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main.go
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main.go
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package main
import (
"bufio"
"bytes"
"encoding/json"
"errors"
"flag"
"fmt"
"go/ast"
"go/format"
"go/parser"
"go/printer"
"go/token"
"io"
"io/ioutil"
"os"
"sort"
"strconv"
"strings"
"unicode"
"github.com/fatih/camelcase"
"github.com/fatih/structtag"
"golang.org/x/tools/go/buildutil"
)
// structType contains a structType node and it's name. It's a convenient
// helper type, because *ast.StructType doesn't contain the name of the struct
type structType struct {
name string
node *ast.StructType
}
// output is used usually by editors
type output struct {
Start int `json:"start"`
End int `json:"end"`
Lines []string `json:"lines"`
Errors []string `json:"errors,omitempty"`
}
// config defines how tags should be modified
type config struct {
file string
output string
quiet bool
write bool
modified io.Reader
offset int
structName string
fieldName string
line string
start, end int
all bool
fset *token.FileSet
remove []string
removeOptions []string
add []string
addOptions []string
override bool
skipUnexportedFields bool
transform string
sort bool
valueFormat string
clear bool
clearOption bool
}
func main() {
if err := realMain(); err != nil {
fmt.Fprintln(os.Stderr, err.Error())
os.Exit(1)
}
}
func realMain() error {
cfg, err := parseConfig(os.Args[1:])
if err != nil {
if err == flag.ErrHelp {
return nil
}
return err
}
err = cfg.validate()
if err != nil {
return err
}
node, err := cfg.parse()
if err != nil {
return err
}
start, end, err := cfg.findSelection(node)
if err != nil {
return err
}
rewrittenNode, errs := cfg.rewrite(node, start, end)
if errs != nil {
if _, ok := errs.(*rewriteErrors); !ok {
return errs
}
}
out, err := cfg.format(rewrittenNode, errs)
if err != nil {
return err
}
if !cfg.quiet {
fmt.Println(out)
}
return nil
}
func parseConfig(args []string) (*config, error) {
var (
// file flags
flagFile = flag.String("file", "", "Filename to be parsed")
flagWrite = flag.Bool("w", false, "Write results to (source) file")
flagQuiet = flag.Bool("quiet", false, "Don't print result to stdout")
flagOutput = flag.String("format", "source", "Output format."+
"By default it's the whole file. Options: [source, json]")
flagModified = flag.Bool("modified", false, "read an archive of modified files from standard input")
// processing modes
flagOffset = flag.Int("offset", 0,
"Byte offset of the cursor position inside a struct."+
"Can be anwhere from the comment until closing bracket")
flagLine = flag.String("line", "",
"Line number of the field or a range of line. i.e: 4 or 4,8")
flagStruct = flag.String("struct", "", "Struct name to be processed")
flagField = flag.String("field", "", "Field name to be processed")
flagAll = flag.Bool("all", false, "Select all structs to be processed")
// tag flags
flagRemoveTags = flag.String("remove-tags", "",
"Remove tags for the comma separated list of keys")
flagClearTags = flag.Bool("clear-tags", false,
"Clear all tags")
flagAddTags = flag.String("add-tags", "",
"Adds tags for the comma separated list of keys."+
"Keys can contain a static value, i,e: json:foo")
flagOverride = flag.Bool("override", false, "Override current tags when adding tags")
flagSkipUnexportedFields = flag.Bool("skip-unexported", false, "Skip unexported fields")
flagTransform = flag.String("transform", "snakecase",
"Transform adds a transform rule when adding tags."+
" Current options: [snakecase, camelcase, lispcase, pascalcase, titlecase, keep]")
flagSort = flag.Bool("sort", false,
"Sort sorts the tags in increasing order according to the key name")
// formatting
flagFormatting = flag.String("template", "",
"Format the given tag's value. i.e: \"column:{field}\", \"field_name={field}\"")
// option flags
flagRemoveOptions = flag.String("remove-options", "",
"Remove the comma separated list of options from the given keys, "+
"i.e: json=omitempty,hcl=squash")
flagClearOptions = flag.Bool("clear-options", false,
"Clear all tag options")
flagAddOptions = flag.String("add-options", "",
"Add the options per given key. i.e: json=omitempty,hcl=squash")
)
// this fails if there are flags re-defined with the same name.
