Emit of union type metadata for decorator to use constituent serialized type if its identifier and same across all constituent types

src/compiler/transformers/ts.ts

@@ -1801,10 +1801,41 @@ namespace ts {
                 case SyntaxKind.TypeReference:
                     return serializeTypeReferenceNode(<TypeReferenceNode>node);
 
+                case SyntaxKind.IntersectionType:
+                case SyntaxKind.UnionType:
+                    {
+                        const unionOrIntersection = <UnionOrIntersectionTypeNode>node;
+                        let serializedUnion: Identifier;
+                        for (const typeNode of unionOrIntersection.types) {
+                            const serializedIndividual = serializeTypeNode(typeNode) as Identifier;
+                            // Non identifier
+                            if (serializedIndividual.kind !== SyntaxKind.Identifier) {
+                                serializedUnion = undefined;
+                                break;
+                            }
+
+                            // One of the individual is global object, return immediately
+                            if (serializedIndividual.text === "Object") {
+                                return serializedIndividual;
+                            }
+
+                            // Different types
+                            if (serializedUnion && serializedUnion.text !== serializedIndividual.text) {
+                                serializedUnion = undefined;
+                                break;
+                            }
+
+                            serializedUnion = serializedIndividual;
+                        }
+
+                        // If we were able to find common type
+                        if (serializedUnion) {
+                            return serializedUnion;
+                        }
+                    }
+                    // Fallthrough
                 case SyntaxKind.TypeQuery:
                 case SyntaxKind.TypeLiteral:
-                case SyntaxKind.UnionType:
-                case SyntaxKind.IntersectionType:
                 case SyntaxKind.AnyKeyword:
                 case SyntaxKind.ThisType:
                     break;

tests/baselines/reference/metadataOfStringLiteral.js

@@ -0,0 +1,28 @@
+//// [metadataOfStringLiteral.ts]
+function PropDeco(target: Object, propKey: string | symbol) { }
+
+class Foo {
+    @PropDeco
+    public foo: "foo" | "bar";
+}
+
+//// [metadataOfStringLiteral.js]
+var __decorate = (this && this.__decorate) || function (decorators, target, key, desc) {
+    var c = arguments.length, r = c < 3 ? target : desc === null ? desc = Object.getOwnPropertyDescriptor(target, key) : desc, d;
+    if (typeof Reflect === "object" && typeof Reflect.decorate === "function") r = Reflect.decorate(decorators, target, key, desc);
+    else for (var i = decorators.length - 1; i >= 0; i--) if (d = decorators[i]) r = (c < 3 ? d(r) : c > 3 ? d(target, key, r) : d(target, key)) || r;
+    return c > 3 && r && Object.defineProperty(target, key, r), r;
+};
+var __metadata = (this && this.__metadata) || function (k, v) {
+    if (typeof Reflect === "object" && typeof Reflect.metadata === "function") return Reflect.metadata(k, v);
+};
+function PropDeco(target, propKey) { }
+var Foo = (function () {
+    function Foo() {
+    }
+    return Foo;
+}());
+__decorate([
+    PropDeco,
+    __metadata("design:type", String)
+], Foo.prototype, "foo");

tests/baselines/reference/metadataOfStringLiteral.symbols

@@ -0,0 +1,16 @@
+=== tests/cases/compiler/metadataOfStringLiteral.ts ===
+function PropDeco(target: Object, propKey: string | symbol) { }
+>PropDeco : Symbol(PropDeco, Decl(metadataOfStringLiteral.ts, 0, 0))
+>target : Symbol(target, Decl(metadataOfStringLiteral.ts, 0, 18))
+>Object : Symbol(Object, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>propKey : Symbol(propKey, Decl(metadataOfStringLiteral.ts, 0, 33))
+
+class Foo {
+>Foo : Symbol(Foo, Decl(metadataOfStringLiteral.ts, 0, 63))
+
+    @PropDeco
+>PropDeco : Symbol(PropDeco, Decl(metadataOfStringLiteral.ts, 0, 0))
+
+    public foo: "foo" | "bar";
+>foo : Symbol(Foo.foo, Decl(metadataOfStringLiteral.ts, 2, 11))
+}

tests/baselines/reference/metadataOfStringLiteral.types

@@ -0,0 +1,16 @@
+=== tests/cases/compiler/metadataOfStringLiteral.ts ===
+function PropDeco(target: Object, propKey: string | symbol) { }
+>PropDeco : (target: Object, propKey: string | symbol) => void
+>target : Object
+>Object : Object
+>propKey : string | symbol
+
+class Foo {
+>Foo : Foo
+
+    @PropDeco
+>PropDeco : (target: Object, propKey: string | symbol) => void
+
+    public foo: "foo" | "bar";
+>foo : "foo" | "bar"
+}

