fix(ivy): support finding the import of namespace-imported identifiers (#27675)

Currently there is no support in ngtsc for imports of the form:

```
import * as core from `@angular/core`

export function forRoot(): core.ModuleWithProviders;
```

This commit modifies the `ReflectionHost.getImportOfIdentifier(id)`
method, so that it supports this kind of return type.

PR Close #27675

packages/compiler-cli/src/ngtsc/annotations/src/ng_module.ts

@@ -286,12 +286,19 @@ export class NgModuleDecoratorHandler implements DecoratorHandler<NgModuleAnalys
    */
   private _reflectModuleFromTypeParam(type: ts.TypeNode): ts.Expression|null {
     // Examine the type of the function to see if it's a ModuleWithProviders reference.
-    if (!ts.isTypeReferenceNode(type) || !ts.isIdentifier(type.typeName)) {
+    if (!ts.isTypeReferenceNode(type)) {
+      return null;
+    }
+
+    const typeName = type && (ts.isIdentifier(type.typeName) && type.typeName ||
+                              ts.isQualifiedName(type.typeName) && type.typeName.right) ||
+        null;
+    if (typeName === null) {
       return null;
     }
 
     // Look at the type itself to see where it comes from.
-    const id = this.reflector.getImportOfIdentifier(type.typeName);
+    const id = this.reflector.getImportOfIdentifier(typeName);
 
     // If it's not named ModuleWithProviders, bail.
     if (id === null || id.name !== 'ModuleWithProviders') {

packages/compiler-cli/src/ngtsc/reflection/src/typescript.ts

@@ -79,35 +79,7 @@ export class TypeScriptReflectionHost implements ReflectionHost {
   }
 
   getImportOfIdentifier(id: ts.Identifier): Import|null {
-    const symbol = this.checker.getSymbolAtLocation(id);
-
-    if (symbol === undefined || symbol.declarations === undefined ||
-        symbol.declarations.length !== 1) {
-      return null;
-    }
-
-    // Ignore decorators that are defined locally (not imported).
-    const decl: ts.Declaration = symbol.declarations[0];
-    if (!ts.isImportSpecifier(decl)) {
-      return null;
-    }
-
-    // Walk back from the specifier to find the declaration, which carries the module specifier.
-    const importDecl = decl.parent !.parent !.parent !;
-
-    // The module specifier is guaranteed to be a string literal, so this should always pass.
-    if (!ts.isStringLiteral(importDecl.moduleSpecifier)) {
-      // Not allowed to happen in TypeScript ASTs.
-      return null;
-    }
-
-    // Read the module specifier.
-    const from = importDecl.moduleSpecifier.text;
-
-    // Compute the name by which the decorator was exported, not imported.
-    const name = (decl.propertyName !== undefined ? decl.propertyName : decl.name).text;
-
-    return {from, name};
+    return this.getDirectImportOfIdentifier(id) || this.getImportOfNamespacedIdentifier(id);
   }
 
   getExportsOfModule(node: ts.Node): Map<string, Declaration>|null {
@@ -179,6 +151,90 @@ export class TypeScriptReflectionHost implements ReflectionHost {
 
