fix: share STDIN across different commands on pre-push hook (#732)

* fix: error and bail if multiple commands useStdin

Since Stdin from Git is not intercepted and forwared to each commands/scripts,
this could lead to hang.

* fix: CommandExecutor.RawExecute forward os.Stdin

This is only used by LFS pre-push Hook which require Stdin.

* fix: use cached reader for stdin when use_stdin is specified

* chore: remove special checks for pre-push hook

* chore: fix typos

* fix: fail the hook if git-lfs command failed

* chore: add more verbose error

---------

Co-authored-by: Thomas Desveaux <[email protected]>

internal/lefthook/run.go

@@ -169,7 +169,10 @@ Run 'lefthook install' manually.`,
 	)
 
 	startTime := time.Now()
-	results := r.RunAll(ctx, sourceDirs)
+	results, runErr := r.RunAll(ctx, sourceDirs)
+	if runErr != nil {
+		return fmt.Errorf("failed to run the hook: %w", runErr)
+	}
 
 	if ctx.Err() != nil {
 		return errors.New("Interrupted")

internal/lefthook/runner/cached_reader.go

@@ -0,0 +1,49 @@
+package runner
+
+import (
+	"bytes"
+	"io"
+)
+
+// cachedReader reads from the provided `io.Reader` until `io.EOF` and saves
+// the read content into the inner buffer.
+//
+// After `io.EOF` it will be providing the read data again and again.
+type cachedReader struct {
+	in        io.Reader
+	useBuffer bool
+	buf       []byte
+	reader    *bytes.Reader
+}
+
+func NewCachedReader(in io.Reader) *cachedReader {
+	return &cachedReader{
+		in:     in,
+		buf:    []byte{},
+		reader: bytes.NewReader([]byte{}),
+	}
+}
+
+func (r *cachedReader) Read(p []byte) (int, error) {
+	if r.useBuffer {
+		n, err := r.reader.Read(p)
+		if err == io.EOF {
+			_, seekErr := r.reader.Seek(0, io.SeekStart)
+			if seekErr != nil {
+				panic(seekErr)
+			}
+
+			return n, err
+		}
+
+		return n, err
+	}
+
+	n, err := r.in.Read(p)
+	r.buf = append(r.buf, p[:n]...)
+	if err == io.EOF {
+		r.useBuffer = true
+		r.reader = bytes.NewReader(r.buf)
+	}
+	return n, err
+}

internal/lefthook/runner/cached_reader_test.go

@@ -0,0 +1,24 @@
+package runner
+
+import (
+	"bytes"
+	"io"
+	"testing"
+)
+
+func TestCachedReader(t *testing.T) {
+	testSlice := []byte("Some example string\nMultiline")
+
+	cachedReader := NewCachedReader(bytes.NewReader(testSlice))
+
+	for range 5 {
+		res, err := io.ReadAll(cachedReader)
+		if err != nil {
+			t.Errorf("unexpected err: %s", err)
+		}
+
+		if !bytes.Equal(res, testSlice) {
+			t.Errorf("expected %v to be equal to %v", res, testSlice)
+		}
+	}
+}

internal/lefthook/runner/exec/execute_unix.go

@@ -28,11 +28,7 @@ type executeArgs struct {
 	interactive, useStdin bool
 }
 
-func (e CommandExecutor) Execute(ctx context.Context, opts Options, out io.Writer) error {
-	var in io.Reader = nullReader{}
-	if opts.UseStdin {
-		in = os.Stdin
-	}
+func (e CommandExecutor) Execute(ctx context.Context, opts Options, in io.Reader, out io.Writer) error {
 	if opts.Interactive && !isatty.IsTerminal(os.Stdin.Fd()) {
 		tty, err := os.Open("/dev/tty")
 		if err == nil {
@@ -72,9 +68,10 @@ func (e CommandExecutor) Execute(ctx context.Context, opts Options, out io.Write
 	return nil
 }
 
-func (e CommandExecutor) RawExecute(ctx context.Context, command []string, out io.Writer) error {
+func (e CommandExecutor) RawExecute(ctx context.Context, command []string, in io.Reader, out io.Writer) error {
 	cmd := exec.CommandContext(ctx, command[0], command[1:]...)
 
