build: use version placeholder in packages (#4065)

* Introduces a version placeholder (as in angular/angular) that will be replaced with the version string form the root `package.json` file.

* This ensures that the different packages are always having the correct version and it also ensures that there is no version-mismatch.

src/lib/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@angular/material",
-  "version": "2.0.0-beta.3",
+  "version": "0.0.0-PLACEHOLDER",
   "description": "Angular Material",
   "main": "./bundles/material.umd.js",
   "module": "./@angular/material.es5.js",

src/material-examples/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@angular/material-examples",
-  "version": "2.0.0-beta.3",
+  "version": "0.0.0-PLACEHOLDER",
   "description": "Angular Material Examples",
   "main": "./bundles/material-examples.umd.js",
   "module": "./@angular/material-examples.es5.js",

tools/gulp/util/package-build.ts

@@ -1,5 +1,4 @@
 import {join, basename, dirname} from 'path';
-import {DIST_BUNDLES, DIST_ROOT, SOURCE_ROOT, PROJECT_ROOT, LICENSE_BANNER} from '../constants';
 import {createRollupBundle} from './rollup-helper';
 import {inlineMetadataResources} from './inline-resources';
 import {transpileFile} from './ts-compiler';
@@ -8,6 +7,9 @@ import {sync as glob} from 'glob';
 import {
   writeFileSync, copySync, mkdirpSync, readFileSync
 } from 'fs-extra';
+import {
+  DIST_BUNDLES, DIST_ROOT, SOURCE_ROOT, PROJECT_ROOT, LICENSE_BANNER, MATERIAL_VERSION
+} from '../constants';
 
 // There are no type definitions available for these imports.
 const uglify = require('uglify-js');
@@ -32,6 +34,7 @@ export function composeRelease(packageName: string) {
   copyFiles(SOURCE_ROOT, 'README', releasePath);
   copyFiles(sourcePath, 'package.json', releasePath);
 
+  updatePackageVersion(releasePath);
   createTypingFile(releasePath, packageName);
   createMetadataFile(releasePath, packageName);
 }
@@ -81,6 +84,17 @@ function copyFiles(fromPath: string, fileGlob: string, outDir: string) {
   });
 }
 
+/** Updates the `package.json` file of the specified package. Replaces the version placeholder. */
+function updatePackageVersion(packageDir: string) {
+  let packagePath = join(packageDir, 'package.json');
+  let packageConfig = require(packagePath);
+
+  // Replace the `0.0.0-PLACEHOLDER` version name with the version of the root package.json file.
+  packageConfig.version = packageConfig.version.replace('0.0.0-PLACEHOLDER', MATERIAL_VERSION);
+
+  writeFileSync(packagePath, JSON.stringify(packageConfig, null, 2));
+}
+
 /** Create a typing file that links to the bundled definitions of NGC. */
 function createTypingFile(outputDir: string, entryName: string) {
   writeFileSync(join(outputDir, `${entryName}.d.ts`),