feat(ivy): add `getBaseClassIdentifier()` to `ReflectionHost` (#31544)

This method will be useful for writing ngcc `Migrations` that
need to be able to find base classes.

PR Close #31544

packages/compiler-cli/ngcc/src/host/esm2015_host.ts

@@ -190,9 +190,21 @@ export class Esm2015ReflectionHost extends TypeScriptReflectionHost implements N
       return false;
     }
 
-    return innerClassDeclaration.heritageClauses !== undefined &&
-        innerClassDeclaration.heritageClauses.some(
-            clause => clause.token === ts.SyntaxKind.ExtendsKeyword);
+    return super.hasBaseClass(innerClassDeclaration);
+  }
+
+  getBaseClassExpression(clazz: ClassDeclaration): ts.Expression|null {
+    // First try getting the base class from the "outer" declaration
+    const superBaseClassIdentifier = super.getBaseClassExpression(clazz);
+    if (superBaseClassIdentifier) {
+      return superBaseClassIdentifier;
+    }
+    // That didn't work so now try getting it from the "inner" declaration.
+    const innerClassDeclaration = getInnerClassDeclaration(clazz);
+    if (innerClassDeclaration === null) {
+      return null;
+    }
+    return super.getBaseClassExpression(innerClassDeclaration);
   }
 
   /**

packages/compiler-cli/ngcc/src/host/esm5_host.ts

@@ -56,6 +56,32 @@ export class Esm5ReflectionHost extends Esm2015ReflectionHost {
     return iife.parameters.length === 1 && isSuperIdentifier(iife.parameters[0].name);
   }
 
+  getBaseClassExpression(clazz: ClassDeclaration): ts.Expression|null {
+    const superBaseClassIdentifier = super.getBaseClassExpression(clazz);
+    if (superBaseClassIdentifier) {
+      return superBaseClassIdentifier;
+    }
+
+    const classDeclaration = this.getClassDeclaration(clazz);
+    if (!classDeclaration) return null;
+
+    const iifeBody = getIifeBody(classDeclaration);
+    if (!iifeBody) return null;
+
+    const iife = iifeBody.parent;
+    if (!iife || !ts.isFunctionExpression(iife)) return null;
+
+    if (iife.parameters.length !== 1 || !isSuperIdentifier(iife.parameters[0].name)) {
+      return null;
+    }
+
+    if (!ts.isCallExpression(iife.parent)) {
+      return null;
+    }
+
+    return iife.parent.arguments[0];
+  }
+
   /**
    * Find the declaration of a class given a node that we think represents the class.
    *

packages/compiler-cli/ngcc/test/host/commonjs_host_spec.ts

@@ -1855,6 +1855,95 @@ exports.ExternalModule = ExternalModule;
         });
       });
 
+      describe('getBaseClassExpression()', () => {
+        function getBaseClassIdentifier(source: string): ts.Identifier|null {
+          const file = {
+            name: _('/synthesized_constructors.js'),
+            contents: source,
+          };
+
+          loadTestFiles([file]);
+          const {program, host: compilerHost} = makeTestBundleProgram(file.name);
+          const host = new CommonJsReflectionHost(new MockLogger(), false, program, compilerHost);
+          const classNode =
+              getDeclaration(program, file.name, 'TestClass', isNamedVariableDeclaration);
+          const expression = host.getBaseClassExpression(classNode);
+          if (expression !== null && !ts.isIdentifier(expression)) {
+            throw new Error(
+                'Expected class to inherit via an identifier but got: ' + expression.getText());
+          }
+          return expression;
+        }
+
+        it('should find the base class of an IIFE with _super parameter', () => {
+          const identifier = getBaseClassIdentifier(`
+          var BaseClass = /** @class */ (function () {
+            function BaseClass() {}
+            return BaseClass;
+          }());
+          var TestClass = /** @class */ (function (_super) {
+            __extends(TestClass, _super);
+            function TestClass() {}
+            return TestClass;
+          }(BaseClass));`);
+          expect(identifier !.text).toBe('BaseClass');
+        });
+
+        it('should find the base class of an IIFE with a unique name generated for the _super parameter',
+           () => {
+             const identifier = getBaseClassIdentifier(`
+          var BaseClass = /** @class */ (function () {
+            function BaseClass() {}
+            return BaseClass;
+          }());
+          var TestClass = /** @class */ (function (_super_1) {
+            __extends(TestClass, _super_1);
+            function TestClass() {}
+            return TestClass;
+          }(BaseClass));`);
+             expect(identifier !.text).toBe('BaseClass');
+           });
+
+        it('should not find a base class for an IIFE without parameter', () => {
+          const identifier = getBaseClassIdentifier(`
+          var BaseClass = /** @class */ (function () {
+            function BaseClass() {}
+            return BaseClass;
+          }());
+          var TestClass = /** @class */ (function () {
+            __extends(TestClass, _super);
+            function TestClass() {}
+            return TestClass;
+          }(BaseClass));`);
+          expect(identifier).toBe(null);
+        });
+
+        it('should find a dynamic base class expression of an IIFE', () => {
+          const file = {
+            name: _('/synthesized_constructors.js'),
+            contents: `
+            var BaseClass = /** @class */ (function () {
+              function BaseClass() {}
+              return BaseClass;
+            }());
+            function foo() { return BaseClass; }
+            var TestClass = /** @class */ (function (_super) {
+              __extends(TestClass, _super);
+              function TestClass() {}
+              return TestClass;
+            }(foo()));`,
+          };
+
+          loadTestFiles([file]);
+          const {program, host: compilerHost} = makeTestBundleProgram(file.name);
+          const host = new CommonJsReflectionHost(new MockLogger(), false, program, compilerHost);
+          const classNode =
+              getDeclaration(program, file.name, 'TestClass', isNamedVariableDeclaration);
+          const expression = host.getBaseClassExpression(classNode) !;
+          expect(expression.getText()).toBe('foo()');
+        });
+      });
+
       describe('findClassSymbols()', () => {
         it('should return an array of all classes in the given source file', () => {
           loadTestFiles(DECORATED_FILES);

