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// Copyright 2020 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 export
import (
"crypto/md5"
"fmt"
"io"
"strconv"
"strings"
"cuelang.org/go/cue/ast"
"cuelang.org/go/cue/literal"
"cuelang.org/go/cue/token"
"cuelang.org/go/internal/core/adt"
)
func (e *exporter) stringLabel(f adt.Feature) ast.Label {
x := f.Index()
switch f.Typ() {
case adt.IntLabel:
return ast.NewLit(token.INT, strconv.Itoa(int(x)))
case adt.DefinitionLabel, adt.HiddenLabel, adt.HiddenDefinitionLabel:
s := e.identString(f)
return ast.NewIdent(s)
case adt.StringLabel:
s := e.ctx.IndexToString(int64(x))
if f == 0 || !ast.IsValidIdent(s) ||
strings.HasPrefix(s, "#") || strings.HasPrefix(s, "_") {
return ast.NewLit(token.STRING, literal.Label.Quote(s))
}
fallthrough
default:
return ast.NewIdent(e.ctx.IndexToString(int64(x)))
}
}
// identString converts the given Feature f to an identifier string.
//
// Hidden field mangling:
//
// If f is a hidden field that comes from an expanded package, it will mangle
// the name by expending it with the MD5 hash of the package name. This is to
// avoid collisions of the hidden identifiers when namespaces are merged.
// It uses the MD5 hash to allow hidden fields from the same package to
// still match across inlining and unifications.
//
// TODO: Alternatives approaches to consider:
// 1. Rewrite to unique hidden field names. This means, though, that hidden
// fields may not match across unifications. That may be okay.
// 2. Force inline hidden fields from such packages, or translate them to let
// expressions when necessary. This should generally preserve semantics
// quite well.
// 3. Allow addressing hidden fields across packages, for instance by allowing
// `_(hiddenField, pkg: "import/path")`. This kind of defeats the purpose
// of hidden fields, though.
//
// Option 2 seems the best long-term solution. It should be possible to
// piggyback on the self containment algorithm for this: basically, whenever
// we see a hidden reference of an inlined package, we treat it as an
// external reference itself.
//
// For now, as this only can occur when the InlineImports feature is used,
// we use this simpler approach.
func (e *exporter) identString(f adt.Feature) string {
s := f.IdentString(e.ctx)
if !f.IsHidden() || !e.cfg.InlineImports {
return s
}
pkg := f.PkgID(e.ctx)
if pkg == "" || pkg == "_" || pkg == e.pkgID {
return s
}
if e.pkgHash == nil {
e.pkgHash = map[string]string{}
}
id, ok := e.pkgHash[pkg]
if !ok {
h := md5.New()
io.WriteString(h, pkg)
b := h.Sum(nil)
id = fmt.Sprintf("_%8X", b[:4])
e.pkgHash[pkg] = id
}
s += id
return s
}
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