playground: Improve update.sh to be more general.

It uses a temporary staging folder to perform the operations.

-	No longer require your GOROOT to be writeable.
-	No longer require your GOPATH list to contain no more than
	1 workspace.
-	It has no side-effects, for example, it no longer leaves the
	$GOPATH/bin/playground.js.map file behind.

Fixes #36.

It doesn't fix a part of #36, but a new issue #43 is created to track that.

Author: dmitshur

playground/README.md

@@ -6,9 +6,9 @@ A secondary motivation is making the playground usable for other projects, such
 
 ## Development
 
-To update the entire playground environment, run the `update.sh` script. It will install your local version of gopherjs compiler, rebuild and copy the standard library into the `pkg` directory, and build the playground.
+To update the entire playground environment, just run `go generate github.com/gopherjs/gopherjs.github.io/playground`. It will install your local version of GopherJS compiler, build the playground, make a temporary copy of Go to /tmp/gopherjsplayground_goroot, rebuild and copy the standard library into the `pkg` directory.
 
-Working on the application itself is made easier by using the `gopherjs serve` command to rebuild and serve the playground every time you refresh the browser.
+Working on the playground application itself is made easier by using the `gopherjs serve` command to rebuild and serve the playground every time you refresh the browser.
 
 ```bash
 gopherjs serve

playground/gen.go

@@ -0,0 +1,3 @@
+//go:generate ./update.sh
+
+package main

playground/update.sh

@@ -1,24 +1,39 @@
-#! /bin/sh
+#!/bin/sh
 set -e
 
 go install github.com/gopherjs/gopherjs/...
 
 go generate github.com/gopherjs/gopherjs.github.io/playground/internal/imports
 
-gopherjs install -m github.com/gopherjs/gopherjs.github.io/playground github.com/gopherjs/gopherjs/js
-cp $GOPATH/bin/playground.js $GOPATH/src/github.com/gopherjs/gopherjs.github.io/playground/playground.js
-cp $GOPATH/bin/playground.js.map $GOPATH/src/github.com/gopherjs/gopherjs.github.io/playground/playground.js.map
+# Build playground itself.
+gopherjs build -m
 
-PKG=$GOPATH/src/github.com/gopherjs/gopherjs.github.io/playground/pkg
+# The GOPATH workspace where the GopherJS project is.
+GOPHERJSGOPATH=$(go list -f '{{.Root}}' github.com/gopherjs/gopherjs)
 
+PKG=pkg
 rm -r $PKG
 
+# Use an empty GOPATH workspace with just gopherjs,
+# so that all the standard library packages get written to GOROOT/pkg.
+export GOPATH=/tmp/gopherjsplayground_gopath
+mkdir -p $GOPATH/src/github.com/gopherjs/gopherjs
+cp -r $GOPHERJSGOPATH/src/github.com/gopherjs/gopherjs/* $GOPATH/src/github.com/gopherjs/gopherjs
+
+gopherjs install -m github.com/gopherjs/gopherjs/js github.com/gopherjs/gopherjs/nosync
 mkdir -p $PKG/github.com/gopherjs/gopherjs
 cp $GOPATH/pkg/darwin_js_min/github.com/gopherjs/gopherjs/js.a $PKG/github.com/gopherjs/gopherjs/js.a
 cp $GOPATH/pkg/darwin_js_min/github.com/gopherjs/gopherjs/nosync.a $PKG/github.com/gopherjs/gopherjs/nosync.a
 
-gopherjs install -m github.com/gopherjs/gopherjs/js archive/tar archive/zip bufio bytes compress/bzip2 compress/flate compress/gzip compress/lzw compress/zlib container/heap container/list container/ring crypto/aes crypto/cipher crypto/des crypto/dsa crypto/ecdsa crypto/elliptic crypto/hmac crypto/md5 crypto/rand crypto/rc4 crypto/rsa crypto/sha1 crypto/sha256 crypto/sha512 crypto/subtle database/sql/driver debug/gosym debug/pe encoding/ascii85 encoding/asn1 encoding/base32 encoding/base64 encoding/binary encoding/csv encoding/gob encoding/hex encoding/json encoding/pem encoding/xml errors fmt go/ast go/doc go/format go/printer go/token hash/adler32 hash/crc32 hash/crc64 hash/fnv html html/template image image/color image/draw image/gif image/jpeg image/png index/suffixarray io io/ioutil math math/big math/cmplx math/rand mime net/http/cookiejar net/http/fcgi net/http/httptest net/http/httputil net/mail net/smtp net/textproto net/url path path/filepath reflect regexp regexp/syntax sort strconv strings sync/atomic testing testing/iotest testing/quick text/scanner text/tabwriter text/template text/template/parse time unicode unicode/utf16 unicode/utf8
+# Make a copy of GOROOT that is user-writeable,
+# use it to build and copy out standard library packages.
+cp -r $(go env GOROOT) /tmp/gopherjsplayground_goroot
+export GOROOT=/tmp/gopherjsplayground_goroot
+gopherjs install -m archive/tar archive/zip bufio bytes compress/bzip2 compress/flate compress/gzip compress/lzw compress/zlib container/heap container/list container/ring crypto/aes crypto/cipher crypto/des crypto/dsa crypto/ecdsa crypto/elliptic crypto/hmac crypto/md5 crypto/rand crypto/rc4 crypto/rsa crypto/sha1 crypto/sha256 crypto/sha512 crypto/subtle database/sql/driver debug/gosym debug/pe encoding/ascii85 encoding/asn1 encoding/base32 encoding/base64 encoding/binary encoding/csv encoding/gob encoding/hex encoding/json encoding/pem encoding/xml errors fmt go/ast go/doc go/format go/printer go/token hash/adler32 hash/crc32 hash/crc64 hash/fnv html html/template image image/color image/draw image/gif image/jpeg image/png index/suffixarray io io/ioutil math math/big math/cmplx math/rand mime net/http/cookiejar net/http/fcgi net/http/httptest net/http/httputil net/mail net/smtp net/textproto net/url path path/filepath reflect regexp regexp/syntax runtime/internal/sys sort strconv strings sync/atomic testing testing/iotest testing/quick text/scanner text/tabwriter text/template text/template/parse time unicode unicode/utf16 unicode/utf8
 cp -r $GOROOT/pkg/darwin_js_min/* $PKG
 cp -r $GOROOT/pkg/darwin_amd64_js_min/* $PKG
 
-rename 's/\.a/\.a.js/' `find $PKG -name "*.a"`
+rm -r /tmp/gopherjsplayground_goroot
+rm -r /tmp/gopherjsplayground_gopath
+
+rename 's/\.a/\.a.js/' $(find $PKG -name "*.a")