Create & Init Project...

app/tool/gengo/generator/BUILD

@@ -0,0 +1,56 @@
+package(default_visibility = ["//visibility:public"])
+
+load(
+    "@io_bazel_rules_go//go:def.bzl",
+    "go_library",
+    "go_test",
+)
+
+go_library(
+    name = "go_default_library",
+    srcs = [
+        "default_generator.go",
+        "default_package.go",
+        "doc.go",
+        "error_tracker.go",
+        "execute.go",
+        "generator.go",
+        "import_tracker.go",
+        "snippet_writer.go",
+    ],
+    importpath = "go-common/app/tool/gengo/generator",
+    tags = ["automanaged"],
+    visibility = ["//visibility:public"],
+    deps = [
+        "//app/tool/gengo/namer:go_default_library",
+        "//app/tool/gengo/parser:go_default_library",
+        "//app/tool/gengo/types:go_default_library",
+        "//vendor/github.com/golang/glog:go_default_library",
+        "//vendor/golang.org/x/tools/imports:go_default_library",
+    ],
+)
+
+go_test(
+    name = "go_default_xtest",
+    srcs = ["snippet_writer_test.go"],
+    tags = ["automanaged"],
+    deps = [
+        "//app/tool/gengo/generator:go_default_library",
+        "//app/tool/gengo/namer:go_default_library",
+        "//app/tool/gengo/parser:go_default_library",
+    ],
+)
+
+filegroup(
+    name = "package-srcs",
+    srcs = glob(["**"]),
+    tags = ["automanaged"],
+    visibility = ["//visibility:private"],
+)
+
+filegroup(
+    name = "all-srcs",
+    srcs = [":package-srcs"],
+    tags = ["automanaged"],
+    visibility = ["//visibility:public"],
+)

app/tool/gengo/generator/default_generator.go

@@ -0,0 +1,47 @@
+package generator
+
+import (
+	"io"
+
+	"go-common/app/tool/gengo/namer"
+	"go-common/app/tool/gengo/types"
+)
+
+// consts
+const (
+	GolangFileType = "golang"
+)
+
+// DefaultGen implements a do-nothing Generator.
+//
+// It can be used to implement static content files.
+type DefaultGen struct {
+	// OptionalName, if present, will be used for the generator's name, and
+	// the filename (with ".go" appended).
+	OptionalName string
+
+	// OptionalBody, if present, will be used as the return from the "Init"
+	// method. This causes it to be static content for the entire file if
+	// no other generator touches the file.
+	OptionalBody []byte
+}
+
+func (d DefaultGen) Name() string                                        { return d.OptionalName }
+func (d DefaultGen) Filter(*Context, *types.Type) bool                   { return true }
+func (d DefaultGen) Namers(*Context) namer.NameSystems                   { return nil }
+func (d DefaultGen) Imports(*Context) []string                           { return []string{} }
+func (d DefaultGen) PackageVars(*Context) []string                       { return []string{} }
+func (d DefaultGen) PackageConsts(*Context) []string                     { return []string{} }
+func (d DefaultGen) GenerateType(*Context, *types.Type, io.Writer) error { return nil }
+func (d DefaultGen) Filename() string                                    { return d.OptionalName + ".go" }
+func (d DefaultGen) FileType() string                                    { return GolangFileType }
+func (d DefaultGen) Finalize(*Context, io.Writer) error                  { return nil }
+
+func (d DefaultGen) Init(c *Context, w io.Writer) error {
+	_, err := w.Write(d.OptionalBody)
+	return err
+}
+
+var (
+	_ = Generator(DefaultGen{})
+)

