/
structtag.go
226 lines (200 loc) · 6.03 KB
/
structtag.go
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// 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 (
"errors"
"go/ast"
"go/token"
"reflect"
"strconv"
"strings"
)
func init() {
register("structtags",
"check that struct field tags have canonical format and apply to exported fields as needed",
checkStructFieldTags,
structType)
}
// checkStructFieldTags checks all the field tags of a struct, including checking for duplicates.
func checkStructFieldTags(f *File, node ast.Node) {
var seen map[[2]string]token.Pos
for _, field := range node.(*ast.StructType).Fields.List {
checkCanonicalFieldTag(f, field, &seen)
}
}
var checkTagDups = []string{"json", "xml"}
var checkTagSpaces = map[string]bool{"json": true, "xml": true, "asn1": true}
// checkCanonicalFieldTag checks a single struct field tag.
func checkCanonicalFieldTag(f *File, field *ast.Field, seen *map[[2]string]token.Pos) {
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
}
if err := validateStructTag(tag); err != nil {
raw, _ := strconv.Unquote(field.Tag.Value) // field.Tag.Value is known to be a quoted string
f.Badf(field.Pos(), "struct field tag %#q not compatible with reflect.StructTag.Get: %s", raw, err)
}
for _, key := range checkTagDups {
val := reflect.StructTag(tag).Get(key)
if val == "" || val == "-" || val[0] == ',' {
continue
}
if key == "xml" && len(field.Names) > 0 && field.Names[0].Name == "XMLName" {
// XMLName defines the XML element name of the struct being
// checked. That name cannot collide with element or attribute
// names defined on other fields of the struct. Vet does not have a
// check for untagged fields of type struct defining their own name
// by containing a field named XMLName; see issue 18256.
continue
}
if i := strings.Index(val, ","); i >= 0 {
if key == "xml" {
// Use a separate namespace for XML attributes.
for _, opt := range strings.Split(val[i:], ",") {
if opt == "attr" {
key += " attribute" // Key is part of the error message.
break
}
}
}
val = val[:i]
}
if *seen == nil {
*seen = map[[2]string]token.Pos{}
}
if pos, ok := (*seen)[[2]string{key, val}]; ok {
var name string
if len(field.Names) > 0 {
name = field.Names[0].Name
} else {
name = field.Type.(*ast.Ident).Name
}
f.Badf(field.Pos(), "struct field %s repeats %s tag %q also at %s", name, key, val, f.loc(pos))
} else {
(*seen)[[2]string{key, val}] = field.Pos()
}
}
// 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 reflect.StructTag(tag).Get(enc) != "" {
f.Badf(field.Pos(), "struct field %s has %s tag but is not exported", field.Names[0].Name, enc)
return
}
}
}
var (
errTagSyntax = errors.New("bad syntax for struct tag pair")
errTagKeySyntax = errors.New("bad syntax for struct tag key")
errTagValueSyntax = errors.New("bad syntax for struct tag value")
errTagValueSpace = errors.New("suspicious space in struct tag value")
errTagSpace = errors.New("key:\"value\" pairs not separated by spaces")
)
// validateStructTag parses the struct tag and returns an error if it is not
// in the canonical format, which is a space-separated list of key:"value"
// settings. The value may contain spaces.
func validateStructTag(tag string) error {
// This code is based on the StructTag.Get code in package reflect.
n := 0
for ; tag != ""; n++ {
if n > 0 && tag != "" && tag[0] != ' ' {
// More restrictive than reflect, but catches likely mistakes
// like `x:"foo",y:"bar"`, which parses as `x:"foo" ,y:"bar"` with second key ",y".
return errTagSpace
}
// Skip leading space.
i := 0
for i < len(tag) && tag[i] == ' ' {
i++
}
tag = tag[i:]
if tag == "" {
break
}
// Scan to colon. A space, a quote or a control character is a syntax error.
// Strictly speaking, control chars include the range [0x7f, 0x9f], not just
// [0x00, 0x1f], but in practice, we ignore the multi-byte control characters
// as it is simpler to inspect the tag's bytes than the tag's runes.
i = 0
for i < len(tag) && tag[i] > ' ' && tag[i] != ':' && tag[i] != '"' && tag[i] != 0x7f {
i++
}
if i == 0 {
return errTagKeySyntax
}
if i+1 >= len(tag) || tag[i] != ':' {
return errTagSyntax
}
if tag[i+1] != '"' {
return errTagValueSyntax
}
key := tag[:i]
tag = tag[i+1:]
// Scan quoted string to find value.
i = 1
for i < len(tag) && tag[i] != '"' {
if tag[i] == '\\' {
i++
}
i++
}
if i >= len(tag) {
return errTagValueSyntax
}
qvalue := tag[:i+1]
tag = tag[i+1:]
value, err := strconv.Unquote(qvalue)
if err != nil {
return errTagValueSyntax
}
if !checkTagSpaces[key] {
continue
}
switch key {
case "xml":
// If the first or last character in the XML tag is a space, it is
// suspicious.
if strings.Trim(value, " ") != value {
return errTagValueSpace
}
// If there are multiple spaces, they are suspicious.
if strings.Count(value, " ") > 1 {
return errTagValueSpace
}
// If there is no comma, skip the rest of the checks.
comma := strings.IndexRune(value, ',')
if comma < 0 {
continue
}
// If the character before a comma is a space, this is suspicious.
if comma > 0 && value[comma-1] == ' ' {
return errTagValueSpace
}
value = value[comma+1:]
case "json":
// JSON allows using spaces in the name, so skip it.
comma := strings.IndexRune(value, ',')
if comma < 0 {
continue
}
value = value[comma+1:]
}
if strings.IndexByte(value, ' ') >= 0 {
return errTagValueSpace
}
}
return nil
}