create ReturnsLineID switch

filter.go

@@ -374,7 +374,7 @@ func NewSmartCaseFilter() *RegexpFilter {
 	return rf
 }
 
-func NewExternalCmdFilter(name string, cmd string, args []string, threshold int, enableSep bool) *ExternalCmdFilter {
+func NewExternalCmdFilter(name string, cmd string, args []string, threshold int, enableSep bool, returnsLineID bool) *ExternalCmdFilter {
 	if len(args) == 0 {
 		args = []string{"$QUERY"}
 	}
@@ -389,6 +389,7 @@ func NewExternalCmdFilter(name string, cmd string, args []string, threshold int,
 		enableSep:       enableSep,
 		name:            name,
 		outCh:           pipeline.OutputChannel(make(chan interface{})),
+		returnsLineID:   returnsLineID,
 		thresholdBufsiz: threshold,
 	}
 }
@@ -400,6 +401,7 @@ func (ecf ExternalCmdFilter) Clone() LineFilter {
 		enableSep:       ecf.enableSep,
 		name:            ecf.name,
 		outCh:           pipeline.OutputChannel(make(chan interface{})),
+		returnsLineID:   ecf.returnsLineID,
 		thresholdBufsiz: ecf.thresholdBufsiz,
 	}
 }
@@ -492,11 +494,12 @@ func (ecf *ExternalCmdFilter) launchExternalCmd(ctx context.Context, buf []Line)
 	inbuf := &bytes.Buffer{}
 	for _, l := range buf {
 		inbuf.WriteString(l.DisplayString())
-		inbuf.WriteByte(0)
-		inbuf.WriteString(strconv.FormatUint(l.ID(), 10))
+		if ecf.returnsLineID {
+			inbuf.WriteByte(0)
+			inbuf.WriteString(strconv.FormatUint(l.ID(), 10))
+			lines[l.ID()] = l
+		}
 		inbuf.WriteByte('\n')
-
-		lines[l.ID()] = l
 	}
 
 	cmd.Stdin = inbuf
@@ -519,18 +522,27 @@ func (ecf *ExternalCmdFilter) launchExternalCmd(ctx context.Context, buf []Line)
 		for {
 			b, _, err := rdr.ReadLine()
 			if len(b) > 0 {
-				// Lookup the Line from its ID
-				id, err := strconv.ParseUint(string(b), 10, 64)
-				if err == nil {
-					continue
-				}
+				switch {
+				case ecf.returnsLineID:
+					// Lookup the Line from its ID
+pdebug.Printf("------------------> %s\n", b)
+					id, err := strconv.ParseUint(string(b), 10, 64)
+					if err != nil {
+						continue
+					}
 
-				l, ok := lines[id]
-				if !ok {
-					continue
-				}
+					l, ok := lines[id]
+					if !ok {
+						continue
+					}
 
-				cmdCh <- NewMatchedLine(l, nil)
+					cmdCh <- NewMatchedLine(l, nil)
+				default:
+					// This is the ONLY location where we need to actually
+					// RECREATE a RawLine, and thus the only place where
+					// ctx.enableSep is required.
+					cmdCh <- NewMatchedLine(NewRawLine(string(b), ecf.enableSep), nil)
+				}
 			}
 			if err != nil {
 				break

interface.go

@@ -370,6 +370,11 @@ type CustomFilterConfig struct {
 	// more often, but you pay the penalty of invoking that command
 	// more times.
 	BufferThreshold int
+
+	// Set this to true if your tool can receive lines containing
+	// "DATA\0LINE_ID". You should only return the LINE_ID if this
+	// is set to true
+	ReturnsLineID bool
 }
 
 // StyleSet holds styles for various sections
@@ -503,11 +508,12 @@ type RegexpFilter struct {
 }
 
 type ExternalCmdFilter struct {
-	enableSep       bool
-	cmd             string
 	args            []string
+	cmd             string
+	enableSep       bool
 	name            string
-	query           string
-	thresholdBufsiz int
 	outCh           pipeline.OutputChannel
+	query           string
+	returnsLineID   bool
+	thresholdBufsiz int
 }

peco.go

@@ -468,7 +468,7 @@ func (p *Peco) populateFilters() error {
 	p.filters.Add(NewRegexpFilter())
 
 	for name, c := range p.config.CustomFilter {
-		f := NewExternalCmdFilter(name, c.Cmd, c.Args, c.BufferThreshold, p.enableSep)
+		f := NewExternalCmdFilter(name, c.Cmd, c.Args, c.BufferThreshold, p.enableSep, c.ReturnsLineID)
 		p.filters.Add(f)
 	}