TypeScriptToLua · Perryvw · Mar 27, 2019 · Mar 27, 2019
diff --git a/src/LuaLib.ts b/src/LuaLib.ts
@@ -29,6 +29,7 @@ export enum LuaLibFeature {
     NewIndex = "NewIndex",
     ObjectAssign = "ObjectAssign",
     ObjectEntries = "ObjectEntries",
+    ObjectFromEntries = "ObjectFromEntries",
     ObjectKeys = "ObjectKeys",
     ObjectValues = "ObjectValues",
     Set = "Set",
@@ -43,6 +44,7 @@ export enum LuaLibFeature {
 
 const luaLibDependencies: {[lib in LuaLibFeature]?: LuaLibFeature[]} = {
     Iterator: [LuaLibFeature.Symbol],
+    ObjectFromEntries: [LuaLibFeature.Iterator, LuaLibFeature.Symbol],
     Map: [LuaLibFeature.InstanceOf, LuaLibFeature.Iterator, LuaLibFeature.Symbol],
     Set: [LuaLibFeature.InstanceOf, LuaLibFeature.Iterator, LuaLibFeature.Symbol],
     WeakMap: [LuaLibFeature.InstanceOf, LuaLibFeature.Iterator, LuaLibFeature.Symbol],

diff --git a/src/LuaTransformer.ts b/src/LuaTransformer.ts
@@ -3707,6 +3707,8 @@ export class LuaTransformer {
                 return this.transformLuaLibFunction(LuaLibFeature.ObjectAssign, expression, ...parameters);
             case "entries":
                 return this.transformLuaLibFunction(LuaLibFeature.ObjectEntries, expression, ...parameters);
+            case "fromEntries":
+                return this.transformLuaLibFunction(LuaLibFeature.ObjectFromEntries, expression, ...parameters);
             case "keys":
                 return this.transformLuaLibFunction(LuaLibFeature.ObjectKeys, expression, ...parameters);
             case "values":

diff --git a/src/lualib/ObjectFromEntries.ts b/src/lualib/ObjectFromEntries.ts
@@ -0,0 +1,24 @@
+function __TS__ObjectFromEntries<T>(
+    this: void,
+    entries: ReadonlyArray<[string, T]> | Iterable<[string, T]>
+): Record<string, T> {
+    const obj: Record<string, T> = {};
+
+    const iterable = entries as Iterable<[string, T]>;
+    if (iterable[Symbol.iterator]) {
+        const iterator = iterable[Symbol.iterator]();
+        while (true) {
+            const result = iterator.next();
+            if (result.done) break;
+
+            const value: [string, T] = result.value;
+            obj[value[0]] = value[1];
+        }
+    } else {
+        for (const entry of entries as ReadonlyArray<[string, T]>) {
+            obj[entry[0]] = entry[1];
+        }
+    }
+
+    return obj;
+}
diff --git a/test/unit/lualib/lualib.spec.ts b/test/unit/lualib/lualib.spec.ts
@@ -408,7 +408,7 @@ test.each([
     { initial: "{}", parameters: "{a: 3}", expected: { a: 3 } },
     { initial: "{a: 3}", parameters: "{a: 5}", expected: { a: 5 } },
     { initial: "{a: 3}", parameters: "{b: 5},{c: 7}", expected: { a: 3, b: 5, c: 7 } },
-])("Object.Assign (%p)", ({ initial, parameters, expected }) => {
+])("Object.assign (%p)", ({ initial, parameters, expected }) => {
     const jsonResult = util.transpileAndExecute(`
         return JSONStringify(Object.assign(${initial},${parameters}));
     `);
@@ -484,3 +484,40 @@ test.each([
         }
     }
 });
+
+// https://github.com/Microsoft/TypeScript/pull/26149
+const objectFromEntriesDeclaration = `
+    interface ObjectConstructor {
+        fromEntries<T>(entries: ReadonlyArray<[string, T]> | Iterable<[string, T]>): Record<string, T>;
+        fromEntries(entries: ReadonlyArray<[string, any]> | Iterable<[string, any]>): Record<string, any>;
+    }
+`;
+
+test.each([
+    { entries: [], expected: [] },
+    { entries: [["a", 1], ["b", 2]], expected: { a: 1, b: 2 } },
+    { entries: [["a", 1], ["a", 2]], expected: { a: 2 } },
+])("Object.fromEntries (%p)", ({ entries, expected }) => {
+    const result = util.transpileAndExecute(
+        `const obj = Object.fromEntries(${JSON.stringify(entries)});
+        return JSONStringify(obj);`,
+        undefined,
+        undefined,
+        objectFromEntriesDeclaration,
+    );
+
+    expect(JSON.parse(result)).toEqual(expected);
+});
+
+test("Object.fromEntries (Map)", () => {
+    const result = util.transpileAndExecute(
+        `const map = new Map([["foo", "bar"]]);
+        const obj = Object.fromEntries(map);
+        return JSONStringify(obj);`,
+        undefined,
+        undefined,
+        objectFromEntriesDeclaration,
+    );
+
+    expect(JSON.parse(result)).toEqual({ foo: "bar" });
+});