Try to figure out attribute checker problem (#33901)

For #31600

modules/git/command.go

@@ -46,6 +46,7 @@ type Command struct {
 	args             []string
 	globalArgsLength int
 	brokenArgs       []string
+	cmd              *exec.Cmd // for debug purpose only
 }
 
 func logArgSanitize(arg string) string {
@@ -314,6 +315,7 @@ func (c *Command) run(ctx context.Context, skip int, opts *RunOpts) error {
 	startTime := time.Now()
 
 	cmd := exec.CommandContext(ctx, c.prog, c.args...)
+	c.cmd = cmd // for debug purpose only
 	if opts.Env == nil {
 		cmd.Env = os.Environ()
 	} else {

modules/git/repo_attribute.go

@@ -9,6 +9,8 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"path/filepath"
+	"time"
 
 	"code.gitea.io/gitea/modules/log"
 )
@@ -102,7 +104,7 @@ type CheckAttributeReader struct {
 
 	stdinReader io.ReadCloser
 	stdinWriter *os.File
-	stdOut      attributeWriter
+	stdOut      *nulSeparatedAttributeWriter
 	cmd         *Command
 	env         []string
 	ctx         context.Context
@@ -152,7 +154,6 @@ func (c *CheckAttributeReader) Init(ctx context.Context) error {
 	return nil
 }
 
-// Run run cmd
 func (c *CheckAttributeReader) Run() error {
 	defer func() {
 		_ = c.stdinReader.Close()
@@ -176,7 +177,7 @@ func (c *CheckAttributeReader) Run() error {
 func (c *CheckAttributeReader) CheckPath(path string) (rs map[string]string, err error) {
 	defer func() {
 		if err != nil && err != c.ctx.Err() {
-			log.Error("Unexpected error when checking path %s in %s. Error: %v", path, c.Repo.Path, err)
+			log.Error("Unexpected error when checking path %s in %s, error: %v", path, filepath.Base(c.Repo.Path), err)
 		}
 	}()
 
@@ -191,9 +192,31 @@ func (c *CheckAttributeReader) CheckPath(path string) (rs map[string]string, err
 		return nil, err
 	}
 
+	reportTimeout := func() error {
+		stdOutClosed := false
+		select {
+		case <-c.stdOut.closed:
+			stdOutClosed = true
+		default:
+		}
+		debugMsg := fmt.Sprintf("check path %q in repo %q", path, filepath.Base(c.Repo.Path))
+		debugMsg += fmt.Sprintf(", stdOut: tmp=%q, pos=%d, closed=%v", string(c.stdOut.tmp), c.stdOut.pos, stdOutClosed)
+		if c.cmd.cmd != nil {
+			debugMsg += fmt.Sprintf(", process state: %q", c.cmd.cmd.ProcessState.String())
+		}
+		_ = c.Close()
+		return fmt.Errorf("CheckPath timeout: %s", debugMsg)
+	}
+
 	rs = make(map[string]string)
 	for range c.Attributes {
 		select {
+		case <-time.After(5 * time.Second):
+			// There is a strange "hang" problem in gitdiff.GetDiff -> CheckPath
+			// So add a timeout here to mitigate the problem, and output more logs for debug purpose
+			// In real world, if CheckPath runs long than seconds, it blocks the end user's operation,
+			// and at the moment the CheckPath result is not so important, so we can just ignore it.
+			return nil, reportTimeout()
 		case attr, ok := <-c.stdOut.ReadAttribute():
 			if !ok {
 				return nil, c.ctx.Err()
@@ -206,18 +229,12 @@ func (c *CheckAttributeReader) CheckPath(path string) (rs map[string]string, err
 	return rs, nil
 }
 
-// Close close pip after use
 func (c *CheckAttributeReader) Close() error {
 	c.cancel()
 	err := c.stdinWriter.Close()
 	return err
 }
 
-type attributeWriter interface {
-	io.WriteCloser
-	ReadAttribute() <-chan attributeTriple
-}
-
 type attributeTriple struct {
 	Filename  string
 	Attribute string
@@ -281,7 +298,7 @@ func (wr *nulSeparatedAttributeWriter) Close() error {
 	return nil
 }
 
