Commit a86362e0 authored by Robert Griesemer's avatar Robert Griesemer

go/printer: don't emit unnecessary //line directives before empty lines

1) Split atLineBegin into its two components: writing of // line directives
and writing of indentation (no functionality changes).

2) Don't call writeLineDirective at the beginning of a line if we're
writing white space - it's not necessary. This is the bug fix.

3) Move testing of the SourcePos mode out of writeLineDirective and
into the (single) caller. Clearer and more efficient.

(Instead of these 3 changes one could also have simply called the
original atLineBegin with position p.out rather than p.pos. This
would have caused atLineBegin to not write a line directive.
Factoring the code seemed like a cleaner and more direct approach.)

Fixes #5945.

Change-Id: Ia8710806b6d3d4e5044116b142c036a4ab5a1764
Reviewed-on: https://go-review.googlesource.com/44651Reviewed-by: default avatarAlan Donovan <adonovan@google.com>
parent 29469d24
......@@ -69,7 +69,7 @@ type printer struct {
// The out position differs from the pos position when the result
// formatting differs from the source formatting (in the amount of
// white space). If there's a difference and SourcePos is set in
// ConfigMode, //line comments are used in the output to restore
// ConfigMode, //line directives are used in the output to restore
// original source positions for a reader.
pos token.Position // current position in AST (source) space
out token.Position // current position in output space
......@@ -203,19 +203,20 @@ func (p *printer) lineFor(pos token.Pos) int {
return p.cachedLine
}
// atLineBegin emits a //line comment if necessary and prints indentation.
func (p *printer) atLineBegin(pos token.Position) {
// write a //line comment if necessary
if p.Config.Mode&SourcePos != 0 && pos.IsValid() && (p.out.Line != pos.Line || p.out.Filename != pos.Filename) {
// writeLineDirective writes a //line directive if necessary.
func (p *printer) writeLineDirective(pos token.Position) {
if pos.IsValid() && (p.out.Line != pos.Line || p.out.Filename != pos.Filename) {
p.output = append(p.output, tabwriter.Escape) // protect '\n' in //line from tabwriter interpretation
p.output = append(p.output, fmt.Sprintf("//line %s:%d\n", pos.Filename, pos.Line)...)
p.output = append(p.output, tabwriter.Escape)
// p.out must match the //line comment
// p.out must match the //line directive
p.out.Filename = pos.Filename
p.out.Line = pos.Line
}
}
// write indentation
// writeIndent writes indentation.
func (p *printer) writeIndent() {
// use "hard" htabs - indentation columns
// must not be discarded by the tabwriter
n := p.Config.Indent + p.indent // include base indentation
......@@ -230,9 +231,11 @@ func (p *printer) atLineBegin(pos token.Position) {
}
// writeByte writes ch n times to p.output and updates p.pos.
// Only used to write formatting (white space) characters.
func (p *printer) writeByte(ch byte, n int) {
if p.out.Column == 1 {
p.atLineBegin(p.pos)
// no need to write line directives before white space
p.writeIndent()
}
for i := 0; i < n; i++ {
......@@ -265,13 +268,16 @@ func (p *printer) writeByte(ch byte, n int) {
//
func (p *printer) writeString(pos token.Position, s string, isLit bool) {
if p.out.Column == 1 {
p.atLineBegin(pos)
if p.Config.Mode&SourcePos != 0 {
p.writeLineDirective(pos)
}
p.writeIndent()
}
if pos.IsValid() {
// update p.pos (if pos is invalid, continue with existing p.pos)
// Note: Must do this after handling line beginnings because
// atLineBegin updates p.pos if there's indentation, but p.pos
// writeIndent updates p.pos if there's indentation, but p.pos
// is the position of s.
p.pos = pos
}
......@@ -1237,7 +1243,7 @@ const (
RawFormat Mode = 1 << iota // do not use a tabwriter; if set, UseSpaces is ignored
TabIndent // use tabs for indentation independent of UseSpaces
UseSpaces // use spaces instead of tabs for alignment
SourcePos // emit //line comments to preserve original source positions
SourcePos // emit //line directives to preserve original source positions
)
// A Config node controls the output of Fprint.
......
......@@ -363,7 +363,7 @@ func identCount(f *ast.File) int {
return n
}
// Verify that the SourcePos mode emits correct //line comments
// Verify that the SourcePos mode emits correct //line directives
// by testing that position information for matching identifiers
// is maintained.
func TestSourcePos(t *testing.T) {
......@@ -394,7 +394,7 @@ func (t *t) foo(a, b, c int) int {
}
// parse pretty printed original
// (//line comments must be interpreted even w/o parser.ParseComments set)
// (//line directives must be interpreted even w/o parser.ParseComments set)
f2, err := parser.ParseFile(fset, "", buf.Bytes(), 0)
if err != nil {
t.Fatalf("%s\n%s", err, buf.Bytes())
......@@ -434,6 +434,53 @@ func (t *t) foo(a, b, c int) int {
}
}
// Verify that the SourcePos mode doesn't emit unnecessary //line directives
// before empty lines.
func TestIssue5945(t *testing.T) {
const orig = `
package p // line 2
func f() {} // line 3
var x, y, z int
func g() { // line 8
}
`
const want = `//line src.go:2
package p
//line src.go:3
func f() {}
var x, y, z int
//line src.go:8
func g() {
}
`
// parse original
f1, err := parser.ParseFile(fset, "src.go", orig, 0)
if err != nil {
t.Fatal(err)
}
// pretty-print original
var buf bytes.Buffer
err = (&Config{Mode: UseSpaces | SourcePos, Tabwidth: 8}).Fprint(&buf, fset, f1)
if err != nil {
t.Fatal(err)
}
got := buf.String()
// compare original with desired output
if got != want {
t.Errorf("got:\n%s\nwant:\n%s\n", got, want)
}
}
var decls = []string{
`import "fmt"`,
"const pi = 3.1415\nconst e = 2.71828\n\nvar x = pi",
......
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