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go/printer: canonicalize //go:build and // +build lines while formatting

Part of //go:build change (#41184).
See https://golang.org/design/draft-gobuild

Gofmt and any other go/printer-using program will now:

 - move //go:build and //+build lines to the appropriate file location
 - if there's no //go:build line, add one derived from the // +build lines
 - if there is a //go:build line, recompute and replace any // +build lines
   to match what the //go:build line says

For Go 1.17.

Change-Id: Ide5cc3b4a07507ba9ed6f8b0de846e840876f49f
Reviewed-on: https://go-review.googlesource.com/c/go/+/240608
Trust: Russ Cox <rsc@golang.org>
Trust: Jay Conrod <jayconrod@google.com>
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>
This commit is contained in:
Russ Cox 2020-06-26 16:22:35 -04:00
parent 5b76343a10
commit 9fd6cc105d
19 changed files with 307 additions and 10 deletions

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@ -279,7 +279,10 @@ var depsRules = `
< go/ast
< go/parser;
go/parser, text/tabwriter
FMT
< go/build/constraint;
go/build/constraint, go/parser, text/tabwriter
< go/printer
< go/format;
@ -292,9 +295,6 @@ var depsRules = `
container/heap, go/constant, go/parser, regexp
< go/types;
FMT
< go/build/constraint;
go/build/constraint, go/doc, go/parser, internal/goroot, internal/goversion
< go/build;

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@ -151,6 +151,10 @@ var tests = []string{
// erroneous programs
"ERROR1 + 2 +",
"ERRORx := 0",
// build comments
"// copyright\n\n//go:build x\n\npackage p\n",
"// copyright\n\n//go:build x\n// +build x\n\npackage p\n",
}
func String(s string) (string, error) {

