all: go2goplay.golang.org source

This CL contains the altered playground source that is served
at go2goplay.golang.org.

It compiles the toolchain at the dev.go2go branch of the main
Go repository, translates .go2 programs using the go2go tool,
and compiles the playground frontend binary using the dev.go2go
toolchain (to support code formatting).

The header and “About” text is updated to differentiate from
the normal playground and explain its differences,
code location, etc.

Most features present on play.golang.org are missing, and this
instance only supports single-file, non-test, main-package
programs. This was done for initial simplicity of the
implementation.

Updates golang/go#39675
Fixes golang/go#39809

Change-Id: Id9461830c4233ab3f938dc6d21da3e5f2d8adbc3
Reviewed-on: https://go-review.googlesource.com/c/playground/+/240541
Reviewed-by: Alexander Rakoczy <[email protected]>

Author: andybons

Dockerfile

@@ -2,8 +2,6 @@
 # Use of this source code is governed by a BSD-style
 # license that can be found in the LICENSE file.
 
-ARG GO_VERSION=go1.14.1
-
 FROM debian:buster AS go-faketime
 LABEL maintainer="[email protected]"
 
@@ -13,8 +11,6 @@ RUN apt-get update && apt-get install -y ${BUILD_DEPS} --no-install-recommends
 ENV GOPATH /go
 ENV PATH /usr/local/go/bin:$GOPATH/bin:$PATH
 ENV GO_BOOTSTRAP_VERSION go1.14.1
-ARG GO_VERSION
-ENV GO_VERSION ${GO_VERSION}
 
 # Get a version of Go for building the playground
 RUN curl -sSL https://dl.google.com/go/$GO_BOOTSTRAP_VERSION.linux-amd64.tar.gz -o /tmp/go.tar.gz
@@ -30,14 +26,25 @@ ENV GOPROXY=https://proxy.golang.org
 
 # Compile Go at target sandbox version and install standard library with --tags=faketime.
 WORKDIR /usr/local
-RUN git clone https://go.googlesource.com/go go-faketime && cd go-faketime && git reset --hard $GO_VERSION
+RUN git clone https://go.googlesource.com/go go-faketime && cd go-faketime && git checkout dev.go2go
 WORKDIR /usr/local/go-faketime/src
 RUN ./make.bash
 ENV GOROOT /usr/local/go-faketime
 RUN ../bin/go install --tags=faketime std
 
 FROM golang:1.14 as build-playground
 
+# Compile Go using dev.go2go branch to get go2go-compatible go/format.
+WORKDIR /usr/local
+RUN git clone https://go.googlesource.com/go go2go && cd go2go && git checkout dev.go2go
+WORKDIR /usr/local/go2go/src
+RUN ./make.bash
+ENV GOROOT /usr/local/go2go
+
+WORKDIR /
+
+ENV PATH /usr/local/go2go/bin:$PATH
+
 COPY go.mod /go/src/playground/go.mod
 COPY go.sum /go/src/playground/go.sum
 WORKDIR /go/src/playground
@@ -55,8 +62,6 @@ RUN apt-get update && apt-get install -y git ca-certificates --no-install-recomm
 
 COPY --from=go-faketime /usr/local/go-faketime /usr/local/go-faketime
 
-ARG GO_VERSION
-ENV GO_VERSION ${GO_VERSION}
 ENV GOPATH /go
 ENV PATH /usr/local/go-faketime/bin:$GOPATH/bin:$PATH
 

Makefile

@@ -7,20 +7,20 @@ GCLOUD_ACCESS_TOKEN := $(shell gcloud auth print-access-token)
 .PHONY: docker test update-cloudbuild-trigger
 
 docker:
-	docker build -t golang/playground .
+	docker build -t golang/playground-go2go .
 
-runlocal:
+runlocal: docker
 	docker network create sandnet || true
 	docker kill play_dev || true
-	docker run --name=play_dev --rm --network=sandnet -ti -p 127.0.0.1:8081:8080/tcp golang/playground --backend-url="http://sandbox_dev.sandnet/run"
+	docker run --name=play_dev --rm --network=sandnet -ti -p 127.0.0.1:8081:8080/tcp golang/playground-go2go --backend-url="http://sandbox_dev.sandnet/run"
 
 test_go:
 	# Run fast tests first: (and tests whether, say, things compile)
 	GO111MODULE=on go test -v ./...
 