if err := flag.CommandLine.Parse(args); err != nil {
return nil, err
}
if flag.NFlag() == 0 {
fmt.Fprintf(os.Stderr, "Usage of %s:\n", os.Args[0])
flag.PrintDefaults()
return nil, flag.ErrHelp
}
cfg := &config{
file: *flagFile,
line: *flagLine,
structName: *flagStruct,
fieldName: *flagField,
offset: *flagOffset,
all: *flagAll,
output: *flagOutput,
write: *flagWrite,
quiet: *flagQuiet,
clear: *flagClearTags,
clearOption: *flagClearOptions,
transform: *flagTransform,
sort: *flagSort,
valueFormat: *flagFormatting,
override: *flagOverride,
skipUnexportedFields: *flagSkipUnexportedFields,
}
if *flagModified {
cfg.modified = os.Stdin
}
if *flagAddTags != "" {
cfg.add = strings.Split(*flagAddTags, ",")
}
if *flagAddOptions != "" {
cfg.addOptions = strings.Split(*flagAddOptions, ",")
}
if *flagRemoveTags != "" {
cfg.remove = strings.Split(*flagRemoveTags, ",")
}
if *flagRemoveOptions != "" {
cfg.removeOptions = strings.Split(*flagRemoveOptions, ",")
}
return cfg, nil
}
func (c *config) parse() (ast.Node, error) {
c.fset = token.NewFileSet()
var contents interface{}
if c.modified != nil {
archive, err := buildutil.ParseOverlayArchive(c.modified)
if err != nil {
return nil, fmt.Errorf("failed to parse -modified archive: %v", err)
}
fc, ok := archive[c.file]
if !ok {
return nil, fmt.Errorf("couldn't find %s in archive", c.file)
}
contents = fc
}
return parser.ParseFile(c.fset, c.file, contents, parser.ParseComments)
}
// findSelection returns the start and end position of the fields that are
// suspect to change. It depends on the line, struct or offset selection.
func (c *config) findSelection(node ast.Node) (int, int, error) {
if c.line != "" {
return c.lineSelection(node)
} else if c.offset != 0 {
return c.offsetSelection(node)
} else if c.structName != "" {
return c.structSelection(node)
} else if c.all {
return c.allSelection(node)
} else {
return 0, 0, errors.New("-line, -offset, -struct or -all is not passed")
}
}
func (c *config) process(fieldName, tagVal string) (string, error) {
var tag string
if tagVal != "" {
var err error
tag, err = strconv.Unquote(tagVal)
if err != nil {
return "", err
}
}
tags, err := structtag.Parse(tag)
if err != nil {
return "", err
}
tags = c.removeTags(tags)
tags, err = c.removeTagOptions(tags)
if err != nil {
return "", err
}
tags = c.clearTags(tags)
tags = c.clearOptions(tags)
tags, err = c.addTags(fieldName, tags)
if err != nil {
return "", err
}
tags, err = c.addTagOptions(tags)
if err != nil {
return "", err
}
if c.sort {
sort.Sort(tags)
}
res := tags.String()
if res != "" {
res = quote(tags.String())
}
return res, nil
}
func (c *config) removeTags(tags *structtag.Tags) *structtag.Tags {
if c.remove == nil || len(c.remove) == 0 {
return tags
}
tags.Delete(c.remove...)
return tags
}
func (c *config) clearTags(tags *structtag.Tags) *structtag.Tags {
if !c.clear {
return tags
}
tags.Delete(tags.Keys()...)
