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read.go
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// Copyright 2018 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 modfile
import (
"bytes"
"errors"
"fmt"
"os"
"strconv"
"strings"
"unicode"
"unicode/utf8"
"golang.org/x/mod/modfile"
)
// An input represents a single input file being parsed.
type input struct {
// Lexing state.
filename string // name of input file, for errors
complete []byte // entire input
remaining []byte // remaining input
tokenStart []byte // token being scanned to end of input
token token // next token to be returned by lex, peek
pos modfile.Position // current input position
comments []modfile.Comment // accumulated comments
// Parser state.
file *modfile.FileSyntax // returned top-level syntax tree
parseErrors modfile.ErrorList // errors encountered during parsing
// Comment assignment state.
pre []modfile.Expr // all expressions, in preorder traversal
post []modfile.Expr // all expressions, in postorder traversal
}
func newInput(filename string, data []byte) *input {
return &input{
filename: filename,
complete: data,
remaining: data,
pos: modfile.Position{Line: 1, LineRune: 1, Byte: 0},
}
}
// parse parses the input file.
func parse(file string, data []byte) (f *modfile.FileSyntax, err error) {
// The parser panics for both routine errors like syntax errors
// and for programmer bugs like array index errors.
// Turn both into error returns. Catching bug panics is
// especially important when processing many files.
in := newInput(file, data)
defer func() {
if e := recover(); e != nil && e != &in.parseErrors {
in.parseErrors = append(in.parseErrors, modfile.Error{
Filename: in.filename,
Pos: in.pos,
Err: fmt.Errorf("internal error: %v", e),
})
}
if err == nil && len(in.parseErrors) > 0 {
err = in.parseErrors
}
}()
// Prime the lexer by reading in the first token. It will be available
// in the next peek() or lex() call.
in.readToken()
// Invoke the parser.
in.parseFile()
if len(in.parseErrors) > 0 {
return nil, in.parseErrors
}
in.file.Name = in.filename
// Assign comments to nearby syntax.
in.assignComments()
return in.file, nil
}
// Error is called to report an error.
// Error does not return: it panics.
func (in *input) Error(s string) {
in.parseErrors = append(in.parseErrors, modfile.Error{
Filename: in.filename,
Pos: in.pos,
Err: errors.New(s),
})
panic(&in.parseErrors)
}
// eof reports whether the input has reached end of file.
func (in *input) eof() bool {
return len(in.remaining) == 0
}
// peekRune returns the next rune in the input without consuming it.
func (in *input) peekRune() int {
if len(in.remaining) == 0 {
return 0
}
r, _ := utf8.DecodeRune(in.remaining)
return int(r)
}
// peekPrefix reports whether the remaining input begins with the given prefix.
func (in *input) peekPrefix(prefix string) bool {
// This is like bytes.HasPrefix(in.remaining, []byte(prefix))
// but without the allocation of the []byte copy of prefix.
for i := 0; i < len(prefix); i++ {
if i >= len(in.remaining) || in.remaining[i] != prefix[i] {
return false
}
}
return true
}
// readRune consumes and returns the next rune in the input.
func (in *input) readRune() int {
if len(in.remaining) == 0 {
in.Error("internal lexer error: readRune at EOF")
}
r, size := utf8.DecodeRune(in.remaining)
in.remaining = in.remaining[size:]
if r == '\n' {
in.pos.Line++
in.pos.LineRune = 1
} else {
in.pos.LineRune++
}
in.pos.Byte += size
return int(r)
}
type token struct {
kind tokenKind
pos modfile.Position
endPos modfile.Position
text string
}
type tokenKind int
const (
_EOF tokenKind = -(iota + 1)
_EOLCOMMENT
_IDENT
_STRING
_COMMENT
// newlines and punctuation tokens are allowed as ASCII codes.
)
func (k tokenKind) isComment() bool {
return k == _COMMENT || k == _EOLCOMMENT
}
// isEOL returns whether a token terminates a line.
func (k tokenKind) isEOL() bool {
return k == _EOF || k == _EOLCOMMENT || k == '\n'
}
// startToken marks the beginning of the next input token.
// It must be followed by a call to endToken, once the token's text has
// been consumed using readRune.
func (in *input) startToken() {
in.tokenStart = in.remaining
in.token.text = ""
in.token.pos = in.pos
}
// endToken marks the end of an input token.
