fix: Wrap native string responses from lambda invocation endpoint

package.json

@@ -148,7 +148,8 @@
     "Vasiliy Solovey (https://github.com/miltador)",
     "Dima Krutolianov (https://github.com/dimadk24)",
     "Bryan Vaz (https://github.com/bryanvaz)",
-    "Justin Ng (https://github.com/njyjn)"
+    "Justin Ng (https://github.com/njyjn)",
+    "Fernando Alvarez (https://github.com/jefer590)"
   ],
   "engines": {
     "node": ">=12.0.0"

src/lambda/__tests__/fixtures/Lambda/LambdaFunctionThatReturnsJSONObject.fixture.js

@@ -0,0 +1,35 @@
+import { resolve } from 'path'
+import LambdaFunction from '../../../LambdaFunction.js'
+
+export default class LambdaFunctionThatReturnsJSONObject {
+  options = {}
+  serverless = {
+    config: {
+      serverlessPath: '',
+      servicePath: resolve(__dirname),
+    },
+    service: {
+      provider: {
+        runtime: 'nodejs12.x',
+      },
+    },
+  }
+
+  listFunctionNames() {
+    return ['foo']
+  }
+
+  getByFunctionName(functionName) {
+    const functionDefinition = {
+      handler:
+        '../../fixtures/lambdaFunction.fixture.asyncFunctionHandlerObject',
+    }
+
+    return new LambdaFunction(
+      functionName,
+      functionDefinition,
+      this.serverless,
+      this.options,
+    )
+  }
+}

src/lambda/__tests__/fixtures/Lambda/LambdaFunctionThatReturnsNativeString.fixture.js

@@ -0,0 +1,34 @@
+import { resolve } from 'path'
+import LambdaFunction from '../../../LambdaFunction.js'
+
+export default class LambdaFunctionThatReturnsNativeString {
+  options = {}
+  serverless = {
+    config: {
+      serverlessPath: '',
+      servicePath: resolve(__dirname),
+    },
+    service: {
+      provider: {
+        runtime: 'nodejs12.x',
+      },
+    },
+  }
+
+  listFunctionNames() {
+    return ['foo']
+  }
+
+  getByFunctionName(functionName) {
+    const functionDefinition = {
+      handler: '../../fixtures/lambdaFunction.fixture.asyncFunctionHandler',
+    }
+
+    return new LambdaFunction(
+      functionName,
+      functionDefinition,
+      this.serverless,
+      this.options,
+    )
+  }
+}

src/lambda/__tests__/fixtures/lambdaFunction.fixture.js

@@ -48,6 +48,12 @@ exports.asyncFunctionHandler = async function asyncFunctionHandler() {
   return 'foo'
 }
 
+exports.asyncFunctionHandlerObject = async function asyncFunctionHandler() {
+  return {
+    foo: 'bar',
+  }
+}
+
 // we deliberately test the case where a 'callback' is defined
 // in the handler, but a promise is being returned to protect from a
 // potential naive implementation, e.g.

src/lambda/__tests__/routes/invocations/InvocationsController.test.js

@@ -0,0 +1,43 @@
+import InvocationsController from '../../../routes/invocations/InvocationsController.js'
+import LambdaFunctionThatReturnsJSONObject from '../../fixtures/Lambda/LambdaFunctionThatReturnsJSONObject.fixture.js'
+import LambdaFunctionThatReturnsNativeString from '../../fixtures/Lambda/LambdaFunctionThatReturnsNativeString.fixture.js'
+
+jest.mock('../../../../serverlessLog')
+
+describe('InvocationController', () => {
+  const functionName = 'foo'
+
+  describe('when event type is "RequestResponse"', () => {
+    const eventType = 'RequestResponse'
+
+    test('should return json object if lambda response is json', async () => {
+      const expected = {
+        Payload: {
+          foo: 'bar',
+        },
+        StatusCode: 200,
+      }
+
+      const invocationController = new InvocationsController(
+        new LambdaFunctionThatReturnsJSONObject(),
+      )
+      const result = await invocationController.invoke(functionName, eventType)
+
+      expect(result).toStrictEqual(expected)
+    })
+
+    test('should wrap native string responses with ""', async () => {
+      const expected = {
+        Payload: '"foo"',
+        StatusCode: 200,
+      }
+
+      const invocationController = new InvocationsController(
+        new LambdaFunctionThatReturnsNativeString(),
+      )
+      const result = await invocationController.invoke(functionName, eventType)
+
+      expect(result).toStrictEqual(expected)
+    })
+  })
+})

src/lambda/routes/invocations/InvocationsController.js

@@ -74,6 +74,14 @@ export default class InvocationsController {
         // RequestTooLargeException, InvalidParameterValueException,
         // and whatever response is thrown when the response is too large.
       }
+
+      // Checking if the result of the Lambda Invoke is a primitive string to wrap it. this is for future post-processing such as Step Functions Tasks
+      if (result) {
+        if (typeof result === 'string') {
+          result = `"${result}"`
+        }
+      }
+
       // result is actually the Payload.
       // So return in a standard structure so Hapi can
       // respond with the correct status codes