fix for vararg access in async functions (#1096)

tomblind · web-flow · commit 01a0fcb4f11a · 2021-08-20T14:51:56.000+02:00
Co-authored-by: Tom &lt;tomblind@users.noreply.github.com&gt;
diff --git a/src/transformation/visitors/function.ts b/src/transformation/visitors/function.ts
@@ -115,7 +115,10 @@ export function transformFunctionBody(
 ): [lua.Statement[], Scope] {
     const scope = pushScope(context, ScopeType.Function);
     scope.node = node;
-    const bodyStatements = transformFunctionBodyContent(context, body);
+    let bodyStatements = transformFunctionBodyContent(context, body);
+    if (node && isAsyncFunction(node)) {
+        bodyStatements = wrapInAsyncAwaiter(context, bodyStatements);
+    }
     const headerStatements = transformFunctionBodyHeader(context, scope, parameters, spreadIdentifier);
     popScope(context);
     return [[...headerStatements, ...bodyStatements], scope];
@@ -197,10 +200,8 @@ export function transformFunctionToExpression(
         node
     );
 
-    const possiblyAsyncBody = isAsyncFunction(node) ? wrapInAsyncAwaiter(context, transformedBody) : transformedBody;
-
     const functionExpression = lua.createFunctionExpression(
-        lua.createBlock(possiblyAsyncBody),
+        lua.createBlock(transformedBody),
         paramNames,
         dotsLiteral,
         flags,
diff --git a/src/transformation/visitors/spread.ts b/src/transformation/visitors/spread.ts
@@ -37,6 +37,11 @@ export function isOptimizedVarArgSpread(context: TransformationContext, symbol:
         return false;
     }
 
+    // Scope cannot be an async function
+    if (scope.node.modifiers?.some(m => m.kind === ts.SyntaxKind.AsyncKeyword)) {
+        return false;
+    }
+
     // Identifier must be a vararg in the local function scope's parameters
     const isSpreadParameter = (p: ts.ParameterDeclaration) =>
         p.dotDotDotToken && ts.isIdentifier(p.name) && context.checker.getSymbolAtLocation(p.name) === symbol;
diff --git a/test/unit/builtins/async-await.spec.ts b/test/unit/builtins/async-await.spec.ts
@@ -333,3 +333,39 @@ test.each([
         .setOptions({ module: ModuleKind.ESNext, target: ScriptTarget.ES2017 })
         .expectToHaveDiagnostics([awaitMustBeInAsyncFunction.code]);
 });
+
+test("async function can access varargs", () => {
+    util.testFunction`
+        const { promise, resolve } = defer<string>();
+
+        async function a(...args: string[]) {
+            log(await promise);
+            log(args[1]);
+        }
+
+        const awaitingPromise = a("A", "B", "C");
+        resolve("resolved");
+
+        return allLogs;
+    `
+        .setTsHeader(promiseTestLib)
+        .expectToEqual(["resolved", "B"]);
+});
+
+test("async function can forward varargs", () => {
+    util.testFunction`
+        const { promise, resolve } = defer<string>();
+
+        async function a(...args: string[]) {
+            log(await promise);
+            log(...args);
+        }
+
+        const awaitingPromise = a("A", "B", "C");
+        resolve("resolved");
+
+        return allLogs;
+    `
+        .setTsHeader(promiseTestLib)
+        .expectToEqual(["resolved", "A", "B", "C"]);
+});
