clipboard kitten: Allow STDIN to be connected to a program that itself uses the tty directly

Read in STDIN first, and only then start terminal IO, hopefully allowing
the other program to finish its terminal IO before we start.

Fixes #5934

tools/cmd/clipboard/legacy.go

@@ -3,6 +3,7 @@
 package clipboard
 
 import (
+	"bytes"
 	"encoding/base64"
 	"errors"
 	"fmt"
@@ -28,17 +29,74 @@ func encode_read_from_clipboard(use_primary bool) string {
 }
 
 type base64_streaming_enc struct {
-	output func(string)
+	output          func(string) loop.IdType
+	last_written_id loop.IdType
 }
 
 func (self *base64_streaming_enc) Write(p []byte) (int, error) {
 	if len(p) > 0 {
-		self.output(string(p))
+		self.last_written_id = self.output(string(p))
 	}
 	return len(p), nil
 }
 
+var ErrTooMuchPipedData = errors.New("Too much piped data")
+
+func read_all_with_max_size(r io.Reader, max_size int) ([]byte, error) {
+	b := make([]byte, 0, utils.Min(8192, max_size))
+	for {
+		if len(b) == cap(b) {
+			new_size := utils.Min(2*cap(b), max_size)
+			if new_size <= cap(b) {
+				return b, ErrTooMuchPipedData
+			}
+			b = append(make([]byte, 0, new_size), b...)
+		}
+		n, err := r.Read(b[len(b):cap(b)])
+		b = b[:len(b)+n]
+		if err != nil {
+			if err == io.EOF {
+				err = nil
+			}
+			return b, err
+		}
+	}
+}
+
 func run_plain_text_loop(opts *Options) (err error) {
+	stdin_is_tty := tty.IsTerminal(os.Stdin.Fd())
+	var stdin_data []byte
+	var data_src io.Reader
+	var tempfile *os.File
+	if !stdin_is_tty {
+		// we pre-read STDIN because otherwise if the output of a command is being piped in
+		// and that command itself transmits on the tty we will break. For example
+		// kitten @ ls | kitten clipboard
+		stdin_data, err = read_all_with_max_size(os.Stdin, 2*1024*1024)
+		if err == nil {
+			os.Stdin.Close()
+		} else if err != ErrTooMuchPipedData {
+			return fmt.Errorf("Failed to read from STDIN pipe with error: %w", err)
+		}
+	}
+	if err == ErrTooMuchPipedData {
+		tempfile, err = utils.CreateAnonymousTemp("")
+		if err != nil {
+			return fmt.Errorf("Failed to create a temporary from STDIN pipe with error: %w", err)
+		}
+		defer tempfile.Close()
+		tempfile.Write(stdin_data)
+		_, err = io.Copy(tempfile, os.Stdin)
+		if err != nil {
+			return fmt.Errorf("Failed to copy data from STDIN pipe to temp file with error: %w", err)
+		}
+		os.Stdin.Close()
+		tempfile.Seek(0, os.SEEK_SET)
+		data_src = tempfile
+	} else if stdin_data != nil {
+		data_src = bytes.NewBuffer(stdin_data)
+	}
+
 	lp, err := loop.New(loop.NoAlternateScreen, loop.NoRestoreColors, loop.NoMouseTracking)
 	if err != nil {
 		return
@@ -47,13 +105,12 @@ func run_plain_text_loop(opts *Options) (err error) {
 	if opts.UsePrimary {
 		dest = "p"
 	}
-	stdin_is_tty := tty.IsTerminal(os.Stdin.Fd())
-	var buf [8192]byte
 
-	send_to_loop := func(data string) {
-		lp.QueueWriteString(data)
+	send_to_loop := func(data string) loop.IdType {
+		return lp.QueueWriteString(data)
 	}
-	enc := base64.NewEncoder(base64.StdEncoding, &base64_streaming_enc{send_to_loop})
+	enc_writer := base64_streaming_enc{output: send_to_loop}
+	enc := base64.NewEncoder(base64.StdEncoding, &enc_writer)
 	transmitting := true
 
 	after_read_from_stdin := func() {
@@ -67,37 +124,38 @@ func run_plain_text_loop(opts *Options) (err error) {
 		}
 	}
 
-	read_from_stdin := func() error {
-		n, err := os.Stdin.Read(buf[:])
+	buf := make([]byte, 8192)
+	write_one_chunk := func() error {
+		n, err := data_src.Read(buf[:cap(buf)])
+		if err != nil && !errors.Is(err, io.EOF) {
+			send_to_loop("\x1b\\")
+			return err
+		}
 		if n > 0 {
 			enc.Write(buf[:n])
 		}
-		if err != nil {
-			if errors.Is(err, io.EOF) {
-				enc.Close()
-				send_to_loop("\x1b\\")
-				os.Stdin.Close()
-				after_read_from_stdin()
-				return nil
-			}
-			return fmt.Errorf("Failed to read from STDIN with error: %w", err)
+		if errors.Is(err, io.EOF) {
+			enc.Close()
+			send_to_loop("\x1b\\")
+			after_read_from_stdin()
 		}
-		lp.WakeupMainThread()
 		return nil
 	}
 
-	lp.OnWakeup = func() error {
-		return read_from_stdin()
+	lp.OnInitialize = func() (string, error) {
+		if data_src != nil {
+			send_to_loop(fmt.Sprintf("\x1b]52;%s;", dest))
+			return "", write_one_chunk()
+		}
+		after_read_from_stdin()
+		return "", nil
 	}
 
-	lp.OnInitialize = func() (string, error) {
-		if !stdin_is_tty {
-			send_to_loop(fmt.Sprintf("\x1b]52;%s;", dest))
-			read_from_stdin()
-		} else {
-			after_read_from_stdin()
+	lp.OnWriteComplete = func(id loop.IdType) error {
+		if id == enc_writer.last_written_id {
+			return write_one_chunk()
 		}
-		return "", nil
+		return nil
 	}
 
 	var clipboard_contents []byte