// It records the actual token string in tok.text.
// A single trailing newline (LF or CRLF) will be removed from comment tokens.
func (in *input) endToken(kind tokenKind) {
in.token.kind = kind
text := string(in.tokenStart[:len(in.tokenStart)-len(in.remaining)])
if kind.isComment() {
if strings.HasSuffix(text, "\r\n") {
text = text[:len(text)-2]
} else {
text = strings.TrimSuffix(text, "\n")
}
}
in.token.text = text
in.token.endPos = in.pos
}
// peek returns the kind of the the next token returned by lex.
func (in *input) peek() tokenKind {
return in.token.kind
}
// lex is called from the parser to obtain the next input token.
func (in *input) lex() token {
tok := in.token
in.readToken()
return tok
}
// readToken lexes the next token from the text and stores it in in.token.
func (in *input) readToken() {
// Skip past spaces, stopping at non-space or EOF.
for !in.eof() {
c := in.peekRune()
if c == ' ' || c == '\t' || c == '\r' {
in.readRune()
continue
}
// Comment runs to end of line.
if in.peekPrefix("//") {
in.startToken()
// Is this comment the only thing on its line?
// Find the last \n before this // and see if it's all
// spaces from there to here.
i := bytes.LastIndex(in.complete[:in.pos.Byte], []byte("\n"))
suffix := len(bytes.TrimSpace(in.complete[i+1:in.pos.Byte])) > 0
in.readRune()
in.readRune()
// Consume comment.
for len(in.remaining) > 0 && in.readRune() != '\n' {
}
// If we are at top level (not in a statement), hand the comment to
// the parser as a _COMMENT token. The grammar is written
// to handle top-level comments itself.
if !suffix {
in.endToken(_COMMENT)
return
}
// Otherwise, save comment for later attachment to syntax tree.
in.endToken(_EOLCOMMENT)
in.comments = append(in.comments, modfile.Comment{in.token.pos, in.token.text, suffix})
return
}
if in.peekPrefix("/*") {
in.Error("mod files must use // comments (not /* */ comments)")
}
// Found non-space non-comment.
break
}
// Found the beginning of the next token.
in.startToken()
// End of file.
if in.eof() {
in.endToken(_EOF)
return
}
// Punctuation tokens.
switch c := in.peekRune(); c {
case '\n', '(', ')', '[', ']', '{', '}', ',':
in.readRune()
in.endToken(tokenKind(c))
return
case '"', '`': // quoted string
quote := c
in.readRune()
for {
if in.eof() {
in.pos = in.token.pos
in.Error("unexpected EOF in string")
}
if in.peekRune() == '\n' {
in.Error("unexpected newline in string")
}
c := in.readRune()
if c == quote {
break
}
if c == '\\' && quote != '`' {
if in.eof() {
in.pos = in.token.pos
in.Error("unexpected EOF in string")
}
in.readRune()
}
}
in.endToken(_STRING)
return
}
// Checked all punctuation. Must be identifier token.
if c := in.peekRune(); !isIdent(c) {
in.Error(fmt.Sprintf("unexpected input character %#q", c))
}
// Scan over identifier.
for isIdent(in.peekRune()) {
if in.peekPrefix("//") {
break
}
if in.peekPrefix("/*") {
in.Error("mod files must use // comments (not /* */ comments)")
}
in.readRune()
}
in.endToken(_IDENT)
}
// isIdent reports whether c is an identifier rune.
// We treat most printable runes as identifier runes, except for a handful of
// ASCII punctuation characters.
func isIdent(c int) bool {
switch r := rune(c); r {
case ' ', '(', ')', '[', ']', '{', '}', ',':
return false
default:
return !unicode.IsSpace(r) && unicode.IsPrint(r)
}
}
// Comment assignment.
// We build two lists of all subexpressions, preorder and postorder.
// The preorder list is ordered by start location, with outer expressions first.
// The postorder list is ordered by end location, with outer expressions last.
// We use the preorder list to assign each whole-line comment to the syntax
// immediately following it, and we use the postorder list to assign each
// end-of-line comment to the syntax immediately preceding it.
