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go/cmd/vet/structtag.go
Josh Bleecher Snyder d46b792624 cmd/vet: check for use of json/xml struct tags with unexported fields
This is a common source of bugs, particularly for those new to Go. Running this on a corpus of public code flagged 114 instances.

This check may need to be updated once issue 7363 is resolved.

LGTM=r
R=golang-codereviews, r
CC=bradfitz, golang-codereviews
https://golang.org/cl/91010047
2014-06-13 18:44:31 -07:00

63 lines
1.5 KiB
Go

// Copyright 2010 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.
// This file contains the test for canonical struct tags.
package main
import (
"go/ast"
"reflect"
"strconv"
)
func init() {
register("structtags",
"check that struct field tags have canonical format and apply to exported fields as needed",
checkCanonicalFieldTag,
field)
}
// checkCanonicalFieldTag checks a struct field tag.
func checkCanonicalFieldTag(f *File, node ast.Node) {
field := node.(*ast.Field)
if field.Tag == nil {
return
}
tag, err := strconv.Unquote(field.Tag.Value)
if err != nil {
f.Badf(field.Pos(), "unable to read struct tag %s", field.Tag.Value)
return
}
// Check tag for validity by appending
// new key:value to end and checking that
// the tag parsing code can find it.
st := reflect.StructTag(tag + ` _gofix:"_magic"`)
if st.Get("_gofix") != "_magic" {
f.Badf(field.Pos(), "struct field tag %s not compatible with reflect.StructTag.Get", field.Tag.Value)
return
}
// Check for use of json or xml tags with unexported fields.
// Embedded struct. Nothing to do for now, but that
// may change, depending on what happens with issue 7363.
if len(field.Names) == 0 {
return
}
if field.Names[0].IsExported() {
return
}
for _, enc := range [...]string{"json", "xml"} {
if st.Get(enc) != "" {
f.Badf(field.Pos(), "struct field %s has %s tag but is not exported", field.Names[0].Name, enc)
return
}
}
}