadMediaAgent("partial-metadata-agent")
+		Expect(ok).To(BeTrue())
+	})
+
+	It("returns data from implemented method (GetArtistBiography)", func() {
+		retriever := partialAgent.(agents.ArtistBiographyRetriever)
+		bio, err := retriever.GetArtistBiography(GinkgoT().Context(), "artist-1", "Test Artist", "mbid")
+		Expect(err).ToNot(HaveOccurred())
+		Expect(bio).To(Equal("Partial agent biography for Test Artist"))
+	})
+
+	It("returns ErrNotFound for unimplemented method (GetArtistMBID)", func() {
+		retriever := partialAgent.(agents.ArtistMBIDRetriever)
+		_, err := retriever.GetArtistMBID(GinkgoT().Context(), "artist-1", "Test Artist")
+		Expect(err).To(MatchError(errNotImplemented))
+	})
+
+	It("returns ErrNotFound for unimplemented method (GetArtistURL)", func() {
+		retriever := partialAgent.(agents.ArtistURLRetriever)
+		_, err := retriever.GetArtistURL(GinkgoT().Context(), "artist-1", "Test Artist", "mbid")
+		Expect(err).To(MatchError(errNotImplemented))
+	})
+
+	It("returns ErrNotFound for unimplemented method (GetArtistImages)", func() {
+		retriever := partialAgent.(agents.ArtistImageRetriever)
+		_, err := retriever.GetArtistImages(GinkgoT().Context(), "artist-1", "Test Artist", "mbid")
+		Expect(err).To(MatchError(errNotImplemented))
+	})
+
+	It("returns ErrNotFound for unimplemented method (GetSimilarArtists)", func() {
+		retriever := partialAgent.(agents.ArtistSimilarRetriever)
+		_, err := retriever.GetSimilarArtists(GinkgoT().Context(), "artist-1", "Test Artist", "mbid", 5)
+		Expect(err).To(MatchError(errNotImplemented))
+
+	})
+
+	It("returns ErrNotFound for unimplemented method (GetArtistTopSongs)", func() {
+		retriever := partialAgent.(agents.ArtistTopSongsRetriever)
+		_, err := retriever.GetArtistTopSongs(GinkgoT().Context(), "artist-1", "Test Artist", "mbid", 5)
+		Expect(err).To(MatchError(errNotImplemented))
+
+	})
+
+	It("returns ErrNotFound for unimplemented method (GetAlbumInfo)", func() {
+		retriever := partialAgent.(agents.AlbumInfoRetriever)
+		_, err := retriever.GetAlbumInfo(GinkgoT().Context(), "Album", "Artist", "mbid")
+		Expect(err).To(MatchError(errNotImplemented))
+
+	})
+
+	It("returns ErrNotFound for unimplemented method (GetAlbumImages)", func() {
+		retriever := partialAgent.(agents.AlbumImageRetriever)
+		_, err := retriever.GetAlbumImages(GinkgoT().Context(), "Album", "Artist", "mbid")
+		Expect(err).To(MatchError(errNotImplemented))
+
+	})
+})

plugins/plugins_suite_test.go

@@ -61,6 +61,13 @@ func createTestManager(pluginConfig map[string]map[string]string) (*Manager, str
 // and specified plugins. It creates a temp directory, copies the specified plugins, and starts the manager.
 // Returns the manager and temp directory path.
 func createTestManagerWithPlugins(pluginConfig map[string]map[string]string, plugins ...string) (*Manager, string) {
+	return createTestManagerWithPluginsAndMetrics(pluginConfig, nil, plugins...)
+}
+
+// createTestManagerWithPluginsAndMetrics creates a new plugin Manager with the given plugin config,
+// metrics recorder, and specified plugins. It creates a temp directory, copies the specified plugins, and starts the manager.
+// Returns the manager and temp directory path.
+func createTestManagerWithPluginsAndMetrics(pluginConfig map[string]map[string]string, metrics PluginMetricsRecorder, plugins ...string) (*Manager, string) {
 	// Create temp directory
 	tmpDir, err := os.MkdirTemp("", "plugins-test-*")
 	Expect(err).ToNot(HaveOccurred())
@@ -115,6 +122,7 @@ func createTestManagerWithPlugins(pluginConfig map[string]map[string]string, plu
 	manager := &Manager{
 		plugins:        make(map[string]*plugin),
 		ds:             dataStore,
+		metrics:        metrics,
 		subsonicRouter: http.NotFoundHandler(), // Stub router for tests
 	}
 	err = manager.Start(GinkgoT().Context())

plugins/testdata/partial-metadata-agent/go.mod

@@ -0,0 +1,16 @@
+module partial-metadata-agent
+
+go 1.25
+
+require github.com/navidrome/navidrome/plugins/pdk/go v0.0.0
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/extism/go-pdk v1.1.3 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/stretchr/objx v0.5.2 // indirect
+	github.com/stretchr/testify v1.11.1 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)
+
+replace github.com/navidrome/navidrome/plugins/pdk/go => ../../pdk/go

plugins/testdata/partial-metadata-agent/go.sum

@@ -0,0 +1,14 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/extism/go-pdk v1.1.3 h1:hfViMPWrqjN6u67cIYRALZTZLk/enSPpNKa+rZ9X2SQ=
+github.com/extism/go-pdk v1.1.3/go.mod h1:Gz+LIU/YCKnKXhgge8yo5Yu1F/lbv7KtKFkiCSzW/P4=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.5.2 h1:xuMeJ0Sdp5ZMRXx/aWO6RZxdr3beISkG5/G/aIRr3pY=
+github.com/stretchr/objx v0.5.2/go.mod h1:FRsXN1f5AsAjCGJKqEizvkpNtU+EGNCLh3NxZ/8L+MA=
+github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
+github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

plugins/testdata/partial-metadata-agent/main.go

@@ -0,0 +1,23 @@
+// Test plugin that only implements some metadata methods.
+// Used to test the "not implemented" code path (-2 return code).
+// Build with: tinygo build -o ../partial-metadata-agent.wasm -target wasip1 -buildmode=c-shared .
+package main
+
+import (
+	"github.com/navidrome/navidrome/plugins/pdk/go/metadata"
+)
+
+func init() {
+	metadata.Register(&partialMetadataAgent{})
+}
+
+// partialMetadataAgent only implements GetArtistBiography.
+// All other methods will return NotImplementedCode (-2).
+type partialMetadataAgent struct{}
+
+// GetArtistBiography is the only method we implement.
+func (t *partialMetadataAgent) GetArtistBiography(input metadata.ArtistRequest) (*metadata.ArtistBiographyResponse, error) {
+	return &metadata.ArtistBiographyResponse{Biography: "Partial agent biography for " + input.Name}, nil
+}
+
+func main() {}

plugins/testdata/partial-metadata-agent/manifest.json

@@ -0,0 +1,6 @@
+{
+  "name": "Partial Metadata Agent",
+  "author": "Navidrome Test",
+  "version": "1.0.0",
+  "description": "A test plugin that only implements some metadata methods"
+}