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expr_lexer.go
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package actionlint
import (
"fmt"
"strconv"
"strings"
"text/scanner"
)
// TokenKind is kind of token.
type TokenKind int
const (
// TokenKindUnknown is a default value of token as unknown token value.
TokenKindUnknown TokenKind = iota
// TokenKindEnd is a token for end of token sequence. Sequence without this
// token means invalid.
TokenKindEnd
// TokenKindIdent is a token for identifier.
TokenKindIdent
// TokenKindString is a token for string literals.
TokenKindString
// TokenKindInt is a token for integers including hex integers.
TokenKindInt
// TokenKindFloat is a token for float numbers.
TokenKindFloat
// TokenKindLeftParen is a token for '('.
TokenKindLeftParen
// TokenKindRightParen is a token for ')'.
TokenKindRightParen
// TokenKindLeftBracket is a token for '['.
TokenKindLeftBracket
// TokenKindRightBracket is a token for ']'.
TokenKindRightBracket
// TokenKindDot is a token for '.'.
TokenKindDot
// TokenKindNot is a token for '!'.
TokenKindNot
// TokenKindLess is a token for '<'.
TokenKindLess
// TokenKindLessEq is a token for '<='.
TokenKindLessEq
// TokenKindGreater is a token for '>'.
TokenKindGreater
// TokenKindGreaterEq is a token for '>='.
TokenKindGreaterEq
// TokenKindEq is a token for '=='.
TokenKindEq
// TokenKindNotEq is a token for '!='.
TokenKindNotEq
// TokenKindAnd is a token for '&&'.
TokenKindAnd
// TokenKindOr is a token for '||'.
TokenKindOr
// TokenKindStar is a token for '*'.
TokenKindStar
// TokenKindComma is a token for ','.
TokenKindComma
)
func (t TokenKind) String() string {
switch t {
case TokenKindUnknown:
return "UNKNOWN"
case TokenKindEnd:
return "END"
case TokenKindIdent:
return "IDENT"
case TokenKindString:
return "STRING"
case TokenKindInt:
return "INTEGER"
case TokenKindFloat:
return "FLOAT"
case TokenKindLeftParen:
return "("
case TokenKindRightParen:
return ")"
case TokenKindLeftBracket:
return "["
case TokenKindRightBracket:
return "]"
case TokenKindDot:
return "."
case TokenKindNot:
return "!"
case TokenKindLess:
return "<"
case TokenKindLessEq:
return "<="
case TokenKindGreater:
return ">"
case TokenKindGreaterEq:
return ">="
case TokenKindEq:
return "=="
case TokenKindNotEq:
return "!="
case TokenKindAnd:
return "&&"
case TokenKindOr:
return "||"
case TokenKindStar:
return "*"
case TokenKindComma:
return ","
default:
panic("unreachable")
}
}
// Token is a token lexed from expression syntax. For more details, see
// https://docs.github.com/en/actions/learn-github-actions/expressions
type Token struct {
// Kind is kind of the token.
Kind TokenKind
// Value is string representation of the token.
Value string
// Offset is byte offset of token string starting.
Offset int
// Line is line number of start position of the token. Note that this value is 1-based.
Line int
// Column is column number of start position of the token. Note that this value is 1-based.
Column int
}
func (t *Token) String() string {
return fmt.Sprintf("%s:%d:%d:%d", t.Kind.String(), t.Line, t.Column, t.Offset)
}
func isWhitespace(r rune) bool {
return r == ' ' || r == '\n' || r == '\r' || r == '\t'
}
func isAlpha(r rune) bool {
return 'a' <= r && r <= 'z' || 'A' <= r && r <= 'Z'
}
func isNum(r rune) bool {
return '0' <= r && r <= '9'
}
func isHexNum(r rune) bool {
return isNum(r) || 'a' <= r && r <= 'f' || 'A' <= r && r <= 'F'
}
func isAlnum(r rune) bool {
return isAlpha(r) || isNum(r)
}
const expectedPunctChars = "''', '}', '(', ')', '[', ']', '.', '!', '<', '>', '=', '&', '|', '*', ',', ' '"
const expectedDigitChars = "'0'..'9'"
const expectedAlphaChars = "'a'..'z', 'A'..'Z', '_'"
const expectedAllChars = expectedAlphaChars + ", " + expectedDigitChars + ", " + expectedPunctChars
// ExprLexer is a struct to lex expression syntax. To know the syntax, see
// https://docs.github.com/en/actions/learn-github-actions/expressions
type ExprLexer struct {
src string
scan scanner.Scanner
lexErr *ExprError
start scanner.Position
}
// NewExprLexer makes new ExprLexer instance.