app/tool/gengo/generator/default_package.go

@@ -0,0 +1,56 @@
+package generator
+
+import (
+	"go-common/app/tool/gengo/types"
+)
+
+// DefaultPackage contains a default implementation of Package.
+type DefaultPackage struct {
+	// Short name of package, used in the "package xxxx" line.
+	PackageName string
+	// Import path of the package, and the location on disk of the package.
+	PackagePath string
+
+	// Emitted at the top of every file.
+	HeaderText []byte
+
+	// Emitted only for a "doc.go" file; appended to the HeaderText for
+	// that file.
+	PackageDocumentation []byte
+
+	// If non-nil, will be called on "Generators"; otherwise, the static
+	// list will be used. So you should set only one of these two fields.
+	GeneratorFunc func(*Context) []Generator
+	GeneratorList []Generator
+
+	// Optional; filters the types exposed to the generators.
+	FilterFunc func(*Context, *types.Type) bool
+}
+
+func (d *DefaultPackage) Name() string { return d.PackageName }
+func (d *DefaultPackage) Path() string { return d.PackagePath }
+
+func (d *DefaultPackage) Filter(c *Context, t *types.Type) bool {
+	if d.FilterFunc != nil {
+		return d.FilterFunc(c, t)
+	}
+	return true
+}
+
+func (d *DefaultPackage) Generators(c *Context) []Generator {
+	if d.GeneratorFunc != nil {
+		return d.GeneratorFunc(c)
+	}
+	return d.GeneratorList
+}
+
+func (d *DefaultPackage) Header(filename string) []byte {
+	if filename == "doc.go" {
+		return append(d.HeaderText, d.PackageDocumentation...)
+	}
+	return d.HeaderText
+}
+
+var (
+	_ = Package(&DefaultPackage{})
+)

app/tool/gengo/generator/doc.go

@@ -0,0 +1,15 @@
+// Package generator defines an interface for code generators to implement.
+//
+// To use this package, you'll implement the "Package" and "Generator"
+// interfaces; you'll call NewContext to load up the types you want to work
+// with, and then you'll call one or more of the Execute methods. See the
+// interface definitions for explanations. All output will have gofmt called on
+// it automatically, so you do not need to worry about generating correct
+// indentation.
+//
+// This package also exposes SnippetWriter. SnippetWriter reduces to a minimum
+// the boilerplate involved in setting up a template from go's text/template
+// package. Additionally, all naming systems in the Context will be added as
+// functions to the parsed template, so that they can be called directly from
+// your templates!
+package generator // import "go-common/app/tool/gengo/generator"

app/tool/gengo/generator/error_tracker.go

@@ -0,0 +1,34 @@
+package generator
+
+import (
+	"io"
+)
+
+// ErrorTracker tracks errors to the underlying writer, so that you can ignore
+// them until you're ready to return.
+type ErrorTracker struct {
+	io.Writer
+	err error
+}
+
+// NewErrorTracker makes a new error tracker; note that it implements io.Writer.
+func NewErrorTracker(w io.Writer) *ErrorTracker {
+	return &ErrorTracker{Writer: w}
+}
+
+// Write intercepts calls to Write.
+func (et *ErrorTracker) Write(p []byte) (n int, err error) {
+	if et.err != nil {
+		return 0, et.err
+	}
+	n, err = et.Writer.Write(p)
+	if err != nil {
+		et.err = err
+	}
+	return n, err
+}
+
+// Error returns nil if no error has occurred, otherwise it returns the error.
+func (et *ErrorTracker) Error() error {
+	return et.err
+}

