- improved comment intersperse heuristic:

  comments should now be indented properly in corner cases
  (at the end of statement lists, for instance)

- changed import decl. formatting as suggested by Russ (no "global"
  indentation of imports if there are renames present)

- better field list handling

- better documentation

R=rsc
DELTA=534  (324 added, 35 deleted, 175 changed)
OCL=35557
CL=35630

src/pkg/go/printer/testdata/comments.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// This is a package for testing purposes.
+// This is a package for testing comment placement by go/printer.
 //
 package main
 
@@ -53,7 +53,7 @@ type I1 interface {
 }
 
 // The I2 interface; all methods are exported.
-type I1 interface {
+type I2 interface {
 	I0;
 	F(x float) float;  // exported method
 	G(x float) float;  // exported method
@@ -91,6 +91,11 @@ func f1() {
 }
 
 
+func _() {
+	// this comment should be properly indented
+}
+
+
 func abs(x int) int {
 	if x < 0 {  // the tab printed before this comment's // must not affect the remaining lines
 		return -x;  // this statement should be properly indented
@@ -114,9 +119,26 @@ func typeswitch(x interface{}) {
 
 	switch v0, ok := x.(int); x.(type) {
 	case bool, int, float:
+		// this comment should be indented
 	case string:
 	default:
+		// this comment should be indented
 	}
+	// this comment should be indented
 }
 
+
+// Line comments with tabs
+func _() {
+var	finput		*bufio.Reader;			// input file
+var	stderr		*bufio.Writer;
+var	ftable		*bufio.Writer;			// y.go file
+var	foutput		*bufio.Writer;			// y.output file
+
+var	oflag		string;				// -o [y.go]		- y.go file
+var	vflag		string;				// -v [y.output]	- y.output file
+var	lflag		bool;				// -l			- disable line directives
+}
+
+
 // This comment is the last entry in this file. It must be printed.

src/pkg/go/printer/testdata/comments.golden

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// This is a package for testing purposes.
+// This is a package for testing comment placement by go/printer.
 //
 package main
 
@@ -53,7 +53,7 @@ type I1 interface {
 }
 
 // The I2 interface; all methods are exported.
-type I1 interface {
+type I2 interface {
 	I0;
 	F(x float) float;	// exported method
 	G(x float) float;	// exported method
@@ -91,6 +91,11 @@ func f1() {
 }
 
 
+func _() {
+	// this comment should be properly indented
+}
+
+
 func abs(x int) int {
 	if x < 0 {	// the tab printed before this comment's // must not affect the remaining lines
 		return -x;	// this statement should be properly indented
@@ -112,9 +117,26 @@ func typeswitch(x interface{}) {
 
 	switch v0, ok := x.(int); x.(type) {
 	case bool, int, float:
+		// this comment should be indented
 	case string:
 	default:
+		// this comment should be indented
 	}
+	// this comment should be indented
 }
 
+
+// Line comments with tabs
+func _() {
+	var finput *bufio.Reader;	// input file
+	var stderr *bufio.Writer;
+	var ftable *bufio.Writer;	// y.go file
+	var foutput *bufio.Writer;	// y.output file
+
+	var oflag string;	// -o [y.go]		- y.go file
+	var vflag string;	// -v [y.output]	- y.output file
+	var lflag bool;		// -l			- disable line directives
+}
+
+
 // This comment is the last entry in this file. It must be printed.

src/pkg/go/printer/testdata/comments.x

-// This is a package for testing purposes.
+// This is a package for testing comment placement by go/printer.
 //
 package main
 
@@ -48,7 +48,7 @@ type I1 interface {
 
 
 // The I2 interface; all methods are exported.
-type I1 interface {
+type I2 interface {
 	I0;
 	F(x float) float;
 	G(x float) float;

src/pkg/go/printer/testdata/declarations.go

@@ -175,6 +175,14 @@ func _() {
 		y = 20;  // comment
 		f, ff, fff, ffff int = 0, 1, 2, 3;  // comment
 	)
+	// respect original line breaks
+	var _ = []T {
+		T{0x20,	"Telugu"}
+	};
+	var _ = []T {
+		// respect original line breaks
+		T{0x20,	"Telugu"}
+	};
 }
 
 func _() {
@@ -194,7 +202,13 @@ func _() {
 
 
 // formatting of structs
-type ES struct{}
+type _ struct{}
+
+type _ struct{ /* this comment should be visible */ }
+
+type _ struct{
+	// this comment should be visible and properly indented
+}
 
 type _ struct {  // this comment must not change indentation
 	f int;

src/pkg/go/printer/testdata/declarations.golden

@@ -19,10 +19,10 @@ import (
 )
 
 import (
-			"io";
-	aLongRename	"io";
-	b		"io";
-	c		"i" "o";
+	"io";
+	aLongRename "io";
+	b "io";
+	c "i" "o";
 )
 
