chore(docs.angularjs.org): serve snapshots for googlebot

This commit restores serving the plain partials (content) when a docs
page is accessed with ?_escaped_fragment_=.
The Google Ajax Crawler accesses these urls when the page has
`<meta type="fragment" content="!">` is set.

During the migration to Firebase, this was lost, which resulted in Google
dropping the docs almost completely from the index.

We are using a Firebase cloud function to serve the partials. Since
we cannot access the static hosted files from the function, we have to
deploy them as part of the function directory instead, from which they
can be read.

Related to angular#16432
Related to angular#16417

Author: Narretz

Gruntfile.js

@@ -13,6 +13,8 @@ var semver = require('semver');
 var exec = require('shelljs').exec;
 var pkg = require(__dirname + '/package.json');
 
+var docsScriptFolder = 'scripts/docs.angularjs.org-firebase';
+
 // Node.js version checks
 if (!semver.satisfies(process.version, pkg.engines.node)) {
   reportOrFail('Invalid node version (' + process.version + '). ' +
@@ -165,7 +167,8 @@ module.exports = function(grunt) {
       tmp: ['tmp'],
       deploy: [
         'deploy/docs',
-        'deploy/code'
+        'deploy/code',
+        docsScriptFolder + '/functions/html'
       ]
     },
 
@@ -340,7 +343,17 @@ module.exports = function(grunt) {
             src: '**',
             dest: 'deploy/docs/',
             expand: true
-          }
+          },
+          {
+            src: ['build/docs/index-production.html'],
+            dest: docsScriptFolder + '/functions/content',
+            expand: true,
+            flatten: true
+          },
+          {
+            cwd: 'build/docs',
+            src: 'partials/**',
+            dest: docsScriptFolder + '/functions/content',
             expand: true
           }
         ]

lib/grunt/utils.js

@@ -303,6 +303,7 @@ module.exports = {
     var json = grunt.file.readJSON(fileName);
 
     json.hosting.public = 'deploy/docs';
+    json.functions.source = docsScriptFolder + 'functions';
 
     grunt.file.write('firebase.json', JSON.stringify(json));
   }

scripts/docs.angularjs.org-firebase/firebase.json

@@ -23,9 +23,14 @@
         "destination": "/index-production.html"
       },
       {
-        "source": "**/*!(.jpg|.jpeg|.gif|.png|.html|.js|.map|.json|.css|.svg|.ttf|.txt|.woff|.woff2|.eot|.xml)",
-        "destination": "/index-production.html"
+        "source": "**/*!(.@(jpg|jpeg|gif|png|html|js|map|json|css|svg|ttf|txt|woff|woff2|eot|xml))",
+        "function": "sendFile"
       }
     ]
+  },
+  "functions": {
+    "predeploy": [
+      "npm --prefix $RESOURCE_DIR run lint"
+    ]
   }
-}
+}

