feat(tsc-wrapped): record arity of generic classes (#14104)

tools/@angular/tsc-wrapped/src/collector.ts

@@ -128,6 +128,12 @@ export class MetadataCollector {
         });
       }
 
+      // Add arity if the type is generic
+      const typeParameters = classDeclaration.typeParameters;
+      if (typeParameters && typeParameters.length) {
+        result.arity = typeParameters.length;
+      }
+
       // Add class decorators
       if (classDeclaration.decorators) {
         result.decorators = getDecorators(classDeclaration.decorators);

tools/@angular/tsc-wrapped/src/schema.ts

@@ -37,6 +37,7 @@ export interface ModuleExportMetadata {
 export interface ClassMetadata {
   __symbolic: 'class';
   extends?: MetadataSymbolicExpression|MetadataError;
+  arity?: number;
   decorators?: (MetadataSymbolicExpression|MetadataError)[];
   members?: MetadataMap;
   statics?: {[name: string]: MetadataValue | FunctionMetadata};

tools/@angular/tsc-wrapped/test/collector.spec.ts

@@ -9,7 +9,7 @@
 import * as ts from 'typescript';
 
 import {MetadataCollector} from '../src/collector';
-import {ClassMetadata, ConstructorMetadata, ModuleMetadata} from '../src/schema';
+import {ClassMetadata, ConstructorMetadata, MetadataEntry, ModuleMetadata, isClassMetadata} from '../src/schema';
 
 import {Directory, Host, expectValidSources} from './typescript.mocks';
 
@@ -28,6 +28,7 @@ describe('Collector', () => {
       '/promise.ts',
       '/unsupported-1.ts',
       '/unsupported-2.ts',
+      'class-arity.ts',
       'import-star.ts',
       'exported-classes.ts',
       'exported-functions.ts',
@@ -666,6 +667,27 @@ describe('Collector', () => {
         }
       });
     });
+
+    function expectClass(entry: MetadataEntry): entry is ClassMetadata {
+      const result = isClassMetadata(entry);
+      expect(result).toBeTruthy();
+      return result;
+    }
+
+    it('should collect the correct arity for a class', () => {
+      const metadata = collector.getMetadata(program.getSourceFile('/class-arity.ts'));
+
+      const zero = metadata.metadata['Zero'];
+      if (expectClass(zero)) expect(zero.arity).toBeUndefined();
+      const one = metadata.metadata['One'];
+      if (expectClass(one)) expect(one.arity).toBe(1);
+      const two = metadata.metadata['Two'];
+      if (expectClass(two)) expect(two.arity).toBe(2);
+      const three = metadata.metadata['Three'];
+      if (expectClass(three)) expect(three.arity).toBe(3);
+      const nine = metadata.metadata['Nine'];
+      if (expectClass(nine)) expect(nine.arity).toBe(9);
+    });
   });
 
   function override(fileName: string, content: string) {
@@ -867,6 +889,13 @@ const FILES: Directory = {
 
     declare var Promise: PromiseConstructor;
   `,
+  'class-arity.ts': `
+    export class Zero {}
+    export class One<T> {}
+    export class Two<T, V> {}
+    export class Three<T1, T2, T3> {}
+    export class Nine<T1, T2, T3, T4, T5, T6, T7, T8, T9> {}
+  `,
   'unsupported-1.ts': `
     export let {a, b} = {a: 1, b: 2};
     export let [c, d] = [1, 2];