From 4fc837b94c07e6e0984f318b41b5c87203698d74 Mon Sep 17 00:00:00 2001
From: zarzet <42882290+zarzet@users.noreply.github.com>
Date: Sun, 6 Sep 2026 16:03:29 +0700
Subject: [PATCH] fix(extensions): preserve verification on availability errors

---
 ...xtension_availability_verification_test.go | 57 +++++++++++++++++++
 go_backend/extension_provider_wrapper.go      | 45 +++++++++++----
 2 files changed, 91 insertions(+), 11 deletions(-)
 create mode 100644 go_backend/extension_availability_verification_test.go

diff --git a/go_backend/extension_availability_verification_test.go b/go_backend/extension_availability_verification_test.go
new file mode 100644
index 00000000..a2acd576
--- /dev/null
+++ b/go_backend/extension_availability_verification_test.go
@@ -0,0 +1,57 @@
+package gobackend
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/dop251/goja"
+)
+
+func TestAvailabilityPreservesCanonicalVerificationOnFailure(t *testing.T) {
+	for _, script := range []string{
+		`throw new Error("VERIFY_REQUIRED");`,
+		`return null;`,
+		`return undefined;`,
+		`return {available:false};`,
+	} {
+		t.Run(script, func(t *testing.T) {
+			ext := newTestLoadedExtension(t, ExtensionTypeDownloadProvider)
+			t.Cleanup(func() { teardownExtension(ext) })
+			if err := ext.ensureRuntimeReady(); err != nil {
+				t.Fatal(err)
+			}
+			if err := ext.VM.Set("requireChallenge", func(goja.FunctionCall) goja.Value {
+				ext.runtime.noteVerificationRequired("https://example.test/challenge")
+				return goja.Undefined()
+			}); err != nil {
+				t.Fatal(err)
+			}
+			if _, err := ext.VM.RunString(`extension.checkAvailability = function(){ requireChallenge(); ` + script + ` };`); err != nil {
+				t.Fatal(err)
+			}
+			_, err := newExtensionProviderWrapper(ext).CheckAvailabilityForItemID("", "Song", "Artist", "", "", "", "", 180000, "")
+			if err == nil || classifyDownloadErrorType(err.Error()) != "verification_required" || !strings.Contains(err.Error(), ext.ID) {
+				t.Fatalf("canonical verification not preserved: %v", err)
+			}
+			if ext.runtime.consumeVerificationRequired() != "" {
+				t.Fatal("verification evidence leaked into the next call")
+			}
+		})
+	}
+}
+
+func TestAvailabilityDoesNotPromoteUntrustedOrStaleVerification(t *testing.T) {
+	ext := newTestLoadedExtension(t, ExtensionTypeDownloadProvider)
+	t.Cleanup(func() { teardownExtension(ext) })
+	if err := ext.ensureRuntimeReady(); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := ext.VM.RunString(`extension.checkAvailability = function(){ throw new Error("VERIFY_REQUIRED"); };`); err != nil {
+		t.Fatal(err)
+	}
+	ext.runtime.noteVerificationRequired("https://example.test/stale-challenge")
+	_, err := newExtensionProviderWrapper(ext).CheckAvailabilityForItemID("", "Song", "Artist", "", "", "", "", 180000, "")
+	if err == nil || classifyDownloadErrorType(err.Error()) == "verification_required" {
+		t.Fatalf("untrusted exception inherited a previous challenge: %v", err)
+	}
+}
diff --git a/go_backend/extension_provider_wrapper.go b/go_backend/extension_provider_wrapper.go
index 893f9507..e015b30a 100644
--- a/go_backend/extension_provider_wrapper.go
+++ b/go_backend/extension_provider_wrapper.go
@@ -529,21 +529,47 @@ func (p *extensionProviderWrapper) CheckAvailabilityForItemID(isrc, trackName, a
 		availabilityOptions["track"] = trackContexts[0]
 	}
 
+	var availabilityRuntime *extensionRuntime
+	consumeVerificationError := func() error {
+		if availabilityRuntime != nil && availabilityRuntime.consumeVerificationRequired() != "" {
+			return fmt.Errorf(
+				"verification_required: extension '%s' needs signed-session verification",
+				p.extension.ID,
+			)
+		}
+		return nil
+	}
+
 	return callExtension(p, extCallOpts{
 		perfName: "checkAvailability",
-		invoke:   extensionMethodInvocation("checkAvailability", isrc, trackName, artistName, availabilityOptions),
-		timeout:  DefaultJSTimeout,
-		itemID:   itemID,
+		invoke: func(vm *goja.Runtime) (goja.Value, error) {
+			result, err := invokeExtensionMethod(vm, "checkAvailability", isrc, trackName, artistName, availabilityOptions)
+			// A thrown JS error must preserve the same canonical runtime evidence
+			// as a returned unavailable result. Cancellation and timeout still
+			// take precedence in callExtension.
+			if err != nil {
+				if verificationErr := consumeVerificationError(); verificationErr != nil {
+					return nil, verificationErr
+				}
+			}
+			return result, err
+		},
+		timeout: DefaultJSTimeout,
+		itemID:  itemID,
 		beforeRun: func() func() {
 			// Drop any stale flag so the post-run check below only sees
 			// verification requested by THIS call.
-			if p.extension.runtime != nil {
-				p.extension.runtime.consumeVerificationRequired()
+			availabilityRuntime = p.extension.runtime
+			if availabilityRuntime != nil {
+				availabilityRuntime.consumeVerificationRequired()
 			}
 			return nil
 		},
 	}, func(perf *extensionCallPerf, result goja.Value) (*ExtAvailabilityResult, error) {
 		if result == nil || goja.IsUndefined(result) || goja.IsNull(result) {
+			if err := consumeVerificationError(); err != nil {
+				return nil, err
+			}
 			return &ExtAvailabilityResult{Available: false, Reason: "not implemented"}, nil
 		}
 		parseStartedAt := time.Now()
@@ -555,12 +581,9 @@ func (p *extensionProviderWrapper) CheckAvailabilityForItemID(isrc, trackName, a
 		// "not available", which would silently skip this provider's
 		// challenge; surface it as an error so the fallback loop pauses and
 		// opens the challenge instead.
-		if !availability.Available && p.extension.runtime != nil {
-			if p.extension.runtime.consumeVerificationRequired() != "" {
-				return nil, fmt.Errorf(
-					"verification_required: extension '%s' needs signed-session verification",
-					p.extension.ID,
-				)
+		if !availability.Available {
+			if err := consumeVerificationError(); err != nil {
+				return nil, err
 			}
 		}
 		return &availability, nil