// order walks the expression adding it and its subexpressions to the
// preorder and postorder lists.
func (in *input) order(x modfile.Expr) {
if x != nil {
in.pre = append(in.pre, x)
}
switch x := x.(type) {
default:
panic(fmt.Errorf("order: unexpected type %T", x))
case nil:
// nothing
case *modfile.LParen, *modfile.RParen:
// nothing
case *modfile.CommentBlock:
// nothing
case *modfile.Line:
// nothing
case *modfile.FileSyntax:
for _, stmt := range x.Stmt {
in.order(stmt)
}
case *modfile.LineBlock:
in.order(&x.LParen)
for _, l := range x.Line {
in.order(l)
}
in.order(&x.RParen)
}
if x != nil {
in.post = append(in.post, x)
}
}
// assignComments attaches comments to nearby syntax.
func (in *input) assignComments() {
const debug = false
// Generate preorder and postorder lists.
in.order(in.file)
// Split into whole-line comments and suffix comments.
var line, suffix []modfile.Comment
for _, com := range in.comments {
if com.Suffix {
suffix = append(suffix, com)
} else {
line = append(line, com)
}
}
if debug {
for _, c := range line {
fmt.Fprintf(os.Stderr, "LINE %q :%d:%d #%d\n", c.Token, c.Start.Line, c.Start.LineRune, c.Start.Byte)
}
}
// Assign line comments to syntax immediately following.
for _, x := range in.pre {
start, _ := x.Span()
if debug {
fmt.Fprintf(os.Stderr, "pre %T :%d:%d #%d\n", x, start.Line, start.LineRune, start.Byte)
}
xcom := x.Comment()
for len(line) > 0 && start.Byte >= line[0].Start.Byte {
if debug {
fmt.Fprintf(os.Stderr, "ASSIGN LINE %q #%d\n", line[0].Token, line[0].Start.Byte)
}
xcom.Before = append(xcom.Before, line[0])
line = line[1:]
}
}
// Remaining line comments go at end of file.
in.file.After = append(in.file.After, line...)
if debug {
for _, c := range suffix {
fmt.Fprintf(os.Stderr, "SUFFIX %q :%d:%d #%d\n", c.Token, c.Start.Line, c.Start.LineRune, c.Start.Byte)
}
}
// Assign suffix comments to syntax immediately before.
for i := len(in.post) - 1; i >= 0; i-- {
x := in.post[i]
start, end := x.Span()
if debug {
fmt.Fprintf(os.Stderr, "post %T :%d:%d #%d :%d:%d #%d\n", x, start.Line, start.LineRune, start.Byte, end.Line, end.LineRune, end.Byte)
}
// Do not assign suffix comments to end of line block or whole file.
// Instead assign them to the last element inside.
switch x.(type) {
case *modfile.FileSyntax:
continue
}
// Do not assign suffix comments to something that starts
// on an earlier line, so that in
//
// x ( y
// z ) // comment
//
// we assign the comment to z and not to x ( ... ).
if start.Line != end.Line {
continue
}
xcom := x.Comment()
for len(suffix) > 0 && end.Byte <= suffix[len(suffix)-1].Start.Byte {
if debug {
fmt.Fprintf(os.Stderr, "ASSIGN SUFFIX %q #%d\n", suffix[len(suffix)-1].Token, suffix[len(suffix)-1].Start.Byte)
}
xcom.Suffix = append(xcom.Suffix, suffix[len(suffix)-1])
suffix = suffix[:len(suffix)-1]
}
}
// We assigned suffix comments in reverse.
// If multiple suffix comments were appended to the same
// expression node, they are now in reverse. Fix that.
for _, x := range in.post {
reverseComments(x.Comment().Suffix)
}
// Remaining suffix comments go at beginning of file.
in.file.Before = append(in.file.Before, suffix...)
}
// reverseComments reverses the []Comment list.