app/tool/gengo/generator/execute.go

@@ -0,0 +1,301 @@
+package generator
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"go-common/app/tool/gengo/namer"
+	"go-common/app/tool/gengo/types"
+
+	"golang.org/x/tools/imports"
+
+	"github.com/golang/glog"
+)
+
+func errs2strings(errors []error) []string {
+	strs := make([]string, len(errors))
+	for i := range errors {
+		strs[i] = errors[i].Error()
+	}
+	return strs
+}
+
+// ExecutePackages runs the generators for every package in 'packages'. 'outDir'
+// is the base directory in which to place all the generated packages; it
+// should be a physical path on disk, not an import path. e.g.:
+// /path/to/home/path/to/gopath/src/
+// Each package has its import path already, this will be appended to 'outDir'.
+func (c *Context) ExecutePackages(outDir string, packages Packages) error {
+	var errors []error
+	for _, p := range packages {
+		if err := c.ExecutePackage(outDir, p); err != nil {
+			errors = append(errors, err)
+		}
+	}
+	if len(errors) > 0 {
+		return fmt.Errorf("some packages had errors:\n%v\n", strings.Join(errs2strings(errors), "\n"))
+	}
+	return nil
+}
+
+// DefaultFileType is
+type DefaultFileType struct {
+	Format   func([]byte) ([]byte, error)
+	Assemble func(io.Writer, *File)
+}
+
+// AssembleFile is
+func (ft DefaultFileType) AssembleFile(f *File, pathname string) error {
+	glog.V(2).Infof("Assembling file %q", pathname)
+	destFile, err := os.Create(pathname)
+	if err != nil {
+		return err
+	}
+	defer destFile.Close()
+
+	b := &bytes.Buffer{}
+	et := NewErrorTracker(b)
+	ft.Assemble(et, f)
+	if et.Error() != nil {
+		return et.Error()
+	}
+	if formatted, err := ft.Format(b.Bytes()); err != nil {
+		err = fmt.Errorf("unable to format file %q (%v)", pathname, err)
+		// Write the file anyway, so they can see what's going wrong and fix the generator.
+		if _, err2 := destFile.Write(b.Bytes()); err2 != nil {
+			return err2
+		}
+		return err
+	} else {
+		_, err = destFile.Write(formatted)
+		return err
+	}
+}
+
+// VerifyFile is
+func (ft DefaultFileType) VerifyFile(f *File, pathname string) error {
+	glog.V(2).Infof("Verifying file %q", pathname)
+	friendlyName := filepath.Join(f.PackageName, f.Name)
+	b := &bytes.Buffer{}
+	et := NewErrorTracker(b)
+	ft.Assemble(et, f)
+	if et.Error() != nil {
+		return et.Error()
+	}
+	formatted, err := ft.Format(b.Bytes())
+	if err != nil {
+		return fmt.Errorf("unable to format the output for %q: %v", friendlyName, err)
+	}
+	existing, err := ioutil.ReadFile(pathname)
+	if err != nil {
+		return fmt.Errorf("unable to read file %q for comparison: %v", friendlyName, err)
+	}
+	if bytes.Compare(formatted, existing) == 0 {
+		return nil
+	}
+	// Be nice and find the first place where they differ
+	i := 0
+	for i < len(formatted) && i < len(existing) && formatted[i] == existing[i] {
+		i++
+	}
+	eDiff, fDiff := existing[i:], formatted[i:]
+	if len(eDiff) > 100 {
+		eDiff = eDiff[:100]
+	}
+	if len(fDiff) > 100 {
+		fDiff = fDiff[:100]
+	}
+	return fmt.Errorf("output for %q differs; first existing/expected diff: \n  %q\n  %q", friendlyName, string(eDiff), string(fDiff))
+}
+
+func assembleGolangFile(w io.Writer, f *File) {
+	w.Write(f.Header)
+	fmt.Fprintf(w, "package %v\n\n", f.PackageName)
+
+	if len(f.Imports) > 0 {
+		fmt.Fprint(w, "import (\n")
+		for i := range f.Imports {
+			if strings.Contains(i, "\"") {
+				// they included quotes, or are using the
+				// `name "path/to/pkg"` format.
+				fmt.Fprintf(w, "\t%s\n", i)
+			} else {
+				fmt.Fprintf(w, "\t%q\n", i)
+			}
+		}
+		fmt.Fprint(w, ")\n\n")
+	}
+
+	if f.Vars.Len() > 0 {
+		fmt.Fprint(w, "var (\n")
+		w.Write(f.Vars.Bytes())
+		fmt.Fprint(w, ")\n\n")
+	}
+
+	if f.Consts.Len() > 0 {
+		fmt.Fprint(w, "const (\n")
+		w.Write(f.Consts.Bytes())
+		fmt.Fprint(w, ")\n\n")
+	}
+
+	w.Write(f.Body.Bytes())
+}
+
+func importsWrapper(src []byte) ([]byte, error) {
+	return imports.Process("", src, nil)
+}
+
+// NewGolangFile is
+func NewGolangFile() *DefaultFileType {
+	return &DefaultFileType{
+		Format:   importsWrapper,
+		Assemble: assembleGolangFile,
+	}
+}
+
+// format should be one line only, and not end with \n.
+func addIndentHeaderComment(b *bytes.Buffer, format string, args ...interface{}) {
