feat(compiler-cli): lower metadata useValue and data literal fiel…

…ds (#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/src/diagnostics/check_types.ts

@@ -166,9 +166,13 @@ function diagnosticMessageToString(message: ts.DiagnosticMessageChain | string):
   return ts.flattenDiagnosticMessageText(message, '\n');
 }
 
+const REWRITE_PREFIX = /^\u0275[0-9]+$/;
+
 function createFactoryInfo(emitter: TypeScriptEmitter, file: GeneratedFile): FactoryInfo {
-  const {sourceText, context} =
-      emitter.emitStatementsAndContext(file.srcFileUrl, file.genFileUrl, file.stmts !);
+  const {sourceText, context} = emitter.emitStatementsAndContext(
+      file.srcFileUrl, file.genFileUrl, file.stmts !,
+      /* preamble */ undefined, /* emitSourceMaps */ undefined,
+      /* referenceFilter */ reference => !!(reference.name && REWRITE_PREFIX.test(reference.name)));
   const source = ts.createSourceFile(
       file.genFileUrl, sourceText, ts.ScriptTarget.Latest, /* setParentNodes */ true);
   return {source, context};

packages/compiler-cli/src/transformers/lower_expressions.ts

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {CollectorOptions, MetadataCollector, MetadataValue, ModuleMetadata} from '@angular/tsc-wrapped';
+import {CollectorOptions, MetadataCollector, MetadataValue, ModuleMetadata, isMetadataGlobalReferenceExpression} from '@angular/tsc-wrapped';
 import * as ts from 'typescript';
 
 export interface LoweringRequest {
@@ -181,6 +181,30 @@ function shouldLower(node: ts.Node | undefined): boolean {
   return true;
 }
 
+const REWRITE_PREFIX = '\u0275';
+
+function isPrimitive(value: any): boolean {
+  return Object(value) !== value;
+}
+
+function isRewritten(value: any): boolean {
+  return isMetadataGlobalReferenceExpression(value) && value.name.startsWith(REWRITE_PREFIX);
+}
+
+function isLiteralFieldNamed(node: ts.Node, names: Set<string>): boolean {
+  if (node.parent && node.parent.kind == ts.SyntaxKind.PropertyAssignment) {
+    const property = node.parent as ts.PropertyAssignment;
+    if (property.parent && property.parent.kind == ts.SyntaxKind.ObjectLiteralExpression &&
+        property.name && property.name.kind == ts.SyntaxKind.Identifier) {
+      const propertyName = property.name as ts.Identifier;
+      return names.has(propertyName.text);
+    }
+  }
+  return false;
+}
+
+const LOWERABLE_FIELD_NAMES = new Set(['useValue', 'useFactory', 'data']);
+
 export class LowerMetadataCache implements RequestsMap {
   private collector: MetadataCollector;
   private metadataCache = new Map<string, MetadataAndLoweringRequests>();
@@ -208,19 +232,41 @@ export class LowerMetadataCache implements RequestsMap {
 
   private getMetadataAndRequests(sourceFile: ts.SourceFile): MetadataAndLoweringRequests {
     let identNumber = 0;
-    const freshIdent = () => '\u0275' + identNumber++;
+    const freshIdent = () => REWRITE_PREFIX + identNumber++;
     const requests = new Map<number, LoweringRequest>();
+
+    const isExportedSymbol = (() => {
+      let exportTable: Set<string>;
+      return (node: ts.Node) => {
+        if (node.kind == ts.SyntaxKind.Identifier) {
+          const ident = node as ts.Identifier;
+
+          if (!exportTable) {
+            exportTable = createExportTableFor(sourceFile);
+          }
+          return exportTable.has(ident.text);
+        }
+        return false;
+      };
+    })();
+
     const replaceNode = (node: ts.Node) => {
       const name = freshIdent();
       requests.set(node.pos, {name, kind: node.kind, location: node.pos, end: node.end});
       return {__symbolic: 'reference', name};
     };
 