   getDtsDeclaration(_: ts.Declaration): ts.Declaration|null { return null; }
 
+
+  protected getDirectImportOfIdentifier(id: ts.Identifier): Import|null {
+    const symbol = this.checker.getSymbolAtLocation(id);
+
+    if (symbol === undefined || symbol.declarations === undefined ||
+        symbol.declarations.length !== 1) {
+      return null;
+    }
+
+    // Ignore decorators that are defined locally (not imported).
+    const decl: ts.Declaration = symbol.declarations[0];
+    if (!ts.isImportSpecifier(decl)) {
+      return null;
+    }
+
+    // Walk back from the specifier to find the declaration, which carries the module specifier.
+    const importDecl = decl.parent !.parent !.parent !;
+
+    // The module specifier is guaranteed to be a string literal, so this should always pass.
+    if (!ts.isStringLiteral(importDecl.moduleSpecifier)) {
+      // Not allowed to happen in TypeScript ASTs.
+      return null;
+    }
+
+    // Read the module specifier.
+    const from = importDecl.moduleSpecifier.text;
+
+    // Compute the name by which the decorator was exported, not imported.
+    const name = (decl.propertyName !== undefined ? decl.propertyName : decl.name).text;
+
+    return {from, name};
+  }
+
+  /**
+   * Try to get the import info for this identifier as though it is a namespaced import.
+   * For example, if the identifier is the `Directive` part of a qualified type chain like:
+   *
+   * ```
+   * core.Directive
+   * ```
+   *
+   * then it might be that `core` is a namespace import such as:
+   *
+   * ```
+   * import * as core from 'tslib';
+   * ```
+   *
+   * @param id the TypeScript identifier to find the import info for.
+   * @returns The import info if this is a namespaced import or `null`.
+   */
+  protected getImportOfNamespacedIdentifier(id: ts.Identifier): Import|null {
+    if (!(ts.isQualifiedName(id.parent) && id.parent.right === id)) {
+      return null;
+    }
+    const namespaceIdentifier = getQualifiedNameRoot(id.parent);
+    if (!namespaceIdentifier) {
+      return null;
+    }
+    const namespaceSymbol = this.checker.getSymbolAtLocation(namespaceIdentifier);
+    if (!namespaceSymbol) {
+      return null;
+    }
+    const declaration =
+        namespaceSymbol.declarations.length === 1 ? namespaceSymbol.declarations[0] : null;
+    if (!declaration) {
+      return null;
+    }
+    const namespaceDeclaration = ts.isNamespaceImport(declaration) ? declaration : null;
+    if (!namespaceDeclaration) {
+      return null;
+    }
+
+    const importDeclaration = namespaceDeclaration.parent.parent;
+    if (!ts.isStringLiteral(importDeclaration.moduleSpecifier)) {
+      // Should not happen as this would be invalid TypesScript
+      return null;
+    }
+
+    return {
+      from: importDeclaration.moduleSpecifier.text,
+      name: id.text,
+    };
+  }
+
   /**
    * Resolve a `ts.Symbol` to its declaration, keeping track of the `viaModule` along the way.
    *
@@ -443,3 +499,16 @@ function propertyNameToString(node: ts.PropertyName): string|null {
     return null;
   }
 }
+
+/**
+ * Compute the left most identifier in a qualified type chain. E.g. the `a` of `a.b.c.SomeType`.
+ * @param qualifiedName The starting property access expression from which we want to compute
+ * the left most identifier.
+ * @returns the left most identifier in the chain or `null` if it is not an identifier.
+ */
+function getQualifiedNameRoot(qualifiedName: ts.QualifiedName): ts.Identifier|null {
+  while (ts.isQualifiedName(qualifiedName.left)) {
+    qualifiedName = qualifiedName.left;
+  }
+  return ts.isIdentifier(qualifiedName.left) ? qualifiedName.left : null;
+}

packages/compiler-cli/test/ngtsc/ngtsc_spec.ts

@@ -1337,6 +1337,39 @@ describe('ngtsc behavioral tests', () => {
                'i0.ɵNgModuleDefWithMeta<TestModule, never, [typeof i1.RouterModule], never>');
      });
 
+  it('should unwrap a namespace imported ModuleWithProviders function if a generic type is provided for it',
+     () => {
+       env.tsconfig();
+       env.write(`test.ts`, `
+        import {NgModule} from '@angular/core';
+        import {RouterModule} from 'router';
+
+        @NgModule({imports: [RouterModule.forRoot()]})
+        export class TestModule {}
+    `);
+
+       env.write('node_modules/router/index.d.ts', `
+        import * as core from '@angular/core';
+        import {RouterModule} from 'router';
+
+        declare class RouterModule {
+          static forRoot(): core.ModuleWithProviders<RouterModule>;
+          static ngModuleDef: ɵNgModuleDefWithMeta<RouterModule, never, never, never>;
+        }
+    `);
+
+       env.driveMain();
+
+       const jsContents = env.getContents('test.js');
+       expect(jsContents).toContain('imports: [[RouterModule.forRoot()]]');
+
+       const dtsContents = env.getContents('test.d.ts');
+       expect(dtsContents).toContain(`import * as i1 from "router";`);
+       expect(dtsContents)
+           .toContain(
+               'i0.ɵNgModuleDefWithMeta<TestModule, never, [typeof i1.RouterModule], never>');
+     });
+
   it('should inject special types according to the metadata', () => {
     env.tsconfig();
     env.write(`test.ts`, `