chore(analytics): Generalize file size analytics

Move file size analytics code into a reusable module.

See angular#5312, angular#5314

gulpfile.js

@@ -1054,34 +1054,9 @@ gulp.task('!bundle.copy', function() {
 });
 
 gulp.task('!bundles.js.checksize', function() {
-  var gzip = require('gulp-gzip');
-  var path = require('path');
-
-  return merge2(gulp.src('dist/js/bundle/**').on('data', checkFileSizeFactory('uncompressed')),
-                gulp.src('dist/js/bundle/**')
-                    .pipe(gzip({gzipOptions: {level: 1}}))  // code.angular.js
-                    .on('data', checkFileSizeFactory('gzip level=1')),
-                gulp.src('dist/js/bundle/**')
-                    .pipe(gzip({gzipOptions: {level: 2}}))  // github pages, most common
-                    .on('data', checkFileSizeFactory('gzip level=2', true)),
-                gulp.src('dist/js/bundle/**')
-                    .pipe(gzip({gzipOptions: {level: 6}}))  // default gzip level
-                    .on('data', checkFileSizeFactory('gzip level=6')),
-                gulp.src('dist/js/bundle/**')
-                    .pipe(gzip({gzipOptions: {level: 9}}))  // max gzip level
-                    .on('data', checkFileSizeFactory('gzip level=9')));
-
-  function checkFileSizeFactory(compressionLevel, printToConsole) {
-    return function checkFileSize(file) {
-      if (file.isNull()) return;
-      var filePath =
-          path.relative(path.join('dist', 'js', 'bundle'), file.path).replace('\.gz', '');
-      analytics.bundleSize(filePath, file.contents.length, compressionLevel);
-      if (printToConsole) {
-        console.log(`  ${filePath} => ${file.contents.length} bytes (${compressionLevel})`)
-      }
-    }
-  }
+  var reportSize = require('./tools/analytics/reportsize');
+  return reportSize('dist/js/bundle/**', {printToConsole: false,
+                    reportAnalytics: true});
 });
 
 gulp.task('bundles.js',

tools/analytics/reportsize.js

@@ -0,0 +1,120 @@
+'use strict';
+
+let analytics = require('./analytics');
+let gulp = require('gulp');
+let gzip = require('gulp-gzip');
+let merge2 = require('merge2');
+let path = require('path');
+let Stream = require('stream');
+
+// Keys are a text description of compressionLevel.
+// Values are "gzipOptions" passed to gzip.
+// We report one `analytics.bundleSize` event
+// * each file in `glob`
+// * each entry in `_gzipConfigs`.
+const _gzipConfigs = {
+  'uncompressed': null,
+  'gzip level=1': {level: 1},  // code.angular.js
+  'gzip level=2': {level: 2},  // github pages, most common
+  'gzip level=6': {level: 6},  // default gzip level
+  'gzip level=9': {level: 9}   // max gzip level
+};
+
+const _defaultOptions = {
+  // @type {Object<string, number>}
+  // - Key(s) must match keys of `_gzipConfigs`.
+  // - Values are the max size (in bytes) allowed for that configuration.
+  failConditions: {},
+  prefix: '',
+  printToConsole: false,
+  reportAnalytics: true
+};
+
+// `glob` is a string representing a glob of files.
+// options is an object containing zero or more of
+// - printToConsole: Write debug to console. Default: false.
+// - reportAnalytics: Report to Google Analytics. Default: true.
+function reportSize(glob, options) {
+  options = options || {};
+  for (const key in _defaultOptions) {
+    if (!options.hasOwnProperty(key)) {
+      options[key] = _defaultOptions[key];
+    }
+  }
+  var errStream = _checkFailConditionConfig(options.failConditions);
+  if (errStream) {
+    return errStream;
+  }
+
+  const allStreams = [];
+  for (const compressionLevel in _gzipConfigs) {
+    if (_gzipConfigs.hasOwnProperty(compressionLevel)) {
+      let stream = gulp.src(glob);
+      if (_gzipConfigs[compressionLevel]) {
+        stream = stream.pipe(gzip({gzipOptions: _gzipConfigs[compressionLevel]}));
+      }
+      allStreams.push(stream.on('data', checkFileSizeFactory(compressionLevel)));
+    }
+  }
+
+  let didRun = false;
+  var errs = [];
+  return merge2(allStreams, {end: false})
+      .on('queueDrain', function() {
+        if (errs.length) {
+          errs.unshift(`Failed with ${errs.length} error(s).`);
+          this.emit('error', new Error(errs.join('\n   ')));
+        }
+        if (!didRun) {
+          this.emit('error', new Error(`No file found for pattern "${glob}".`));
+        }
+        this.emit('end');
+      });
+
+  function checkFileSizeFactory(compressionLevel) {
+    return function checkFileSize(file) {
+      if (file.isNull()) return;
+      didRun = true;
+      var filePath = path.basename(file.path).replace('\.gz', '');
+      if (options.prefix) {
+        filePath = path.join(options.prefix, filePath);
+      }
+      const fileLen = file.contents.length;
+      if (options.reportAnalytics) {
+        analytics.bundleSize(filePath, fileLen, compressionLevel);
+      }
+      if (options.printToConsole) {
+        console.log(`  ${filePath} => ${fileLen} bytes (${compressionLevel})`)
+      }
+      if (options.failConditions.hasOwnProperty(compressionLevel)) {
+        if (options.failConditions[compressionLevel] < fileLen) {
+          errs.push(`Max size for "${compressionLevel}" is ` +
+                    `${options.failConditions[compressionLevel]}, but the size is now ${fileLen}.`);
+          if (options.printToConsole) {
+            console.log(`    !!! ${errs[errs.length - 1]}`);
+          }
+        }
+      }
+    }
+  }
+}
+
+// Returns an error stream if the fail conditions are not provided property.
+// Returns `null` if everything is fine.
+function _checkFailConditionConfig(failConditions) {
+  for (const key in failConditions) {
+    if (failConditions.hasOwnProperty(key)) {
+      if (!_gzipConfigs.hasOwnProperty(key)) {
+        var stream = new Stream();
+        stream.emit(
+            'error',
+            new Error(`failCondition for "${key}" will not be tested. Check _gzipConfigs.`));
+        stream.emit('end');
+        return stream;
+      }
+    }
+  }
+  return null;
+}
+
+module.exports = reportSize;