simplify.go

Documentation: cuelang.org/go/cue/format

     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 format
    16  
    17  import (
    18  	"strconv"
    19  
    20  	"cuelang.org/go/cue/ast"
    21  	"cuelang.org/go/cue/ast/astutil"
    22  	"cuelang.org/go/internal"
    23  )
    24  
    25  // labelSimplifier rewrites string labels to identifiers if
    26  // no identifiers will subsequently bind to the exposed label.
    27  // In other words, string labels are only replaced if this does
    28  // not change the semantics of the CUE code.
    29  type labelSimplifier struct {
    30  	parent *labelSimplifier
    31  	scope  map[string]bool
    32  }
    33  
    34  func (s *labelSimplifier) processDecls(decls []ast.Decl) {
    35  	sc := labelSimplifier{parent: s, scope: map[string]bool{}}
    36  	for _, d := range decls {
    37  		switch x := d.(type) {
    38  		case *ast.Field:
    39  			ast.Walk(x.Label, sc.markStrings, nil)
    40  		}
    41  	}
    42  
    43  	for _, d := range decls {
    44  		switch x := d.(type) {
    45  		case *ast.Field:
    46  			ast.Walk(x.Value, sc.markReferences, nil)
    47  		default:
    48  			ast.Walk(x, sc.markReferences, nil)
    49  		}
    50  	}
    51  
    52  	for _, d := range decls {
    53  		switch x := d.(type) {
    54  		case *ast.Field:
    55  			x.Label = astutil.Apply(x.Label, sc.replace, nil).(ast.Label)
    56  		}
    57  	}
    58  }
    59  
    60  func (s *labelSimplifier) markReferences(n ast.Node) bool {
    61  	// Record strings at this level.
    62  	switch x := n.(type) {
    63  	case *ast.File:
    64  		s.processDecls(x.Decls)
    65  		return false
    66  
    67  	case *ast.StructLit:
    68  		s.processDecls(x.Elts)
    69  		return false
    70  
    71  	case *ast.SelectorExpr:
    72  		ast.Walk(x.X, s.markReferences, nil)
    73  		return false
    74  
    75  	case *ast.Ident:
    76  		for c := s; c != nil; c = c.parent {
    77  			if _, ok := c.scope[x.Name]; ok {
    78  				c.scope[x.Name] = false
    79  				break
    80  			}
    81  		}
    82  	}
    83  	return true
    84  }
    85  
    86  func (s *labelSimplifier) markStrings(n ast.Node) bool {
    87  	switch x := n.(type) {
    88  	case *ast.BasicLit:
    89  		str, err := strconv.Unquote(x.Value)
    90  		if err != nil || !ast.IsValidIdent(str) || internal.IsDefOrHidden(str) {
    91  			return false
    92  		}
    93  		s.scope[str] = true
    94  
    95  	case *ast.Ident:
    96  		s.scope[x.Name] = true
    97  
    98  	case *ast.ListLit, *ast.Interpolation:
    99  		return false
   100  	}
   101  	return true
   102  }
   103  
   104  func (s *labelSimplifier) replace(c astutil.Cursor) bool {
   105  	switch x := c.Node().(type) {
   106  	case *ast.BasicLit:
   107  		str, err := strconv.Unquote(x.Value)
   108  		if err == nil && s.scope[str] && !internal.IsDefOrHidden(str) {
   109  			c.Replace(ast.NewIdent(str))
   110  		}
   111  	}
   112  	return true
   113  }
   114
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