cmd/go: add $GOLINE to generate

Also use os.Expand for variable substitution so ${x}y works.

Fixes #9960.

Change-Id: Ic8239b2e737d1f41910dde8ee9524ac48907cb03
Reviewed-on: https://go-review.googlesource.com/9007Reviewed-by: Russ Cox <rsc@golang.org>

src/cmd/go/doc.go

@@ -276,6 +276,8 @@ Go generate sets several variables when it runs the generator:
 		The execution operating system (linux, windows, etc.)
 	$GOFILE
 		The base name of the file.
+	$GOLINE
+		The line number of the directive in the source file.
 	$GOPACKAGE
 		The name of the package of the file containing the directive.
 	$DOLLAR

src/cmd/go/generate.go

@@ -18,7 +18,6 @@ import (
 	"strconv"
 	"strings"
 	"unicode"
-	"unicode/utf8"
 )
 
 var cmdGenerate = &Command{
@@ -63,6 +62,8 @@ Go generate sets several variables when it runs the generator:
 		The execution operating system (linux, windows, etc.)
 	$GOFILE
 		The base name of the file.
+	$GOLINE
+		The line number of the directive in the source file.
 	$GOPACKAGE
 		The name of the package of the file containing the directive.
 	$DOLLAR
@@ -177,7 +178,7 @@ type Generator struct {
 	file     string // base name of file.
 	pkg      string
 	commands map[string][]string
-	lineNum  int
+	lineNum  int // current line number.
 }
 
 // run runs the generators in the current file.
@@ -325,7 +326,7 @@ Words:
 	}
 	// Substitute environment variables.
 	for i, word := range words {
-		words[i] = g.expandEnv(word)
+		words[i] = os.Expand(word, g.expandVar)
 	}
 	return words
 }
@@ -341,40 +342,25 @@ func (g *Generator) errorf(format string, args ...interface{}) {
 	panic(stop)
 }
 
-// expandEnv expands any $XXX invocations in word.
-func (g *Generator) expandEnv(word string) string {
-	if !strings.ContainsRune(word, '$') {
-		return word
-	}
-	var buf bytes.Buffer
-	var w int
-	var r rune
-	for i := 0; i < len(word); i += w {
-		r, w = utf8.DecodeRuneInString(word[i:])
-		if r != '$' {
-			buf.WriteRune(r)
-			continue
-		}
-		w += g.identLength(word[i+w:])
-		envVar := word[i+1 : i+w]
-		var sub string
-		switch envVar {
+// expandVar expands the $XXX invocation in word. It is called
+// by os.Expand.
+func (g *Generator) expandVar(word string) string {
+	switch word {
 	case "GOARCH":
-			sub = runtime.GOARCH
+		return runtime.GOARCH
 	case "GOOS":
-			sub = runtime.GOOS
+		return runtime.GOOS
 	case "GOFILE":
-			sub = g.file
+		return g.file
+	case "GOLINE":
+		return fmt.Sprint(g.lineNum)
 	case "GOPACKAGE":
-			sub = g.pkg
+		return g.pkg
 	case "DOLLAR":
-			sub = "$"
+		return "$"
 	default:
-			sub = os.Getenv(envVar)
-		}
-		buf.WriteString(sub)
+		return os.Getenv(word)
 	}
-	return buf.String()
 }
 
 // identLength returns the length of the identifier beginning the string.

src/cmd/go/test.bash

@@ -1089,20 +1089,20 @@ TEST 'go generate variable substitution'
 if ! ./testgo generate ./testdata/generate/test3.go > testdata/std.out; then
 	echo "go generate ./testdata/generate/test3.go failed to run"
 	ok=false
-elif ! grep "$GOARCH test3.go p xyzp/test3.go/123" testdata/std.out > /dev/null; then
+elif ! grep "$GOARCH test3.go:7 pabc xyzp/test3.go/123" testdata/std.out > /dev/null; then
 	echo "go generate ./testdata/generate/test3.go generated wrong output"
 	ok=false
 fi
 
 TEST 'go generate run flag'
 if ! ./testgo generate -run y.s ./testdata/generate/test4.go > testdata/std.out; then
-	echo "go test -run y.s ./testdata/generate/test4.go failed to run"
+	echo "go test -run yes ./testdata/generate/test4.go failed to run"
 	ok=false
 elif ! grep "yes" testdata/std.out > /dev/null; then
-	echo "go generate -run y.s ./testdata/generate/test4.go did not select yes"
+	echo "go generate -run yes ./testdata/generate/test4.go did not select yes"
 	ok=false
 elif grep "no" testdata/std.out > /dev/null; then
-	echo "go generate -run y.s ./testdata/generate/test4.go selected no"
+	echo "go generate -run yes ./testdata/generate/test4.go selected no"
 	ok=false
 fi
 

src/cmd/go/testdata/generate/test3.go

@@ -4,6 +4,6 @@
 
 // Test go generate variable substitution.
 
-//go:generate echo $GOARCH $GOFILE $GOPACKAGE xyz$GOPACKAGE/$GOFILE/123
+//go:generate echo $GOARCH $GOFILE:$GOLINE ${GOPACKAGE}abc xyz$GOPACKAGE/$GOFILE/123
 
 package p