feat: change @Injectable() to support tree-shakeable tokens (#22005)

This commit bundles 3 important changes, with the goal of enabling tree-shaking
of services which are never injected. Ordinarily, this tree-shaking is prevented
by the existence of a hard dependency on the service by the module in which it
is declared.

Firstly, @Injectable() is modified to accept a 'scope' parameter, which points
to an @NgModule(). This reverses the dependency edge, permitting the module to
not depend on the service which it "provides".

Secondly, the runtime is modified to understand the new relationship created
above. When a module receives a request to inject a token, and cannot find that
token in its list of providers, it will then look at the token for a special
ngInjectableDef field which indicates which module the token is scoped to. If
that module happens to be in the injector, it will behave as if the token
itself was in the injector to begin with.

Thirdly, the compiler is modified to read the @Injectable() metadata and to
generate the special ngInjectableDef field as part of TS compilation, using the
PartialModules system.

Additionally, this commit adds several unit and integration tests of various
flavors to test this change.

PR Close #22005

packages/compiler/src/injectable_compiler.ts

@@ -0,0 +1,111 @@
+/**
+ * @license
+ * Copyright Google Inc. All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import {CompileInjectableMetadata, CompileNgModuleMetadata, CompileProviderMetadata, identifierName} from './compile_metadata';
+import {CompileReflector} from './compile_reflector';
+import {InjectFlags, NodeFlags} from './core';
+import {Identifiers} from './identifiers';
+import * as o from './output/output_ast';
+import {convertValueToOutputAst} from './output/value_util';
+import {typeSourceSpan} from './parse_util';
+import {NgModuleProviderAnalyzer} from './provider_analyzer';
+import {OutputContext} from './util';
+import {componentFactoryResolverProviderDef, depDef, providerDef} from './view_compiler/provider_compiler';
+
+type MapEntry = {
+  key: string,
+  quoted: boolean,
+  value: o.Expression
+};
+type MapLiteral = MapEntry[];
+
+function mapEntry(key: string, value: o.Expression): MapEntry {
+  return {key, value, quoted: false};
+}
+
+export class InjectableCompiler {
+  constructor(private reflector: CompileReflector) {}
+
+  private depsArray(deps: any[], ctx: OutputContext): o.Expression[] {
+    return deps.map(dep => {
+      let token = dep;
+      let defaultValue = undefined;
+      let args = [token];
+      let flags: InjectFlags = InjectFlags.Default;
+      if (Array.isArray(dep)) {
+        for (let i = 0; i < dep.length; i++) {
+          const v = dep[i];
+          if (v) {
+            if (v.ngMetadataName === 'Optional') {
+              defaultValue = null;
+            } else if (v.ngMetadataName === 'SkipSelf') {
+              flags |= InjectFlags.SkipSelf;
+            } else if (v.ngMetadataName === 'Self') {
+              flags |= InjectFlags.Self;
+            } else if (v.ngMetadataName === 'Inject') {
+              throw new Error('@Inject() is not implemented');
+            } else {
+              token = v;
+            }
+          }
+        }
+        args = [ctx.importExpr(token), o.literal(defaultValue), o.literal(flags)];
+      } else {
+        args = [ctx.importExpr(token)];
+      }
+      return o.importExpr(Identifiers.inject).callFn(args);
+    });
+  }
+
+  private factoryFor(injectable: CompileInjectableMetadata, ctx: OutputContext): o.Expression {
+    let retValue: o.Expression;
+    if (injectable.useExisting) {
+      retValue = o.importExpr(Identifiers.inject).callFn([ctx.importExpr(injectable.useExisting)]);
+    } else if (injectable.useFactory) {
+      const deps = injectable.deps || [];
+      if (deps.length > 0) {
+        retValue = ctx.importExpr(injectable.useFactory).callFn(this.depsArray(deps, ctx));
+      } else {
+        return ctx.importExpr(injectable.useFactory);
+      }
+    } else if (injectable.useValue) {
+      retValue = convertValueToOutputAst(ctx, injectable.useValue);
+    } else {
+      const clazz = injectable.useClass || injectable.symbol;
+      const depArgs = this.depsArray(this.reflector.parameters(clazz), ctx);
+      retValue = new o.InstantiateExpr(ctx.importExpr(clazz), depArgs);
+    }
+    return o.fn(
+        [], [new o.ReturnStatement(retValue)], undefined, undefined,
+        injectable.symbol.name + '_Factory');
+  }
+
+  injectableDef(injectable: CompileInjectableMetadata, ctx: OutputContext): o.Expression {
+    const def: MapLiteral = [
+      mapEntry('factory', this.factoryFor(injectable, ctx)),
+      mapEntry('token', ctx.importExpr(injectable.type.reference)),
+      mapEntry('scope', ctx.importExpr(injectable.module !)),
+    ];
+    return o.importExpr(Identifiers.defineInjectable).callFn([o.literalMap(def)]);
+  }
+
+  compile(injectable: CompileInjectableMetadata, ctx: OutputContext): void {
+    if (injectable.module) {
+      const className = identifierName(injectable.type) !;
+      const clazz = new o.ClassStmt(
+          className, null,
+          [
+            new o.ClassField(
+                'ngInjectableDef', o.INFERRED_TYPE, [o.StmtModifier.Static],
+                this.injectableDef(injectable, ctx)),
+          ],
+          [], new o.ClassMethod(null, [], []), []);
+      ctx.statements.push(clazz);
+    }
+  }
+}