Ignore Sync errors on pipes when doing CheckAttributeReader.CheckPath, fix the hang of git cat-file (#17096)

* Ignore Sync errors on pipes when doing `CheckAttributeReader.CheckPath`

* apply env patch

* Drop the Sync and fix a number of issues with the Close function

Signed-off-by: Andrew Thornton <art27@cantab.net>

* add logs for DBIndexer and CheckPath

* Fix some more closing bugs

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Add test case for language_stats

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Update modules/indexer/stats/db.go

Co-authored-by: Lauris BH <lauris@nix.lv>

Co-authored-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: Lauris BH <lauris@nix.lv>
Co-authored-by: 6543 <6543@obermui.de>

modules/git/repo_attribute.go

@@ -12,6 +12,8 @@ import (
 	"os"
 	"strconv"
 	"strings"
+
+	"code.gitea.io/gitea/modules/log"
 )
 
 // CheckAttributeOpts represents the possible options to CheckAttribute
@@ -112,42 +114,48 @@ func (c *CheckAttributeReader) Init(ctx context.Context) error {
 
 	if len(c.IndexFile) > 0 && CheckGitVersionAtLeast("1.7.8") == nil {
 		cmdArgs = append(cmdArgs, "--cached")
-		c.env = []string{"GIT_INDEX_FILE=" + c.IndexFile}
+		c.env = append(c.env, "GIT_INDEX_FILE="+c.IndexFile)
 	}
 
 	if len(c.WorkTree) > 0 && CheckGitVersionAtLeast("1.7.8") == nil {
-		c.env = []string{"GIT_WORK_TREE=" + c.WorkTree}
+		c.env = append(c.env, "GIT_WORK_TREE="+c.WorkTree)
 	}
 
-	if len(c.Attributes) > 0 {
-		cmdArgs = append(cmdArgs, c.Attributes...)
-		cmdArgs = append(cmdArgs, "--")
-	} else {
+	c.env = append(c.env, "GIT_FLUSH=1")
+
+	if len(c.Attributes) == 0 {
 		lw := new(nulSeparatedAttributeWriter)
 		lw.attributes = make(chan attributeTriple)
+		lw.closed = make(chan struct{})
 
 		c.stdOut = lw
 		c.stdOut.Close()
 		return fmt.Errorf("no provided Attributes to check")
 	}
 
+	cmdArgs = append(cmdArgs, c.Attributes...)
+	cmdArgs = append(cmdArgs, "--")
+
 	c.ctx, c.cancel = context.WithCancel(ctx)
 	c.cmd = NewCommandContext(c.ctx, cmdArgs...)
+
 	var err error
+
 	c.stdinReader, c.stdinWriter, err = os.Pipe()
 	if err != nil {
+		c.cancel()
 		return err
 	}
 
 	if CheckGitVersionAtLeast("1.8.5") == nil {
 		lw := new(nulSeparatedAttributeWriter)
 		lw.attributes = make(chan attributeTriple, 5)
-
+		lw.closed = make(chan struct{})
 		c.stdOut = lw
 	} else {
 		lw := new(lineSeparatedAttributeWriter)
 		lw.attributes = make(chan attributeTriple, 5)
-
+		lw.closed = make(chan struct{})
 		c.stdOut = lw
 	}
 	return nil
@@ -155,13 +163,14 @@ func (c *CheckAttributeReader) Init(ctx context.Context) error {
 
 // Run run cmd
 func (c *CheckAttributeReader) Run() error {
+	defer func() {
+		_ = c.Close()
+	}()
 	stdErr := new(bytes.Buffer)
 	err := c.cmd.RunInDirTimeoutEnvFullPipelineFunc(c.env, -1, c.Repo.Path, c.stdOut, stdErr, c.stdinReader, func(_ context.Context, _ context.CancelFunc) error {
 		close(c.running)
 		return nil
 	})
-	defer c.cancel()
-	_ = c.stdOut.Close()
 	if err != nil && c.ctx.Err() != nil && err.Error() != "signal: killed" {
 		return fmt.Errorf("failed to run attr-check. Error: %w\nStderr: %s", err, stdErr.String())
 	}
@@ -170,27 +179,31 @@ func (c *CheckAttributeReader) Run() error {
 }
 
 // CheckPath check attr for given path
-func (c *CheckAttributeReader) CheckPath(path string) (map[string]string, error) {
+func (c *CheckAttributeReader) CheckPath(path string) (rs map[string]string, err error) {
+	defer func() {
+		if err != nil {
+			log.Error("CheckPath returns error: %v", err)
+		}
+	}()
+
 	select {
 	case <-c.ctx.Done():
 		return nil, c.ctx.Err()
 	case <-c.running:
 	}
 
-	if _, err := c.stdinWriter.Write([]byte(path + "\x00")); err != nil {
-		defer c.cancel()
+	if _, err = c.stdinWriter.Write([]byte(path + "\x00")); err != nil {
+		defer c.Close()
 		return nil, err
 	}
 
-	if err := c.stdinWriter.Sync(); err != nil {
-		defer c.cancel()
-		return nil, err
-	}
-
-	rs := make(map[string]string)
+	rs = make(map[string]string)
 	for range c.Attributes {
 		select {
-		case attr := <-c.stdOut.ReadAttribute():
+		case attr, ok := <-c.stdOut.ReadAttribute():
+			if !ok {
+				return nil, c.ctx.Err()
+			}
 			rs[attr.Attribute] = attr.Value
 		case <-c.ctx.Done():
 			return nil, c.ctx.Err()
@@ -201,13 +214,16 @@ func (c *CheckAttributeReader) CheckPath(path string) (map[string]string, error)
 
 // Close close pip after use
 func (c *CheckAttributeReader) Close() error {
+	err := c.stdinWriter.Close()
+	_ = c.stdinReader.Close()
+	_ = c.stdOut.Close()
+	c.cancel()
 	select {
 	case <-c.running:
 	default:
 		close(c.running)
 	}
-	defer c.cancel()
-	return c.stdinWriter.Close()
+	return err
 }
 
 type attributeWriter interface {
@@ -224,6 +240,7 @@ type attributeTriple struct {
 type nulSeparatedAttributeWriter struct {
 	tmp        []byte
 	attributes chan attributeTriple
+	closed     chan struct{}
 	working    attributeTriple
 	pos        int
 }
@@ -267,13 +284,20 @@ func (wr *nulSeparatedAttributeWriter) ReadAttribute() <-chan attributeTriple {
 }
 
 func (wr *nulSeparatedAttributeWriter) Close() error {
+	select {
+	case <-wr.closed:
+		return nil
+	default:
+	}
 	close(wr.attributes)
+	close(wr.closed)
 	return nil
 }
 
 type lineSeparatedAttributeWriter struct {
 	tmp        []byte
 	attributes chan attributeTriple
+	closed     chan struct{}
 }
 
 func (wr *lineSeparatedAttributeWriter) Write(p []byte) (n int, err error) {
@@ -356,6 +380,12 @@ func (wr *lineSeparatedAttributeWriter) ReadAttribute() <-chan attributeTriple {
 }
 
 func (wr *lineSeparatedAttributeWriter) Close() error {
+	select {
+	case <-wr.closed:
+		return nil
+	default:
+	}
 	close(wr.attributes)
+	close(wr.closed)
 	return nil
 }