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// Copyright 2019 CUE Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package ast
import (
"strconv"
"strings"
"unicode"
"unicode/utf8"
"cuelang.org/go/cue/errors"
"cuelang.org/go/cue/token"
)
func isLetter(ch rune) bool {
return 'a' <= ch && ch <= 'z' || 'A' <= ch && ch <= 'Z' || ch >= utf8.RuneSelf && unicode.IsLetter(ch)
}
func isDigit(ch rune) bool {
// TODO(mpvl): Is this correct?
return '0' <= ch && ch <= '9' || ch >= utf8.RuneSelf && unicode.IsDigit(ch)
}
// IsValidIdent reports whether str is a valid identifier.
// Note that the underscore "_" string is considered valid, for top.
func IsValidIdent(ident string) bool {
if ident == "" {
return false
}
consumed := false
if strings.HasPrefix(ident, "_") {
ident = ident[1:]
consumed = true
if len(ident) == 0 {
return true
}
}
if strings.HasPrefix(ident, "#") {
ident = ident[1:]
// Note: _#0 is not allowed by the spec, although _0 is.
// TODO: set consumed to true here to allow #0.
consumed = false
}
if !consumed {
if r, _ := utf8.DecodeRuneInString(ident); isDigit(r) {
return false
}
}
for _, r := range ident {
if isLetter(r) || isDigit(r) || r == '_' || r == '$' {
continue
}
return false
}
return true
}
// LabelName reports the name of a label, whether it is an identifier
// (it binds a value to a scope), and whether it is valid.
// Keywords that are allowed in label positions are interpreted accordingly.
//
// Examples:
//
// Label Result
// foo "foo" true nil
// true "true" true nil
// "foo" "foo" false nil
// "x-y" "x-y" false nil
// "foo "" false invalid string
// "\(x)" "" false errors.Is(err, ErrIsExpression)
// X=foo "foo" true nil
func LabelName(l Label) (name string, isIdent bool, err error) {
if a, ok := l.(*Alias); ok {
l, _ = a.Expr.(Label)
}
switch n := l.(type) {
case *ListLit:
// An expression, but not one that can evaluated.
return "", false, errors.Newf(l.Pos(),
"cannot reference fields with square brackets labels outside the field value")
case *Ident:
name = n.Name
if !IsValidIdent(name) {
return "", false, errors.Newf(l.Pos(), "invalid identifier")
}
return name, true, err
case *BasicLit:
switch n.Kind {
case token.STRING:
// Use strconv to only allow double-quoted, single-line strings.
name, err = strconv.Unquote(n.Value)
if err != nil {
err = errors.Newf(l.Pos(), "invalid")
}
case token.NULL, token.TRUE, token.FALSE:
name = n.Value
isIdent = true
default:
// TODO: allow numbers to be fields
// This includes interpolation and template labels.
return "", false, errors.Wrapf(ErrIsExpression, l.Pos(),
"cannot use numbers as fields")
}
return name, isIdent, err
default:
// This includes interpolation and template labels.
return "", false, errors.Wrapf(ErrIsExpression, l.Pos(),
"label is an expression")
}
}
// ErrIsExpression reports whether a label is an expression.
// This error is never returned directly. Use [errors.Is].
var ErrIsExpression = errors.New("not a concrete label")
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