Skip invalid GitHub packages instead of failing the scan

Wrap package parse errors in provider.ErrInvalidPackage so only transient
asset and insert errors fail the scan; cover rpm, deb and alpine.

internal/provider/alpine/github.go

@@ -372,8 +372,8 @@ func (p *GitHubProvider) scanWithState(ctx context.Context, remote models.Remote
 		return newEtag, false, err
 	}
 
-	// A failed asset fails the scan so the ETag is not advanced and the retry
-	// re-derives it; assets that did derive are kept and served meanwhile.
+	// A transiently failed asset fails the scan so the ETag is not advanced and
+	// the retry re-derives it; an invalid package is skipped as no retry fixes it.
 	var failed []error
 	seen := map[string]bool{}
 	for _, rel := range releases {
@@ -403,7 +403,9 @@ func (p *GitHubProvider) scanWithState(ctx context.Context, remote models.Remote
 			meta, err := p.deriveAsset(ctx, remote, asset, fp)
 			if err != nil {
 				slog.Warn("github_alpine: derive asset failed", "remote", remote.Name, "asset", asset.Name, "error", err)
-				failed = append(failed, fmt.Errorf("%s: %w", asset.Name, err))
+				if !errors.Is(err, provider.ErrInvalidPackage) {
+					failed = append(failed, fmt.Errorf("%s: %w", asset.Name, err))
+				}
 				continue
 			}
 			if err := inserter.InsertAlpineMetadata(ctx, meta); err != nil {
@@ -501,7 +503,7 @@ func (p *GitHubProvider) deriveAsset(ctx context.Context, remote models.Remote,
 		return nil, err
 	}
 	if meta.Name == "" || meta.Arch == "" {
-		return nil, errors.New(".PKGINFO missing pkgname/arch")
+		return nil, fmt.Errorf("%w: .PKGINFO missing pkgname/arch", provider.ErrInvalidPackage)
 	}
 
 	meta.RepoName = remote.Name
@@ -531,13 +533,13 @@ func (p *GitHubProvider) fetchPkginfo(ctx context.Context, remote models.Remote,
 		}
 		meta, complete, perr := pkginfoFromPrefix(body)
 		if perr != nil {
-			return nil, fmt.Errorf("parse apk .PKGINFO: %w", perr)
+			return nil, fmt.Errorf("%w: parse apk .PKGINFO: %w", provider.ErrInvalidPackage, perr)
 		}
 		if complete {
 			return meta, nil
 		}
 		if full || n >= p.headerMax {
-			return nil, fmt.Errorf(".PKGINFO not found within %d bytes of %s", n, downloadURL)
+			return nil, fmt.Errorf("%w: .PKGINFO not found within %d bytes of %s", provider.ErrInvalidPackage, n, downloadURL)
 		}
 		n *= 2
 		if n > p.headerMax {

internal/provider/alpine/github_test.go

@@ -88,15 +88,17 @@ type githubFixture struct {
 	notModHit   int
 	releaseAuth string
 	assetAuth   string
+	assetFail   map[string]int // asset filename -> downloads left to answer 500
 	mu          sync.Mutex
 }
 
 func newGitHubFixture(t *testing.T, withDigest bool) *githubFixture {
 	t.Helper()
 	f := &githubFixture{
-		apkBytes: map[string][]byte{},
-		rangeHit: map[string]int{},
-		fullHit:  map[string]int{},
+		apkBytes:  map[string][]byte{},
+		rangeHit:  map[string]int{},
+		fullHit:   map[string]int{},
+		assetFail: map[string]int{},
 	}
 	f.apkBytes["demo-1.2.3-r0.apk"] = testsupport.MinimalApk("demo", "1.2.3-r0", "x86_64")
 
@@ -146,6 +148,12 @@ func newGitHubFixture(t *testing.T, withDigest bool) *githubFixture {
 		}
 		rng := r.Header.Get("Range")
 		f.mu.Lock()
+		if f.assetFail[name] > 0 {
+			f.assetFail[name]--
+			f.mu.Unlock()
+			http.Error(w, "boom", http.StatusInternalServerError)
+			return
+		}
 		f.assetAuth = r.Header.Get("Authorization")
 		if rng != "" {
 			f.rangeHit[name]++

internal/provider/alpine/syncer_test.go

@@ -308,3 +308,58 @@ func TestSyncerPrimeBypassesRecencyPeriodicDoesNot(t *testing.T) {
 		t.Fatalf("periodic scan ran inside recency window: %d -> %d releases calls", releasesAfterPrime, fx.releasesHit)
 	}
 }
+
+// A transiently failed asset fails the scan: the ETag is not advanced, a retry
+// is scheduled, and the retry against the unchanged release list derives it. An
+// invalid package is skipped instead, since no retry can fix it.
+func TestSyncerFailedAssetRetry(t *testing.T) {
+	for _, tc := range []struct {
+		name      string
+		corrupt   bool
+		wantRetry bool
+	}{
+		{name: "transient", wantRetry: true},
+		{name: "invalid package", corrupt: true},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			fx := newGitHubFixture(t, true)
+			fx.etag = `"v1"`
+			if tc.corrupt {
+				fx.apkBytes["other-9-r0.apk"] = []byte("not a package")
+			} else {
+				fx.apkBytes["other-9-r0.apk"] = testsupport.MinimalApk("other", "9-r0", "aarch64")
+				fx.assetFail["other-9-r0.apk"] = 1
+			}
+			store := newFakeSyncStore()
+			s := newSyncer(store, newTestProvider(), testSyncConfig())
+			remote := fx.remote()
+			bg := context.Background()
+
+			s.process(bg, syncJob{remote: remote, prime: true})
+			_, pending := store.retryAt[remote.Name]
+			if pending != tc.wantRetry {
+				t.Fatalf("retry pending=%v, want %v", pending, tc.wantRetry)
+			}
+			if _, saved := store.etags[remote.Name]; saved == tc.wantRetry {
+				t.Fatalf("etag saved=%v after first scan", saved)
+			}
+			if rows, _ := store.ListAlpineMetadataEntries(bg, remote.Name); len(rows) != 1 {
+				t.Fatalf("healthy asset not served: %d rows", len(rows))
+			}
+			if !tc.wantRetry {
+				return
+			}
+
+			store.mu.Lock()
+			store.retryAt[remote.Name] = time.Now().Add(-time.Second)
+			store.mu.Unlock()
+			s.process(bg, syncJob{remote: remote})
+			if _, pending := store.retryAt[remote.Name]; pending || store.etags[remote.Name] != `"v1"` {
+				t.Fatalf("retry not recorded: pending=%v etag=%q", pending, store.etags[remote.Name])
+			}
+			if rows, _ := store.ListAlpineMetadataEntries(bg, remote.Name); len(rows) != 2 {
+				t.Fatalf("retry did not derive the failed asset: %d rows", len(rows))
+			}
+		})
+	}
+}