packages/compiler-cli/ngcc/test/host/esm2015_host_spec.ts

@@ -1680,6 +1680,77 @@ runInEachFileSystem(() => {
       });
     });
 
+    describe('getBaseClassExpression()', () => {
+      it('should not consider a class without extends clause as having a base class', () => {
+        const file = {
+          name: _('/base_class.js'),
+          contents: `class TestClass {}`,
+        };
+        loadTestFiles([file]);
+        const {program} = makeTestBundleProgram(file.name);
+        const host = new Esm2015ReflectionHost(new MockLogger(), false, program.getTypeChecker());
+        const classNode = getDeclaration(program, file.name, 'TestClass', isNamedClassDeclaration);
+        expect(host.getBaseClassExpression(classNode)).toBe(null);
+      });
+
+      it('should find the base class of a class with an `extends` clause', () => {
+        const file = {
+          name: _('/base_class.js'),
+          contents: `
+        class BaseClass {}
+        class TestClass extends BaseClass {}`,
+        };
+        loadTestFiles([file]);
+        const {program} = makeTestBundleProgram(file.name);
+        const host = new Esm2015ReflectionHost(new MockLogger(), false, program.getTypeChecker());
+        const classNode = getDeclaration(program, file.name, 'TestClass', isNamedClassDeclaration);
+        const baseIdentifier = host.getBaseClassExpression(classNode) !;
+        if (!ts.isIdentifier(baseIdentifier)) {
+          throw new Error(`Expected ${baseIdentifier.getText()} to be an identifier.`);
+        }
+        expect(baseIdentifier.text).toEqual('BaseClass');
+      });
+
+      it('should find the base class of an aliased class with an `extends` clause', () => {
+        const file = {
+          name: _('/base_class.js'),
+          contents: `
+        let TestClass_1;
+        class BaseClass {}
+        let TestClass = TestClass_1 = class TestClass extends BaseClass {}`,
+        };
+        loadTestFiles([file]);
+        const {program} = makeTestBundleProgram(file.name);
+        const host = new Esm2015ReflectionHost(new MockLogger(), false, program.getTypeChecker());
+        const classNode =
+            getDeclaration(program, file.name, 'TestClass', isNamedVariableDeclaration);
+        const baseIdentifier = host.getBaseClassExpression(classNode) !;
+        if (!ts.isIdentifier(baseIdentifier)) {
+          throw new Error(`Expected ${baseIdentifier.getText()} to be an identifier.`);
+        }
+        expect(baseIdentifier.text).toEqual('BaseClass');
+      });
+
+      it('should find the base class expression of a class with a dynamic `extends` expression',
+         () => {
+           const file = {
+             name: _('/base_class.js'),
+             contents: `
+        class BaseClass {}
+        function foo() { return BaseClass; }
+        class TestClass extends foo() {}`,
+           };
+           loadTestFiles([file]);
+           const {program} = makeTestBundleProgram(file.name);
+           const host =
+               new Esm2015ReflectionHost(new MockLogger(), false, program.getTypeChecker());
+           const classNode =
+               getDeclaration(program, file.name, 'TestClass', isNamedClassDeclaration);
+           const baseExpression = host.getBaseClassExpression(classNode) !;
+           expect(baseExpression.getText()).toEqual('foo()');
+         });
+    });
+
     describe('getGenericArityOfClass()', () => {
       it('should properly count type parameters', () => {
         loadTestFiles(ARITY_CLASSES);

packages/compiler-cli/ngcc/test/host/esm5_host_spec.ts

@@ -2022,6 +2022,95 @@ runInEachFileSystem(() => {
       });
     });
 
