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package common
import (
"fmt"
"strings"
"text/scanner"
"github.com/graph-gophers/graphql-go/errors"
)
type syntaxError string
type Lexer struct {
sc *scanner.Scanner
next rune
descComment string
}
type Ident struct {
Name string
Loc errors.Location
}
func NewLexer(s string) *Lexer {
sc := &scanner.Scanner{
Mode: scanner.ScanIdents | scanner.ScanInts | scanner.ScanFloats | scanner.ScanStrings,
}
sc.Init(strings.NewReader(s))
return &Lexer{sc: sc}
}
func (l *Lexer) CatchSyntaxError(f func()) (errRes *errors.QueryError) {
defer func() {
if err := recover(); err != nil {
if err, ok := err.(syntaxError); ok {
errRes = errors.Errorf("syntax error: %s", err)
errRes.Locations = []errors.Location{l.Location()}
return
}
panic(err)
}
}()
f()
return
}
func (l *Lexer) Peek() rune {
return l.next
}
// Consume whitespace and tokens equivalent to whitespace (e.g. commas and comments).
//
// Consumed comment characters will build the description for the next type or field encountered.
// The description is available from `DescComment()`, and will be reset every time `Consume()` is
// executed.
func (l *Lexer) Consume() {
l.descComment = ""
for {
l.next = l.sc.Scan()
if l.next == ',' {
// Similar to white space and line terminators, commas (',') are used to improve the
// legibility of source text and separate lexical tokens but are otherwise syntactically and
// semanitcally insignificant within GraphQL documents.
//
// http://facebook.github.io/graphql/draft/#sec-Insignificant-Commas
continue
}
if l.next == '#' {
// GraphQL source documents may contain single-line comments, starting with the '#' marker.
//
// A comment can contain any Unicode code point except `LineTerminator` so a comment always
// consists of all code points starting with the '#' character up to but not including the
// line terminator.
l.consumeComment()
continue
}
break
}
}
func (l *Lexer) ConsumeIdent() string {
name := l.sc.TokenText()
l.ConsumeToken(scanner.Ident)
return name
}
func (l *Lexer) ConsumeIdentWithLoc() Ident {
loc := l.Location()
name := l.sc.TokenText()
l.ConsumeToken(scanner.Ident)
return Ident{name, loc}
}
func (l *Lexer) ConsumeKeyword(keyword string) {
if l.next != scanner.Ident || l.sc.TokenText() != keyword {
l.SyntaxError(fmt.Sprintf("unexpected %q, expecting %q", l.sc.TokenText(), keyword))
}
l.Consume()
}
func (l *Lexer) ConsumeLiteral() *BasicLit {
lit := &BasicLit{Type: l.next, Text: l.sc.TokenText()}
l.Consume()
return lit
}
func (l *Lexer) ConsumeToken(expected rune) {
if l.next != expected {
l.SyntaxError(fmt.Sprintf("unexpected %q, expecting %s", l.sc.TokenText(), scanner.TokenString(expected)))
}
l.Consume()
}
func (l *Lexer) DescComment() string {
return l.descComment
}
func (l *Lexer) SyntaxError(message string) {
panic(syntaxError(message))
}
func (l *Lexer) Location() errors.Location {
return errors.Location{
Line: l.sc.Line,
Column: l.sc.Column,
}
}
// consumeComment consumes all characters from `#` to the first encountered line terminator.
// The characters are appended to `l.descComment`.
func (l *Lexer) consumeComment() {
if l.next != '#' {
return
}
// TODO: count and trim whitespace so we can dedent any following lines.
if l.sc.Peek() == ' ' {
l.sc.Next()
}
if l.descComment != "" {
// TODO: use a bytes.Buffer or strings.Builder instead of this.
l.descComment += "\n"
}
for {
next := l.sc.Next()
if next == '\r' || next == '\n' || next == scanner.EOF {
break
}
// TODO: use a bytes.Buffer or strings.Build instead of this.
l.descComment += string(next)
}
}
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