refactor(compiler-cli): account for spread elements in translator

Adds the ability to generate spread elements in the linker.

Author: crisbeto

packages/compiler-cli/linker/babel/src/ast/babel_ast_factory.ts

@@ -21,7 +21,7 @@ import {
 /**
  * A Babel flavored implementation of the AstFactory.
  */
-export class BabelAstFactory implements AstFactory<t.Statement, t.Expression> {
+export class BabelAstFactory implements AstFactory<t.Statement, t.Expression | t.SpreadElement> {
   constructor(
     /** The absolute path to the source file being compiled. */
     private sourceUrl: string,
@@ -74,7 +74,11 @@ export class BabelAstFactory implements AstFactory<t.Statement, t.Expression> {
 
   createBlock = t.blockStatement;
 
-  createCallExpression(callee: t.Expression, args: t.Expression[], pure: boolean): t.Expression {
+  createCallExpression(
+    callee: t.Expression,
+    args: (t.Expression | t.SpreadElement)[],
+    pure: boolean,
+  ): t.Expression {
     const call = t.callExpression(callee, args);
     if (pure) {
       t.addComment(call, 'leading', ' @__PURE__ ', /* line */ false);
@@ -90,6 +94,10 @@ export class BabelAstFactory implements AstFactory<t.Statement, t.Expression> {
 
   createExpressionStatement = t.expressionStatement;
 
+  createSpreadElement(expression: t.Expression): t.SpreadElement {
+    return t.spreadElement(expression);
+  }
+
   createFunctionDeclaration(
     functionName: string,
     parameters: string[],
@@ -158,7 +166,9 @@ export class BabelAstFactory implements AstFactory<t.Statement, t.Expression> {
     }
   }
 
-  createNewExpression = t.newExpression;
+  createNewExpression(expression: t.Expression, args: t.Expression[]): t.Expression {
+    return t.newExpression(expression, args);
+  }
 
   createObjectLiteral(properties: ObjectLiteralProperty<t.Expression>[]): t.Expression {
     return t.objectExpression(
@@ -181,7 +191,9 @@ export class BabelAstFactory implements AstFactory<t.Statement, t.Expression> {
     return t.memberExpression(expression, t.identifier(propertyName), /* computed */ false);
   }
 
-  createReturnStatement = t.returnStatement;
+  createReturnStatement(expression: t.Expression | null): t.Statement {
+    return t.returnStatement(expression);
+  }
 
   createTaggedTemplate(tag: t.Expression, template: TemplateLiteral<t.Expression>): t.Expression {
     return t.taggedTemplateExpression(tag, this.createTemplateLiteral(template));
@@ -223,7 +235,7 @@ export class BabelAstFactory implements AstFactory<t.Statement, t.Expression> {
     return t.regExpLiteral(body, flags ?? undefined);
   }
 
-  setSourceMapRange<T extends t.Statement | t.Expression | t.TemplateElement>(
+  setSourceMapRange<T extends t.Statement | t.Expression | t.TemplateElement | t.SpreadElement>(
     node: T,
     sourceMapRange: SourceMapRange | null,
   ): T {

packages/compiler-cli/linker/babel/src/es2015_linker_plugin.ts

@@ -26,7 +26,11 @@ export function createEs2015LinkerPlugin({
   logger,
   ...options
 }: LinkerPluginOptions): PluginObj {
-  let fileLinker: FileLinker<ConstantScopePath, t.Statement, t.Expression> | null = null;
+  let fileLinker: FileLinker<
+    ConstantScopePath,
+    t.Statement,
+    t.Expression | t.SpreadElement
+  > | null = null;
 
   return {
     visitor: {
@@ -47,13 +51,10 @@ export function createEs2015LinkerPlugin({
           }
           const sourceUrl = fileSystem.resolve(file.opts.cwd ?? '.', filename);
 
-          const linkerEnvironment = LinkerEnvironment.create<t.Statement, t.Expression>(
-            fileSystem,
-            logger,
-            new BabelAstHost(),
-            new BabelAstFactory(sourceUrl),
-            options,
-          );
+          const linkerEnvironment = LinkerEnvironment.create<
+            t.Statement,
+            t.Expression | t.SpreadElement
+          >(fileSystem, logger, new BabelAstHost(), new BabelAstFactory(sourceUrl), options);
           fileLinker = new FileLinker(linkerEnvironment, sourceUrl, file.code);
         },
 

packages/compiler-cli/linker/babel/test/ast/babel_ast_factory_spec.ts

@@ -412,6 +412,23 @@ describe('BabelAstFactory', () => {
     });
   });
 
+  describe('createSpreadElement()', () => {
+    it('should create a spread element in an array', () => {
+      const before = factory.createIdentifier('a');
+      const spread = factory.createSpreadElement(factory.createIdentifier('b'));
+      const array = factory.createArrayLiteral([before, spread]);
+      expect(generate(array).code).toEqual('[a, ...b]');
+    });
+
+    it('should create a spread in a call expression', () => {
+      const fn = factory.createIdentifier('fn');
+      const before = factory.createIdentifier('a');
+      const spread = factory.createSpreadElement(factory.createIdentifier('b'));
+      const call = factory.createCallExpression(fn, [before, spread], false);
+      expect(generate(call).code).toEqual('fn(a, ...b)');
+    });
+  });
+
   describe('setSourceMapRange()', () => {
     it('should attach the `sourceMapRange` to the given `node`', () => {
       const expr = expression.ast`42`;

packages/compiler-cli/src/ngtsc/translator/src/api/ast_factory.ts

@@ -280,6 +280,13 @@ export interface AstFactory<TStatement, TExpression> {
    */
   createRegularExpressionLiteral(body: string, flags: string | null): TExpression;
 
+  /**
+   * Create a spread element, typically in an array or function call. E.g. `[...a]` or `fn(...b)`.
+   *
+   * @param target Expression of the spread element.
+   */
+  createSpreadElement(expression: TExpression): TExpression;
+
   /**
    * Attach a source map range to the given node.
    *

packages/compiler-cli/src/ngtsc/translator/src/typescript_ast_factory.ts

@@ -262,6 +262,8 @@ export class TypeScriptAstFactory implements AstFactory<ts.Statement, ts.Express
 
   createPropertyAccess = ts.factory.createPropertyAccessExpression;
 
+  createSpreadElement = ts.factory.createSpreadElement;
+
   createReturnStatement(expression: ts.Expression | null): ts.Statement {
     return ts.factory.createReturnStatement(expression ?? undefined);
   }

packages/compiler-cli/src/ngtsc/translator/test/typescript_ast_factory_spec.ts

@@ -490,6 +490,25 @@ describe('TypeScriptAstFactory', () => {
     });
   });
 
+  describe('createSpreadElement()', () => {
+    it('should create a spread element in an array', () => {
+      const {generate} = setupStatements();
+      const before = factory.createIdentifier('a');
+      const spread = factory.createSpreadElement(factory.createIdentifier('b'));
+      const array = factory.createArrayLiteral([before, spread]);
+      expect(generate(array)).toEqual('[a, ...b]');
+    });
+
+    it('should create a spread in a call expression', () => {
+      const {generate} = setupStatements();
+      const fn = factory.createIdentifier('fn');
+      const before = factory.createIdentifier('a');
+      const spread = factory.createSpreadElement(factory.createIdentifier('b'));
+      const call = factory.createCallExpression(fn, [before, spread], false);
+      expect(generate(call)).toEqual('fn(a, ...b)');
+    });
+  });
+
   describe('setSourceMapRange()', () => {
     it('should attach the `sourceMapRange` to the given `node`', () => {
       const {