Ignore EPIPE errors when writing to a closed pager

While a gh command is writing stdout to a pager, the user may choose to
close the pager program before the pager has read all the data on its
standard input. In that case, the parent gh process will receive an
EPIPE error, which would bubble up its error handling and cause it to
print something like:

    write |1: broken pipe

Since this was caused by an explicit user action of closing the pager,
and since the user probably doesn't want to see this uninformative
error, this informs our global error handling of this error and causes
it to be ignored.

cmd/gh/main.go

@@ -24,6 +24,7 @@ import (
 	"github.com/cli/cli/v2/pkg/cmd/factory"
 	"github.com/cli/cli/v2/pkg/cmd/root"
 	"github.com/cli/cli/v2/pkg/cmdutil"
+	"github.com/cli/cli/v2/pkg/iostreams"
 	"github.com/cli/cli/v2/utils"
 	"github.com/cli/safeexec"
 	"github.com/mattn/go-colorable"
@@ -201,6 +202,7 @@ func mainRun() exitCode {
 	rootCmd.SetArgs(expandedArgs)
 
 	if cmd, err := rootCmd.ExecuteC(); err != nil {
+		var pagerPipeError *iostreams.ErrClosedPagerPipe
 		if err == cmdutil.SilentError {
 			return exitError
 		} else if cmdutil.IsUserCancellation(err) {
@@ -211,6 +213,9 @@ func mainRun() exitCode {
 			return exitCancel
 		} else if errors.Is(err, authError) {
 			return exitAuth
+		} else if errors.As(err, &pagerPipeError) {
+			// ignore the error raised when piping to a closed pager
+			return exitOK
 		}
 
 		printError(stderr, err, cmd, hasDebug)

pkg/cmd/api/api.go

@@ -3,7 +3,6 @@ package api
 import (
 	"bytes"
 	"encoding/json"
-	"errors"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -13,7 +12,6 @@ import (
 	"sort"
 	"strconv"
 	"strings"
-	"syscall"
 	"time"
 
 	"github.com/MakeNowJust/heredoc"
@@ -384,11 +382,7 @@ func processResponse(resp *http.Response, opts *ApiOptions, headersOutputStream
 		_, err = io.Copy(opts.IO.Out, responseBody)
 	}
 	if err != nil {
-		if errors.Is(err, syscall.EPIPE) {
-			err = nil
-		} else {
-			return
-		}
+		return
 	}
 
 	if serverError == "" && resp.StatusCode > 299 {

pkg/cmd/pr/diff/diff.go

@@ -7,7 +7,6 @@ import (
 	"io"
 	"net/http"
 	"strings"
-	"syscall"
 
 	"github.com/MakeNowJust/heredoc"
 	"github.com/cli/cli/v2/api"
@@ -112,9 +111,6 @@ func diffRun(opts *DiffOptions) error {
 
 	if !opts.UseColor {
 		_, err = io.Copy(opts.IO.Out, diff)
-		if errors.Is(err, syscall.EPIPE) {
-			return nil
-		}
 		return err
 	}
 

pkg/cmd/repo/view/view.go

@@ -6,7 +6,6 @@ import (
 	"net/http"
 	"net/url"
 	"strings"
-	"syscall"
 	"text/template"
 
 	"github.com/MakeNowJust/heredoc"
@@ -213,12 +212,7 @@ func viewRun(opts *ViewOptions) error {
 		View:        cs.Gray(fmt.Sprintf("View this repository on GitHub: %s", openURL)),
 	}
 
-	err = tmpl.Execute(stdout, repoData)
-	if err != nil && !errors.Is(err, syscall.EPIPE) {
-		return err
-	}
-
-	return nil
+	return tmpl.Execute(stdout, repoData)
 }
 
 func isMarkdownFile(filename string) bool {

pkg/iostreams/epipe_other.go

@@ -0,0 +1,13 @@
+//go:build !windows
+// +build !windows
+
+package iostreams
+
+import (
+	"errors"
+	"syscall"
+)
+
+func isEpipeError(err error) bool {
+	return errors.Is(err, syscall.EPIPE)
+}

pkg/iostreams/epipe_windows.go

@@ -0,0 +1,11 @@
+package iostreams
+
+import (
+	"errors"
+	"syscall"
+)
+
+func isEpipeError(err error) bool {
+	// 232 is Windows error code ERROR_NO_DATA, "The pipe is being closed".
+	return errors.Is(err, syscall.Errno(232))
+}

pkg/iostreams/iostreams.go

@@ -24,6 +24,11 @@ import (
 
 const DefaultWidth = 80
 
+// ErrClosedPagerPipe is the error returned when writing to a pager that has been closed.
+type ErrClosedPagerPipe struct {
+	error
+}
+
 type IOStreams struct {
 	In     io.ReadCloser
 	Out    io.Writer
@@ -197,7 +202,7 @@ func (s *IOStreams) StartPager() error {
 	if err != nil {
 		return err
 	}
-	s.Out = pagedOut
+	s.Out = &pagerWriter{pagedOut}
 	err = pagerCmd.Start()
 	if err != nil {
 		return err
@@ -211,7 +216,7 @@ func (s *IOStreams) StopPager() {
 		return
 	}
 
-	_ = s.Out.(io.ReadCloser).Close()
+	_ = s.Out.(io.WriteCloser).Close()
 	_, _ = s.pagerProcess.Wait()
 	s.pagerProcess = nil
 }
@@ -430,3 +435,16 @@ func terminalSize(w io.Writer) (int, int, error) {
 	}
 	return 0, 0, fmt.Errorf("%v is not a file", w)
 }
+
+// pagerWriter implements a WriteCloser that wraps all EPIPE errors in an ErrClosedPagerPipe type.
+type pagerWriter struct {
+	io.WriteCloser
+}
+
+func (w *pagerWriter) Write(d []byte) (int, error) {
+	n, err := w.WriteCloser.Write(d)
+	if err != nil && (errors.Is(err, io.ErrClosedPipe) || isEpipeError(err)) {
+		return n, &ErrClosedPagerPipe{err}
+	}
+	return n, err
+}