Generate accessors for structs with pointer fields

Fixes #45.

Change-Id: Ib2b6cc5d713e2eb833ee3c7fcfbd804bfe8fa313

Author: gmlewis

cmd/tools/gen-accessors.go

@@ -0,0 +1,300 @@
+// Copyright 2017 The go-github AUTHORS. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// gen-accessors generates accessor methods for structs with pointer fields.
+//
+// It is meant to be used by the go-github authors in conjunction with the
+// go generate tool before sending a commit to GitHub.
+package main
+
+import (
+	"bytes"
+	"flag"
+	"fmt"
+	"go/ast"
+	"go/format"
+	"go/parser"
+	"go/token"
+	"io/ioutil"
+	"log"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+	"text/template"
+	"time"
+)
+
+const (
+	fileSuffix = "-accessors.go"
+)
+
+var (
+	verbose = flag.Bool("v", false, "Print verbose log messages")
+
+	sourceTmpl = template.Must(template.New("source").Parse(source))
+
+	// blacklist lists which "struct.method" combos to not generate.
+	blacklist = map[string]bool{
+		"RepositoryContent.GetContent":    true,
+		"Client.GetBaseURL":               true,
+		"Client.GetUploadURL":             true,
+		"ErrorResponse.GetResponse":       true,
+		"RateLimitError.GetResponse":      true,
+		"AbuseRateLimitError.GetResponse": true,
+	}
+)
+
+func logf(fmt string, args ...interface{}) {
+	if *verbose {
+		log.Printf(fmt, args...)
+	}
+}
+
+func main() {
+	flag.Parse()
+	fset := token.NewFileSet()
+
+	pkgs, err := parser.ParseDir(fset, ".", sourceFilter, 0)
+	if err != nil {
+		log.Fatal(err)
+		return
+	}
+
+	for pkgName, pkg := range pkgs {
+		t := &templateData{
+			Year:     time.Now().Year(),
+			Filename: pkgName + fileSuffix,
+			Package:  pkgName,
+			Imports:  map[string]string{},
+		}
+		for filename, f := range pkg.Files {
+			logf("Processing %v...", filename)
+			t.sourceFile = filename
+			if err := t.processAST(f); err != nil {
+				log.Fatal(err)
+			}
+		}
+		if err := t.dump(); err != nil {
+			log.Fatal(err)
+		}
+	}
+	logf("Done.")
+}
+
+func (t *templateData) processAST(f *ast.File) error {
+	for _, decl := range f.Decls {
+		gd, ok := decl.(*ast.GenDecl)
+		if !ok {
+			continue
+		}
+		for _, spec := range gd.Specs {
+			ts, ok := spec.(*ast.TypeSpec)
+			if !ok {
+				continue
+			}
+			st, ok := ts.Type.(*ast.StructType)
+			if !ok {
+				continue
+			}
+			for _, field := range st.Fields.List {
+				se, ok := field.Type.(*ast.StarExpr)
+				if len(field.Names) == 0 || !ok {
+					continue
+				}
+
+				fieldName := field.Names[0]
+				if key := fmt.Sprintf("%v.Get%v", ts.Name, fieldName); blacklist[key] {
+					logf("Method %v blacklisted; skipping.", key)
+					continue
+				}
+
+				switch x := se.X.(type) {
+				case *ast.ArrayType:
+					t.addArrayType(x, ts.Name.String(), fieldName.String())
+				case *ast.Ident:
+					t.addIdent(x, ts.Name.String(), fieldName.String())
+				case *ast.MapType:
+					t.addMapType(x, ts.Name.String(), fieldName.String())
+				case *ast.SelectorExpr:
+					t.addSelectorExpr(x, ts.Name.String(), fieldName.String())
+				default:
+					logf("processAST: type %q, field %q, unknown %T: %+v", ts.Name, fieldName, x, x)
+				}
+			}
+		}
+	}
+	return nil
+}
+
+func sourceFilter(fi os.FileInfo) bool {
+	return !strings.HasSuffix(fi.Name(), "_test.go") && !strings.HasSuffix(fi.Name(), fileSuffix)
+}
+
+func (t *templateData) dump() error {
+	if len(t.Getters) == 0 {
+		logf("No getters for %v; skipping.", t.Filename)
+		return nil
+	}
+
+	// Sort getters by ReceiverType.FieldName
+	sort.Sort(byName(t.Getters))
+
+	var buf bytes.Buffer
+	if err := sourceTmpl.Execute(&buf, t); err != nil {
+		return err
+	}
+	clean, err := format.Source(buf.Bytes())
+	if err != nil {
+		return err
+	}
+
+	outFile := filepath.Join(filepath.Dir(t.sourceFile), t.Filename)
+	logf("Writing %v...", outFile)
+	return ioutil.WriteFile(outFile, clean, 0644)
+}
+
+func newGetter(receiverType, fieldName, fieldType, zeroValue string) *getter {
+	return &getter{
+		sortVal:      strings.ToLower(receiverType) + "." + strings.ToLower(fieldName),