+	cmd.Stdin = in
 	cmd.Stdout = out
 	cmd.Stderr = os.Stderr
 

internal/lefthook/runner/exec/execute_windows.go

@@ -23,11 +23,7 @@ type executeArgs struct {
 	root string
 }
 
-func (e CommandExecutor) Execute(ctx context.Context, opts Options, out io.Writer) error {
-	var in io.Reader = nullReader{}
-	if opts.UseStdin {
-		in = os.Stdin
-	}
+func (e CommandExecutor) Execute(ctx context.Context, opts Options, in io.Reader, out io.Writer) error {
 	if opts.Interactive && !isatty.IsTerminal(os.Stdin.Fd()) {
 		tty, err := tty.Open()
 		if err == nil {
@@ -63,9 +59,10 @@ func (e CommandExecutor) Execute(ctx context.Context, opts Options, out io.Write
 	return nil
 }
 
-func (e CommandExecutor) RawExecute(ctx context.Context, command []string, out io.Writer) error {
-	cmd := exec.Command(command[0], command[1:]...)
+func (e CommandExecutor) RawExecute(ctx context.Context, command []string, in io.Reader, out io.Writer) error {
+	cmd := exec.CommandContext(ctx, command[0], command[1:]...)
 
+	cmd.Stdin = in
 	cmd.Stdout = out
 	cmd.Stderr = os.Stderr
 

internal/lefthook/runner/exec/executor.go

@@ -16,6 +16,6 @@ type Options struct {
 // Executor provides an interface for command execution.
 // It is used here for testing purpose mostly.
 type Executor interface {
-	Execute(ctx context.Context, opts Options, out io.Writer) error
-	RawExecute(ctx context.Context, command []string, out io.Writer) error
+	Execute(ctx context.Context, opts Options, in io.Reader, out io.Writer) error
+	RawExecute(ctx context.Context, command []string, in io.Reader, out io.Writer) error
 }

internal/lefthook/runner/null_reader.go

@@ -0,0 +1,15 @@
+package runner
+
+import "io"
+
+// nullReader always returns `io.EOF`.
+type nullReader struct{}
+
+func NewNullReader() io.Reader {
+	return nullReader{}
+}
+
+// Implements io.Reader interface.
+func (nullReader) Read(b []byte) (int, error) {
+	return 0, io.EOF
+}

internal/lefthook/runner/null_reader_test.go

@@ -0,0 +1,20 @@
+package runner
+
+import (
+	"bytes"
+	"io"
+	"testing"
+)
+
+func TestNullReader(t *testing.T) {
+	nullReader := NewNullReader()
+
+	res, err := io.ReadAll(nullReader)
+	if err != nil {
+		t.Errorf("unexpected err: %s", err)
+	}
+
+	if !bytes.Equal(res, []byte{}) {
+		t.Errorf("expected %v to be equal to %v", res, []byte{})
+	}
+}

internal/lefthook/runner/runner.go

@@ -51,14 +51,19 @@ type Options struct {
 type Runner struct {
 	Options
 
+	stdin                io.Reader
 	partiallyStagedFiles []string
 	failed               atomic.Bool
 	executor             exec.Executor
 }
 
 func New(opts Options) *Runner {
 	return &Runner{
-		Options:  opts,
+		Options: opts,
+
+		// Some hooks use STDIN for parsing data from Git. To allow multiple commands
+		// and scripts access the same Git data STDIN is cached via cachedReader.
+		stdin:    NewCachedReader(os.Stdin),
 		executor: exec.CommandExecutor{},
 	}
 }
@@ -79,16 +84,16 @@ type executable interface {
 
