solver: Resolve infinite loop when record is ErrNotFound

solver/exporter.go

@@ -55,8 +55,10 @@ func addBacklinks(t CacheExporterTarget, rec CacheExporterRecord, cm *cacheManag
 
 type contextT string
 
-var backlinkKey = contextT("solver/exporter/backlinks")
-var resKey = contextT("solver/exporter/res")
+var (
+	backlinkKey = contextT("solver/exporter/backlinks")
+	resKey      = contextT("solver/exporter/res")
+)
 
 func (e *exporter) ExportTo(ctx context.Context, t CacheExporterTarget, opt CacheExportOpt) ([]CacheExporterRecord, error) {
 	var bkm map[string]CacheExporterRecord
@@ -109,9 +111,11 @@ func (e *exporter) ExportTo(ctx context.Context, t CacheExporterTarget, opt Cach
 
 	var remote *Remote
 	var i int
+
+	v := e.record
+
 	for exportRecord && addRecord {
 		var variants []CacheExporterRecord
-		v := e.record
 		if v == nil {
 			if i < len(records) {
 				v = records[i]
@@ -125,6 +129,7 @@ func (e *exporter) ExportTo(ctx context.Context, t CacheExporterTarget, opt Cach
 		res, err := cm.backend.Load(key, v.ID)
 		if err != nil {
 			if errors.Is(err, ErrNotFound) {
+				v = nil
 				continue
 			}
 			return nil, err
@@ -222,7 +227,7 @@ func (e *exporter) ExportTo(ctx context.Context, t CacheExporterTarget, opt Cach
 		}
 	}
 
-	if v := e.record; v != nil && len(deps) == 0 {
+	if v != nil && len(deps) == 0 {
 		cm := v.cacheManager
 		key := cm.getID(v.key)
 		if err := cm.backend.WalkIDsByResult(v.ID, func(id string) error {

solver/scheduler_test.go

@@ -3210,6 +3210,56 @@ func TestMergedEdgesCycleMultipleOwners(t *testing.T) {
 	}
 }
 
+func TestCacheErrNotFound(t *testing.T) {
+	ctx := context.TODO()
+
+	cm := newTrackingCacheManager(NewInMemoryCacheManager())
+	l := NewSolver(SolverOpt{
+		ResolveOpFunc: testOpResolver,
+		DefaultCache:  cm,
+	})
+	defer l.Close()
+
+	j0, err := l.NewJob("j0")
+	require.NoError(t, err)
+
+	defer func() {
+		if j0 != nil {
+			j0.Discard()
+		}
+	}()
+
+	g0 := Edge{
+		Vertex: vtxSum(1, vtxOpt{
+			inputs: []Edge{
+				{Vertex: vtxConst(2, vtxOpt{})},
+				{Vertex: vtxConst(3, vtxOpt{})},
+			},
+		}),
+	}
+
+	res, err := j0.Build(ctx, g0)
+	require.NoError(t, err)
+	require.Equal(t, 6, unwrapInt(res))
+
+	require.NoError(t, j0.Discard())
+	j0 = nil
+
+	expTarget := newTestExporterTarget()
+
+	key := res.CacheKeys()[0]
+	internal := cm.CacheManager.(*cacheManager)
+	store := internal.backend.(*inMemoryStore)
+	exporter := key.Exporter.(*mergedExporter).exporters[0].(*exporter)
+	record := exporter.record
+
+	// Remove The first record from the internal store CacheManager to trigger an ErrNotFound
+	delete(store.byID[internal.getID(record.key)].results, record.ID)
+	_, err = exporter.ExportTo(ctx, expTarget, testExporterOpts(true))
+
+	require.NoError(t, err)
+}
+
 func TestCacheLoadError(t *testing.T) {
 	t.Parallel()