Merge pull request #20 from nineinchnick/ignore-broken-pipe

Detect and ignore broken pipe when pager was enabled

encode.go

@@ -5,10 +5,12 @@ import (
 	"bytes"
 	"encoding/csv"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"os/exec"
 	"strings"
+	"syscall"
 
 	runewidth "github.com/mattn/go-runewidth"
 )
@@ -214,7 +216,7 @@ func (enc *TableEncoder) Encode(w io.Writer) error {
 			}
 
 			if err := exp.encodeVals(vals); err != nil {
-				return nil
+				return checkErr(err, cmd)
 			}
 			continue
 		}
@@ -236,7 +238,7 @@ func (enc *TableEncoder) Encode(w io.Writer) error {
 		}
 
 		if err := enc.encodeVals(vals); err != nil {
-			return err
+			return checkErr(err, cmd)
 		}
 
 		// draw end border
@@ -248,10 +250,8 @@ func (enc *TableEncoder) Encode(w io.Writer) error {
 	// add summary
 	enc.summarize(w)
 
-	// flush will return the error code
-	err = enc.w.Flush()
-	if err != nil {
-		return err
+	if err := enc.w.Flush(); err != nil {
+		return checkErr(err, cmd)
 	}
 	if cmd != nil {
 		cmdBuf.Close()
@@ -268,11 +268,17 @@ func startPager(pagerCmd string, w io.Writer) (*exec.Cmd, io.WriteCloser, error)
 	if err != nil {
 		return nil, nil, err
 	}
-	// TODO when pager exits early, writes and flushes
-	// will start producing "broken pipe" errors, how to detect them?
 	return cmd, cmdBuf, cmd.Start()
 }
 
+func checkErr(err error, cmd *exec.Cmd) error {
+	if cmd != nil && errors.Is(err, syscall.EPIPE) {
+		// broken pipe means pager quit before consuming all data, which might be expected
+		return nil
+	}
+	return err
+}
+
 func (enc *TableEncoder) encodeVals(vals [][]*Value) error {
 	rs := enc.rowStyle(enc.lineStyle.Row)
 	// print buffered vals
@@ -762,17 +768,15 @@ func (enc *ExpandedEncoder) Encode(w io.Writer) error {
 		}
 
 		if err := enc.encodeVals(vals); err != nil {
-			return err
+			return checkErr(err, cmd)
 		}
 	}
 
 	// add summary
 	enc.summarize(w)
 
-	// flush will return the error code
-	err = enc.w.Flush()
-	if err != nil {
-		return err
+	if err := enc.w.Flush(); err != nil {
+		return checkErr(err, cmd)
 	}
 	if cmd != nil {
 		cmdBuf.Close()

opts.go

@@ -72,9 +72,6 @@ func FromMap(opts map[string]string) (Builder, []Option) {
 				}
 			}
 		}
-		builder := NewTableEncoder
-		// TODO detect "pager" option, on means auto, always means on
-		// TODO pager should check both width and height in both TableEncoder and ExpandedEncoder
 		pager := opts["pager"]
 		pagerCmd := opts["pager_cmd"]
 		if pager != "" && pagerCmd != "" {
@@ -97,6 +94,7 @@ func FromMap(opts map[string]string) (Builder, []Option) {
 				tableOpts = append(tableOpts, WithMinPagerWidth(-1), WithMinPagerHeight(-1))
 			}
 		}
+		builder := NewTableEncoder
 		if e, ok := opts["expanded"]; ok {
 			switch e {
 			case "auto":