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// Copyright 2018 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 protogen
import (
"fmt"
"go/token"
"strconv"
"strings"
"unicode"
"unicode/utf8"
"google.golang.org/protobuf/reflect/protoreflect"
)
// A GoIdent is a Go identifier, consisting of a name and import path.
// The name is a single identifier and may not be a dot-qualified selector.
type GoIdent struct {
GoName string
GoImportPath GoImportPath
}
func (id GoIdent) String() string { return fmt.Sprintf("%q.%v", id.GoImportPath, id.GoName) }
// newGoIdent returns the Go identifier for a descriptor.
func newGoIdent(f *File, d protoreflect.Descriptor) GoIdent {
name := strings.TrimPrefix(string(d.FullName()), string(f.Desc.Package())+".")
return GoIdent{
GoName: camelCase(name),
GoImportPath: f.GoImportPath,
}
}
// A GoImportPath is the import path of a Go package. e.g., "google.golang.org/genproto/protobuf".
type GoImportPath string
func (p GoImportPath) String() string { return strconv.Quote(string(p)) }
// Ident returns a GoIdent with s as the GoName and p as the GoImportPath.
func (p GoImportPath) Ident(s string) GoIdent {
return GoIdent{GoName: s, GoImportPath: p}
}
// A GoPackageName is the name of a Go package. e.g., "protobuf".
type GoPackageName string
// cleanPackageName converts a string to a valid Go package name.
func cleanPackageName(name string) GoPackageName {
return GoPackageName(cleanGoName(name))
}
// cleanGoName converts a string to a valid Go identifier.
func cleanGoName(s string) string {
// Sanitize the input to the set of valid characters,
// which must be '_' or be in the Unicode L or N categories.
s = strings.Map(func(r rune) rune {
if unicode.IsLetter(r) || unicode.IsDigit(r) {
return r
}
return '_'
}, s)
// Prepend '_' in the event of a Go keyword conflict or if
// the identifier is invalid (does not start in the Unicode L category).
r, _ := utf8.DecodeRuneInString(s)
if token.Lookup(s).IsKeyword() || !unicode.IsLetter(r) {
return "_" + s
}
return s
}
// baseName returns the last path element of the name, with the last dotted suffix removed.
func baseName(name string) string {
// First, find the last element
if i := strings.LastIndex(name, "/"); i >= 0 {
name = name[i+1:]
}
// Now drop the suffix
if i := strings.LastIndex(name, "."); i >= 0 {
name = name[:i]
}
return name
}
// camelCase converts a name to CamelCase.
//
// If there is an interior underscore followed by a lower case letter,
// drop the underscore and convert the letter to upper case.
// There is a remote possibility of this rewrite causing a name collision,
// but it's so remote we're prepared to pretend it's nonexistent - since the
// C++ generator lowercases names, it's extremely unlikely to have two fields
// with different capitalizations.
func camelCase(s string) string {
// Invariant: if the next letter is lower case, it must be converted
// to upper case.
// That is, we process a word at a time, where words are marked by _ or
// upper case letter. Digits are treated as words.
var b []byte
for i := 0; i < len(s); i++ {
c := s[i]
switch {
case c == '.' && i+1 < len(s) && isASCIILower(s[i+1]):
// Skip over '.' in ".{{lowercase}}".
case c == '.':
b = append(b, '_') // convert '.' to '_'
case c == '_' && (i == 0 || s[i-1] == '.'):
// Convert initial '_' to ensure we start with a capital letter.
// Do the same for '_' after '.' to match historic behavior.
b = append(b, 'X') // convert '_' to 'X'
case c == '_' && i+1 < len(s) && isASCIILower(s[i+1]):
// Skip over '_' in "_{{lowercase}}".
case isASCIIDigit(c):
b = append(b, c)
default:
// Assume we have a letter now - if not, it's a bogus identifier.
// The next word is a sequence of characters that must start upper case.
if isASCIILower(c) {
c -= 'a' - 'A' // convert lowercase to uppercase
}
b = append(b, c)
// Accept lower case sequence that follows.
for ; i+1 < len(s) && isASCIILower(s[i+1]); i++ {
b = append(b, s[i+1])
}
}
}
return string(b)
}
// Is c an ASCII lower-case letter?
func isASCIILower(c byte) bool {
return 'a' <= c && c <= 'z'
}
// Is c an ASCII digit?
func isASCIIDigit(c byte) bool {
return '0' <= c && c <= '9'
}