fix: apig vtl stringify

src/api.ts

@@ -653,6 +653,37 @@ export class APIGatewayVTL extends VTL {
     return super.eval(node as any, returnVar);
   }
 
+  /**
+   * Attempt to return the expression as a valid escaped json string.
+   *
+   * ```ts
+   * {
+   *    x: input
+   * }
+   * ```
+   *
+   * =>
+   *
+   * ```ts
+   * { "x": $input.json('$') }
+   * ```
+   *
+   * =>
+   *
+   * ```ts
+   * "{ \"x\": $util.escapeJavaScript($input.json('$')) }"
+   * ```
+   */
+  public stringify(expr: Expr): string {
+    const json = this.exprToJson(expr);
+    return `"${json
+      .replace(/"/g, '\\"')
+      .replace(
+        /\$input\.json\('([^']*)'\)/g,
+        "$util.escapeJavaScript($input.json('$1'))"
+      )}"`;
+  }
+
   /**
    * Renders a VTL string that will emit a JSON String representation of the {@link expr} to the VTL output.
    *

src/step-function.ts

@@ -571,9 +571,7 @@ abstract class BaseStepFunction<
         .map(([argName, argVal]) => {
           if (argName === "input") {
             // stringify the JSON input
-            return `"${argName}":"$util.escapeJavaScript(${context.exprToJson(
-              argVal
-            )})"`;
+            return `"${argName}":${context.stringify(argVal)}`;
           } else {
             return `"${argName}":${context.exprToJson(argVal)}`;
           }

test/api.test.ts

@@ -167,6 +167,52 @@ test("AWS integration with Standard Step Function", () => {
   expect(getTemplates(method)).toMatchSnapshot();
 });
 
+test("AWS integration with Standard Step Function using input data", () => {
+  const api = new aws_apigateway.RestApi(stack, "API");
+
+  const sfn = new StepFunction(
+    stack,
+    "SFN",
+    (_input: {
+      num: number;
+      obj: {
+        value: string;
+      };
+    }) => {
+      return "done";
+    }
+  );
+
+  const method = new AwsMethod(
+    {
+      httpMethod: "GET",
+      resource: api.root,
+    },
+    (
+      $input: ApiGatewayInput<{
+        query: {
+          num: string;
+          str: string;
+        };
+        body: {
+          value: string;
+        };
+      }>
+    ) =>
+      sfn({
+        input: {
+          num: Number($input.params("num")),
+          obj: $input.data,
+        },
+      }),
+    ($input) => {
+      return $input.data.executionArn;
+    }
+  );
+
+  expect(getTemplates(method)).toMatchSnapshot();
+});
+
 test("AWS integration with DynamoDB Table", () => {
   const api = new aws_apigateway.RestApi(stack, "API");
   const table = Table.fromTable(