+	if b.Len() > 0 {
+		fmt.Fprintf(b, "\n// "+format+"\n", args...)
+	} else {
+		fmt.Fprintf(b, "// "+format+"\n", args...)
+	}
+}
+
+func (c *Context) filteredBy(f func(*Context, *types.Type) bool) *Context {
+	c2 := *c
+	c2.Order = []*types.Type{}
+	for _, t := range c.Order {
+		if f(c, t) {
+			c2.Order = append(c2.Order, t)
+		}
+	}
+	return &c2
+}
+
+// make a new context; inheret c.Namers, but add on 'namers'. In case of a name
+// collision, the namer in 'namers' wins.
+func (c *Context) addNameSystems(namers namer.NameSystems) *Context {
+	if namers == nil {
+		return c
+	}
+	c2 := *c
+	// Copy the existing name systems so we don't corrupt a parent context
+	c2.Namers = namer.NameSystems{}
+	for k, v := range c.Namers {
+		c2.Namers[k] = v
+	}
+
+	for name, namer := range namers {
+		c2.Namers[name] = namer
+	}
+	return &c2
+}
+
+// ExecutePackage executes a single package. 'outDir' is the base directory in
+// which to place the package; it should be a physical path on disk, not an
+// import path. e.g.: '/path/to/home/path/to/gopath/src/' The package knows its
+// import path already, this will be appended to 'outDir'.
+func (c *Context) ExecutePackage(outDir string, p Package) error {
+	path := filepath.Join(outDir, p.Path())
+	glog.V(2).Infof("Processing package %q, disk location %q", p.Name(), path)
+	// Filter out any types the *package* doesn't care about.
+	packageContext := c.filteredBy(p.Filter)
+	os.MkdirAll(path, 0755)
+	files := map[string]*File{}
+	for _, g := range p.Generators(packageContext) {
+		// Filter out types the *generator* doesn't care about.
+		genContext := packageContext.filteredBy(g.Filter)
+		// Now add any extra name systems defined by this generator
+		genContext = genContext.addNameSystems(g.Namers(genContext))
+
+		fileType := g.FileType()
+		if len(fileType) == 0 {
+			return fmt.Errorf("generator %q must specify a file type", g.Name())
+		}
+		f := files[g.Filename()]
+		if f == nil {
+			// This is the first generator to reference this file, so start it.
+			f = &File{
+				Name:        g.Filename(),
+				FileType:    fileType,
+				PackageName: p.Name(),
+				Header:      p.Header(g.Filename()),
+				Imports:     map[string]struct{}{},
+			}
+			files[f.Name] = f
+		} else {
+			if f.FileType != g.FileType() {
+				return fmt.Errorf("file %q already has type %q, but generator %q wants to use type %q", f.Name, f.FileType, g.Name(), g.FileType())
+			}
+		}
+
+		if vars := g.PackageVars(genContext); len(vars) > 0 {
+			addIndentHeaderComment(&f.Vars, "Package-wide variables from generator %q.", g.Name())
+			for _, v := range vars {
+				if _, err := fmt.Fprintf(&f.Vars, "%s\n", v); err != nil {
+					return err
+				}
+			}
+		}
+		if consts := g.PackageConsts(genContext); len(consts) > 0 {
+			addIndentHeaderComment(&f.Consts, "Package-wide consts from generator %q.", g.Name())
+			for _, v := range consts {
+				if _, err := fmt.Fprintf(&f.Consts, "%s\n", v); err != nil {
+					return err
+				}
+			}
+		}
+		if err := genContext.executeBody(&f.Body, g); err != nil {
+			return err
+		}
+		if imports := g.Imports(genContext); len(imports) > 0 {
+			for _, i := range imports {
+				f.Imports[i] = struct{}{}
+			}
+		}
+	}
+
+	var errors []error
+	for _, f := range files {
+		finalPath := filepath.Join(path, f.Name)
+		assembler, ok := c.FileTypes[f.FileType]
+		if !ok {
+			return fmt.Errorf("the file type %q registered for file %q does not exist in the context", f.FileType, f.Name)
+		}
+		var err error
+		if c.Verify {
+			err = assembler.VerifyFile(f, finalPath)
+		} else {
+			err = assembler.AssembleFile(f, finalPath)
+		}
+		if err != nil {
+			errors = append(errors, err)
+		}
+	}
+	if len(errors) > 0 {
+		return fmt.Errorf("errors in package %q:\n%v", p.Path(), strings.Join(errs2strings(errors), "\n"))
+	}
+	return nil
+}
+
+func (c *Context) executeBody(w io.Writer, generator Generator) error {
+	et := NewErrorTracker(w)
+	if err := generator.Init(c, et); err != nil {
+		return err
+	}
+	for _, t := range c.Order {
+		if err := generator.GenerateType(c, t, et); err != nil {
+			return err
+		}
+	}
+	if err := generator.Finalize(c, et); err != nil {
+		return err
+	}
+	return et.Error()
+}