func reverseComments(list []modfile.Comment) {
for i, j := 0, len(list)-1; i < j; i, j = i+1, j-1 {
list[i], list[j] = list[j], list[i]
}
}
func (in *input) parseFile() {
in.file = new(modfile.FileSyntax)
var cb *modfile.CommentBlock
for {
switch in.peek() {
case '\n':
in.lex()
if cb != nil {
in.file.Stmt = append(in.file.Stmt, cb)
cb = nil
}
case _COMMENT:
tok := in.lex()
if cb == nil {
cb = &modfile.CommentBlock{Start: tok.pos}
}
com := cb.Comment()
com.Before = append(com.Before, modfile.Comment{Start: tok.pos, Token: tok.text})
case _EOF:
if cb != nil {
in.file.Stmt = append(in.file.Stmt, cb)
}
return
default:
in.parseStmt()
if cb != nil {
in.file.Stmt[len(in.file.Stmt)-1].Comment().Before = cb.Before
cb = nil
}
}
}
}
func (in *input) parseStmt() {
tok := in.lex()
start := tok.pos
end := tok.endPos
tokens := []string{tok.text}
for {
tok := in.lex()
switch {
case tok.kind.isEOL():
in.file.Stmt = append(in.file.Stmt, &modfile.Line{
Start: start,
Token: tokens,
End: end,
})
return
case tok.kind == '(':
if next := in.peek(); next.isEOL() {
// Start of block: no more tokens on this line.
in.file.Stmt = append(in.file.Stmt, in.parseLineBlock(start, tokens, tok))
return
} else if next == ')' {
rparen := in.lex()
if in.peek().isEOL() {
// Empty block.
in.lex()
in.file.Stmt = append(in.file.Stmt, &modfile.LineBlock{
Start: start,
Token: tokens,
LParen: modfile.LParen{Pos: tok.pos},
RParen: modfile.RParen{Pos: rparen.pos},
})
return
}
// '( )' in the middle of the line, not a block.
tokens = append(tokens, tok.text, rparen.text)
} else {
// '(' in the middle of the line, not a block.
tokens = append(tokens, tok.text)
}
default:
tokens = append(tokens, tok.text)
end = tok.endPos
}
}
}
func (in *input) parseLineBlock(start modfile.Position, token []string, lparen token) *modfile.LineBlock {
x := &modfile.LineBlock{
Start: start,
Token: token,
LParen: modfile.LParen{Pos: lparen.pos},
}
var comments []modfile.Comment
for {
switch in.peek() {
case _EOLCOMMENT:
// Suffix comment, will be attached later by assignComments.
in.lex()
case '\n':
// Blank line. Add an empty comment to preserve it.
in.lex()
if len(comments) == 0 && len(x.Line) > 0 || len(comments) > 0 && comments[len(comments)-1].Token != "" {
comments = append(comments, modfile.Comment{})
}
case _COMMENT:
tok := in.lex()
comments = append(comments, modfile.Comment{Start: tok.pos, Token: tok.text})
case _EOF:
in.Error(fmt.Sprintf("syntax error (unterminated block started at %s:%d:%d)", in.filename, x.Start.Line, x.Start.LineRune))
case ')':
rparen := in.lex()
x.RParen.Before = comments
x.RParen.Pos = rparen.pos
if !in.peek().isEOL() {
in.Error("syntax error (expected newline after closing paren)")
}
in.lex()
return x
default:
l := in.parseLine()
x.Line = append(x.Line, l)
l.Comment().Before = comments
comments = nil
}
}
}
func (in *input) parseLine() *modfile.Line {
tok := in.lex()
if tok.kind.isEOL() {
in.Error("internal parse error: parseLine at end of line")
}
start := tok.pos
end := tok.endPos
tokens := []string{tok.text}
for {
tok := in.lex()
if tok.kind.isEOL() {
return &modfile.Line{
Start: start,
Token: tokens,
End: end,
InBlock: true,
}
}
tokens = append(tokens, tok.text)
end = tok.endPos
}
}
var (
slashSlash = []byte("//")
moduleStr = []byte("module")
)
// ModulePath returns the module path from the gomod file text.
// If it cannot find a module path, it returns an empty string.
// It is tolerant of unrelated problems in the go.mod file.
func ModulePath(mod []byte) string {
for len(mod) > 0 {
line := mod
mod = nil
if i := bytes.IndexByte(line, '\n'); i >= 0 {
line, mod = line[:i], line[i+1:]
}
if i := bytes.Index(line, slashSlash); i >= 0 {
line = line[:i]
}
line = bytes.TrimSpace(line)
if !bytes.HasPrefix(line, moduleStr) {
continue
}
line = line[len(moduleStr):]
n := len(line)
line = bytes.TrimSpace(line)
if len(line) == n || len(line) == 0 {
continue
}
if line[0] == '"' || line[0] == '`' {
p, err := strconv.Unquote(string(line))
if err != nil {
return "" // malformed quoted string or multiline module path
}
return p
}
return string(line)
}
return "" // missing module path
}