Fixed unexpected lua error from Object.GetOwnPropertyDescriptors returning nil (#994)

Perryvw · web-flow · commit 0299d71a0e89 · 2021-03-02T19:14:01.000+01:00
diff --git a/src/lualib/ObjectGetOwnPropertyDescriptors.ts b/src/lualib/ObjectGetOwnPropertyDescriptors.ts
@@ -1,5 +1,5 @@
 function __TS__ObjectGetOwnPropertyDescriptors(this: void, object: any): Record<any, PropertyDescriptor | undefined> {
     const metatable = getmetatable(object);
     if (!metatable) return {};
-    return rawget(metatable, "_descriptors");
+    return rawget(metatable, "_descriptors") || {};
 }
diff --git a/test/unit/builtins/object.spec.ts b/test/unit/builtins/object.spec.ts
@@ -211,3 +211,27 @@ describe("Object.getOwnPropertyDescriptors", () => {
         `.expectToMatchJsResult();
     });
 });
+
+describe("delete from object", () => {
+    test("delete from object", () => {
+        util.testFunction`
+            const obj = { foo: "bar", bar: "baz" };
+            delete obj["foo"];
+            return obj;
+        `
+            .setTsHeader("declare function setmetatable<T extends object>(this: void, table: T, metatable: any): T;")
+            .expectToEqual({ bar: "baz" });
+    });
+
+    // https://github.com/TypeScriptToLua/TypeScriptToLua/issues/993
+    test("delete from object with metatable", () => {
+        util.testFunction`
+        const obj = { foo: "bar", bar: "baz" };
+        setmetatable(obj, {});
+        delete obj["foo"];
+        return obj;
+    `
+            .setTsHeader("declare function setmetatable<T extends object>(this: void, table: T, metatable: any): T;")
+            .expectToEqual({ bar: "baz" });
+    });
+});

Original file line number	Diff line number	Diff line change
`@@ -1,5 +1,5 @@`
`1`	`1`	`function __TS__ObjectGetOwnPropertyDescriptors(this: void, object: any): Record<any, PropertyDescriptor \| undefined> {`
`2`	`2`	`const metatable = getmetatable(object);`
`3`	`3`	`if (!metatable) return {};`
`4`		`- return rawget(metatable, "_descriptors");`
	`4`	`+ return rawget(metatable, "_descriptors") \|\| {};`
`5`	`5`	`}`