Parse an object literal property as shorthand unless followed by '(' or ':' (#28121)

src/compiler/parser.ts

@@ -4738,8 +4738,7 @@ namespace ts {
             // CoverInitializedName[Yield] :
             //     IdentifierReference[?Yield] Initializer[In, ?Yield]
             // this is necessary because ObjectLiteral productions are also used to cover grammar for ObjectAssignmentPattern
-            const isShorthandPropertyAssignment =
-                tokenIsIdentifier && (token() === SyntaxKind.CommaToken || token() === SyntaxKind.CloseBraceToken || token() === SyntaxKind.EqualsToken);
+            const isShorthandPropertyAssignment = tokenIsIdentifier && (token() !== SyntaxKind.ColonToken);
             if (isShorthandPropertyAssignment) {
                 node.kind = SyntaxKind.ShorthandPropertyAssignment;
                 const equalsToken = parseOptionalToken(SyntaxKind.EqualsToken);

src/testRunner/unittests/convertCompilerOptionsFromJson.ts

@@ -596,7 +596,8 @@ namespace ts {
                 {
                     compilerOptions: {
                         target: undefined,
-                        module: ModuleKind.ESNext
+                        module: ModuleKind.ESNext,
+                        experimentalDecorators: true,
                     },
                     hasParseErrors: true
                 }

src/testRunner/unittests/tsconfigParsing.ts

@@ -141,7 +141,7 @@ namespace ts {
 
         it("returns object with error when json is invalid", () => {
             const parsed = parseConfigFileTextToJson("/apath/tsconfig.json", "invalid");
-            assert.deepEqual(parsed.config, { invalid: undefined });
+            assert.deepEqual(parsed.config, {});
             const expected = createCompilerDiagnostic(Diagnostics._0_expected, "{");
             const error = parsed.error!;
             assert.equal(error.messageText, expected.messageText);