gitpipe: Handle error in DiffTree skip function

Change the prototype of the gitpipe.DiffTree skipResult function so it
also can return an error and the gitpipe can be aborted.

3 files changed, 41 insertions, 9 deletions

diff --git a/internal/git/gitpipe/diff_tree.go b/internal/git/gitpipe/diff_tree.go
index cf81a1ba3..4133c5085 100644
--- a/internal/git/gitpipe/diff_tree.go
+++ b/internal/git/gitpipe/diff_tree.go
@@ -15,7 +15,7 @@ import (
 type diffTreeConfig struct {
 	recursive        bool
 	ignoreSubmodules bool
-	skipResult       func(*RevisionResult) bool
+	skipResult       func(*RevisionResult) (bool, error)
 }
 
 // DiffTreeOption is an option for the DiffTree pipeline step.
@@ -38,7 +38,7 @@ func DiffTreeWithIgnoreSubmodules() DiffTreeOption {
 // DiffTreeWithSkip will execute the given function for each RevisionResult processed by the
 // pipeline. If the callback returns `true`, then the object will be skipped and not passed down
 // the pipeline.
-func DiffTreeWithSkip(skipResult func(*RevisionResult) bool) DiffTreeOption {
+func DiffTreeWithSkip(skipResult func(*RevisionResult) (bool, error)) DiffTreeOption {
 	return func(cfg *diffTreeConfig) {
 		cfg.skipResult = skipResult
 	}
@@ -116,8 +116,17 @@ func DiffTree(
 				ObjectName: attrsAndFile[1],
 			}
 
-			if cfg.skipResult != nil && cfg.skipResult(&result) {
-				continue
+			if cfg.skipResult != nil {
+				skip, err := cfg.skipResult(&result)
+				if err != nil {
+					sendRevisionResult(ctx, resultChan, RevisionResult{
+						err: fmt.Errorf("diff-tree skip: %q", err),
+					})
+					return
+				}
+				if skip {
+					continue
+				}
 			}
 
 			if isDone := sendRevisionResult(ctx, resultChan, result); isDone {
diff --git a/internal/git/gitpipe/diff_tree_test.go b/internal/git/gitpipe/diff_tree_test.go
index 616fb8291..fb90b01ac 100644
--- a/internal/git/gitpipe/diff_tree_test.go
+++ b/internal/git/gitpipe/diff_tree_test.go
@@ -188,12 +188,35 @@ func TestDiffTree(t *testing.T) {
 				}
 			},
 			options: []DiffTreeOption{
-				DiffTreeWithSkip(func(r *RevisionResult) bool {
-					return bytes.Equal(r.ObjectName, []byte("b"))
+				DiffTreeWithSkip(func(r *RevisionResult) (bool, error) {
+					return bytes.Equal(r.ObjectName, []byte("b")), nil
 				}),
 			},
 		},
 		{
+			desc: "with skip failure",
+			setup: func(t *testing.T, repoPath string) (git.Revision, git.Revision, []RevisionResult) {
+				treeA := gittest.WriteTree(t, cfg, repoPath, []gittest.TreeEntry{
+					{Path: "a", Mode: "100644", Content: "1"},
+					{Path: "b", Mode: "100644", Content: "2"},
+				})
+
+				changedBlobA := gittest.WriteBlob(t, cfg, repoPath, []byte("x"))
+				treeB := gittest.WriteTree(t, cfg, repoPath, []gittest.TreeEntry{
+					{Path: "a", Mode: "100644", OID: changedBlobA},
+					{Path: "b", Mode: "100644", Content: "y"},
+				})
+
+				return treeA.Revision(), treeB.Revision(), nil
+			},
+			options: []DiffTreeOption{
+				DiffTreeWithSkip(func(r *RevisionResult) (bool, error) {
+					return true, errors.New("broken")
+				}),
+			},
+			expectedErr: errors.New(`diff-tree skip: "broken"`),
+		},
+		{
 			desc: "invalid revision",
 			setup: func(t *testing.T, repoPath string) (git.Revision, git.Revision, []RevisionResult) {
 				gittest.WriteCommit(t, cfg, repoPath, gittest.WithBranch("main"))
diff --git a/internal/gitaly/linguist/linguist.go b/internal/gitaly/linguist/linguist.go
index f5f11b067..8083bfea6 100644
--- a/internal/gitaly/linguist/linguist.go
+++ b/internal/gitaly/linguist/linguist.go
@@ -153,7 +153,7 @@ func (inst *Instance) enryStats(ctx context.Context, commitID string) (ByteCount
 		// Stats are cached for one commit, so get the git-diff-tree(1)
 		// between that commit and the one we're calculating stats for.
 
-		skipFunc := func(result *gitpipe.RevisionResult) bool {
+		skipFunc := func(result *gitpipe.RevisionResult) (bool, error) {
 			// Skip files that are deleted, or
 			// an excluded filetype based on filename.
 			if git.ObjectHashSHA1.IsZeroOID(result.OID) ||
@@ -162,9 +162,9 @@ func (inst *Instance) enryStats(ctx context.Context, commitID string) (ByteCount
 				// function, but for every file that's deleted,
 				// remove the stats.
 				stats.drop(string(result.ObjectName))
-				return true
+				return true, nil
 			}
-			return false
+			return false, nil
 		}
 
 		revlistIt = gitpipe.DiffTree(ctx, inst.repo,