tests/baselines/reference/metadataOfUnion.js

@@ -0,0 +1,50 @@
+//// [metadataOfUnion.ts]
+function PropDeco(target: Object, propKey: string | symbol) { }
+
+class A {
+}
+
+class B {
+    @PropDeco
+    x: "foo" | A;
+
+    @PropDeco
+    y: true | boolean;
+
+    @PropDeco
+    z: "foo" | boolean;
+}
+
+//// [metadataOfUnion.js]
+var __decorate = (this && this.__decorate) || function (decorators, target, key, desc) {
+    var c = arguments.length, r = c < 3 ? target : desc === null ? desc = Object.getOwnPropertyDescriptor(target, key) : desc, d;
+    if (typeof Reflect === "object" && typeof Reflect.decorate === "function") r = Reflect.decorate(decorators, target, key, desc);
+    else for (var i = decorators.length - 1; i >= 0; i--) if (d = decorators[i]) r = (c < 3 ? d(r) : c > 3 ? d(target, key, r) : d(target, key)) || r;
+    return c > 3 && r && Object.defineProperty(target, key, r), r;
+};
+var __metadata = (this && this.__metadata) || function (k, v) {
+    if (typeof Reflect === "object" && typeof Reflect.metadata === "function") return Reflect.metadata(k, v);
+};
+function PropDeco(target, propKey) { }
+var A = (function () {
+    function A() {
+    }
+    return A;
+}());
+var B = (function () {
+    function B() {
+    }
+    return B;
+}());
+__decorate([
+    PropDeco,
+    __metadata("design:type", Object)
+], B.prototype, "x");
+__decorate([
+    PropDeco,
+    __metadata("design:type", Boolean)
+], B.prototype, "y");
+__decorate([
+    PropDeco,
+    __metadata("design:type", Object)
+], B.prototype, "z");

tests/baselines/reference/metadataOfUnion.symbols

@@ -0,0 +1,33 @@
+=== tests/cases/compiler/metadataOfUnion.ts ===
+function PropDeco(target: Object, propKey: string | symbol) { }
+>PropDeco : Symbol(PropDeco, Decl(metadataOfUnion.ts, 0, 0))
+>target : Symbol(target, Decl(metadataOfUnion.ts, 0, 18))
+>Object : Symbol(Object, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>propKey : Symbol(propKey, Decl(metadataOfUnion.ts, 0, 33))
+
+class A {
+>A : Symbol(A, Decl(metadataOfUnion.ts, 0, 63))
+}
+
+class B {
+>B : Symbol(B, Decl(metadataOfUnion.ts, 3, 1))
+
+    @PropDeco
+>PropDeco : Symbol(PropDeco, Decl(metadataOfUnion.ts, 0, 0))
+
+    x: "foo" | A;
+>x : Symbol(B.x, Decl(metadataOfUnion.ts, 5, 9))
+>A : Symbol(A, Decl(metadataOfUnion.ts, 0, 63))
+
+    @PropDeco
+>PropDeco : Symbol(PropDeco, Decl(metadataOfUnion.ts, 0, 0))
+
+    y: true | boolean;
+>y : Symbol(B.y, Decl(metadataOfUnion.ts, 7, 17))
+
+    @PropDeco
+>PropDeco : Symbol(PropDeco, Decl(metadataOfUnion.ts, 0, 0))
+
+    z: "foo" | boolean;
+>z : Symbol(B.z, Decl(metadataOfUnion.ts, 10, 22))
+}

tests/baselines/reference/metadataOfUnion.types

@@ -0,0 +1,34 @@
+=== tests/cases/compiler/metadataOfUnion.ts ===
+function PropDeco(target: Object, propKey: string | symbol) { }
+>PropDeco : (target: Object, propKey: string | symbol) => void
+>target : Object
+>Object : Object
+>propKey : string | symbol
+
+class A {
+>A : A
+}
+
+class B {
+>B : B
+
+    @PropDeco
+>PropDeco : (target: Object, propKey: string | symbol) => void
+
+    x: "foo" | A;
+>x : A | "foo"
+>A : A
+
+    @PropDeco
+>PropDeco : (target: Object, propKey: string | symbol) => void
+
+    y: true | boolean;
+>y : boolean
+>true : true
+
+    @PropDeco
+>PropDeco : (target: Object, propKey: string | symbol) => void
+
+    z: "foo" | boolean;
+>z : boolean | "foo"
+}

tests/cases/compiler/metadataOfStringLiteral.ts

@@ -0,0 +1,8 @@
+// @experimentalDecorators: true
+// @emitDecoratorMetadata: true
+function PropDeco(target: Object, propKey: string | symbol) { }
+
+class Foo {
+    @PropDeco
+    public foo: "foo" | "bar";
+}

tests/cases/compiler/metadataOfUnion.ts

@@ -0,0 +1,17 @@
+// @experimentalDecorators: true
+// @emitDecoratorMetadata: true
+function PropDeco(target: Object, propKey: string | symbol) { }
+
+class A {
+}
+
+class B {
+    @PropDeco
+    x: "foo" | A;
+
+    @PropDeco
+    y: true | boolean;
+
+    @PropDeco
+    z: "foo" | boolean;
+}