     const substituteExpression = (value: MetadataValue, node: ts.Node): MetadataValue => {
-      if ((node.kind === ts.SyntaxKind.ArrowFunction ||
-           node.kind === ts.SyntaxKind.FunctionExpression) &&
-          shouldLower(node)) {
-        return replaceNode(node);
+      if (!isPrimitive(value) && !isRewritten(value)) {
+        if ((node.kind === ts.SyntaxKind.ArrowFunction ||
+             node.kind === ts.SyntaxKind.FunctionExpression) &&
+            shouldLower(node)) {
+          return replaceNode(node);
+        }
+        if (isLiteralFieldNamed(node, LOWERABLE_FIELD_NAMES) && shouldLower(node) &&
+            !isExportedSymbol(node)) {
+          return replaceNode(node);
+        }
       }
       return value;
     };
@@ -229,4 +275,44 @@ export class LowerMetadataCache implements RequestsMap {
 
     return {metadata, requests};
   }
-}
+}
+
+function createExportTableFor(sourceFile: ts.SourceFile): Set<string> {
+  const exportTable = new Set<string>();
+  // Lazily collect all the exports from the source file
+  ts.forEachChild(sourceFile, function scan(node) {
+    switch (node.kind) {
+      case ts.SyntaxKind.ClassDeclaration:
+      case ts.SyntaxKind.FunctionDeclaration:
+      case ts.SyntaxKind.InterfaceDeclaration:
+        if ((ts.getCombinedModifierFlags(node) & ts.ModifierFlags.Export) != 0) {
+          const classDeclaration =
+              node as(ts.ClassDeclaration | ts.FunctionDeclaration | ts.InterfaceDeclaration);
+          const name = classDeclaration.name;
+          if (name) exportTable.add(name.text);
+        }
+        break;
+      case ts.SyntaxKind.VariableStatement:
+        const variableStatement = node as ts.VariableStatement;
+        for (const declaration of variableStatement.declarationList.declarations) {
+          scan(declaration);
+        }
+        break;
+      case ts.SyntaxKind.VariableDeclaration:
+        const variableDeclaration = node as ts.VariableDeclaration;
+        if ((ts.getCombinedModifierFlags(node) & ts.ModifierFlags.Export) != 0 &&
+            variableDeclaration.name.kind == ts.SyntaxKind.Identifier) {
+          const name = variableDeclaration.name as ts.Identifier;
+          exportTable.add(name.text);
+        }
+        break;
+      case ts.SyntaxKind.ExportDeclaration:
+        const exportDeclaration = node as ts.ExportDeclaration;
+        const {moduleSpecifier, exportClause} = exportDeclaration;
+        if (!moduleSpecifier && exportClause) {
+          exportClause.elements.forEach(spec => { exportTable.add(spec.name.text); });
+        }
+    }
+  });
+  return exportTable;
+}

packages/compiler-cli/test/diagnostics/check_types_spec.ts

@@ -12,14 +12,15 @@ import * as ts from 'typescript';
 
 import {TypeChecker} from '../../src/diagnostics/check_types';
 import {Diagnostic} from '../../src/transformers/api';
+import {LowerMetadataCache} from '../../src/transformers/lower_expressions';
 
 function compile(
     rootDirs: MockData, options: AotCompilerOptions = {},
     tsOptions: ts.CompilerOptions = {}): Diagnostic[] {
   const rootDirArr = toMockFileArray(rootDirs);
   const scriptNames = rootDirArr.map(entry => entry.fileName).filter(isSource);
   const host = new MockCompilerHost(scriptNames, arrayToMockDir(rootDirArr));
-  const aotHost = new MockAotCompilerHost(host);
+  const aotHost = new MockAotCompilerHost(host, new LowerMetadataCache({}));
   const tsSettings = {...settings, ...tsOptions};
   const program = ts.createProgram(host.scriptNames.slice(0), tsSettings, host);
   const ngChecker = new TypeChecker(program, tsSettings, host, aotHost, options);
@@ -80,6 +81,12 @@ describe('ng type checker', () => {
     it('should accept a safe property access of a nullable field reference of a method result',
        () => { a('{{getMaybePerson()?.name}}'); });
   });
+
+  describe('with lowered expressions', () => {
+    it('should not report lowered expressions as errors', () => {
+      expectNoDiagnostics(compile([angularFiles, LOWERING_QUICKSTART]));
+    });
+  });
 });
 