 // RunAll runs scripts and commands.
 // LFS hook is executed at first if needed.
-func (r *Runner) RunAll(ctx context.Context, sourceDirs []string) []Result {
+func (r *Runner) RunAll(ctx context.Context, sourceDirs []string) ([]Result, error) {
 	results := make([]Result, 0, len(r.Hook.Commands)+len(r.Hook.Scripts))
 
 	if err := r.runLFSHook(ctx); err != nil {
-		log.Error(err)
+		return results, err
 	}
 
 	if r.Hook.DoSkip(r.Repo.State()) {
 		r.logSkip(r.HookName, "hook setting")
-		return results
+		return results, nil
 	}
 
 	if !r.DisableTTY && !r.Hook.Follow {
@@ -113,7 +118,7 @@ func (r *Runner) RunAll(ctx context.Context, sourceDirs []string) []Result {
 
 	r.postHook()
 
-	return results
+	return results, nil
 }
 
 func (r *Runner) runLFSHook(ctx context.Context) error {
@@ -144,6 +149,7 @@ func (r *Runner) runLFSHook(ctx context.Context) error {
 				[]string{"git", "lfs", r.HookName},
 				r.GitArgs...,
 			),
+			r.stdin,
 			out,
 		)
 
@@ -490,6 +496,12 @@ func (r *Runner) run(ctx context.Context, opts exec.Options, follow bool) bool {
 	log.SetName(opts.Name)
 	defer log.UnsetName(opts.Name)
 
+	// If the command does not explicitly `use_stdin` no input will be provided.
+	var in io.Reader = NewNullReader()
+	if opts.UseStdin {
+		in = r.stdin
+	}
+
 	if (follow || opts.Interactive) && r.LogSettings.LogExecution() {
 		r.logExecute(opts.Name, nil, nil)
 
@@ -500,12 +512,14 @@ func (r *Runner) run(ctx context.Context, opts exec.Options, follow bool) bool {
 			out = io.Discard
 		}
 
-		err := r.executor.Execute(ctx, opts, out)
+		err := r.executor.Execute(ctx, opts, in, out)
+
 		return err == nil
 	}
 
 	out := bytes.NewBuffer(make([]byte, 0))
-	err := r.executor.Execute(ctx, opts, out)
+
+	err := r.executor.Execute(ctx, opts, in, out)
 
 	r.logExecute(opts.Name, err, out)
 

internal/lefthook/runner/runner_test.go

@@ -21,7 +21,7 @@ import (
 
 type TestExecutor struct{}
 
-func (e TestExecutor) Execute(_ctx context.Context, opts exec.Options, _out io.Writer) (err error) {
+func (e TestExecutor) Execute(_ctx context.Context, opts exec.Options, _in io.Reader, _out io.Writer) (err error) {
 	if strings.HasPrefix(opts.Commands[0], "success") {
 		err = nil
 	} else {
@@ -31,7 +31,7 @@ func (e TestExecutor) Execute(_ctx context.Context, opts exec.Options, _out io.W
 	return
 }
 
-func (e TestExecutor) RawExecute(_ctx context.Context, _command []string, _out io.Writer) error {
+func (e TestExecutor) RawExecute(_ctx context.Context, _command []string, _in io.Reader, _out io.Writer) error {
 	return nil
 }
 
@@ -766,7 +766,10 @@ func TestRunAll(t *testing.T) {
 		}
 
 		t.Run(fmt.Sprintf("%d: %s", i, tt.name), func(t *testing.T) {
-			results := runner.RunAll(context.Background(), tt.sourceDirs)
+			results, err := runner.RunAll(context.Background(), tt.sourceDirs)
+			if err != nil {
+				t.Errorf("unexpected error %s", err)
+			}
 
 			var success, fail []Result
 			for _, result := range results {