fix(lib): Correctly render string tokens that contain plain objects (#…

…3545)

Fixes #3540

packages/cdktf/lib/tfExpression.ts

@@ -36,7 +36,13 @@ class TFExpression extends Intrinsic implements IResolvable {
     const resolvedArg = context.resolve(arg);
 
     if (typeof arg === "string") {
-      return this.resolveString(arg, resolvedArg);
+      const str = this.resolveString(arg, resolvedArg);
+      // When Token.asString() is used on an object, str will be the object and needs to be resolved differently
+      // This happens for example in MapTerraformIterator#_getForEachExpression and can cause issues like #3540
+      if (typeof str !== "string") {
+        return this.resolveExpressionPart(context, str);
+      }
+      return str;
     }
 
     return this.resolveExpressionPart(context, arg);

packages/cdktf/test/tfExpression.test.ts

@@ -270,3 +270,10 @@ test("nesting can undo the wrapping", () => {
     `"\${x(docker_container.foo.bar, "this is the ref: \${y("my ref: \${docker_container.foo.bar}", docker_container.foo.bar)}")}"`
   );
 });
+
+test("expressions correctly resolve string wrapped objects", () => {
+  const expr = call("keys", [Token.asString({ a: "b" })]);
+  expect(resolveExpression(expr)).toMatchInlineSnapshot(
+    `"\${keys({"a" = "b"})}"`
+  );
+});