build: fail build for prerender errors in lifecycle hooks (#5459)

* Currently the build won't fail if an error is thrown inside a lifecycle hook, because `platform-server` writes it to STDERR, but still exits with a 0 code. These changes set up the Universal testing task to fail for these cases as well. This should prevent issues like #5455 in the future.
* Stops logging the entire rendered document after the prerender task is done. This makes the log a bit easier to look through.

src/universal-app/prerender.ts

@@ -5,6 +5,7 @@ import {enableProdMode} from '@angular/core';
 import {renderModuleFactory} from '@angular/platform-server';
 import {join} from 'path';
 import {readFileSync} from 'fs-extra';
+import {log} from 'gulp-util';
 import {KitchenSinkServerModuleNgFactory} from './kitchen-sink/kitchen-sink.ngfactory';
 
 enableProdMode();
@@ -14,7 +15,7 @@ const result = renderModuleFactory(KitchenSinkServerModuleNgFactory, {
 });
 
 result
-  .then(html => console.log(html))
+  .then(() => log('Prerender done.'))
   // If rendering the module factory fails, exit the process with an error code because otherwise
   // the CI task will not recognize the failure and will show as "success". The error message
   // will be printed automatically by the `renderModuleFactory` method.

tools/gulp/tasks/universal.ts

@@ -25,7 +25,10 @@ const prerenderOutFile = join(outDir, 'prerender.js');
 task('universal:test-prerender', ['universal:build'], execTask(
   // Runs node with the tsconfig-paths module to alias the @angular/material dependency.
   'node', ['-r', 'tsconfig-paths/register', prerenderOutFile], {
-    env: {TS_NODE_PROJECT: tsconfigPrerenderPath}
+    env: {TS_NODE_PROJECT: tsconfigPrerenderPath},
+    // Errors in lifecycle hooks will write to STDERR, but won't exit the process with an
+    // error code, however we still want to catch those cases in the CI.
+    failOnStderr: true
   }
 ));
 

tools/gulp/util/task_helpers.ts

@@ -49,6 +49,8 @@ export interface ExecTaskOptions {
   errMessage?: string;
   // Environment variables being passed to the child process.
   env?: any;
+  // Whether the task should fail if the process writes to STDERR.
+  failOnStderr?: boolean;
 }
 
 /** Create a task that executes a binary as if from the command line. */
@@ -56,24 +58,23 @@ export function execTask(binPath: string, args: string[], options: ExecTaskOptio
   return (done: (err?: string) => void) => {
     const env = Object.assign({}, process.env, options.env);
     const childProcess = child_process.spawn(binPath, args, {env});
+    const stderrData: string[] = [];
 
     if (!options.silentStdout && !options.silent) {
       childProcess.stdout.on('data', (data: string) => process.stdout.write(data));
     }
 
-    if (!options.silent) {
-      childProcess.stderr.on('data', (data: string) => process.stderr.write(data));
+    if (!options.silent || options.failOnStderr) {
+      childProcess.stderr.on('data', (data: string) => {
+        options.failOnStderr ? stderrData.push(data) : process.stderr.write(data);
+      });
     }
 
     childProcess.on('close', (code: number) => {
-      if (code != 0) {
-        if (options.errMessage === undefined) {
-          done('Process failed with code ' + code);
-        } else {
-          done(options.errMessage);
-        }
+      if (options.failOnStderr && stderrData.length) {
+        done(stderrData.join('\n'));
       } else {
-        done();
+        code != 0 ? done(options.errMessage || `Process failed with code ${code}`) : done();
       }
     });
   };