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// Copyright 2015 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(gri): This file and the file src/cmd/gofmt/internal.go are
// the same (but for this comment and the package name). Do not modify
// one without the other. Determine if we can factor out functionality
// in a public API. See also #11844 for context.
package format
import (
"bytes"
"go/ast"
"go/parser"
"go/printer"
"go/token"
"strings"
)
// parse parses src, which was read from the named file,
// as a Go source file, declaration, or statement list.
func parse(fset *token.FileSet, filename string, src []byte, fragmentOk bool) (
file *ast.File,
sourceAdj func(src []byte, indent int) []byte,
indentAdj int,
err error,
) {
// Try as whole source file.
file, err = parser.ParseFile(fset, filename, src, parserMode)
// If there's no error, return. If the error is that the source file didn't begin with a
// package line and source fragments are ok, fall through to
// try as a source fragment. Stop and return on any other error.
if err == nil || !fragmentOk || !strings.Contains(err.Error(), "expected 'package'") {
return
}
// If this is a declaration list, make it a source file
// by inserting a package clause.
// Insert using a ';', not a newline, so that the line numbers
// in psrc match the ones in src.
psrc := append([]byte("package p;"), src...)
file, err = parser.ParseFile(fset, filename, psrc, parserMode)
if err == nil {
sourceAdj = func(src []byte, indent int) []byte {
// Remove the package clause.
// Gofmt has turned the ';' into a '\n'.
src = src[indent+len("package p\n"):]
return bytes.TrimSpace(src)
}
return
}
// If the error is that the source file didn't begin with a
// declaration, fall through to try as a statement list.
// Stop and return on any other error.
if !strings.Contains(err.Error(), "expected declaration") {
return
}
// If this is a statement list, make it a source file
// by inserting a package clause and turning the list
// into a function body. This handles expressions too.
// Insert using a ';', not a newline, so that the line numbers
// in fsrc match the ones in src. Add an extra '\n' before the '}'
// to make sure comments are flushed before the '}'.
fsrc := append(append([]byte("package p; func _() {"), src...), '\n', '\n', '}')
file, err = parser.ParseFile(fset, filename, fsrc, parserMode)
if err == nil {
sourceAdj = func(src []byte, indent int) []byte {
// Cap adjusted indent to zero.
if indent < 0 {
indent = 0
}
// Remove the wrapping.
// Gofmt has turned the "; " into a "\n\n".
// There will be two non-blank lines with indent, hence 2*indent.
src = src[2*indent+len("package p\n\nfunc _() {"):]
// Remove only the "}\n" suffix: remaining whitespaces will be trimmed anyway
src = src[:len(src)-len("}\n")]
return bytes.TrimSpace(src)
}
// Gofmt has also indented the function body one level.
// Adjust that with indentAdj.
indentAdj = -1
}
// Succeeded, or out of options.
return
}
// format formats the given package file originally obtained from src
// and adjusts the result based on the original source via sourceAdj
// and indentAdj.
func format(
fset *token.FileSet,
file *ast.File,
sourceAdj func(src []byte, indent int) []byte,
indentAdj int,
src []byte,
cfg printer.Config,
) ([]byte, error) {
if sourceAdj == nil {
// Complete source file.
var buf bytes.Buffer
err := cfg.Fprint(&buf, fset, file)
if err != nil {
return nil, err
}
return buf.Bytes(), nil
}
// Partial source file.
// Determine and prepend leading space.
i, j := 0, 0
for j < len(src) && isSpace(src[j]) {
if src[j] == '\n' {
i = j + 1 // byte offset of last line in leading space
}
j++
}
var res []byte
res = append(res, src[:i]...)
// Determine and prepend indentation of first code line.
// Spaces are ignored unless there are no tabs,
// in which case spaces count as one tab.
indent := 0
hasSpace := false
for _, b := range src[i:j] {
switch b {
case ' ':
hasSpace = true
case '\t':
indent++
}
}
if indent == 0 && hasSpace {
indent = 1
}
for i := 0; i < indent; i++ {
res = append(res, '\t')
}
// Format the source.
// Write it without any leading and trailing space.
cfg.Indent = indent + indentAdj
var buf bytes.Buffer
err := cfg.Fprint(&buf, fset, file)
if err != nil {
return nil, err
}
out := sourceAdj(buf.Bytes(), cfg.Indent)
// If the adjusted output is empty, the source
// was empty but (possibly) for white space.
// The result is the incoming source.
if len(out) == 0 {
return src, nil
}
// Otherwise, append output to leading space.
res = append(res, out...)
// Determine and append trailing space.
i = len(src)
for i > 0 && isSpace(src[i-1]) {
i--
}
return append(res, src[i:]...), nil
}
// isSpace reports whether the byte is a space character.
// isSpace defines a space as being among the following bytes: ' ', '\t', '\n' and '\r'.
func isSpace(b byte) bool {
return b == ' ' || b == '\t' || b == '\n' || b == '\r'
}
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