return tags
}
func (c *config) clearOptions(tags *structtag.Tags) *structtag.Tags {
if !c.clearOption {
return tags
}
for _, t := range tags.Tags() {
t.Options = nil
}
return tags
}
func (c *config) removeTagOptions(tags *structtag.Tags) (*structtag.Tags, error) {
if c.removeOptions == nil || len(c.removeOptions) == 0 {
return tags, nil
}
for _, val := range c.removeOptions {
// syntax key=option
splitted := strings.Split(val, "=")
if len(splitted) < 2 {
return nil, errors.New("wrong syntax to remove an option. i.e key=option")
}
key := splitted[0]
option := strings.Join(splitted[1:], "=")
tags.DeleteOptions(key, option)
}
return tags, nil
}
func (c *config) addTagOptions(tags *structtag.Tags) (*structtag.Tags, error) {
if c.addOptions == nil || len(c.addOptions) == 0 {
return tags, nil
}
for _, val := range c.addOptions {
// syntax key=option
splitted := strings.Split(val, "=")
if len(splitted) < 2 {
return nil, errors.New("wrong syntax to add an option. i.e key=option")
}
key := splitted[0]
option := strings.Join(splitted[1:], "=")
tags.AddOptions(key, option)
}
return tags, nil
}
func (c *config) addTags(fieldName string, tags *structtag.Tags) (*structtag.Tags, error) {
if c.add == nil || len(c.add) == 0 {
return tags, nil
}
splitted := camelcase.Split(fieldName)
name := ""
unknown := false
switch c.transform {
case "snakecase":
var lowerSplitted []string
for _, s := range splitted {
s = strings.Trim(s, "_")
if s == "" {
continue
}
lowerSplitted = append(lowerSplitted, strings.ToLower(s))
}
name = strings.Join(lowerSplitted, "_")
case "lispcase":
var lowerSplitted []string
for _, s := range splitted {
lowerSplitted = append(lowerSplitted, strings.ToLower(s))
}
name = strings.Join(lowerSplitted, "-")
case "camelcase":
var titled []string
for _, s := range splitted {
titled = append(titled, strings.Title(s))
}
titled[0] = strings.ToLower(titled[0])
name = strings.Join(titled, "")
case "pascalcase":
var titled []string
for _, s := range splitted {
titled = append(titled, strings.Title(s))
}
name = strings.Join(titled, "")
case "titlecase":
var titled []string
for _, s := range splitted {
titled = append(titled, strings.Title(s))
}
name = strings.Join(titled, " ")
case "keep":
name = fieldName
default:
unknown = true
}
if c.valueFormat != "" {
prevName := name
name = strings.ReplaceAll(c.valueFormat, "{field}", name)
if name == c.valueFormat {
// support old style for backward compatibility
name = strings.ReplaceAll(c.valueFormat, "$field", prevName)
}
}
for _, key := range c.add {
splitted = strings.SplitN(key, ":", 2)
if len(splitted) >= 2 {
key = splitted[0]
name = strings.Join(splitted[1:], "")
} else if unknown {
// the user didn't pass any value but want to use an unknown
// transform. We don't return above in the default as the user
// might pass a value
return nil, fmt.Errorf("unknown transform option %q", c.transform)
}
tag, err := tags.Get(key)
if err != nil {
// tag doesn't exist, create a new one
tag = &structtag.Tag{
Key: key,
Name: name,
}
} else if c.override {
tag.Name = name
}
if err := tags.Set(tag); err != nil {
return nil, err
}
}
return tags, nil
}
// collectStructs collects and maps structType nodes to their positions
func collectStructs(node ast.Node) map[token.Pos]*structType {
structs := make(map[token.Pos]*structType, 0)
collectStructs := func(n ast.Node) bool {
var t ast.Expr
var structName string
switch x := n.(type) {
case *ast.TypeSpec:
if x.Type == nil {
return true
}
structName = x.Name.Name
t = x.Type
case *ast.CompositeLit:
t = x.Type
case *ast.ValueSpec:
structName = x.Names[0].Name
t = x.Type
case *ast.Field:
// this case also catches struct fields and the structName
// therefore might contain the field name (which is wrong)
// because `x.Type` in this case is not a *ast.StructType.
//
// We're OK with it, because, in our case *ast.Field represents
// a parameter declaration, i.e:
//
// func test(arg struct {
// Field int
// }) {
// }
//
// and hence the struct name will be `arg`.
if len(x.Names) != 0 {
structName = x.Names[0].Name
}
t = x.Type
}
// if expression is in form "*T" or "[]T", dereference to check if "T"
// contains a struct expression
t = deref(t)
x, ok := t.(*ast.StructType)
if !ok {
return true
}
structs[x.Pos()] = &structType{
name: structName,
node: x,
}
return true
}
ast.Inspect(node, collectStructs)
return structs
}
func (c *config) format(file ast.Node, rwErrs error) (string, error) {
switch c.output {
case "source":
var buf bytes.Buffer
err := format.Node(&buf, c.fset, file)
if err != nil {
return "", err
}
if c.write {
err = ioutil.WriteFile(c.file, buf.Bytes(), 0)
if err != nil {
return "", err
}
}
return buf.String(), nil
case "json":
// NOTE(arslan): print first the whole file and then cut out our
// selection. The reason we don't directly print the struct is that the
// printer is not capable of printing loosy comments, comments that are
// not part of any field inside a struct. Those are part of *ast.File
// and only printed inside a struct if we print the whole file. This
// approach is the sanest and simplest way to get a struct printed
// back. Second, our cursor might intersect two different structs with
// other declarations in between them. Printing the file and cutting
// the selection is the easier and simpler to do.
