feat(compiler-cli): lower metadata useValue and data literal fields (#18905)

With this commit the compiler will "lower" expressions into exported
variables for values the compiler does not need to know statically
in order to be able to generate a factory. For example:

```
  providers: [{provider: 'token', useValue: calculated()}]
```

produced an error as the expression `calculated()` is not supported
by the compiler because `calculated` is not a
[known function](https://angular.io/guide/metadata#annotationsdecorators)

With this commit this is rewritten, during emit of the .js file, into
something like:

```
export var ɵ0 = calculated();

  ...

  provdiers: [{provider: 'token', useValue: ɵ0}]
```

The compiler then will now generate a reference to the exported `ɵ0`
instead of failing to evaluate `calculated()`.

PR Close #18905

packages/compiler-cli/test/transformers/lower_expressions_spec.ts

@@ -6,29 +6,92 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
+import {ModuleMetadata} from '@angular/tsc-wrapped';
 import * as ts from 'typescript';
 
-import {LoweringRequest, RequestLocationMap, getExpressionLoweringTransformFactory} from '../../src/transformers/lower_expressions';
+import {LowerMetadataCache, LoweringRequest, RequestLocationMap, getExpressionLoweringTransformFactory} from '../../src/transformers/lower_expressions';
 import {Directory, MockAotContext, MockCompilerHost} from '../mocks';
 
 describe('Expression lowering', () => {
-  it('should be able to lower a simple expression', () => {
-    expect(convert('const a = 1 +◊b: 2◊;')).toBe('const b = 2; const a = 1 + b; export { b };');
+  describe('transform', () => {
+    it('should be able to lower a simple expression', () => {
+      expect(convert('const a = 1 +◊b: 2◊;')).toBe('const b = 2; const a = 1 + b; export { b };');
+    });
+
+    it('should be able to lower an expression in a decorator', () => {
+      expect(convert(`
+          import {Component} from '@angular/core';
+
+          @Component({
+            provider: [{provide: 'someToken', useFactory:◊l: () => null◊}]
+          })
+          class MyClass {}
+      `)).toContain('const l = () => null; exports.l = l;');
+    });
   });
 
-  it('should be able to lower an expression in a decorator', () => {
-    expect(convert(`
+  describe('collector', () => {
+    it('should request a lowering for useValue', () => {
+      const collected = collect(`
         import {Component} from '@angular/core';
-        
+
+        enum SomeEnum {
+          OK,
+          NotOK
+        }
+
         @Component({
-          provider: [{provide: 'someToken', useFactory:◊l: () => null◊}]
+          provider: [{provide: 'someToken', useValue:◊enum: SomeEnum.OK◊}]
         })
-        class MyClass {}
-    `)).toContain('const l = () => null; exports.l = l;');
+        export class MyClass {}
+      `);
+      expect(collected.requests.has(collected.annotations[0].start))
+          .toBeTruthy('did not find the useValue');
+    });
+
+    it('should request a lowering for useFactory', () => {
+      const collected = collect(`
+        import {Component} from '@angular/core';
+
+        @Component({
+          provider: [{provide: 'someToken', useFactory:◊lambda: () => null◊}]
+        })
+        export class MyClass {}
+      `);
+      expect(collected.requests.has(collected.annotations[0].start))
+          .toBeTruthy('did not find the useFactory');
+    });
+
+    it('should request a lowering for data', () => {
+      const collected = collect(`
+        import {Component} from '@angular/core';
+
+        enum SomeEnum {
+          OK,
+          NotOK
+        }
+
+        @Component({
+          provider: [{provide: 'someToken', data:◊enum: SomeEnum.OK◊}]
+        })
+        export class MyClass {}
+      `);
+      expect(collected.requests.has(collected.annotations[0].start))
+          .toBeTruthy('did not find the data field');
+    });
   });
 });
 
-function convert(annotatedSource: string) {
+// Helpers
+
+interface Annotation {
+  start: number;
+  length: number;
+  name: string;
+}
+
+function getAnnotations(annotatedSource: string):
+    {unannotatedSource: string, annotations: Annotation[]} {
   const annotations: {start: number, length: number, name: string}[] = [];
   let adjustment = 0;
   const unannotatedSource = annotatedSource.replace(
@@ -38,6 +101,13 @@ function convert(annotatedSource: string) {
         adjustment -= text.length - source.length;
         return source;
       });
+  return {unannotatedSource, annotations};
+}
+
+// Transform helpers
+
+function convert(annotatedSource: string) {
+  const {annotations, unannotatedSource} = getAnnotations(annotatedSource);
 
   const baseFileName = 'someFile';
   const moduleName = '/' + baseFileName;
@@ -103,3 +173,16 @@ function normalizeResult(result: string): string {
       .replace(/^ /g, '')
       .replace(/ $/g, '');
 }
+
+// Collector helpers
+
+function collect(annotatedSource: string) {
+  const {annotations, unannotatedSource} = getAnnotations(annotatedSource);
+  const cache = new LowerMetadataCache({});
+  const sourceFile = ts.createSourceFile(
+      'someName.ts', unannotatedSource, ts.ScriptTarget.Latest, /* setParentNodes */ true);
+  return {
+    metadata: cache.getMetadata(sourceFile),
+    requests: cache.getRequests(sourceFile), annotations
+  };
+}