+		ReceiverVar:  strings.ToLower(receiverType[:1]),
+		ReceiverType: receiverType,
+		FieldName:    fieldName,
+		FieldType:    fieldType,
+		ZeroValue:    zeroValue,
+	}
+}
+
+func (t *templateData) addArrayType(x *ast.ArrayType, receiverType, fieldName string) {
+	var eltType string
+	switch elt := x.Elt.(type) {
+	case *ast.Ident:
+		eltType = elt.String()
+	default:
+		logf("addArrayType: type %q, field %q: unknown elt type: %T %+v; skipping.", receiverType, fieldName, elt, elt)
+		return
+	}
+
+	t.Getters = append(t.Getters, newGetter(receiverType, fieldName, "[]"+eltType, "nil"))
+}
+
+func (t *templateData) addIdent(x *ast.Ident, receiverType, fieldName string) {
+	var zeroValue string
+	switch x.String() {
+	case "int":
+		zeroValue = "0"
+	case "string":
+		zeroValue = `""`
+	case "bool":
+		zeroValue = "false"
+	case "Timestamp":
+		zeroValue = "Timestamp{}"
+	default: // other structs handled by their receivers directly.
+		return
+	}
+
+	t.Getters = append(t.Getters, newGetter(receiverType, fieldName, x.String(), zeroValue))
+}
+
+func (t *templateData) addMapType(x *ast.MapType, receiverType, fieldName string) {
+	var keyType string
+	switch key := x.Key.(type) {
+	case *ast.Ident:
+		keyType = key.String()
+	default:
+		logf("addMapType: type %q, field %q: unknown key type: %T %+v; skipping.", receiverType, fieldName, key, key)
+		return
+	}
+
+	var valueType string
+	switch value := x.Value.(type) {
+	case *ast.Ident:
+		valueType = value.String()
+	default:
+		logf("addMapType: type %q, field %q: unknown value type: %T %+v; skipping.", receiverType, fieldName, value, value)
+		return
+	}
+
+	fieldType := fmt.Sprintf("map[%v]%v", keyType, valueType)
+	zeroValue := fmt.Sprintf("map[%v]%v{}", keyType, valueType)
+	t.Getters = append(t.Getters, newGetter(receiverType, fieldName, fieldType, zeroValue))
+}
+
+func (t *templateData) addSelectorExpr(x *ast.SelectorExpr, receiverType, fieldName string) {
+	if strings.ToLower(fieldName[:1]) == fieldName[:1] { // non-exported field
+		return
+	}
+
+	var xX string
+	if xx, ok := x.X.(*ast.Ident); ok {
+		xX = xx.String()
+	}
+
+	switch xX {
+	case "time", "json":
+		if xX == "json" {
+			t.Imports["encoding/json"] = "encoding/json"
+		} else {
+			t.Imports[xX] = xX
+		}
+		fieldType := fmt.Sprintf("%v.%v", xX, x.Sel.Name)
+		zeroValue := fmt.Sprintf("%v.%v{}", xX, x.Sel.Name)
+		if xX == "time" && x.Sel.Name == "Duration" {
+			zeroValue = "0"
+		}
+		t.Getters = append(t.Getters, newGetter(receiverType, fieldName, fieldType, zeroValue))
+	default:
+		logf("addSelectorExpr: xX %q, type %q, field %q: unknown x=%+v; skipping.", xX, receiverType, fieldName, x)
+	}
+}
+
+type templateData struct {
+	sourceFile string
+	Year       int
+	Filename   string
+	Package    string
+	Imports    map[string]string
+	Getters    []*getter
+}
+
+type getter struct {
+	sortVal      string // lower-case version of "ReceiverType.FieldName"
+	ReceiverVar  string // the one-letter variable name to match the ReceiverType
+	ReceiverType string
+	FieldName    string
+	FieldType    string
+	ZeroValue    string
+}
+
+type byName []*getter
+
+func (b byName) Len() int           { return len(b) }
+func (b byName) Less(i, j int) bool { return b[i].sortVal < b[j].sortVal }
+func (b byName) Swap(i, j int)      { b[i], b[j] = b[j], b[i] }
+
+const source = `// Copyright {{.Year}} The go-github AUTHORS. All rights reserved.
+//
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// {{.Filename}} generated by gen-accessors; DO NOT EDIT
+
+package {{.Package}}
+{{if .Imports}}
+import (
+  {{range .Imports}}
+  "{{.}}"{{end}}
+)
+{{end}}
+{{range .Getters}}
+// Get{{.FieldName}} returns the {{.FieldName}} field if it's non-nil, zero value otherwise.
+func ({{.ReceiverVar}} *{{.ReceiverType}}) Get{{.FieldName}}() {{.FieldType}} {
+  if {{.ReceiverVar}} == nil || {{.ReceiverVar}}.{{.FieldName}} == nil {
+    return {{.ZeroValue}}
+  }
+  return *{{.ReceiverVar}}.{{.FieldName}}
+}
+{{end}}
+`