var buf bytes.Buffer
// this is the default config from `format.Node()`, but we add
// `printer.SourcePos` to get the original source position of the
// modified lines
cfg := printer.Config{Mode: printer.SourcePos | printer.UseSpaces | printer.TabIndent, Tabwidth: 8}
err := cfg.Fprint(&buf, c.fset, file)
if err != nil {
return "", err
}
lines, err := parseLines(&buf)
if err != nil {
return "", err
}
// prevent selection to be larger than the actual number of lines
if c.start > len(lines) || c.end > len(lines) {
return "", errors.New("line selection is invalid")
}
out := &output{
Start: c.start,
End: c.end,
Lines: lines[c.start-1 : c.end],
}
if rwErrs != nil {
if r, ok := rwErrs.(*rewriteErrors); ok {
for _, err := range r.errs {
out.Errors = append(out.Errors, err.Error())
}
}
}
o, err := json.MarshalIndent(out, "", " ")
if err != nil {
return "", err
}
return string(o), nil
default:
return "", fmt.Errorf("unknown output mode: %s", c.output)
}
}
func (c *config) lineSelection(file ast.Node) (int, int, error) {
var err error
splitted := strings.Split(c.line, ",")
start, err := strconv.Atoi(splitted[0])
if err != nil {
return 0, 0, err
}
end := start
if len(splitted) == 2 {
end, err = strconv.Atoi(splitted[1])
if err != nil {
return 0, 0, err
}
}
if start > end {
return 0, 0, errors.New("wrong range. start line cannot be larger than end line")
}
return start, end, nil
}
func (c *config) structSelection(file ast.Node) (int, int, error) {
structs := collectStructs(file)
var encStruct *ast.StructType
for _, st := range structs {
if st.name == c.structName {
encStruct = st.node
}
}
if encStruct == nil {
return 0, 0, errors.New("struct name does not exist")
}
// if field name has been specified as well, only select the given field
if c.fieldName != "" {
return c.fieldSelection(encStruct)
}
start := c.fset.Position(encStruct.Pos()).Line
end := c.fset.Position(encStruct.End()).Line
return start, end, nil
}
func (c *config) fieldSelection(st *ast.StructType) (int, int, error) {
var encField *ast.Field
for _, f := range st.Fields.List {
for _, field := range f.Names {
if field.Name == c.fieldName {
encField = f
}
}
}
if encField == nil {
return 0, 0, fmt.Errorf("struct %q doesn't have field name %q",
c.structName, c.fieldName)
}
start := c.fset.Position(encField.Pos()).Line
end := c.fset.Position(encField.End()).Line
return start, end, nil
}
func (c *config) offsetSelection(file ast.Node) (int, int, error) {
structs := collectStructs(file)
var encStruct *ast.StructType
for _, st := range structs {
structBegin := c.fset.Position(st.node.Pos()).Offset
structEnd := c.fset.Position(st.node.End()).Offset
if structBegin <= c.offset && c.offset <= structEnd {
encStruct = st.node
break
}
}
if encStruct == nil {
return 0, 0, errors.New("offset is not inside a struct")
}
// offset selects all fields
start := c.fset.Position(encStruct.Pos()).Line
end := c.fset.Position(encStruct.End()).Line
return start, end, nil
}
// allSelection selects all structs inside a file
func (c *config) allSelection(file ast.Node) (int, int, error) {
start := 1
end := c.fset.File(file.Pos()).LineCount()
return start, end, nil
}
func isPublicName(name string) bool {
for _, c := range name {
return unicode.IsUpper(c)
}
return false
}
// rewrite rewrites the node for structs between the start and end
// positions
func (c *config) rewrite(node ast.Node, start, end int) (ast.Node, error) {
errs := &rewriteErrors{errs: make([]error, 0)}
rewriteFunc := func(n ast.Node) bool {
x, ok := n.(*ast.StructType)
if !ok {
return true
}
for _, f := range x.Fields.List {
line := c.fset.Position(f.Pos()).Line
if !(start <= line && line <= end) {
continue
}
fieldName := ""
if len(f.Names) != 0 {
for _, field := range f.Names {
