165 lines
3.3 KiB
Go
165 lines
3.3 KiB
Go
// Copyright 2018 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package modfile implements parsing and formatting for
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// go.mod files.
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package modfile
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import (
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"bytes"
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"fmt"
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"strings"
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)
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func Format(f *FileSyntax) []byte {
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pr := &printer{}
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pr.file(f)
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return pr.Bytes()
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}
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// A printer collects the state during printing of a file or expression.
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type printer struct {
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bytes.Buffer // output buffer
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comment []Comment // pending end-of-line comments
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margin int // left margin (indent), a number of tabs
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}
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// printf prints to the buffer.
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func (p *printer) printf(format string, args ...interface{}) {
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fmt.Fprintf(p, format, args...)
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}
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// indent returns the position on the current line, in bytes, 0-indexed.
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func (p *printer) indent() int {
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b := p.Bytes()
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n := 0
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for n < len(b) && b[len(b)-1-n] != '\n' {
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n++
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}
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return n
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}
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// newline ends the current line, flushing end-of-line comments.
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func (p *printer) newline() {
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if len(p.comment) > 0 {
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p.printf(" ")
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for i, com := range p.comment {
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if i > 0 {
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p.trim()
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p.printf("\n")
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for i := 0; i < p.margin; i++ {
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p.printf("\t")
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}
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}
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p.printf("%s", strings.TrimSpace(com.Token))
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}
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p.comment = p.comment[:0]
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}
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p.trim()
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p.printf("\n")
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for i := 0; i < p.margin; i++ {
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p.printf("\t")
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}
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}
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// trim removes trailing spaces and tabs from the current line.
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func (p *printer) trim() {
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// Remove trailing spaces and tabs from line we're about to end.
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b := p.Bytes()
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n := len(b)
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for n > 0 && (b[n-1] == '\t' || b[n-1] == ' ') {
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n--
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}
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p.Truncate(n)
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}
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// file formats the given file into the print buffer.
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func (p *printer) file(f *FileSyntax) {
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for _, com := range f.Before {
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p.printf("%s", strings.TrimSpace(com.Token))
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p.newline()
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}
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for i, stmt := range f.Stmt {
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switch x := stmt.(type) {
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case *CommentBlock:
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// comments already handled
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p.expr(x)
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default:
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p.expr(x)
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p.newline()
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}
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for _, com := range stmt.Comment().After {
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p.printf("%s", strings.TrimSpace(com.Token))
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p.newline()
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}
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if i+1 < len(f.Stmt) {
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p.newline()
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}
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}
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}
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func (p *printer) expr(x Expr) {
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// Emit line-comments preceding this expression.
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if before := x.Comment().Before; len(before) > 0 {
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// Want to print a line comment.
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// Line comments must be at the current margin.
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p.trim()
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if p.indent() > 0 {
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// There's other text on the line. Start a new line.
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p.printf("\n")
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}
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// Re-indent to margin.
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for i := 0; i < p.margin; i++ {
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p.printf("\t")
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}
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for _, com := range before {
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p.printf("%s", strings.TrimSpace(com.Token))
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p.newline()
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}
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}
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switch x := x.(type) {
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default:
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panic(fmt.Errorf("printer: unexpected type %T", x))
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case *CommentBlock:
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// done
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case *LParen:
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p.printf("(")
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case *RParen:
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p.printf(")")
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case *Line:
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sep := ""
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for _, tok := range x.Token {
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p.printf("%s%s", sep, tok)
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sep = " "
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}
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case *LineBlock:
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for _, tok := range x.Token {
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p.printf("%s ", tok)
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}
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p.expr(&x.LParen)
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p.margin++
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for _, l := range x.Line {
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p.newline()
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p.expr(l)
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}
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p.margin--
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p.newline()
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p.expr(&x.RParen)
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}
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// Queue end-of-line comments for printing when we
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// reach the end of the line.
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p.comment = append(p.comment, x.Comment().Suffix...)
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}
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