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// Copyright 2012 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package composite defines an Analyzer that checks for unkeyed
// composite literals.
package composite
import (
"fmt"
"go/ast"
"go/types"
"strings"
"golang.org/x/tools/go/analysis"
"golang.org/x/tools/go/analysis/passes/inspect"
"golang.org/x/tools/go/ast/inspector"
"golang.org/x/tools/internal/aliases"
"golang.org/x/tools/internal/typeparams"
)
const Doc = `check for unkeyed composite literals
This analyzer reports a diagnostic for composite literals of struct
types imported from another package that do not use the field-keyed
syntax. Such literals are fragile because the addition of a new field
(even if unexported) to the struct will cause compilation to fail.
As an example,
err = &net.DNSConfigError{err}
should be replaced by:
err = &net.DNSConfigError{Err: err}
`
var Analyzer = &analysis.Analyzer{
Name: "composites",
Doc: Doc,
URL: "https://pkg.go.dev/golang.org/x/tools/go/analysis/passes/composite",
Requires: []*analysis.Analyzer{inspect.Analyzer},
RunDespiteErrors: true,
Run: run,
}
var whitelist = true
func init() {
Analyzer.Flags.BoolVar(&whitelist, "whitelist", whitelist, "use composite white list; for testing only")
}
// runUnkeyedLiteral checks if a composite literal is a struct literal with
// unkeyed fields.
func run(pass *analysis.Pass) (interface{}, error) {
inspect := pass.ResultOf[inspect.Analyzer].(*inspector.Inspector)
nodeFilter := []ast.Node{
(*ast.CompositeLit)(nil),
}
inspect.Preorder(nodeFilter, func(n ast.Node) {
cl := n.(*ast.CompositeLit)
typ := pass.TypesInfo.Types[cl].Type
if typ == nil {
// cannot determine composite literals' type, skip it
return
}
typeName := typ.String()
if whitelist && unkeyedLiteral[typeName] {
// skip whitelisted types
return
}
var structuralTypes []types.Type
switch typ := aliases.Unalias(typ).(type) {
case *types.TypeParam:
terms, err := typeparams.StructuralTerms(typ)
if err != nil {
return // invalid type
}
for _, term := range terms {
structuralTypes = append(structuralTypes, term.Type())
}
default:
structuralTypes = append(structuralTypes, typ)
}
for _, typ := range structuralTypes {
strct, ok := typeparams.Deref(typ).Underlying().(*types.Struct)
if !ok {
// skip non-struct composite literals
continue
}
if isLocalType(pass, typ) {
// allow unkeyed locally defined composite literal
continue
}
// check if the struct contains an unkeyed field
allKeyValue := true
var suggestedFixAvailable = len(cl.Elts) == strct.NumFields()
var missingKeys []analysis.TextEdit
for i, e := range cl.Elts {
if _, ok := e.(*ast.KeyValueExpr); !ok {
allKeyValue = false
if i >= strct.NumFields() {
break
}
field := strct.Field(i)
if !field.Exported() {
// Adding unexported field names for structs not defined
// locally will not work.
suggestedFixAvailable = false
break
}
missingKeys = append(missingKeys, analysis.TextEdit{
Pos: e.Pos(),
End: e.Pos(),
NewText: []byte(fmt.Sprintf("%s: ", field.Name())),
})
}
}
if allKeyValue {
// all the struct fields are keyed
continue
}
diag := analysis.Diagnostic{
Pos: cl.Pos(),
End: cl.End(),
Message: fmt.Sprintf("%s struct literal uses unkeyed fields", typeName),
}
if suggestedFixAvailable {
diag.SuggestedFixes = []analysis.SuggestedFix{{
Message: "Add field names to struct literal",
TextEdits: missingKeys,
}}
}
pass.Report(diag)
return
}
})
return nil, nil
}
// isLocalType reports whether typ belongs to the same package as pass.
// TODO(adonovan): local means "internal to a function"; rename to isSamePackageType.
func isLocalType(pass *analysis.Pass, typ types.Type) bool {
switch x := aliases.Unalias(typ).(type) {
case *types.Struct:
// struct literals are local types
return true
case *types.Pointer:
return isLocalType(pass, x.Elem())
case interface{ Obj() *types.TypeName }: // *Named or *TypeParam (aliases were removed already)
// names in package foo are local to foo_test too
return strings.TrimSuffix(x.Obj().Pkg().Path(), "_test") == strings.TrimSuffix(pass.Pkg.Path(), "_test")
}
return false
}
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