app/tool/gengo/generator/generator.go

@@ -0,0 +1,205 @@
+package generator
+
+import (
+	"bytes"
+	"io"
+
+	"go-common/app/tool/gengo/namer"
+	"go-common/app/tool/gengo/parser"
+	"go-common/app/tool/gengo/types"
+)
+
+// Package contains the contract for generating a package.
+type Package interface {
+	// Name returns the package short name.
+	Name() string
+	// Path returns the package import path.
+	Path() string
+
+	// Filter should return true if this package cares about this type.
+	// Otherwise, this type will be omitted from the type ordering for
+	// this package.
+	Filter(*Context, *types.Type) bool
+
+	// Header should return a header for the file, including comment markers.
+	// Useful for copyright notices and doc strings. Include an
+	// autogeneration notice! Do not include the "package x" line.
+	Header(filename string) []byte
+
+	// Generators returns the list of generators for this package. It is
+	// allowed for more than one generator to write to the same file.
+	// A Context is passed in case the list of generators depends on the
+	// input types.
+	Generators(*Context) []Generator
+}
+
+// File is
+type File struct {
+	Name        string
+	FileType    string
+	PackageName string
+	Header      []byte
+	Imports     map[string]struct{}
+	Vars        bytes.Buffer
+	Consts      bytes.Buffer
+	Body        bytes.Buffer
+}
+
+// FileType is
+type FileType interface {
+	AssembleFile(f *File, path string) error
+	VerifyFile(f *File, path string) error
+}
+
+// Packages is a list of packages to generate.
+type Packages []Package
+
+// Generator is the contract for anything that wants to do auto-generation.
+// It's expected that the io.Writers passed to the below functions will be
+// ErrorTrackers; this allows implementations to not check for io errors,
+// making more readable code.
+//
+// The call order for the functions that take a Context is:
+// 1. Filter()        // Subsequent calls see only types that pass this.
+// 2. Namers()        // Subsequent calls see the namers provided by this.
+// 3. PackageVars()
+// 4. PackageConsts()
+// 5. Init()
+// 6. GenerateType()  // Called N times, once per type in the context's Order.
+// 7. Imports()
+//
+// You may have multiple generators for the same file.
+type Generator interface {
+	// The name of this generator. Will be included in generated comments.
+	Name() string
+
+	// Filter should return true if this generator cares about this type.
+	// (otherwise, GenerateType will not be called.)
+	//
+	// Filter is called before any of the generator's other functions;
+	// subsequent calls will get a context with only the types that passed
+	// this filter.
+	Filter(*Context, *types.Type) bool
+
+	// If this generator needs special namers, return them here. These will
+	// override the original namers in the context if there is a collision.
+	// You may return nil if you don't need special names. These names will
+	// be available in the context passed to the rest of the generator's
+	// functions.
+	//
+	// A use case for this is to return a namer that tracks imports.
+	Namers(*Context) namer.NameSystems
+
+	// Init should write an init function, and any other content that's not
+	// generated per-type. (It's not intended for generator specific
+	// initialization! Do that when your Package constructs the
+	// Generators.)
+	Init(*Context, io.Writer) error
+
+	// Finalize should write finish up functions, and any other content that's not
+	// generated per-type.
+	Finalize(*Context, io.Writer) error
+
+	// PackageVars should emit an array of variable lines. They will be
+	// placed in a var ( ... ) block. There's no need to include a leading
+	// \t or trailing \n.
+	PackageVars(*Context) []string
+