 function appComponentSource(template: string): string {
@@ -134,8 +141,38 @@ const QUICKSTART: MockDirectory = {
   }
 };
 
+const LOWERING_QUICKSTART: MockDirectory = {
+  quickstart: {
+    app: {
+      'app.component.ts': appComponentSource('<h1>Hello {{name}}</h1>'),
+      'app.module.ts': `
+        import { NgModule, Component }      from '@angular/core';
+        import { toString }      from './utils';
+
+        import { AppComponent }  from './app.component';
+
+        class Foo {}
+
+        @Component({
+          template: '',
+          providers: [
+            {provide: 'someToken', useFactory: () => new Foo()}
+          ]
+        })
+        export class Bar {}
+
+        @NgModule({
+          declarations: [ AppComponent, Bar ],
+          bootstrap:    [ AppComponent ]
+        })
+        export class AppModule { }
+      `
+    }
+  }
+};
+
 function expectNoDiagnostics(diagnostics: Diagnostic[]) {
   if (diagnostics && diagnostics.length) {
     throw new Error(diagnostics.map(d => `${d.span}: ${d.message}`).join('\n'));
   }
-}
+}

packages/compiler-cli/test/ngc_spec.ts

@@ -848,4 +848,78 @@ describe('ngc transformer command-line', () => {
       shouldExist('app/main.js');
     });
   });
+
+  describe('expression lowering', () => {
+    const shouldExist = (fileName: string) => {
+      if (!fs.existsSync(path.resolve(basePath, fileName))) {
+        throw new Error(`Expected ${fileName} to be emitted (basePath: ${basePath})`);
+      }
+    };
+
+    it('should be able to lower supported expressions', () => {
+      writeConfig(`{
+        "extends": "./tsconfig-base.json",
+        "files": ["module.ts"]
+      }`);
+      write('module.ts', `
+        import {NgModule, InjectionToken} from '@angular/core';
+        import {AppComponent} from './app';
+
+        export interface Info {
+          route: string;
+          data: string;
+        }
+
+        export const T1 = new InjectionToken<string>('t1');
+        export const T2 = new InjectionToken<string>('t2');
+        export const T3 = new InjectionToken<number>('t3');
+        export const T4 = new InjectionToken<Info[]>('t4');
+
+        enum SomeEnum {
+          OK,
+          Cancel
+        }
+
+        function calculateString() {
+          return 'someValue';
+        }
+
+        const routeLikeData = [{
+           route: '/home',
+           data: calculateString() 
+        }];
+
+        @NgModule({
+          declarations: [AppComponent],
+          providers: [
+            { provide: T1, useValue: calculateString() },
+            { provide: T2, useFactory: () => 'someValue' },
+            { provide: T3, useValue: SomeEnum.OK },
+            { provide: T4, useValue: routeLikeData }
+          ]
+        })
+        export class MyModule {}
+      `);
+      write('app.ts', `
+        import {Component, Inject} from '@angular/core';
+        import * as m from './module';
+
+        @Component({
+          selector: 'my-app',
+          template: ''
+        })
+        export class AppComponent {
+          constructor(
+            @Inject(m.T1) private t1: string,
+            @Inject(m.T2) private t2: string,
+            @Inject(m.T3) private t3: number,
+            @Inject(m.T4) private t4: m.Info[],
+          ) {}
+        }
+      `);
+
+      expect(mainSync(['-p', basePath], s => {})).toBe(0);
+      shouldExist('built/module.js');
+    });
+  });
 });