func NewExprLexer(src string) *ExprLexer {
l := &ExprLexer{
src: src,
start: scanner.Position{
Offset: 0,
Line: 1,
Column: 1,
},
}
l.scan.Init(strings.NewReader(src))
l.scan.Error = func(_ *scanner.Scanner, m string) {
l.error(fmt.Sprintf("scan error while lexing expression: %s", m))
}
return l
}
func (lex *ExprLexer) error(msg string) {
if lex.lexErr == nil {
p := lex.scan.Pos()
lex.lexErr = &ExprError{
Message: msg,
Offset: p.Offset,
Line: p.Line,
Column: p.Column,
}
}
}
func (lex *ExprLexer) token(kind TokenKind) *Token {
p := lex.scan.Pos()
s := lex.start
t := &Token{
Kind: kind,
Value: lex.src[s.Offset:p.Offset],
Offset: s.Offset,
Line: s.Line,
Column: s.Column,
}
lex.start = p
return t
}
func (lex *ExprLexer) eof() *Token {
return &Token{
Kind: TokenKindEnd,
Value: "",
Offset: lex.start.Offset,
Line: lex.start.Line,
Column: lex.start.Column,
}
}
func (lex *ExprLexer) eat() rune {
lex.scan.Next()
return lex.scan.Peek() // unlike lex.scan.Next(), return top char *after* eating
}
func (lex *ExprLexer) skipWhite() {
for {
if r := lex.scan.Peek(); !isWhitespace(r) {
return
}
lex.scan.Next()
lex.start = lex.scan.Pos()
}
}
func (lex *ExprLexer) unexpected(r rune, where string, expected string) *Token {
var what string
if r == scanner.EOF {
what = "EOF"
} else {
what = "character " + strconv.QuoteRune(r)
}
var note string
if r == '"' {
note = ". do you mean string literals? only single quotes are available for string delimiter"
}
msg := fmt.Sprintf(
"got unexpected %s while lexing %s, expecting %s%s",
what,
where,
expected,
note,
)
lex.error(msg)
return lex.eof()
}
func (lex *ExprLexer) unexpectedEOF() *Token {
lex.error("unexpected EOF while lexing expression")
return lex.eof()
}
func (lex *ExprLexer) lexIdent() *Token {
for {
// a-z, A-Z, 0-9, - or _
// https://docs.github.com/en/actions/learn-github-actions/contexts
if r := lex.eat(); !isAlnum(r) && r != '_' && r != '-' {
return lex.token(TokenKindIdent)
}
}
}
func (lex *ExprLexer) lexNum() *Token {
// The official document says number literals are 'Any number format supported by JSON' but actually
// hex numbers starting with 0x are supported.
r := lex.scan.Peek() // precond: r is digit or '-'
if r == '-' {
r = lex.eat()
}
if r == '0' {
r = lex.eat()
if r == 'x' {
lex.scan.Next()
return lex.lexHexInt()
}
} else {
// r is 1..9
if !isNum(r) {
return lex.unexpected(r, "integer part of number", expectedDigitChars)
}
for {
r = lex.eat()
if !isNum(r) {
break
}
}
}
k := TokenKindInt
if r == '.' {
r = lex.eat() // eat '.'
if !isNum(r) {
return lex.unexpected(r, "fraction part of float number", expectedDigitChars)
}
for {
r = lex.eat()
if !isNum(r) {
break
}
}
k = TokenKindFloat
}
if r == 'e' || r == 'E' {
r = lex.eat() // eat 'e' or 'E'
if r == '-' {
r = lex.eat()
}
if r == '0' {
r = lex.eat() // eat the '0'
} else {
// r is 1..9
if !isNum(r) {
return lex.unexpected(r, "exponent part of float number", expectedDigitChars)
}
for {
r = lex.eat()
if !isNum(r) {
break
}
}
}
k = TokenKindFloat
}
if isAlnum(r) {
s := lex.src[lex.start.Offset:lex.scan.Pos().Offset]
return lex.unexpected(r, "character following number "+s, expectedPunctChars)
}
return lex.token(k)
}
func (lex *ExprLexer) lexHexInt() *Token {
r := lex.scan.Peek()
if r == '0' {
r = lex.eat()
} else {
if !isHexNum(r) {
e := expectedDigitChars + ", 'a'..'f', 'A'..'F'"
return lex.unexpected(r, "hex integer", e)
}
for {
r = lex.eat()
if !isHexNum(r) {<
67F4
/div>
break
}
}
}
// Note: GitHub Actions does not support exponent part like 0x1f2p-a8
if isAlnum(r) {
s := lex.src[lex.start.Offset:lex.scan.Pos().Offset]
return lex.unexpected(r, "character following hex integer "+s, expectedPunctChars)
}
return lex.token(TokenKindInt)
}