+	// PackageConsts should emit an array of constant lines. They will be
+	// placed in a const ( ... ) block. There's no need to include a leading
+	// \t or trailing \n.
+	PackageConsts(*Context) []string
+
+	// GenerateType should emit the code for a particular type.
+	GenerateType(*Context, *types.Type, io.Writer) error
+
+	// Imports should return a list of necessary imports. They will be
+	// formatted correctly. You do not need to include quotation marks,
+	// return only the package name; alternatively, you can also return
+	// imports in the format `name "path/to/pkg"`. Imports will be called
+	// after Init, PackageVars, PackageConsts, and GenerateType, to allow
+	// you to keep track of what imports you actually need.
+	Imports(*Context) []string
+
+	// Preferred file name of this generator, not including a path. It is
+	// allowed for multiple generators to use the same filename, but it's
+	// up to you to make sure they don't have colliding import names.
+	// TODO: provide per-file import tracking, removing the requirement
+	// that generators coordinate..
+	Filename() string
+
+	// A registered file type in the context to generate this file with. If
+	// the FileType is not found in the context, execution will stop.
+	FileType() string
+}
+
+// Context is global context for individual generators to consume.
+type Context struct {
+	// A map from the naming system to the names for that system. E.g., you
+	// might have public names and several private naming systems.
+	Namers namer.NameSystems
+
+	// All the types, in case you want to look up something.
+	Universe types.Universe
+
+	// All the user-specified packages.  This is after recursive expansion.
+	Inputs []string
+
+	// The canonical ordering of the types (will be filtered by both the
+	// Package's and Generator's Filter methods).
+	Order []*types.Type
+
+	// A set of types this context can process. If this is empty or nil,
+	// the default "golang" filetype will be provided.
+	FileTypes map[string]FileType
+
+	// If true, Execute* calls will just verify that the existing output is
+	// correct. (You may set this after calling NewContext.)
+	Verify bool
+
+	// Allows generators to add packages at runtime.
+	builder *parser.Builder
+}
+
+// NewContext generates a context from the given builder, naming systems, and
+// the naming system you wish to construct the canonical ordering from.
+func NewContext(b *parser.Builder, nameSystems namer.NameSystems, canonicalOrderName string) (*Context, error) {
+	universe, err := b.FindTypes()
+	if err != nil {
+		return nil, err
+	}
+
+	c := &Context{
+		Namers:   namer.NameSystems{},
+		Universe: universe,
+		Inputs:   b.FindPackages(),
+		FileTypes: map[string]FileType{
+			GolangFileType: NewGolangFile(),
+		},
+		builder: b,
+	}
+
+	for name, systemNamer := range nameSystems {
+		c.Namers[name] = systemNamer
+		if name == canonicalOrderName {
+			orderer := namer.Orderer{Namer: systemNamer}
+			c.Order = orderer.OrderUniverse(universe)
+		}
+	}
+	return c, nil
+}
+
+// AddDir adds a Go package to the context. The specified path must be a single
+// go package import path.  GOPATH, GOROOT, and the location of your go binary
+// (`which go`) will all be searched, in the normal Go fashion.
+// Deprecated. Please use AddDirectory.
+func (ctxt *Context) AddDir(path string) error {
+	return ctxt.builder.AddDirTo(path, &ctxt.Universe)
+}
+
+// AddDirectory adds a Go package to the context. The specified path must be a
+// single go package import path.  GOPATH, GOROOT, and the location of your go
+// binary (`which go`) will all be searched, in the normal Go fashion.
+func (ctxt *Context) AddDirectory(path string) (*types.Package, error) {
+	return ctxt.builder.AddDirectoryTo(path, &ctxt.Universe)
+}