if !c.skipUnexportedFields || isPublicName(field.Name) {
fieldName = field.Name
break
}
}
}
// anonymous field
if f.Names == nil {
ident, ok := f.Type.(*ast.Ident)
if !ok {
continue
}
if !c.skipUnexportedFields {
fieldName = ident.Name
}
}
// nothing to process, continue with next line
if fieldName == "" {
continue
}
if f.Tag == nil {
f.Tag = &ast.BasicLit{}
}
res, err := c.process(fieldName, f.Tag.Value)
if err != nil {
errs.Append(fmt.Errorf("%s:%d:%d:%s",
c.fset.Position(f.Pos()).Filename,
c.fset.Position(f.Pos()).Line,
c.fset.Position(f.Pos()).Column,
err))
continue
}
f.Tag.Value = res
}
return true
}
ast.Inspect(node, rewriteFunc)
c.start = start
c.end = end
if len(errs.errs) == 0 {
return node, nil
}
return node, errs
}
// validate validates whether the config is valid or not
func (c *config) validate() error {
if c.file == "" {
return errors.New("no file is passed")
}
if c.line == "" && c.offset == 0 && c.structName == "" && !c.all {
return errors.New("-line, -offset, -struct or -all is not passed")
}
if c.line != "" && c.offset != 0 ||
c.line != "" && c.structName != "" ||
c.offset != 0 && c.structName != "" {
return errors.New("-line, -offset or -struct cannot be used together. pick one")
}
if (c.add == nil || len(c.add) == 0) &&
(c.addOptions == nil || len(c.addOptions) == 0) &&
!c.clear &&
!c.clearOption &&
(c.removeOptions == nil || len(c.removeOptions) == 0) &&
(c.remove == nil || len(c.remove) == 0) {
return errors.New("one of " +
"[-add-tags, -add-options, -remove-tags, -remove-options, -clear-tags, -clear-options]" +
" should be defined")
}
if c.fieldName != "" && c.structName == "" {
return errors.New("-field is requiring -struct")
}
return nil
}
func quote(tag string) string {
return "`" + tag + "`"
}
type rewriteErrors struct {
errs []error
}
func (r *rewriteErrors) Error() string {
var buf bytes.Buffer
for _, e := range r.errs {
buf.WriteString(fmt.Sprintf("%s\n", e.Error()))
}
return buf.String()
}
func (r *rewriteErrors) Append(err error) {
if err == nil {
return
}
r.errs = append(r.errs, err)
}
// parseLines parses the given buffer and returns a slice of lines
func parseLines(buf io.Reader) ([]string, error) {
var lines []string
scanner := bufio.NewScanner(buf)
for scanner.Scan() {
txt := scanner.Text()
// check for any line directive and store it for next iteration to
// re-construct the original file. If it's not a line directive,
// continue consturcting the original file
if !strings.HasPrefix(txt, "//line") {
lines = append(lines, txt)
continue
}
lineNr, err := split(txt)
if err != nil {
return nil, err
}
for i := len(lines); i < lineNr-1; i++ {
lines = append(lines, "")
}
lines = lines[:lineNr-1]
}
if err := scanner.Err(); err != nil {
return nil, fmt.Errorf("invalid scanner inputl: %s", err)
}
return lines, nil
}
// split splits the given line directive and returns the line number
// see https://golang.org/cmd/compile/#hdr-Compiler_Directives for more
// information
// NOTE(arslan): this only splits the line directive that the go.Parser
// outputs. If the go parser changes the format of the line directive, make
// sure to fix it in the below function
func split(line string) (int, error) {
for i := len(line) - 1; i >= 0; i-- {
if line[i] != ':' {
continue
}
nr, err := strconv.Atoi(line[i+1:])
if err != nil {
return 0, err
}
return nr, nil
}
return 0, fmt.Errorf("couldn't parse line: '%s'", line)
}
// deref takes an expression, and removes all its leading "*" and "[]"
// operator. Uuse case : if found expression is a "*t" or "[]t", we need to
// check if "t" contains a struct expression.
func deref(x ast.Expr) ast.Expr {
switch t := x.(type) {
case *ast.StarExpr:
return deref(t.X)
case *ast.ArrayType:
return deref(t.Elt)
}
return x
}