 test_gvisor: docker
 	docker kill sandbox_front_test || true
-	docker run --rm --name=sandbox_front_test --network=sandnet -t golang/playground --runtests
+	docker run --rm --name=sandbox_front_test --network=sandnet -t golang/playground-go2go --runtests
 
 # Note: test_gvisor is not included in "test" yet, because it requires
 # running a separate server first ("make runlocal" in the sandbox

README.md

@@ -56,9 +56,9 @@ Alternatively, to avoid Cloud Build and build locally:
 
 ```bash
 make docker
-docker tag golang/playground:latest gcr.io/golang-org/playground:latest
-docker push gcr.io/golang-org/playground:latest
-gcloud --project=golang-org [email protected] app deploy app.yaml --image-url=gcr.io/golang-org/playground:latest
+docker tag golang/playground-go2go:latest gcr.io/golang-org/playground-go2go:latest
+docker push gcr.io/golang-org/playground-go2go:latest
+gcloud --project=golang-org [email protected] app deploy app.yaml --image-url=gcr.io/golang-org/playground-go2go:latest
 ```
 
 Then:

app.yaml

@@ -1,4 +1,4 @@
-service: play
+service: go2goplay
 runtime: custom
 env: flex
 
@@ -13,7 +13,7 @@ automatic_scaling:
   min_num_instances: 5
 
 readiness_check:
-  path: "/_ah/health"
+  path: '/_ah/health'
   check_interval_sec: 10
 
 env_variables:

edit.go

@@ -14,7 +14,8 @@ import (
 	"cloud.google.com/go/datastore"
 )
 
-const hostname = "play.golang.org"
+// TODO(golang.org/issue/39675): parameterize before merging.
+const hostname = "go2goplay.golang.org"
 
 var editTemplate = template.Must(template.ParseFiles("edit.html"))
 
@@ -95,7 +96,13 @@ import (
 	"fmt"
 )
 
+func Print(type T)(s []T) {
+	for _, v := range s {
+		fmt.Print(v)
+	}
+}
+
 func main() {
-	fmt.Println("Hello, playground")
+	Print([]string{"Hello, ", "playground\n"})
 }
 `

edit.html

@@ -1,7 +1,7 @@
 <!doctype html>
 <html>
 	<head>
-		<title>The Go Playground</title>
+		<title>The go2go Playground</title>
 		<link rel="stylesheet" href="/static/style.css">
 		{{if .Analytics}}
 		<script async src="https://www.googletagmanager.com/gtag/js?id=UA-11222381-7"></script>
@@ -103,7 +103,11 @@
 	<body itemscope itemtype="http://schema.org/CreativeWork">
 		<input type="button" value="Run" id="embedRun">
 		<div id="banner">
-			<div id="head" itemprop="name">The Go Playground</div>
+			<div id="head" itemprop="name">
+			  The
+				<a href="https://blog.golang.org/generics-next-step">go2go</a>
+				Playground
+			</div>
 			<input type="button" value="Run" id="run">
 			<input type="button" value="Format" id="fmt">
 			<div id="importsBox">
@@ -122,11 +126,8 @@
 			{{end}}
 			<select class="js-playgroundToysEl">
 				<option value="hello.txt">Hello, playground</option>
-				<option value="test.txt">Tests</option>
-				<option value="multi.txt">Multiple files</option>
-				<option value="image.txt">Display image</option>
-				<option value="sleep.txt">Sleep</option>
-				<option value="clear.txt">Clear</option>
+				<option value="min.txt">Min function</option>
+				<option value="queue.txt">Basic queue</option>
 			</select>
 			<input type="button" value="About" id="aboutButton">
 		</div>
@@ -139,17 +140,37 @@
 <p><b>About the Playground</b></p>
 
 <p>
-The Go Playground is a web service that runs on
+The go2go Playground is a web service that runs on
 <a href="https://golang.org/">golang.org</a>'s servers.
 The service receives a Go program, <a href="https://golang.org/cmd/vet/">vets</a>, compiles, links, and
 runs the program inside a sandbox, then returns the output.
 </p>
 
