ident.go

Documentation: cuelang.org/go/cue/ast

     1  // Copyright 2019 CUE Authors
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package ast
    16  
    17  import (
    18  	"strconv"
    19  	"strings"
    20  	"unicode"
    21  	"unicode/utf8"
    22  
    23  	"cuelang.org/go/cue/errors"
    24  	"cuelang.org/go/cue/token"
    25  )
    26  
    27  func isLetter(ch rune) bool {
    28  	return 'a' <= ch && ch <= 'z' || 'A' <= ch && ch <= 'Z' || ch >= utf8.RuneSelf && unicode.IsLetter(ch)
    29  }
    30  
    31  func isDigit(ch rune) bool {
    32  	// TODO(mpvl): Is this correct?
    33  	return '0' <= ch && ch <= '9' || ch >= utf8.RuneSelf && unicode.IsDigit(ch)
    34  }
    35  
    36  // IsValidIdent reports whether str is a valid identifier.
    37  // Note that the underscore "_" string is considered valid, for top.
    38  func IsValidIdent(ident string) bool {
    39  	if ident == "" {
    40  		return false
    41  	}
    42  
    43  	consumed := false
    44  	if strings.HasPrefix(ident, "_") {
    45  		ident = ident[1:]
    46  		consumed = true
    47  		if len(ident) == 0 {
    48  			return true
    49  		}
    50  	}
    51  	if strings.HasPrefix(ident, "#") {
    52  		ident = ident[1:]
    53  		// Note: _#0 is not allowed by the spec, although _0 is.
    54  		// TODO: set consumed to true here to allow #0.
    55  		consumed = false
    56  	}
    57  
    58  	if !consumed {
    59  		if r, _ := utf8.DecodeRuneInString(ident); isDigit(r) {
    60  			return false
    61  		}
    62  	}
    63  
    64  	for _, r := range ident {
    65  		if isLetter(r) || isDigit(r) || r == '_' || r == '$' {
    66  			continue
    67  		}
    68  		return false
    69  	}
    70  	return true
    71  }
    72  
    73  // ParseIdent unquotes a possibly quoted identifier and validates
    74  // if the result is valid.
    75  //
    76  // Deprecated: quoted identifiers are deprecated. Use aliases.
    77  func ParseIdent(n *Ident) (string, error) {
    78  	return parseIdent(n.NamePos, n.Name)
    79  }
    80  
    81  func parseIdent(pos token.Pos, ident string) (string, error) {
    82  	if ident == "" {
    83  		return "", errors.Newf(pos, "empty identifier")
    84  	}
    85  	quoted := false
    86  	if ident[0] == '`' {
    87  		u, err := strconv.Unquote(ident)
    88  		if err != nil {
    89  			return "", errors.Newf(pos, "invalid quoted identifier")
    90  		}
    91  		ident = u
    92  		quoted = true
    93  	}
    94  
    95  	p := 0
    96  	if strings.HasPrefix(ident, "_") {
    97  		p++
    98  		if len(ident) == 1 {
    99  			return ident, nil
   100  		}
   101  	}
   102  	if strings.HasPrefix(ident[p:], "#") {
   103  		p++
   104  		// if len(ident) == p {
   105  		// 	return "", errors.Newf(pos, "invalid identifier '_#'")
   106  		// }
   107  	}
   108  
   109  	if p == 0 || ident[p-1] == '#' {
   110  		if r, _ := utf8.DecodeRuneInString(ident[p:]); isDigit(r) {
   111  			return "", errors.Newf(pos, "invalid character '%s' in identifier", string(r))
   112  		}
   113  	}
   114  
   115  	for _, r := range ident[p:] {
   116  		if isLetter(r) || isDigit(r) || r == '_' || r == '$' {
   117  			continue
   118  		}
   119  		if r == '-' && quoted {
   120  			continue
   121  		}
   122  		return "", errors.Newf(pos, "invalid character '%s' in identifier", string(r))
   123  	}
   124  
   125  	return ident, nil
   126  }
   127  
   128  // LabelName reports the name of a label, whether it is an identifier
   129  // (it binds a value to a scope), and whether it is valid.
   130  // Keywords that are allowed in label positions are interpreted accordingly.
   131  //
   132  // Examples:
   133  //
   134  //	Label   Result
   135  //	foo     "foo"  true   nil
   136  //	true    "true" true   nil
   137  //	"foo"   "foo"  false  nil
   138  //	"x-y"   "x-y"  false  nil
   139  //	"foo    ""     false  invalid string
   140  //	"\(x)"  ""     false  errors.Is(err, ErrIsExpression)
   141  //	X=foo   "foo"  true   nil
   142  func LabelName(l Label) (name string, isIdent bool, err error) {
   143  	if a, ok := l.(*Alias); ok {
   144  		l, _ = a.Expr.(Label)
   145  	}
   146  	switch n := l.(type) {
   147  	case *ListLit:
   148  		// An expression, but not one that can evaluated.
   149  		return "", false, errors.Newf(l.Pos(),
   150  			"cannot reference fields with square brackets labels outside the field value")
   151  
   152  	case *Ident:
   153  		// TODO(legacy): use name = n.Name
   154  		name, err = ParseIdent(n)
   155  		if err != nil {
   156  			return "", false, err
   157  		}
   158  		isIdent = true
   159  		// TODO(legacy): remove this return once quoted identifiers are removed.
   160  		return name, isIdent, err
   161  
   162  	case *BasicLit:
   163  		switch n.Kind {
   164  		case token.STRING:
   165  			// Use strconv to only allow double-quoted, single-line strings.
   166  			name, err = strconv.Unquote(n.Value)
   167  			if err != nil {
   168  				err = errors.Newf(l.Pos(), "invalid")
   169  			}
   170  
   171  		case token.NULL, token.TRUE, token.FALSE:
   172  			name = n.Value
   173  			isIdent = true
   174  
   175  		default:
   176  			// TODO: allow numbers to be fields
   177  			// This includes interpolation and template labels.
   178  			return "", false, errors.Wrapf(ErrIsExpression, l.Pos(),
   179  				"cannot use numbers as fields")
   180  		}
   181  
   182  	default:
   183  		// This includes interpolation and template labels.
   184  		return "", false, errors.Wrapf(ErrIsExpression, l.Pos(),
   185  			"label is an expression")
   186  	}
   187  	if !IsValidIdent(name) {
   188  		isIdent = false
   189  	}
   190  	return name, isIdent, err
   191  
   192  }
   193  
   194  // ErrIsExpression reports whether a label is an expression.
   195  // This error is never returned directly. Use errors.Is.
   196  var ErrIsExpression = errors.New("not a concrete label")
   197
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