170
src/go/printer/gobuild.go Normal file
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@ -0,0 +1,170 @@
// Copyright 2020 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package printer
import (
"go/build/constraint"
"sort"
"text/tabwriter"
)
func (p *printer) fixGoBuildLines() {
if len(p.goBuild)+len(p.plusBuild) == 0 {
return
}
// Find latest possible placement of //go:build and // +build comments.
// That's just after the last blank line before we find a non-comment.
// (We'll add another blank line after our comment block.)
// When we start dropping // +build comments, we can skip over /* */ comments too.
// Note that we are processing tabwriter input, so every comment
// begins and ends with a tabwriter.Escape byte.
// And some newlines have turned into \f bytes.
insert := 0
for pos := 0; ; {
// Skip leading space at beginning of line.
blank := true
for pos < len(p.output) && (p.output[pos] == ' ' || p.output[pos] == '\t') {
pos++
}
// Skip over // comment if any.
if pos+3 < len(p.output) && p.output[pos] == tabwriter.Escape && p.output[pos+1] == '/' && p.output[pos+2] == '/' {
blank = false
for pos < len(p.output) && !isNL(p.output[pos]) {
pos++
}
}
// Skip over \n at end of line.
if pos >= len(p.output) || !isNL(p.output[pos]) {
break
}
pos++
if blank {
insert = pos
}
}
// If there is a //go:build comment before the place we identified,
// use that point instead. (Earlier in the file is always fine.)
if len(p.goBuild) > 0 && p.goBuild[0] < insert {
insert = p.goBuild[0]
} else if len(p.plusBuild) > 0 && p.plusBuild[0] < insert {
insert = p.plusBuild[0]
}
var x constraint.Expr
switch len(p.goBuild) {
case 0:
// Synthesize //go:build expression from // +build lines.
for _, pos := range p.plusBuild {
y, err := constraint.Parse(p.commentTextAt(pos))
if err != nil {
x = nil
break
}
if x == nil {
x = y
} else {
x = &constraint.AndExpr{X: x, Y: y}
}
}
case 1:
// Parse //go:build expression.
x, _ = constraint.Parse(p.commentTextAt(p.goBuild[0]))
}
var block []byte
if x == nil {
// Don't have a valid //go:build expression to treat as truth.
// Bring all the lines together but leave them alone.
// Note that these are already tabwriter-escaped.
for _, pos := range p.goBuild {
block = append(block, p.lineAt(pos)...)
}
for _, pos := range p.plusBuild {
block = append(block, p.lineAt(pos)...)
}
} else {
block = append(block, tabwriter.Escape)
block = append(block, "//go:build "...)
block = append(block, x.String()...)
block = append(block, tabwriter.Escape, '\n')
if len(p.plusBuild) > 0 {
lines, err := constraint.PlusBuildLines(x)
if err != nil {
lines = []string{"// +build error: " + err.Error()}
}
for _, line := range lines {
block = append(block, tabwriter.Escape)
block = append(block, line...)
block = append(block, tabwriter.Escape, '\n')
}
}
}
block = append(block, '\n')
// Build sorted list of lines to delete from remainder of output.
toDelete := append(p.goBuild, p.plusBuild...)
sort.Ints(toDelete)
// Collect output after insertion point, with lines deleted, into after.
var after []byte
start := insert
for _, end := range toDelete {
if end < start {
continue
}
after = appendLines(after, p.output[start:end])
start = end + len(p.lineAt(end))
}
after = appendLines(after, p.output[start:])
if n := len(after); n >= 2 && isNL(after[n-1]) && isNL(after[n-2]) {
after = after[:n-1]
}
p.output = p.output[:insert]
p.output = append(p.output, block...)
p.output = append(p.output, after...)
}
// appendLines is like append(x, y...)
// but it avoids creating doubled blank lines,
// which would not be gofmt-standard output.
// It assumes that only whole blocks of lines are being appended,
// not line fragments.
func appendLines(x, y []byte) []byte {
if len(y) > 0 && isNL(y[0]) && // y starts in blank line
(len(x) == 0 || len(x) >= 2 && isNL(x[len(x)-1]) && isNL(x[len(x)-2])) { // x is empty or ends in blank line
y = y[1:] // delete y's leading blank line
}
return append(x, y...)
}
func (p *printer) lineAt(start int) []byte {
pos := start
for pos < len(p.output) && !isNL(p.output[pos]) {
pos++
}
if pos < len(p.output) {
pos++
}
return p.output[start:pos]
}
func (p *printer) commentTextAt(start int) string {
if start < len(p.output) && p.output[start] == tabwriter.Escape {
start++
}
pos := start
for pos < len(p.output) && p.output[pos] != tabwriter.Escape && !isNL(p.output[pos]) {
pos++
}
return string(p.output[start:pos])
}
func isNL(b byte) bool {
return b == '\n' || b == '\f'
}

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@ -8,6 +8,7 @@ package printer
import (
"fmt"
"go/ast"
"go/build/constraint"
"go/token"
"io"
"os"
@ -64,6 +65,8 @@ type printer struct {
lastTok token.Token // last token printed (token.ILLEGAL if it's whitespace)
prevOpen token.Token // previous non-brace "open" token (, [, or token.ILLEGAL
wsbuf []whiteSpace // delayed white space
goBuild []int // start index of all //go:build comments in output
plusBuild []int // start index of all // +build comments in output
// Positions
// The out position differs from the pos position when the result
@ -649,6 +652,11 @@ func (p *printer) writeComment(comment *ast.Comment) {
// shortcut common case of //-style comments
if text[1] == '/' {
if constraint.IsGoBuild(text) {
p.goBuild = append(p.goBuild, len(p.output))
} else if constraint.IsPlusBuild(text) {
p.plusBuild = append(p.plusBuild, len(p.output))
}
p.writeString(pos, trimRight(text), true)
return
}
@ -1122,6 +1130,8 @@ func (p *printer) printNode(node interface{}) error {
// get comments ready for use
p.nextComment()
p.print(pmode(0))
// format node
switch n := node.(type) {
case ast.Expr:
@ -1313,6 +1323,10 @@ func (cfg *Config) fprint(output io.Writer, fset *token.FileSet, node interface{
p.impliedSemi = false // EOF acts like a newline
p.flush(token.Position{Offset: infinity, Line: infinity}, token.EOF)
// output is buffered in p.output now.
// fix //go:build and // +build comments if needed.
p.fixGoBuildLines()
// redirect output through a trimmer to eliminate trailing whitespace
// (Input to a tabwriter must be untrimmed since trailing tabs provide
// formatting information. The tabwriter could provide trimming