 <p>
-If the program contains <a href="https://golang.org/pkg/testing">tests or examples</a>
-and no main function, the service runs the tests.
-Benchmarks will likely not be supported since the program runs in a sandboxed
-environment with limited resources.
+  <b>
+	  This experimental instance of the playground supports the syntax described in the
+		<a href="https://go.googlesource.com/proposal/+/refs/heads/master/design/go2draft-type-parameters.md">Type Parameters design draft</a>,
+		utilizing the
+		<a href="https://go.googlesource.com/go/+/refs/heads/dev.go2go/README.go2go.md">go2go tool</a>.
+	</b>
+</p>
+
+<p>
+  The best way to provide feedback for the language changes will be on the mailing list [email protected].
+	Mailing lists are imperfect, but they seem like our best option for initial discussion.
+	When writing about the design draft, please put [generics] at the start of the Subject line and to start different
+	threads for different specific topics.
+</p>
+
+<p>
+  If you find bugs in the generics type checker, the translation tool, or this playground instance they should be
+	filed in the standard Go issue tracker at <a href="https://golang.org/issue/new?title=cmd%2Fgo2go%3A">https://golang.org/issue</a>.
+	Please start the issue title with cmd/go2go:. Note that the issue tracker is not the best place to discuss
+	changes to the language, because it does not provide threading and it is not well suited to lengthy conversations.
+</p>
+
+<p>
+  We look forward to your feedback.
 </p>
 
 <p>
@@ -158,6 +179,11 @@
 
 <ul>
 
+<li>
+Not all features of the normal playground are supported.
+<a href="https://golang.org/issue/39675">This issue</a> tracks feature parity with play.golang.org.
+</li>
+
 <li>
 The playground can use most of the standard library, with some exceptions.
 The only communication a playground program has to the outside world
@@ -177,25 +203,8 @@
 </ul>
 
 <p>
-The article "<a href="https://blog.golang.org/playground" target="_blank" rel="noopener">Inside
-the Go Playground</a>" describes how the playground is implemented.
-The source code is available at <a href="https://go.googlesource.com/playground" target="_blank" rel="noopener">
-https://go.googlesource.com/playground</a>.
-</p>
-
-<p>
-The playground uses the latest stable release of Go.<br>
-The current version is <a href="/p/Ztyu2FJaajl">{{.GoVersion}}</a>.
-</p>
-
-<p>
-The playground service is used by more than just the official Go project
-(<a href="https://gobyexample.com/">Go by Example</a> is one other instance)
-and we are happy for you to use it on your own site.
-All we ask is that you
-<a href="mailto:[email protected]">contact us first (note this is a public mailing list)</a>,
-use a unique user agent in your requests (so we can identify you),
-and that your service is of benefit to the Go community.
+The source code is available at <a href="https://go.googlesource.com/playground/+/refs/heads/dev.go2go" target="_blank" rel="noopener">
+https://go.googlesource.com/playground/+/refs/heads/dev.go2go</a>.
 </p>
 
 <p>

examples/clear.txt

@@ -4,6 +4,12 @@ import (
 	"fmt"
 )
 
+func Print(type T)(s []T) {
+	for _, v := range s {
+		fmt.Print(v)
+	}
+}
+
 func main() {
-	fmt.Println("Hello, playground")
+	Print([]string{"Hello, ", "playground\n"})
 }

examples/hello.txt

@@ -0,0 +1,21 @@
+package main
+
+import (
+	"fmt"
+)
+
+type numeric interface {
+	type int, int8, int16, int32, int64, uint, uint8, uint16, uint32, uint64, float32, float64
+}
+
+func min(type T numeric)(a, b T) T {
+	if a < b {
+		return a
+	}
+	return b
+}
+
+func main() {
+	fmt.Println(min(42, 84))
+	fmt.Println(min(3.14159, 2.7182))
+}

examples/image.txt

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"fmt"
+)
+
+type queue(type T) []T
+
+func (q *queue(T)) enqueue(v T) {
+	*q = append(*q, v)
+}
+
+func (q *queue(T)) dequeue() (T, bool) {
+	if len(*q) == 0 {
+		var zero T
+		return zero, false
+	}
+	r := (*q)[0]
+	*q = (*q)[1:]
+	return r, true
+}
+
+func main() {
+	q := new(queue(int))
+	q.enqueue(5)
+	q.enqueue(6)
+	fmt.Println(q)
+	fmt.Println(q.dequeue())
+	fmt.Println(q.dequeue())
+	fmt.Println(q.dequeue())
+}

examples/min.txt

@@ -34,7 +34,9 @@ func handleFmt(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	fixImports := r.FormValue("imports") != ""
+	// TODO(golang.org/issue/39675): goimports does not currently support the
+	// dev.go2go branch.
+	fixImports := r.FormValue("imports") != "" && false
 	for _, f := range fs.files {
 		switch {
 		case path.Ext(f) == ".go":