app/tool/gengo/generator/import_tracker.go

@@ -0,0 +1,49 @@
+package generator
+
+import (
+	"strings"
+
+	"github.com/golang/glog"
+
+	"go-common/app/tool/gengo/namer"
+	"go-common/app/tool/gengo/types"
+)
+
+// NewImportTracker is
+func NewImportTracker(typesToAdd ...*types.Type) namer.ImportTracker {
+	tracker := namer.NewDefaultImportTracker(types.Name{})
+	tracker.IsInvalidType = func(*types.Type) bool { return false }
+	tracker.LocalName = func(name types.Name) string { return golangTrackerLocalName(&tracker, name) }
+	tracker.PrintImport = func(path, name string) string { return name + " \"" + path + "\"" }
+
+	tracker.AddTypes(typesToAdd...)
+	return &tracker
+
+}
+
+func golangTrackerLocalName(tracker namer.ImportTracker, t types.Name) string {
+	path := t.Package
+
+	// Using backslashes in package names causes gengo to produce Go code which
+	// will not compile with the gc compiler. See the comment on GoSeperator.
+	if strings.ContainsRune(path, '\\') {
+		glog.Warningf("Warning: backslash used in import path '%v', this is unsupported.\n", path)
+	}
+
+	dirs := strings.Split(path, namer.GoSeperator)
+	for n := len(dirs) - 1; n >= 0; n-- {
+		// follow kube convention of not having anything between directory names
+		name := strings.Join(dirs[n:], "")
+		name = strings.Replace(name, "_", "", -1)
+		// These characters commonly appear in import paths for go
+		// packages, but aren't legal go names. So we'll sanitize.
+		name = strings.Replace(name, ".", "", -1)
+		name = strings.Replace(name, "-", "", -1)
+		if _, found := tracker.PathOf(name); found {
+			// This name collides with some other package
+			continue
+		}
+		return name
+	}
+	panic("can't find import for " + path)
+}

app/tool/gengo/generator/snippet_writer.go

@@ -0,0 +1,140 @@
+package generator
+
+import (
+	"fmt"
+	"io"
+	"runtime"
+	"text/template"
+)
+
+// SnippetWriter is an attempt to make the template library usable.
+// Methods are chainable, and you don't have to check Error() until you're all
+// done.
+type SnippetWriter struct {
+	w       io.Writer
+	context *Context
+	// Left & right delimiters. text/template defaults to "{{" and "}}"
+	// which is totally unusable for go code based templates.
+	left, right string
+	funcMap     template.FuncMap
+	err         error
+}
+
+// NewSnippetWriter is
+// w is the destination; left and right are the delimiters; @ and $ are both
+// reasonable choices.
+//
+// c is used to make a function for every naming system, to which you can pass
+// a type and get the corresponding name.
+func NewSnippetWriter(w io.Writer, c *Context, left, right string) *SnippetWriter {
+	sw := &SnippetWriter{
+		w:       w,
+		context: c,
+		left:    left,
+		right:   right,
+		funcMap: template.FuncMap{},
+	}
+	for name, namer := range c.Namers {
+		sw.funcMap[name] = namer.Name
+	}
+	return sw
+}
+
+// Do parses format and runs args through it. You can have arbitrary logic in
+// the format (see the text/template documentation), but consider running many
+// short templaces, with ordinary go logic in between--this may be more
+// readable. Do is chainable. Any error causes every other call to do to be
+// ignored, and the error will be returned by Error(). So you can check it just
+// once, at the end of your function.
+//
+// 'args' can be quite literally anything; read the text/template documentation
+// for details. Maps and structs work particularly nicely. Conveniently, the
+// types package is designed to have structs that are easily referencable from
+// the template language.
+//
+// Example:
+//
+// sw := generator.NewSnippetWriter(outBuffer, context, "$", "$")
+// sw.Do(`The public type name is: $.type|public$`, map[string]interface{}{"type": t})
+// return sw.Error()
+//
+// Where:
+// * "$" starts a template directive
+// * "." references the entire thing passed as args
+// * "type" therefore sees a map and looks up the key "type"
+// * "|" means "pass the thing on the left to the thing on the right"
+// * "public" is the name of a naming system, so the SnippetWriter has given
+//   the template a function called "public" that takes a *types.Type and
+//   returns the naming system's name. E.g., if the type is "string" this might
+//   return "String".
+// * the second "$" ends the template directive.
+//
+// The map is actually not necessary. The below does the same thing:
+//
+// sw.Do(`The public type name is: $.|public$`, t)
+//
+// You may or may not find it more readable to use the map with a descriptive
+// key, but if you want to pass more than one arg, the map or a custom struct
+// becomes a requirement. You can do arbitrary logic inside these templates,
+// but you should consider doing the logic in go and stitching them together
+// for the sake of your readers.
+//
+// TODO: Change Do() to optionally take a list of pairs of parameters (key, value)
+// and have it construct a combined map with that and args.
+func (s *SnippetWriter) Do(format string, args interface{}) *SnippetWriter {
+	if s.err != nil {
+		return s
+	}
+	// Name the template by source file:line so it can be found when
+	// there's an error.
+	_, file, line, _ := runtime.Caller(1)
+	tmpl, err := template.
+		New(fmt.Sprintf("%s:%d", file, line)).
+		Delims(s.left, s.right).
+		Funcs(s.funcMap).
+		Parse(format)
+	if err != nil {
+		s.err = err
+		return s
+	}
+	err = tmpl.Execute(s.w, args)
+	if err != nil {
+		s.err = err
+	}
+	return s
+}
+
+// Args exists to make it convenient to construct arguments for
+// SnippetWriter.Do.
+type Args map[interface{}]interface{}
+
+// With makes a copy of a and adds the given key, value pair.
+func (a Args) With(key, value interface{}) Args {
+	a2 := Args{key: value}
+	for k, v := range a {
+		a2[k] = v
+	}
+	return a2
+}
+
+// WithArgs makes a copy of a and adds the given arguments.
+func (a Args) WithArgs(rhs Args) Args {
+	a2 := Args{}
+	for k, v := range rhs {
+		a2[k] = v
+	}
+	for k, v := range a {
+		a2[k] = v
+	}
+	return a2
+}
+
+// Out is
+func (s *SnippetWriter) Out() io.Writer {
+	return s.w
+}
+
+// Error returns any encountered error.
+func (s *SnippetWriter) Error() error {
+	return s.err
+}

