Fix destructuring assignment of multiReturn (closes #995) (#997)

yancouto · web-flow · commit b84686ffc7c5 · 2021-03-06T18:19:48.000+01:00
* Fix destructuring assignment of multiReturn (closes #995) Added a test. * Rename test and add test for null return * Splitting tests
diff --git a/src/transformation/visitors/variable-declaration.ts b/src/transformation/visitors/variable-declaration.ts
@@ -6,7 +6,7 @@ import { isTupleReturnCall } from "../utils/annotations";
 import { validateAssignment } from "../utils/assignment-validation";
 import { unsupportedVarDeclaration } from "../utils/diagnostics";
 import { addExportToIdentifier } from "../utils/export";
-import { createLocalOrExportedOrGlobalDeclaration, createUnpackCall } from "../utils/lua-ast";
+import { createLocalOrExportedOrGlobalDeclaration, createUnpackCall, wrapInTable } from "../utils/lua-ast";
 import { LuaLibFeature, transformLuaLibFunction } from "../utils/lualib";
 import { transformIdentifier } from "./identifier";
 import { isMultiReturnCall } from "./language-extensions/multi";
@@ -158,9 +158,11 @@ export function transformBindingVariableDeclaration(
             // Contain the expression in a temporary variable
             table = lua.createAnonymousIdentifier();
             if (initializer) {
-                statements.push(
-                    lua.createVariableDeclarationStatement(table, context.transformExpression(initializer))
-                );
+                let expression = context.transformExpression(initializer);
+                if (isTupleReturnCall(context, initializer) || isMultiReturnCall(context, initializer)) {
+                    expression = wrapInTable(expression);
+                }
+                statements.push(lua.createVariableDeclarationStatement(table, expression));
             }
         }
         statements.push(...transformBindingPattern(context, bindingPattern, table));
diff --git a/test/unit/language-extensions/__snapshots__/multi.spec.ts.snap b/test/unit/language-extensions/__snapshots__/multi.spec.ts.snap
@@ -69,7 +69,9 @@ exports[`invalid $multi call (const [a = 0] = $multi()): diagnostics 1`] = `"mai
 
 exports[`invalid $multi call (const {} = $multi();): code 1`] = `
 "local ____ = {
-    ____(_G)
+    {
+        ____(_G)
+    }
 }"
 `;
 
diff --git a/test/unit/language-extensions/multi.spec.ts b/test/unit/language-extensions/multi.spec.ts
@@ -24,6 +24,33 @@ test("multi example use case", () => {
         .expectToEqual({ a: "foo", b: 5 });
 });
 
+// https://github.com/TypeScriptToLua/TypeScriptToLua/issues/995
+test("Destructuring assignment of LuaMultiReturn", () => {
+    util.testModule`
+        function multiReturn(): LuaMultiReturn<[number, number, number]> {
+            return $multi(1, 2, 3);
+        }
+
+        const [a, ...b] = multiReturn();
+        export {a, b};
+    `
+        .setOptions(multiProjectOptions)
+        .expectToEqual({ a: 1, b: [2, 3] });
+});
+
+test("Destructuring assignment of LuaMultiReturn returning nil", () => {
+    util.testModule`
+        function multiReturn(): LuaMultiReturn<[number, number, number]> {
+            return;
+        }
+
+        const [a, ...b] = multiReturn();
+        export {a, b};
+    `
+        .setOptions(multiProjectOptions)
+        .expectToEqual({ a: undefined, b: [] });
+});
+
 test.each<[string, any]>([
     ["$multi()", undefined],
     ["$multi(true)", true],