func (lex *ExprLexer) lexString() *Token {
// precond: current char is '
for {
switch lex.eat() {
case '\'':
if lex.eat() != '\'' { // when not escaped single quote ''
return lex.token(TokenKindString)
}
case scanner.EOF:
return lex.unexpected(scanner.EOF, "end of string literal", "'''")
}
}
}
func (lex *ExprLexer) lexEnd() *Token {
r := lex.eat() // eat the first '}'
if r != '}' {
return lex.unexpected(r, "end marker }}", "'}'")
}
lex.scan.Next()
// }} is an end marker of interpolation
return lex.token(TokenKindEnd)
}
func (lex *ExprLexer) lexLess() *Token {
k := TokenKindLess
if lex.eat() == '=' { // eat '<'
k = TokenKindLessEq
lex.scan.Next()
}
return lex.token(k)
}
func (lex *ExprLexer) lexGreater() *Token {
k := TokenKindGreater
if lex.eat() == '=' { // eat '>'
k = TokenKindGreaterEq
lex.scan.Next()
}
return lex.token(k)
}
func (lex *ExprLexer) lexEq() *Token {
if r := lex.eat(); r != '=' { // eat '='
return lex.unexpected(r, "== operator", "'='")
}
lex.scan.Next()
return lex.token(TokenKindEq)
}
func (lex *ExprLexer) lexBang() *Token {
k := TokenKindNot
if lex.eat() == '=' { // eat '!'
lex.scan.Next() // eat '='
k = TokenKindNotEq
}
return lex.token(k)
}
func (lex *ExprLexer) lexAnd() *Token {
if r := lex.eat(); r != '&' { // eat the first '&'
return lex.unexpected(r, "&& operator", "'&'")
}
lex.scan.Next() // eat the second '&'
return lex.token(TokenKindAnd)
}
func (lex *ExprLexer) lexOr() *Token {
if r := lex.eat(); r != '|' { // eat the first '|'
return lex.unexpected(r, "|| operator", "'|'")
}
lex.scan.Next() // eat the second '|'
return lex.token(TokenKindOr)
}
func (lex *ExprLexer) lexChar(k TokenKind) *Token {
lex.scan.Next()
return lex.token(k)
}
// Next lexes next token to lex input incrementally. Lexer must be initialized with Init() method
// before the first call of this method. This method is stateful. Lexer advances offset by lexing
// token. To get the offset, use Offset() method.
func (lex *ExprLexer) Next() *Token {
lex.skipWhite()
r := lex.scan.Peek()
if r == scanner.EOF {
return lex.unexpectedEOF()
}
// Ident starts with a-z or A-Z or _
// https://docs.github.com/en/actions/learn-github-actions/contexts
if isAlpha(r) || r == '_' {
return lex.lexIdent()
}
if isNum(r) || r == '-' {
return lex.lexNum()
}
switch r {
case '\'':
return lex.lexString()
case '}':
return lex.lexEnd()
case '!':
return lex.lexBang()
case '<':
return lex.lexLess()
case '>':
return lex.lexGreater()
case '=':
return lex.lexEq()
case '&':
return lex.lexAnd()
case '|':
return lex.lexOr()
case '(':
return lex.lexChar(TokenKindLeftParen)
case ')':
return lex.lexChar(TokenKindRightParen)
case '[':
return lex.lexChar(TokenKindLeftBracket)
case ']':
return lex.lexChar(TokenKindRightBracket)
case '.':
return lex.lexChar(TokenKindDot)
case '*':
return lex.lexChar(TokenKindStar)
case ',':
return lex.lexChar(TokenKindComma)
default:
return lex.unexpected(r, "expression", expectedAllChars)
}
}
// Offset returns the current offset (scanning position).
func (lex *ExprLexer) Offset() int {
return lex.scan.Pos().Offset
}
// Err returns an error while lexing. When multiple errors occur, the first one is returned.
func (lex *ExprLexer) Err() *ExprError {
return lex.lexErr
}
// LexExpression lexes the given string as expression syntax. The parameter must contain '}}' which
// represents end of expression. Otherwise this function will report an error that it encountered
// unexpected EOF.
func LexExpression(src string) ([]*Token, int, *ExprError) {
l := NewExprLexer(src)
ts := []*Token{}
for {
t := l.Next()
if l.lexErr != nil {
return nil, l.scan.Pos().Offset, l.lexErr
}
ts = append(ts, t)
if t.Kind == TokenKindEnd {
return ts, l.scan.Pos().Offset, nil
}
}
}