-// Create a check attribute reader for the current repository and provided commit ID
+// CheckAttributeReader creates a check attribute reader for the current repository and provided commit ID
 func (repo *Repository) CheckAttributeReader(commitID string) (*CheckAttributeReader, context.CancelFunc) {
 	indexFilename, worktree, deleteTemporaryFile, err := repo.ReadTreeToTemporaryIndex(commitID)
 	if err != nil {
@@ -303,21 +320,21 @@ func (repo *Repository) CheckAttributeReader(commitID string) (*CheckAttributeRe
 	}
 	ctx, cancel := context.WithCancel(repo.Ctx)
 	if err := checker.Init(ctx); err != nil {
-		log.Error("Unable to open checker for %s. Error: %v", commitID, err)
+		log.Error("Unable to open attribute checker for commit %s, error: %v", commitID, err)
 	} else {
 		go func() {
 			err := checker.Run()
-			if err != nil && err != ctx.Err() {
+			if err != nil && !IsErrCanceledOrKilled(err) {
-				log.Error("Unable to open checker for %s. Error: %v", commitID, err)
+				log.Error("Attribute checker for commit %s exits with error: %v", commitID, err)
 			}
 			cancel()
 		}()
 	}
-	deferable := func() {
+	deferrable := func() {
 		_ = checker.Close()
 		cancel()
 		deleteTemporaryFile()
 	}
 
-	return checker, deferable
+	return checker, deferrable
 }

modules/git/repo_attribute_test.go

@@ -4,10 +4,16 @@
 package git
 
 import (
+	"context"
+	mathRand "math/rand/v2"
+	"path/filepath"
+	"slices"
+	"sync"
 	"testing"
 	"time"
 
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func Test_nulSeparatedAttributeWriter_ReadAttribute(t *testing.T) {
@@ -95,3 +101,57 @@ func Test_nulSeparatedAttributeWriter_ReadAttribute(t *testing.T) {
 		Value:     "unspecified",
 	}, attr)
 }
+
+func TestAttributeReader(t *testing.T) {
+	t.Skip() // for debug purpose only, do not run in CI
+
+	ctx := t.Context()
+
+	timeout := 1 * time.Second
+	repoPath := filepath.Join(testReposDir, "language_stats_repo")
+	commitRef := "HEAD"
+
+	oneRound := func(t *testing.T, roundIdx int) {
+		ctx, cancel := context.WithTimeout(ctx, timeout)
+		_ = cancel
+		gitRepo, err := OpenRepository(ctx, repoPath)
+		require.NoError(t, err)
+		defer gitRepo.Close()
+
+		commit, err := gitRepo.GetCommit(commitRef)
+		require.NoError(t, err)
+
+		files, err := gitRepo.LsFiles()
+		require.NoError(t, err)
+
+		randomFiles := slices.Clone(files)
+		randomFiles = append(randomFiles, "any-file-1", "any-file-2")
+
+		t.Logf("Round %v with %d files", roundIdx, len(randomFiles))
+
+		attrReader, deferrable := gitRepo.CheckAttributeReader(commit.ID.String())
+		defer deferrable()
+
+		wg := sync.WaitGroup{}
+		wg.Add(1)
+
+		go func() {
+			for {
+				file := randomFiles[mathRand.IntN(len(randomFiles))]
+				_, err := attrReader.CheckPath(file)
+				if err != nil {
+					for i := 0; i < 10; i++ {
+						_, _ = attrReader.CheckPath(file)
+					}
+					break
+				}
+			}
+			wg.Done()
+		}()
+		wg.Wait()
+	}
+
+	for i := 0; i < 100; i++ {
+		oneRound(t, i)
+	}
+}

services/gitdiff/gitdiff.go

@@ -1253,6 +1253,8 @@ func GetDiffForRender(ctx context.Context, gitRepo *git.Repository, opts *DiffOp
 				if language.Has() {
 					diffFile.Language = language.Value()
 				}
+			} else {
+				checker = nil // CheckPath fails, it's not impossible to "check" anymore
 			}
 		}