x/tools/cmd/heapview: add basic client serving

This change primarily exists to import Typescript and the
ES6 module loader polyfill as dependencies for this project.
Both dependencies are relatively lightweight and can be easily
removed if we decide we don't need them.

The module loader polyfill implements support for an upcoming
browser feature in ES6 (the next version of JavaScript). This
feature helps modularize Javascript code and conveniently split it
into multiple files. It should be supported by the stable versions
of the four major browsers (Chrome, Firefox, Safari and Edge)
by the end of the year. Once that happens, we can remove the polyfill.

The Typescript compiler provides two things: First, it compiles
new, but not-yet-supported ES6 Javascript features into ES5. It
also provides a typechecker similar to what Closure does, but types
are indicated in syntax rather than JSDoc comments. If we decide
we don't want this dependency, we can compile the Typescript code
into human-readable JavaScript code. (The compiler basically
strips out types and replaces ES6 language features with more
well-supported JavaScript equivalents). The Typescript compiler
is not required for development. typescript.js and a feature in
the module loader will be used to compile Typescript into JavaScript
at serving time. (We might want to do something different for the
production version, but we can get to that later).

The change also adds code to serve the HTML and Javascript files.

Updates golang/go#16410

Change-Id: I42c669d1de636d8b221fc03ed22aa7ac60554610
Reviewed-on: https://go-review.googlesource.com/25240
Reviewed-by: Austin Clements <austin@google.com>

cmd/heapview/client/.gitignore

@@ -0,0 +1 @@
+/node_modules/

cmd/heapview/client/README.md

@@ -0,0 +1,45 @@
+# Go Heap Viewer Client
+
+This directory contains the client Typescript code for the Go
+heap viewer.
+
+## Typescript Tooling
+
+Below are instructions for downloading tooling and files to
+help make the development process more convenient. These tools
+are not required for contributing or running the heap viewer-
+they are just meant as development aids.
+
+## Node and NPM
+
+We use npm to manage the dependencies for these tools. There are
+a couple of ways of installing npm on your system, but we recommend
+using nvm.
+
+Run the following command to install nvm:
+
+    [shell]$ curl -o- https://raw.githubusercontent.com/creationix/nvm/v0.31.3/install.sh | bash
+
+or see the instructions on [the nvm github page](github.com/creationix/nvm)
+for alternative methods. This will put the nvm tool in your home directory
+and edit your path to add nvm, node and other tools you install using them.
+Once nvm is installed, use
+
+    [shell]$ nvm install node
+
+then
+
+    [shell]$ nvm use node
+
+to install node.js.
+
+Once node is installed, you can install typescript using
+
+    [shell]$ npm install -g typescript
+
+Finally, import type definitions into this project by running
+
+    [shell]$ npm install
+
+in this directory. They will be imported into the node_packages directory
+and be automatically available to the Typescript compiler.

cmd/heapview/client/main.ts

@@ -0,0 +1,8 @@
+// Copyright 2016 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.
+
+export function main() {
+    document.title = "Go Heap Viewer"; 
+} 
+ 

cmd/heapview/client/package.json

@@ -0,0 +1,21 @@
+{
+  "//": [
+    "Copyright 2016 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 exists to help import typescript typings",
+    "for web features used in this project. Neither the",
+    "typings nor node or npm are required to do development",
+    "on the code in this project.",
+
+    "If you do have npm installed, use the `npm i` command",
+    "in this directory to install the typings."
+  ],
+
+  "private": true,
+  "dependencies": {
+    "@types/es6-promise": "0.0.28",
+    "@types/whatwg-fetch": "0.0.27"
+  }
+}

cmd/heapview/client/tsconfig.json

@@ -0,0 +1,15 @@
+// Copyright 2016 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 configuration for the Typescript
+// compiler if you're running it locally for typechecking
+// and other tooling. The Typescript compiler is
+// not necessary to do development on this project.
+
+{
+  "compilerOptions": {
+    "noEmit": true,
+    "strictNullChecks": true
+  }
+}

cmd/heapview/main.go

@@ -5,5 +5,54 @@
 // heapview is a tool for viewing Go heap dumps.
 package main
 
-func main() {
+import (
+	"io"
+	"log"
+	"net/http"
+	"os"
+	"path"
+	"path/filepath"
+)
+
+var index = `<!DOCTYPE html>
+<script src="js/typescript.js"></script>
+<script src="js/moduleloader.js"></script>
+<script>
+  System.transpiler = 'typescript';
+  System.locate = (load) => load.name + '.ts';
+</script>
+<script type="module">
+  import {main} from './client/main';
+  main();
+</script>
+`
+
+func toolsDir() string {
+	gopath := os.Getenv("GOPATH")
+	if gopath == "" {
+		log.Println("error: GOPATH not set. Can't find client files")
+		os.Exit(1)
+	}
+	return filepath.Join(filepath.SplitList(gopath)[0], "/src/golang.org/x/tools")
+}
+
+func main() {
+	// Directly serve typescript code in client directory for development.
+	http.Handle("/client/", http.StripPrefix("/client",
+		http.FileServer(http.Dir(filepath.Join(toolsDir(), "cmd/heapview/client")))))
+	// Serve typescript.js and moduleloader.js for development.
+	log.Print(http.Dir(path.Join(toolsDir() + "/cmd/heapview/client")))
+	http.HandleFunc("/js/typescript.js", func(w http.ResponseWriter, r *http.Request) {
+		http.ServeFile(w, r, filepath.Join(toolsDir(), "third_party/typescript/typescript.js"))
+	})
+	http.HandleFunc("/js/moduleloader.js", func(w http.ResponseWriter, r *http.Request) {
+		http.ServeFile(w, r, filepath.Join(toolsDir(), "third_party/moduleloader/moduleloader.js"))
+	})
+	// Serve index.html using html string above.
+	http.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set("Content-Type", "text/html")
+		io.WriteString(w, index)
+	})
+
+	http.ListenAndServe(":8080", nil)
 }

third_party/moduleloader/LICENSE

@@ -0,0 +1,22 @@
+Copyright (c) 2013-2016 Guy Bedford, Luke Hoban, Addy Osmani
+
+Permission is hereby granted, free of charge, to any person
+obtaining a copy of this software and associated documentation
+files (the "Software"), to deal in the Software without
+restriction, including without limitation the rights to use,
+copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following
+conditions:
+
+The above copyright notice and this permission notice shall be
+included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
+OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
+HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+OTHER DEALINGS IN THE SOFTWARE.

third_party/typescript/LICENSE

@@ -0,0 +1,55 @@
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