chore: fix installing from GitHub URL (#5669)

The change to the install script to require TypeScript works fine when
installing from npm (because on npm the `lib` directory with the
compiled code already exists) but doesn't if you install from a GitHub
URL. By default it seems npm uses the `files` list when you install from
GitHub which means it's missing a bunch of files that we need to
compile.

Additionally by default when installing from a GitHub URL npm doesn't
install the dependencies which is an issue for us when we need to
compile TypeScript.

The fix is to create a `prepare` script that runs TypeScript if
required. From the npm docs [1]:

> `prepare`: Run both BEFORE the package is packed and published, on
> local npm install without any arguments, and when installing git
> dependencies

And from the npm docs on install [2], it confirms that if a package has
a `prepare` script it is run when installing from GitHub:

> As with regular git dependencies, dependencies and devDependencies
> will be installed if the package has a prepare script, before the
> package is done installing.

Despite having the `prepare` script we still need the TypeScript check
in `install.js` to satisfy the 3rd scenario below where we need to force
a compile:

* If I'm a user installing `puppeteer@X` from npm, the module is
published with the `lib/` directory of compiled code, so I'm set.
* If I'm a user installing Puppeteer from GitHub, the `prepare` script
will run TypeScript for me so I'm set.
* If I'm a developer working on Puppeteer, the `prepare` script also
runs but _after_ `npm install` which means `install.js` fails as it
requires `./lib/helper.js`. So in `install.js` we call
`compileTypeScriptIfRequired` to catch this case.

[1]: https://docs.npmjs.com/misc/scripts
[2]: https://docs.npmjs.com/cli/install

Co-authored-by: Mathias Bynens <mathias@qiwi.be>

Fixes #5660.

install.js

@@ -14,45 +14,6 @@
  * limitations under the License.
  */
 
-const fs = require('fs');
-const path = require('path');
-const child_process = require('child_process');
-const {promisify} = require('util');
-
-const fsAccess = promisify(fs.access);
-const exec = promisify(child_process.exec);
-
-const fileExists = async filePath => fsAccess(filePath).then(() => true).catch(() => false);
-
-/*
- * Now Puppeteer is built with TypeScript, we need to ensure that
- * locally we have the generated output before trying to install.
- *
- * For users installing puppeteer this is fine, they will have the
- * generated lib/ directory as we ship it when we publish to npm.
- *
- * However, if you're cloning the repo to contribute, you won't have the
- * generated lib/ directory so this script checks if we need to run
- * TypeScript first to ensure the output exists and is in the right
- * place.
- */
-async function compileTypeScript() {
-  return exec('npm run tsc').catch(err => {
-    console.error('Error running TypeScript', err);
-    process.exit(1);
-  });
-}
-
-async function ensureLibDirectoryExists() {
-  const libPath = path.join(__dirname, 'lib');
-  const libExists = await fileExists(libPath);
-  if (libExists) return;
-
-  logPolitely('Compiling TypeScript before install...');
-  await compileTypeScript();
-}
-
-
 /**
  * This file is part of public API.
  *
@@ -62,13 +23,16 @@ async function ensureLibDirectoryExists() {
  * still possible to install a supported browser using this script when
  * necessary.
  */
+
+const compileTypeScriptIfRequired = require('./typescript-if-required');
+
 const supportedProducts = {
   'chrome': 'Chromium',
   'firefox': 'Firefox Nightly'
 };
 
 async function download() {
-  await ensureLibDirectoryExists();
+  await compileTypeScriptIfRequired();
 
   const downloadHost = process.env.PUPPETEER_DOWNLOAD_HOST || process.env.npm_config_puppeteer_download_host || process.env.npm_package_config_puppeteer_download_host;
   const puppeteer = require('./index');

package.json

@@ -18,6 +18,7 @@
     "debug-unit": "node --inspect-brk test/test.js",
     "test-doclint": "mocha --config mocha-config/doclint-tests.js",
     "test": "npm run tsc && npm run lint --silent && npm run coverage && npm run test-doclint && npm run test-types",
+    "prepare": "node typescript-if-required.js",
     "prepublishOnly": "npm run tsc",
     "dev-install": "npm run tsc && node install.js",
     "install": "node install.js",

typescript-if-required.js

@@ -0,0 +1,59 @@
+/**
+ * Copyright 2020 Google Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+const child_process = require('child_process');
+const path = require('path');
+const fs = require('fs');
+const {promisify} = require('util');
+
+const exec = promisify(child_process.exec);
+const fsAccess = promisify(fs.access);
+
+const fileExists = async filePath => fsAccess(filePath).then(() => true).catch(() => false);
+/*
+
+ * Now Puppeteer is built with TypeScript, we need to ensure that
+ * locally we have the generated output before trying to install.
+ *
+ * For users installing puppeteer this is fine, they will have the
+ * generated lib/ directory as we ship it when we publish to npm.
+ *
+ * However, if you're cloning the repo to contribute, you won't have the
+ * generated lib/ directory so this script checks if we need to run
+ * TypeScript first to ensure the output exists and is in the right
+ * place.
+ */
+async function compileTypeScript() {
+  return exec('npm run tsc').catch(err => {
+    console.error('Error running TypeScript', err);
+    process.exit(1);
+  });
+}
+
+async function compileTypeScriptIfRequired() {
+  const libPath = path.join(__dirname, 'lib');
+  const libExists = await fileExists(libPath);
+  if (libExists) return;
+
+  console.log('Puppeteer:', 'Compiling TypeScript...');
+  await compileTypeScript();
+}
+
+// It's being run as node typescript-if-required.js, not require('..')
+if (require.main === module)
+  compileTypeScriptIfRequired();
+
+module.exports = compileTypeScriptIfRequired;