fix: await on function calls returning async functions

Signed-off-by: Christian Stewart <christian@aperture.us>

Author: paralin

AGENTS.md

@@ -24,6 +24,8 @@ GoScript is an experimental Go to TypeScript transpiler that enables developers
 
 **This is an experimental project** - we do not maintain backwards compatibility and prioritize simplicity and correctness over legacy support. You may sometimes encounter a problem that requires a complete re-design or re-think or re-architecting of an aspect of goscript, which is perfectly okay, in this case write a design to `compliance/WIP.md` and think it through extensively before performing your refactor. It's perfectly OK to delete large swaths of code as needed. Focus on correctness.
 
+If you want to overwrite WIP.md you must `rm` it first.
+
 The GoScript runtime, located in `gs/builtin/builtin.ts`, provides necessary helper functions and is imported in generated code using the `@goscript/builtin` alias.
 
 **Output Style**: Generated TypeScript should not use semicolons and should always focus on code clarity and correctness.

compiler/expr-call.go

@@ -117,14 +117,26 @@ func (c *GoToTSCompiler) WriteCallExpr(exp *ast.CallExpr) error {
 		}
 		c.tsw.WriteLiterally(")")
 	} else {
+		// Check if this is a function call that returns a function (e.g., simpleIterator(m)())
+		// and if the inner call is async, wrap it in parentheses
+		innerCallExpr, isCallExpr := expFun.(*ast.CallExpr)
+		needsParens := isCallExpr && c.isCallExprAsync(innerCallExpr)
+
+		if needsParens {
+			c.tsw.WriteLiterally("(")
+		}
+
 		// Not an identifier (e.g., method call on a value, function call result)
 		if err := c.WriteValueExpr(expFun); err != nil {
 			return fmt.Errorf("failed to write method expression in call: %w", err)
 		}
 
-		// Check if this is a function call that returns a function (e.g., simpleIterator(m)())
+		if needsParens {
+			c.tsw.WriteLiterally(")")
+		}
+
 		// Add non-null assertion since the returned function could be null
-		if _, isCallExpr := expFun.(*ast.CallExpr); isCallExpr {
+		if isCallExpr {
 			c.tsw.WriteLiterally("!")
 		} else {
 			c.addNonNullAssertion(expFun)

compliance/deps/encoding/json/encode.gs.ts

@@ -382,7 +382,7 @@ export class encodeState {
 
 	public async reflectValue(v: reflect.Value, opts: encOpts): Promise<void> {
 		const e = this
-		await valueEncoder(v)!(e, v, opts)
+		(await valueEncoder(v))!(e, v, opts)
 	}
 
 	// Register this type with the runtime type system

compliance/tests/call_async_returned_function/call_async_returned_function.go

@@ -0,0 +1,20 @@
+package main
+
+import "sync"
+
+var cache sync.Map
+
+// Async function that returns a function
+func getCallback() func(string) {
+	cache.Load(1)
+	return func(msg string) {
+		println("Callback:", msg)
+	}
+}
+
+func main() {
+	// Call the function returned by an async function
+	// This should generate: (await getCallback())!("hello")
+	// NOT: await getCallback()!("hello")
+	getCallback()("hello")
+}

compliance/tests/call_async_returned_function/call_async_returned_function.gs.ts

@@ -0,0 +1,24 @@
+// Generated file based on call_async_returned_function.go
+// Updated when compliance tests are re-run, DO NOT EDIT!
+
+import * as $ from "@goscript/builtin/index.js"
+
+import * as sync from "@goscript/sync/index.js"
+
+let cache: $.VarRef<sync.Map> = $.varRef(new sync.Map())
+
+// Async function that returns a function
+export async function getCallback(): Promise<((p0: string) => void) | null> {
+	await cache!.value.Load(1)
+	return (msg: string): void => {
+		console.log("Callback:", msg)
+	}
+}
+
+export async function main(): Promise<void> {
+	// Call the function returned by an async function
+	// This should generate: (await getCallback())!("hello")
+	// NOT: await getCallback()!("hello")
+	(await getCallback())!("hello")
+}
+

compliance/tests/call_async_returned_function/expected.log

@@ -0,0 +1 @@
+Callback: hello

compliance/tests/call_async_returned_function/index.ts

@@ -0,0 +1,32 @@
+{
+  "compilerOptions": {
+    "allowImportingTsExtensions": true,
+    "lib": [
+      "es2022",
+      "esnext.disposable",
+      "dom"
+    ],
+    "module": "nodenext",
+    "moduleResolution": "nodenext",
+    "noEmit": true,
+    "paths": {
+      "*": [
+        "./*"
+      ],
+      "@goscript/*": [
+        "../../../gs/*",
+        "../../../compliance/deps/*"
+      ],
+      "@goscript/github.com/aperturerobotics/goscript/compliance/tests/call_async_returned_function/*": [
+        "./*"
+      ]
+    },
+    "sourceMap": true,
+    "target": "es2022"
+  },
+  "extends": "../../../tsconfig.json",
+  "include": [
+    "call_async_returned_function.gs.ts",
+    "index.ts"
+  ]
+}

compliance/tests/call_async_returned_function/tsconfig.json

@@ -0,0 +1,27 @@
+package main
+
+func getAdder(x int) func(int) int {
+	return func(y int) int {
+		return x + y
+	}
+}
+
+func asyncAdd(a, b int) int {
+	return a + b
+}
+
+func getAsyncAdder(x int) func(int) int {
+	return func(y int) int {
+		return asyncAdd(x, y)
+	}
+}
+
+func main() {
+	// Direct call of returned function - not async
+	result1 := getAdder(5)(3)
+	println("Result 1:", result1)
+
+	// Direct call of returned function - with async call inside
+	result2 := getAsyncAdder(10)(7)
+	println("Result 2:", result2)
+}

compliance/tests/call_returned_function_async/call_returned_function_async.go

@@ -0,0 +1,31 @@
+// Generated file based on call_returned_function_async.go
+// Updated when compliance tests are re-run, DO NOT EDIT!
+
+import * as $ from "@goscript/builtin/index.js"
+
+export function getAdder(x: number): ((p0: number) => number) | null {
+	return (y: number): number => {
+		return x + y
+	}
+}
+
+export function asyncAdd(a: number, b: number): number {
+	return a + b
+}
+
+export function getAsyncAdder(x: number): ((p0: number) => number) | null {
+	return (y: number): number => {
+		return asyncAdd(x, y)
+	}
+}
+
+export async function main(): Promise<void> {
+	// Direct call of returned function - not async
+	let result1 = getAdder(5)!(3)
+	console.log("Result 1:", result1)
+
+	// Direct call of returned function - with async call inside
+	let result2 = getAsyncAdder(10)!(7)
+	console.log("Result 2:", result2)
+}
+