scripts/docs.angularjs.org-firebase/functions/.eslintrc.json

@@ -0,0 +1,123 @@
+{
+  "parserOptions": {
+    // Required for certain syntax usages
+    "ecmaVersion": 6
+  },
+  "plugins": [
+    "promise"
+  ],
+  "extends": "eslint:recommended",
+  "rules": {
+    // Removed rule "disallow the use of console" from recommended eslint rules
+    "no-console": "off",
+
+    // Removed rule "disallow multiple spaces in regular expressions" from recommended eslint rules
+    "no-regex-spaces": "off",
+
+    // Removed rule "disallow the use of debugger" from recommended eslint rules
+    "no-debugger": "off",
+
+    // Removed rule "disallow unused variables" from recommended eslint rules
+    "no-unused-vars": "off",
+
+    // Removed rule "disallow mixed spaces and tabs for indentation" from recommended eslint rules
+    "no-mixed-spaces-and-tabs": "off",
+
+    // Removed rule "disallow the use of undeclared variables unless mentioned in /*global */ comments" from recommended eslint rules
+    "no-undef": "off",
+
+    // Warn against template literal placeholder syntax in regular strings
+    "no-template-curly-in-string": 1,
+
+    // Warn if return statements do not either always or never specify values
+    "consistent-return": 1,
+
+    // Warn if no return statements in callbacks of array methods
+    "array-callback-return": 1,
+
+    // Require the use of === and !==
+    "eqeqeq": 2,
+
+    // Disallow the use of alert, confirm, and prompt
+    "no-alert": 2,
+
+    // Disallow the use of arguments.caller or arguments.callee
+    "no-caller": 2,
+
+    // Disallow null comparisons without type-checking operators
+    "no-eq-null": 2,
+
+    // Disallow the use of eval()
+    "no-eval": 2,
+
+    // Warn against extending native types
+    "no-extend-native": 1,
+
+    // Warn against unnecessary calls to .bind()
+    "no-extra-bind": 1,
+
+    // Warn against unnecessary labels    
+    "no-extra-label": 1,
+
+    // Disallow leading or trailing decimal points in numeric literals
+    "no-floating-decimal": 2,
+
+    // Warn against shorthand type conversions
+    "no-implicit-coercion": 1,
+
+    // Warn against function declarations and expressions inside loop statements
+    "no-loop-func": 1,
+
+    // Disallow new operators with the Function object
+    "no-new-func": 2,
+
+    // Warn against new operators with the String, Number, and Boolean objects
+    "no-new-wrappers": 1,
+
+    // Disallow throwing literals as exceptions
+    "no-throw-literal": 2,
+
+    // Require using Error objects as Promise rejection reasons
+    "prefer-promise-reject-errors": 2,
+
+    // Enforce “for” loop update clause moving the counter in the right direction
+    "for-direction": 2,
+
+    // Enforce return statements in getters
+    "getter-return": 2,
+
+    // Disallow await inside of loops
+    "no-await-in-loop": 2,
+
+    // Disallow comparing against -0
+    "no-compare-neg-zero": 2,
+
+    // Warn against catch clause parameters from shadowing variables in the outer scope
+    "no-catch-shadow": 1,
+
+    // Disallow identifiers from shadowing restricted names
+    "no-shadow-restricted-names": 2,
+
+    // Enforce return statements in callbacks of array methods
+    "callback-return": 2,
+
+    // Require error handling in callbacks
+    "handle-callback-err": 2,
+
+    // Warn against string concatenation with __dirname and __filename
+    "no-path-concat": 1,
+
+    // Prefer using arrow functions for callbacks
+    "prefer-arrow-callback": 1,
+
+    // Return inside each then() to create readable and reusable Promise chains.
+    // Forces developers to return console logs and http calls in promises. 
+    "promise/always-return": 2,
+
+    //Enforces the use of catch() on un-returned promises
+    "promise/catch-or-return": 2,
+
+    // Warn against nested then() or catch() statements
+    "promise/no-nesting": 1
+  }
+}

scripts/docs.angularjs.org-firebase/functions/index.js

@@ -0,0 +1,50 @@
+'use strict';
+
+const functions = require('firebase-functions');
+const path = require('path');
+const fs = require('fs');
+
+const BROWSER_CACHE_DURATION = 60 * 60;
+const CDN_CACHE_DURATION = 60 * 60 * 12;
+
+const headers = {
+  'Cache-Control': `public max-age=${BROWSER_CACHE_DURATION} s-maxage=${CDN_CACHE_DURATION}`
+};
+
+const buildSnapshot = data => `<!DOCTYPE html>
+  <html lang="en">
+    <head>
+      <meta charset="utf-8" />
+      <meta name="viewport" content="width=device-width, initial-scale=1">
+      <base href="/">
+    </head>
+    <body>
+      ${data}
+    </body>
+  </html>`;
+
+function sendFile(request, response) {
+
+  const snapshotRequested = typeof request.query._escaped_fragment_ !== 'undefined';
+  const filePath = `content/${snapshotRequested ? `partials${request.path}` : 'index-production'}.html`;
+
+  if (snapshotRequested) {
+    fs.readFile(filePath, {encoding: 'utf8'}, (error, data) => {
+      if (error) {
+        response
+          .status(404)
+          .end();
+      } else {
+        response
+          .set(headers)
+          .send(buildSnapshot(data));
+      }
+    });
+  } else {
+    response
+      .set(headers)
+      .sendFile(filePath, {root: __dirname});
+  }
+}
+
+exports.sendFile = functions.https.onRequest(sendFile);