+    describe('getBaseClassExpression()', () => {
+      function getBaseClassIdentifier(source: string): ts.Identifier|null {
+        const file = {
+          name: _('/synthesized_constructors.js'),
+          contents: source,
+        };
+
+        loadTestFiles([file]);
+        const {program} = makeTestBundleProgram(file.name);
+        const host = new Esm5ReflectionHost(new MockLogger(), false, program.getTypeChecker());
+        const classNode =
+            getDeclaration(program, file.name, 'TestClass', isNamedVariableDeclaration);
+        const expression = host.getBaseClassExpression(classNode);
+        if (expression !== null && !ts.isIdentifier(expression)) {
+          throw new Error(
+              'Expected class to inherit via an identifier but got: ' + expression.getText());
+        }
+        return expression;
+      }
+
+      it('should find the base class of an IIFE with _super parameter', () => {
+        const identifier = getBaseClassIdentifier(`
+        var BaseClass = /** @class */ (function () {
+          function BaseClass() {}
+          return BaseClass;
+        }());
+        var TestClass = /** @class */ (function (_super) {
+          __extends(TestClass, _super);
+          function TestClass() {}
+          return TestClass;
+        }(BaseClass));`);
+        expect(identifier !.text).toBe('BaseClass');
+      });
+
+      it('should find the base class of an IIFE with a unique name generated for the _super parameter',
+         () => {
+           const identifier = getBaseClassIdentifier(`
+        var BaseClass = /** @class */ (function () {
+          function BaseClass() {}
+          return BaseClass;
+        }());
+        var TestClass = /** @class */ (function (_super_1) {
+          __extends(TestClass, _super_1);
+          function TestClass() {}
+          return TestClass;
+        }(BaseClass));`);
+           expect(identifier !.text).toBe('BaseClass');
+         });
+
+      it('should not find a base class for an IIFE without parameter', () => {
+        const identifier = getBaseClassIdentifier(`
+        var BaseClass = /** @class */ (function () {
+          function BaseClass() {}
+          return BaseClass;
+        }());
+        var TestClass = /** @class */ (function () {
+          __extends(TestClass, _super);
+          function TestClass() {}
+          return TestClass;
+        }(BaseClass));`);
+        expect(identifier).toBe(null);
+      });
+
+      it('should find a dynamic base class expression of an IIFE', () => {
+        const file = {
+          name: _('/synthesized_constructors.js'),
+          contents: `
+          var BaseClass = /** @class */ (function () {
+            function BaseClass() {}
+            return BaseClass;
+          }());
+          function foo() { return BaseClass; }
+          var TestClass = /** @class */ (function (_super) {
+            __extends(TestClass, _super);
+            function TestClass() {}
+            return TestClass;
+          }(foo()));`,
+        };
+
+        loadTestFiles([file]);
+        const {program} = makeTestBundleProgram(file.name);
+        const host = new Esm5ReflectionHost(new MockLogger(), false, program.getTypeChecker());
+        const classNode =
+            getDeclaration(program, file.name, 'TestClass', isNamedVariableDeclaration);
+        const expression = host.getBaseClassExpression(classNode) !;
+        expect(expression.getText()).toBe('foo()');
+      });
+    });
+
     describe('findClassSymbols()', () => {
       it('should return an array of all classes in the given source file', () => {
         loadTestFiles(DECORATED_FILES);

packages/compiler-cli/ngcc/test/host/umd_host_spec.ts

@@ -1934,6 +1934,95 @@ runInEachFileSystem(() => {
         });
       });
 
