fix(ivy): ngcc - identify all ESM5 decorated classes (#27848)

In ESM5 decorated classes can be indicated by calls to `__decorate()`.
Previously the `ReflectionHost.findDecoratedClasses()` call would identify
helper calls of the form:

```
SomeClass = tslib_1.__decorate(...);
```

But it was missing calls of the form:

```
SomeClass = SomeClass_1 = tslib_1.__decorate(...);
```

This form is common in `@NgModule()` decorations, where the class
being decorated is referenced inside the decorator or another
member.

This commit now ensures that a chain of assignments, of any length,
is now identified as a class decoration if it results in a call to
`__decorate()`.

Fixes #27841

PR Close #27848

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

@@ -661,8 +661,10 @@ export class Esm2015ReflectionHost extends TypeScriptReflectionHost implements N
    */
   protected getHelperCall(statement: ts.Statement, helperName: string): ts.CallExpression|null {
     if (ts.isExpressionStatement(statement)) {
-      const expression =
-          isAssignmentStatement(statement) ? statement.expression.right : statement.expression;
+      let expression = statement.expression;
+      while (isAssignment(expression)) {
+        expression = expression.right;
+      }
       if (ts.isCallExpression(expression) && getCalleeName(expression) === helperName) {
         return expression;
       }

packages/compiler-cli/src/ngcc/test/host/esm5_host_import_helper_spec.ts

@@ -304,6 +304,27 @@ describe('Esm5ReflectionHost [import helper style]', () => {
         });
       });
 
+      describe('findDecoratedClasses', () => {
+        it('should return an array of all decorated classes in the given source file', () => {
+          const program = makeTestProgram(...fileSystem.files);
+          const host = new Esm5ReflectionHost(false, program.getTypeChecker());
+
+          const ngModuleFile = program.getSourceFile('/ngmodule.js') !;
+          const ngModuleClasses = host.findDecoratedClasses(ngModuleFile);
+          expect(ngModuleClasses.length).toEqual(1);
+          const ngModuleClass = ngModuleClasses.find(c => c.name === 'HttpClientXsrfModule') !;
+          expect(ngModuleClass.decorators.map(decorator => decorator.name)).toEqual(['NgModule']);
+
+          const someDirectiveFile = program.getSourceFile('/some_directive.js') !;
+          const someDirectiveClasses = host.findDecoratedClasses(someDirectiveFile);
+          expect(someDirectiveClasses.length).toEqual(1);
+          const someDirectiveClass = someDirectiveClasses.find(c => c.name === 'SomeDirective') !;
+          expect(someDirectiveClass.decorators.map(decorator => decorator.name)).toEqual([
+            'Directive'
+          ]);
+        });
+      });
+
       describe('getDeclarationOfIdentifier', () => {
         it('should return the declaration of a locally defined identifier', () => {
           const program = makeTestProgram(fileSystem.files[0]);