app/tool/gengo/generator/snippet_writer_test.go

@@ -0,0 +1,72 @@
+package generator_test
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+
+	"go-common/app/tool/gengo/generator"
+	"go-common/app/tool/gengo/namer"
+	"go-common/app/tool/gengo/parser"
+)
+
+func construct(t *testing.T, files map[string]string) *generator.Context {
+	b := parser.New()
+	for name, src := range files {
+		if err := b.AddFileForTest("/tmp/"+name, name, []byte(src)); err != nil {
+			t.Fatal(err)
+		}
+	}
+	c, err := generator.NewContext(b, namer.NameSystems{
+		"public":  namer.NewPublicNamer(0),
+		"private": namer.NewPrivateNamer(0),
+	}, "public")
+	if err != nil {
+		t.Fatal(err)
+	}
+	return c
+}
+
+func TestSnippetWriter(t *testing.T) {
+	var structTest = map[string]string{
+		"base/foo/proto/foo.go": `
+package foo
+
+// Blah is a test.
+// A test, I tell you.
+type Blah struct {
+	// A is the first field.
+	A int64 ` + "`" + `json:"a"` + "`" + `
+
+	// B is the second field.
+	// Multiline comments work.
+	B string ` + "`" + `json:"b"` + "`" + `
+}
+`,
+	}
+
+	c := construct(t, structTest)
+	b := &bytes.Buffer{}
+	err := generator.NewSnippetWriter(b, c, "$", "$").
+		Do("$.|public$$.|private$", c.Order[0]).
+		Error()
+	if err != nil {
+		t.Errorf("Unexpected error %v", err)
+	}
+	if e, a := "Blahblah", b.String(); e != a {
+		t.Errorf("Expected %q, got %q", e, a)
+	}
+
+	err = generator.NewSnippetWriter(b, c, "$", "$").
+		Do("$.|public", c.Order[0]).
+		Error()
+	if err == nil {
+		t.Errorf("expected error on invalid template")
+	} else {
+		// Dear reader, I apologize for making the worst change
+		// detection test in the history of ever.
+		if e, a := "snippet_writer_test.go", err.Error(); !strings.Contains(a, e) {
+			t.Errorf("Expected %q but didn't find it in %q", e, a)
+		}
+	}
+}