+      describe('getBaseClassExpression()', () => {
+        function getBaseClassIdentifier(source: string): ts.Identifier|null {
+          const file = {
+            name: _('/synthesized_constructors.js'),
+            contents: source,
+          };
+
+          loadTestFiles([file]);
+          const {program, host: compilerHost} = makeTestBundleProgram(file.name);
+          const host = new UmdReflectionHost(new MockLogger(), false, program, compilerHost);
+          const classNode =
+              getDeclaration(program, file.name, 'TestClass', isNamedVariableDeclaration);
+          const expression = host.getBaseClassExpression(classNode);
+          if (expression !== null && !ts.isIdentifier(expression)) {
+            throw new Error(
+                'Expected class to inherit via an identifier but got: ' + expression.getText());
+          }
+          return expression;
+        }
+
+        it('should find the base class of an IIFE with _super parameter', () => {
+          const identifier = getBaseClassIdentifier(`
+          var BaseClass = /** @class */ (function () {
+            function BaseClass() {}
+            return BaseClass;
+          }());
+          var TestClass = /** @class */ (function (_super) {
+            __extends(TestClass, _super);
+            function TestClass() {}
+            return TestClass;
+          }(BaseClass));`);
+          expect(identifier !.text).toBe('BaseClass');
+        });
+
+        it('should find the base class of an IIFE with a unique name generated for the _super parameter',
+           () => {
+             const identifier = getBaseClassIdentifier(`
+          var BaseClass = /** @class */ (function () {
+            function BaseClass() {}
+            return BaseClass;
+          }());
+          var TestClass = /** @class */ (function (_super_1) {
+            __extends(TestClass, _super_1);
+            function TestClass() {}
+            return TestClass;
+          }(BaseClass));`);
+             expect(identifier !.text).toBe('BaseClass');
+           });
+
+        it('should not find a base class for an IIFE without parameter', () => {
+          const identifier = getBaseClassIdentifier(`
+          var BaseClass = /** @class */ (function () {
+            function BaseClass() {}
+            return BaseClass;
+          }());
+          var TestClass = /** @class */ (function () {
+            __extends(TestClass, _super);
+            function TestClass() {}
+            return TestClass;
+          }(BaseClass));`);
+          expect(identifier).toBe(null);
+        });
+
+        it('should find a dynamic base class expression of an IIFE', () => {
+          const file = {
+            name: _('/synthesized_constructors.js'),
+            contents: `
+            var BaseClass = /** @class */ (function () {
+              function BaseClass() {}
+              return BaseClass;
+            }());
+            function foo() { return BaseClass; }
+            var TestClass = /** @class */ (function (_super) {
+              __extends(TestClass, _super);
+              function TestClass() {}
+              return TestClass;
+            }(foo()));`,
+          };
+
+          loadTestFiles([file]);
+          const {program, host: compilerHost} = makeTestBundleProgram(file.name);
+          const host = new UmdReflectionHost(new MockLogger(), false, program, compilerHost);
+          const classNode =
+              getDeclaration(program, file.name, 'TestClass', isNamedVariableDeclaration);
+          const expression = host.getBaseClassExpression(classNode) !;
+          expect(expression.getText()).toBe('foo()');
+        });
+      });
+
       describe('findClassSymbols()', () => {
         it('should return an array of all classes in the given source file', () => {
           loadTestFiles(DECORATED_FILES);

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

@@ -505,6 +505,16 @@ export interface ReflectionHost {
    */
   hasBaseClass(clazz: ClassDeclaration): boolean;
 
+  /**
+   * Get an expression representing the base class (if any) of the given `clazz`.
+   *
+   * This expression is most commonly an Identifier, but is possible to inherit from a more dynamic
+   * expression.
+   *
+   * @param clazz the class whose base we want to get.
+   */
+  getBaseClassExpression(clazz: ClassDeclaration): ts.Expression|null;
+
   /**
    * Get the number of generic type parameters of a given class.
    *

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

@@ -121,10 +121,28 @@ export class TypeScriptReflectionHost implements ReflectionHost {
   }
 
   hasBaseClass(clazz: ClassDeclaration): boolean {
-    return ts.isClassDeclaration(clazz) && clazz.heritageClauses !== undefined &&
+    return (ts.isClassDeclaration(clazz) || ts.isClassExpression(clazz)) &&
+        clazz.heritageClauses !== undefined &&
         clazz.heritageClauses.some(clause => clause.token === ts.SyntaxKind.ExtendsKeyword);
   }
 
+  getBaseClassExpression(clazz: ClassDeclaration): ts.Expression|null {
+    if (!(ts.isClassDeclaration(clazz) || ts.isClassExpression(clazz)) ||
+        clazz.heritageClauses === undefined) {
+      return null;
+    }
+    const extendsClause =
+        clazz.heritageClauses.find(clause => clause.token === ts.SyntaxKind.ExtendsKeyword);
+    if (extendsClause === undefined) {
+      return null;
+    }
+    const extendsType = extendsClause.types[0];
+    if (extendsType === undefined) {
+      return null;
+    }
+    return extendsType.expression;
+  }
+
   getDeclarationOfIdentifier(id: ts.Identifier): Declaration|null {
     // Resolve the identifier to a Symbol, and return the declaration of that.
     let symbol: ts.Symbol|undefined = this.checker.getSymbolAtLocation(id);