 // no newlines between consecutive single imports, but
@@ -173,6 +173,11 @@ func _() {
 		y				= 20;		// comment
 		f, ff, fff, ffff	int	= 0, 1, 2, 3;	// comment
 	)
+	// respect original line breaks
+	var _ = []T{T{0x20, "Telugu"}};
+	var _ = []T{
+	// respect original line breaks
+	T{0x20, "Telugu"}};
 }
 
 func _() {
@@ -192,7 +197,13 @@ func _() {
 
 
 // formatting of structs
-type ES struct{}
+type _ struct{}
+
+type _ struct {	/* this comment should be visible */}
+
+type _ struct {
+	// this comment should be visible and properly indented
+}
 
 type _ struct {	// this comment must not change indentation
 	f			int;
@@ -235,7 +246,7 @@ type _ struct {
 	bool;
 	a, b, c			int;
 	int			"tag";
-	ES;			// comment
+	ES;				// comment
 	float			"tag";	// comment
 	f			int;	// comment
 	f, ff, fff, ffff	int;	// comment
@@ -246,7 +257,7 @@ type _ struct {
 
 // difficult cases
 type _ struct {
-	bool;	// comment
+	bool;		// comment
 	text	[]byte;	// comment
 }
 

src/pkg/go/printer/testdata/expressions.go

@@ -165,3 +165,14 @@ func (p *parser) charClass() {
 		p.re.add(nl);
 	}
 }
+
+
+func addState(s []state, inst instr, match []int) {
+	// handle comments correctly in multi-line expressions
+	for i := 0; i < l; i++ {
+		if s[i].inst.index() == index && // same instruction
+		   s[i].match[0] < pos {	// earlier match already going; leftmost wins
+		   	return s
+		 }
+	}
+}

src/pkg/go/printer/testdata/expressions.golden

@@ -108,11 +108,9 @@ func _() {
 	// do not modify `` strings
 	_ = ``;
 	_ = `
-`;
-	// TODO(gri): fix line breaks here
+`;	// TODO(gri): fix line breaks here
 	_ = `foo
 		bar`;
-
 }
 
 
@@ -140,8 +138,8 @@ func _() {
 		b < a;
 	_ = "1234567890"
 	"1234567890";
-// TODO(gri): add more test cases
-// TODO(gri): these comments should be indented
+	// TODO(gri): add more test cases
+	// TODO(gri): these comments should be indented
 }
 
 
@@ -167,3 +165,15 @@ func (p *parser) charClass() {
 		p.re.add(nl);
 	}
 }
+
+
+func addState(s []state, inst instr, match []int) {
+	// handle comments correctly in multi-line expressions
+	for i := 0; i < l; i++ {
+		if s[i].inst.index() == index &&
+						// same instruction
+			s[i].match[0] < pos {	// earlier match already going; leftmost wins
+			return s;
+		}
+	}
+}

src/pkg/go/printer/testdata/linebreaks.golden

@@ -181,7 +181,9 @@ var facts = map[int]string{
 
 func usage() {
 	fmt.Fprintf(os.Stderr,
-		// TODO(gri): the 2nd string of this string list should not be indented
+
+
+	// TODO(gri): the 2nd string of this string list should not be indented
 		"usage: godoc package [name ...]\n"
 		"	godoc -http=:6060\n");
 	flag.PrintDefaults();

src/pkg/go/printer/testdata/statements.go

@@ -123,6 +123,18 @@ func _() {
 
 
 func _() {
+	// this comment should be indented
+	L:
+}
+
+
+func _() {
+	L: _ = 0;
+}
+
+
+func _() {
+	// this comment should be indented
 	L: _ = 0;
 }
 
@@ -134,3 +146,13 @@ func _() {
 		_ = 0;
 	}
 }
+
+
+func _() {
+		// this comment should be indented
+	for {
+	L1: _ = 0;
+	L2:
+		_ = 0;
+	}
+}

src/pkg/go/printer/testdata/statements.golden

@@ -139,6 +139,19 @@ L:
 
 
 func _() {
+	// this comment should be indented
+L:
+	;
+}
+
+
+func _() {
+L:	_ = 0;
+}
+
+
+func _() {
+	// this comment should be indented
 L:	_ = 0;
 }
 
@@ -150,3 +163,13 @@ func _() {
 		_ = 0;
 	}
 }
+
+
+func _() {
+	// this comment should be indented
+	for {
+	L1:	_ = 0;
+	L2:
+		_ = 0;
+	}
+}