query.go

Documentation: cuelang.org/go/cue

     1  // Copyright 2021 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 cue
    16  
    17  import (
    18  	"cuelang.org/go/internal/core/adt"
    19  )
    20  
    21  // This file contains query-related code.
    22  
    23  // getScopePrefix finds the Vertex that exists in v for the longest prefix of p.
    24  //
    25  // It is used to make the parent scopes visible when resolving expressions.
    26  func getScopePrefix(v Value, p Path) Value {
    27  	for _, sel := range p.Selectors() {
    28  		w := v.LookupPath(MakePath(sel))
    29  		if !w.Exists() {
    30  			break
    31  		}
    32  		v = w
    33  	}
    34  	return v
    35  }
    36  
    37  // LookupPath reports the value for path p relative to v.
    38  func (v Value) LookupPath(p Path) Value {
    39  	if v.v == nil {
    40  		return Value{}
    41  	}
    42  	n := v.v
    43  	parent := v.parent_
    44  	ctx := v.ctx()
    45  
    46  outer:
    47  	for _, sel := range p.path {
    48  		f := sel.sel.feature(v.idx)
    49  		for _, a := range n.Arcs {
    50  			if a.Label == f {
    51  				if a.IsConstraint() && !sel.sel.isConstraint() {
    52  					break
    53  				}
    54  				parent = linkParent(parent, n, a)
    55  				n = a
    56  				continue outer
    57  			}
    58  		}
    59  		if sel.sel.isConstraint() {
    60  			x := &adt.Vertex{
    61  				Parent: n,
    62  				Label:  sel.sel.feature(ctx),
    63  			}
    64  			n.MatchAndInsert(ctx, x)
    65  			if len(x.Conjuncts) > 0 {
    66  				x.Finalize(ctx)
    67  				parent = linkParent(parent, n, x)
    68  				n = x
    69  				continue
    70  			}
    71  		}
    72  
    73  		var x *adt.Bottom
    74  		if err, ok := sel.sel.(pathError); ok {
    75  			x = &adt.Bottom{Err: err.Error}
    76  		} else {
    77  			x = mkErr(v.idx, n, adt.EvalError, "field not found: %v", sel.sel)
    78  			if n.Accept(ctx, f) {
    79  				x.Code = adt.IncompleteError
    80  			}
    81  			x.NotExists = true
    82  		}
    83  		v := makeValue(v.idx, n, parent)
    84  		return newErrValue(v, x)
    85  	}
    86  	return makeValue(v.idx, n, parent)
    87  }
    88
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