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@ -88,8 +88,11 @@ func lineAt(text []byte, offs int) []byte {
// diff compares a and b.
func diff(aname, bname string, a, b []byte) error {
var buf bytes.Buffer // holding long error message
if bytes.Equal(a, b) {
return nil
}
var buf bytes.Buffer // holding long error message
// compare lengths
if len(a) != len(b) {
fmt.Fprintf(&buf, "\nlength changed: len(%s) = %d, len(%s) = %d", aname, len(a), bname, len(b))
@ -97,7 +100,7 @@ func diff(aname, bname string, a, b []byte) error {
// compare contents
line := 1
offs := 1
offs := 0
for i := 0; i < len(a) && i < len(b); i++ {
ch := a[i]
if ch != b[i] {
@ -112,10 +115,8 @@ func diff(aname, bname string, a, b []byte) error {
}
}
if buf.Len() > 0 {
return errors.New(buf.String())
}
return nil
fmt.Fprintf(&buf, "\n%s:\n%s\n%s:\n%s", aname, a, bname, b)
return errors.New(buf.String())
}
func runcheck(t *testing.T, source, golden string, mode checkMode) {
@ -207,6 +208,13 @@ var data = []entry{
{"go2numbers.input", "go2numbers.golden", idempotent},
{"go2numbers.input", "go2numbers.norm", normNumber | idempotent},
{"generics.input", "generics.golden", idempotent},
{"gobuild1.input", "gobuild1.golden", idempotent},
{"gobuild2.input", "gobuild2.golden", idempotent},
{"gobuild3.input", "gobuild3.golden", idempotent},
{"gobuild4.input", "gobuild4.golden", idempotent},
{"gobuild5.input", "gobuild5.golden", idempotent},
{"gobuild6.input", "gobuild6.golden", idempotent},
{"gobuild7.input", "gobuild7.golden", idempotent},
}
func TestFiles(t *testing.T) {

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@ -0,0 +1,6 @@
//go:build x
// +build x
package p
func f()

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@ -0,0 +1,7 @@
package p
//go:build x
func f()
// +build y

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@ -0,0 +1,8 @@
//go:build x
// +build x
// other comment
package p
func f()

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@ -0,0 +1,9 @@
// +build y
// other comment
package p
func f()
//go:build x

10
src/go/printer/testdata/gobuild3.golden vendored Normal file
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@ -0,0 +1,10 @@
// other comment
//go:build x
// +build x
// yet another comment
package p
func f()

11
src/go/printer/testdata/gobuild3.input vendored Normal file
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@ -0,0 +1,11 @@
// other comment
// +build y
// yet another comment
package p
//go:build x
func f()

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@ -0,0 +1,6 @@
//go:build (x || y) && z
// +build x y
// +build z
// doc comment
package p

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@ -0,0 +1,5 @@
// doc comment
package p
// +build x y
// +build z

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@ -0,0 +1,4 @@
//go:build !(x || y) && z
// +build !x,!y,z
package p

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@ -0,0 +1,4 @@
//go:build !(x || y) && z
// +build something else
package p

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@ -0,0 +1,5 @@
//go:build !(x || y) && z
// no +build line
package p

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@ -0,0 +1,4 @@
//go:build !(x || y) && z
// no +build line
package p

11
src/go/printer/testdata/gobuild7.golden vendored Normal file
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@ -0,0 +1,11 @@
// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// TODO(rsc): Delete this file once Go 1.17 comes out and we can retire Go 1.15 support.
//go:build !go1.16
// +build !go1.16
// Package buildtag defines an Analyzer that checks build tags.
package buildtag

11
src/go/printer/testdata/gobuild7.input vendored Normal file
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@ -0,0 +1,11 @@
// Copyright 2013 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// TODO(rsc): Delete this file once Go 1.17 comes out and we can retire Go 1.15 support.
//go:build !go1.16
// +build !go1.16
// Package buildtag defines an Analyzer that checks build tags.
package buildtag