From e44e10bb815ec6f93b9737c0fe42f5587d68e7b5 Mon Sep 17 00:00:00 2001
From: ayazhafiz <ayaz.hafiz.1@gmail.com>
Date: Fri, 2 Oct 2020 23:25:38 -0500
Subject: [PATCH] feat(compiler): support recovery of malformed property writes
 (#39103)

This feature is trivial to support since
89c5255b8ca59eed27ede9e1fad69857ab0c6f4f has landed.

PR Close #39103
---
 .../compiler/src/expression_parser/parser.ts  |  8 ++++-
 .../test/expression_parser/parser_spec.ts     | 32 +++++++++++++++++++
 2 files changed, 39 insertions(+), 1 deletion(-)

diff --git a/packages/compiler/src/expression_parser/parser.ts b/packages/compiler/src/expression_parser/parser.ts
index 707f4f02a2..751e8533ab 100644
--- a/packages/compiler/src/expression_parser/parser.ts
+++ b/packages/compiler/src/expression_parser/parser.ts
@@ -848,7 +848,13 @@ export class _ParseAST {
   parseAccessMemberOrMethodCall(receiver: AST, isSafe: boolean = false): AST {
     const start = receiver.span.start;
     const nameStart = this.inputIndex;
-    const id = this.expectIdentifierOrKeyword();
+    const id = this.withContext(ParseContextFlags.Writable, () => {
+      const id = this.expectIdentifierOrKeyword();
+      if (id.length === 0) {
+        this.error(`Expected identifier for property access`, receiver.span.end);
+      }
+      return id;
+    });
     const nameSpan = this.sourceSpan(nameStart);
 
     if (this.consumeOptionalCharacter(chars.$LPAREN)) {
diff --git a/packages/compiler/test/expression_parser/parser_spec.ts b/packages/compiler/test/expression_parser/parser_spec.ts
index 91a7de4621..f6786bc267 100644
--- a/packages/compiler/test/expression_parser/parser_spec.ts
+++ b/packages/compiler/test/expression_parser/parser_spec.ts
@@ -146,6 +146,38 @@ describe('parser', () => {
       });
     });
 
+    describe('property write', () => {
+      it('should parse property writes', () => {
+        checkAction('a.a = 1 + 2');
+        checkAction('this.a.a = 1 + 2', 'a.a = 1 + 2');
+        checkAction('a.a.a = 1 + 2');
+      });
+
+      describe('malformed property writes', () => {
+        it('should recover on empty rvalues', () => {
+          checkActionWithError('a.a = ', 'a.a = ', 'Unexpected end of expression');
+        });
+
+        it('should recover on incomplete rvalues', () => {
+          checkActionWithError('a.a = 1 + ', 'a.a = 1 + ', 'Unexpected end of expression');
+        });
+
+        it('should recover on missing properties', () => {
+          checkActionWithError(
+              'a. = 1', 'a. = 1', 'Expected identifier for property access at column 2');
+        });
+
+        it('should error on writes after a property write', () => {
+          const ast = parseAction('a.a = 1 = 2');
+          expect(unparse(ast)).toEqual('a.a = 1');
+          validate(ast);
+
+          expect(ast.errors.length).toBe(1);
+          expect(ast.errors[0].message).toContain('Unexpected token \'=\'');
+        });
+      });
+    });
+
     describe('method calls', () => {
       it('should parse method calls', () => {
         checkAction('fn()');