Fix class .toString inheritance (#882)

ark120202 · web-flow · commit 42b356868c43 · 2020-05-24T15:22:05.000+02:00
* Fix class .toString inheritance

* Move tests to builtins/object and add few more toString tests
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -25,6 +25,8 @@
 
 - Fixed iteration over generators stopping at first yielded `nil` value
 
+- Fixed extending a class not keeping `toString` implementation from a super class
+
 ## 0.33.0
 
 - Added support for nullish coalescing `A ?? B`.
diff --git a/src/lualib/ClassExtends.ts b/src/lualib/ClassExtends.ts
@@ -16,4 +16,5 @@ function __TS__ClassExtends(this: void, target: LuaClass, base: LuaClass): void
     // Re-add metatable events defined by accessors with `__TS__SetDescriptor`
     if (typeof base.prototype.__index === "function") target.prototype.__index = base.prototype.__index;
     if (typeof base.prototype.__newindex === "function") target.prototype.__newindex = base.prototype.__newindex;
+    if (typeof base.prototype.__tostring === "function") target.prototype.__tostring = base.prototype.__tostring;
 }
diff --git a/src/lualib/declarations/tstl.d.ts b/src/lualib/declarations/tstl.d.ts
@@ -10,6 +10,7 @@ interface Metatable {
     _descriptors?: Record<string, PropertyDescriptor>;
     __index?: any;
     __newindex?: any;
+    __tostring?: any;
 }
 
 interface LuaClass extends Metatable {
diff --git a/test/unit/builtins/object.spec.ts b/test/unit/builtins/object.spec.ts
@@ -28,3 +28,96 @@ test.each(["[]", '[["a", 1], ["b", 2]]', '[["a", 1], ["a", 2]]', 'new Map([["foo
         util.testExpression`Object.fromEntries(${entries})`.expectToMatchJsResult();
     }
 );
+
+describe(".toString()", () => {
+    const toStringDeclaration = `
+        function toString(value: object) {
+            const result = value.toString();
+            return result === "[object Object]" || result.startsWith("table: ") ? "table" : result;
+        }
+    `;
+
+    test("class override", () => {
+        util.testFunction`
+            ${toStringDeclaration}
+            class A {
+                public toString() {
+                    return "A";
+                }
+            }
+
+            return toString(new A());
+        `.expectToMatchJsResult();
+    });
+
+    test("inherited class override", () => {
+        util.testFunction`
+            ${toStringDeclaration}
+            class A {
+                public toString() {
+                    return "A";
+                }
+            }
+
+            class B extends A {}
+
+            return { A: toString(new A()), B: toString(new B()) };
+        `.expectToMatchJsResult();
+    });
+
+    test("don't affect inherited class", () => {
+        util.testFunction`
+            ${toStringDeclaration}
+            class A {}
+
+            class B extends A {
+                public toString() {
+                    return "B";
+                }
+            }
+
+            return { A: toString(new A()), B: toString(new B()) };
+        `.expectToMatchJsResult();
+    });
+
+    test("override inherited class override", () => {
+        util.testFunction`
+            ${toStringDeclaration}
+            class A {
+                public toString() {
+                    return "A";
+                }
+            }
+
+            class B extends A {
+                public toString() {
+                    return "B";
+                }
+            }
+
+            return { A: toString(new A()), B: toString(new B()) };
+        `.expectToMatchJsResult();
+    });
+});
+
+describe(".hasOwnProperty()", () => {
+    test("class field", () => {
+        util.testFunction`
+            class A {
+                public field = true;
+            }
+
+            return new A().hasOwnProperty("field");
+        `.expectToMatchJsResult();
+    });
+
+    test("class method", () => {
+        util.testFunction`
+            class A {
+                public method() {}
+            }
+
+            return new A().hasOwnProperty("method");
+        `.expectToMatchJsResult();
+    });
+});
diff --git a/test/unit/classes/classes.spec.ts b/test/unit/classes/classes.spec.ts
@@ -352,42 +352,6 @@ test("ClassComputedMethodCall", () => {
     `.expectToMatchJsResult();
 });
 
-test("ClassToString", () => {
-    util.testFunction`
-        class a {
-            public toString(): string {
-                return "instance of a";
-            }
-        }
-        let inst = new a();
-        return inst.toString();
-    `.expectToMatchJsResult();
-});
-
-test("HasOwnProperty true", () => {
-    util.testFunction`
-        class a {
-            public test(): void {
-            }
-        }
-        let inst = new a();
-        inst["prop"] = 17;
-        return inst.hasOwnProperty("prop");
-    `.expectToMatchJsResult();
-});
-
-test("HasOwnProperty false", () => {
-    util.testFunction`
-        class a {
-            public test(): void {
-            }
-        }
-        let inst = new a();
-        inst["prop"] = 17;
-        return inst.hasOwnProperty("test");
-    `.expectToMatchJsResult();
-});
-
 test("CastClassMethodCall", () => {
     util.testFunction`
         interface result

Original file line number	Diff line number	Diff line change
`@@ -16,4 +16,5 @@ function __TS__ClassExtends(this: void, target: LuaClass, base: LuaClass): void`
`16`	`16`	// Re-add metatable events defined by accessors with `__TS__SetDescriptor`
`17`	`17`	`if (typeof base.prototype.__index === "function") target.prototype.__index = base.prototype.__index;`
`18`	`18`	`if (typeof base.prototype.__newindex === "function") target.prototype.__newindex = base.prototype.__newindex;`
	`19`	`+ if (typeof base.prototype.__tostring === "function") target.prototype.__tostring = base.prototype.__tostring;`
`19`	`20`	`}`
Original file line number	Diff line number	Diff line change
`@@ -10,6 +10,7 @@ interface Metatable {`
`10`	`10`	`_descriptors?: Record<string, PropertyDescriptor>;`
`11`	`11`	`__index?: any;`
`12`	`12`	`__newindex?: any;`
	`13`	`+ __tostring?: any;`
`13`	`14`	`}`
`14`	`15`
`15`	`16`	`interface LuaClass extends Metatable {`