build: publish tree of files rather than FESMs (#18541)

* Remove now unnecessary portions of build.
* Add a compilePackageES5 method to build ES5 from sources
* Rework all package.json and rollup config files to new format
* Remove "extends" from tsconfig-build.json files and fixup compilation roots

PR Close #18541

packages/forms/package.json

@@ -3,9 +3,9 @@
   "version": "0.0.0-PLACEHOLDER",
   "description": "Angular - directives and services for creating forms",
   "main": "./bundles/forms.umd.js",
-  "module": "./@angular/forms.es5.js",
-  "es2015": "./@angular/forms.js",
-  "typings": "./forms.d.ts",
+  "module": "./esm5/index.js",
+  "es2015": "./esm15/index.js",
+  "typings": "./index.d.ts",
   "author": "angular",
   "license": "MIT",
   "dependencies": {

packages/forms/public_api.ts

@@ -9,7 +9,7 @@
 /**
  * @module
  * @description
- * Entry point for all public APIs of the forms package.
+ * Entry point for all public APIs of this package.
  */
 export * from './src/forms';
 

packages/forms/rollup.config.js

@@ -7,6 +7,7 @@
  */
 
 import resolve from 'rollup-plugin-node-resolve';
+import sourcemaps from 'rollup-plugin-sourcemaps';
 
 const globals = {
   '@angular/core': 'ng.core',
@@ -21,12 +22,12 @@ const globals = {
 };
 
 export default {
-  entry: '../../dist/packages-dist/forms/@angular/forms.es5.js',
+  entry: '../../dist/packages-dist/forms/esm5/index.js',
   dest: '../../dist/packages-dist/forms/bundles/forms.umd.js',
   format: 'umd',
   exports: 'named',
   moduleName: 'ng.forms',
-  plugins: [resolve()],
+  plugins: [resolve(), sourcemaps()],
   external: Object.keys(globals),
   globals: globals
 };

packages/forms/tsconfig-build.json

@@ -1,13 +1,9 @@
 {
+  "extends": "../tsconfig-build.json",
+
   "compilerOptions": {
     "baseUrl": ".",
-    "declaration": true,
-    "stripInternal": true,
-    "experimentalDecorators": true,
-    "strictNullChecks": true,
-    "module": "es2015",
-    "moduleResolution": "node",
-    "outDir": "../../dist/packages/forms",
+    "rootDir": ".",
     "paths": {
       "@angular/core": ["../../dist/packages/core"],
       "@angular/core/testing": ["../../dist/packages/core/testing"],
@@ -17,19 +13,14 @@
       "@angular/compiler/testing": ["../../dist/packages/compiler/testing"],
       "@angular/platform-browser": ["../../dist/packages/platform-browser"]
     },
-    "rootDir": ".",
-    "sourceMap": true,
-    "inlineSources": true,
-    "target": "es2015",
-    "skipLibCheck": true,
-    "lib": ["es2015", "dom"],
-    // don't auto-discover @types/node, it results in a ///<reference in the .d.ts output
-    "types": []
+    "outDir": "../../dist/packages/forms"
   },
+
   "files": [
     "public_api.ts",
     "../../node_modules/zone.js/dist/zone.js.d.ts"
   ],
+
   "angularCompilerOptions": {
     "annotateForClosureCompiler": true,
     "strictMetadataEmit": true,