feat: add UnescapeMappingTemplate to state machine Api event

integration/resources/expected/single/state_machine_with_api.json

@@ -0,0 +1,10 @@
+[
+  { "LogicalResourceId": "HelloWorldFunction", "ResourceType": "AWS::Lambda::Function" },
+  { "LogicalResourceId": "HelloWorldFunctionRole", "ResourceType": "AWS::IAM::Role" },
+  { "LogicalResourceId": "MyApi", "ResourceType": "AWS::ApiGateway::RestApi" },
+  { "LogicalResourceId": "MyApiDeployment", "ResourceType": "AWS::ApiGateway::Deployment" },
+  { "LogicalResourceId": "MyApiProdStage", "ResourceType": "AWS::ApiGateway::Stage" },
+  { "LogicalResourceId": "Post", "ResourceType": "AWS::StepFunctions::StateMachine" },
+  { "LogicalResourceId": "PostPostEchoRole", "ResourceType": "AWS::IAM::Role" },
+  { "LogicalResourceId": "PostRole", "ResourceType": "AWS::IAM::Role" }
+]

integration/resources/templates/single/state_machine_with_api.yaml

@@ -0,0 +1,39 @@
+Transform: AWS::Serverless-2016-10-31
+Resources:
+  MyApi:
+    Type: AWS::Serverless::Api
+    Properties:
+      StageName: Prod
+  HelloWorldFunction:
+    Type: AWS::Serverless::Function
+    Properties:
+      InlineCode: |
+        def handler(event, context):
+            print(event)
+            return "do nothing"
+      Handler: index.handler
+      Runtime: python3.8
+  Post:
+    Type: AWS::Serverless::StateMachine
+    Properties:
+      Policies:
+        - arn:aws:iam::aws:policy/AWSLambda_FullAccess
+      Definition:
+        StartAt: One
+        States:
+          One:
+            Type: Task
+            Resource: !GetAtt HelloWorldFunction.Arn
+            End: true
+      Events:
+        PostEcho:
+          Type: Api
+          Properties:
+            RestApiId: !Ref MyApi
+            Path: /echo
+            Method: POST
+            UnescapeMappingTemplate: true
+
+Outputs:
+  ApiEndpoint:
+    Value: !Sub "https://${MyApi}.execute-api.${AWS::Region}.amazonaws.com/Prod/echo"

integration/single/test_basic_api.py

@@ -1,6 +1,8 @@
+import json
 import logging
 from unittest.case import skipIf
 
+import requests
 from tenacity import stop_after_attempt, wait_exponential, retry_if_exception_type, after_log, wait_random
 
 from integration.helpers.base_test import BaseTest
@@ -113,3 +115,22 @@ def test_basic_api_with_tags(self):
         self.assertIsNotNone(stage)
         self.assertEqual(stage["tags"]["TagKey1"], "TagValue1")
         self.assertEqual(stage["tags"]["TagKey2"], "")
+
+    def test_state_machine_with_api_single_quotes_input(self):
+        """
+        Pass single quotes in input JSON to a StateMachine
+        See https://github.com/aws/serverless-application-model/issues/1895
+        """
+        self.create_and_verify_stack("single/state_machine_with_api")
+
+        stack_output = self.get_stack_outputs()
+        api_endpoint = stack_output.get("ApiEndpoint")
+
+        input_json = {"f'oo": {"hello": "'wor'l'd'''"}}
+        response = requests.post(api_endpoint, json=input_json)
+        self.assertEqual(response.status_code, 200)
+
+        execution_arn = response.json()["executionArn"]
+        execution = self.client_provider.sfn_client.describe_execution(executionArn=execution_arn)
+        execution_input = json.loads(execution["input"])
+        self.assertEqual(execution_input, input_json)

samtranslator/model/stepfunctions/events.py

@@ -252,6 +252,7 @@ class Api(EventSource):
         "RestApiId": PropertyType(True, is_str()),
         "Stage": PropertyType(False, is_str()),
         "Auth": PropertyType(False, is_type(dict)),
+        "UnescapeMappingTemplate": PropertyType(False, is_type(bool)),
     }
 
     def resources_to_link(self, resources):
@@ -356,12 +357,18 @@ def _add_swagger_integration(self, api, resource, role, intrinsics_resolver):
         if CONDITION in resource.resource_attributes:
             condition = resource.resource_attributes[CONDITION]
 
+        request_template = (
+            self._generate_request_template_unescaped(resource)
+            if self.UnescapeMappingTemplate
+            else self._generate_request_template(resource)
+        )
+
         editor.add_state_machine_integration(
             self.Path,
             self.Method,
             integration_uri,
             role.get_runtime_attr("arn"),
-            self._generate_request_template(resource),
+            request_template,
             condition=condition,
         )
 
@@ -453,3 +460,27 @@ def _generate_request_template(self, resource):
             )
         }
         return request_templates
+
+    def _generate_request_template_unescaped(self, resource):
+        """Generates the Body mapping request template for the Api. This allows for the input
+        request to the Api to be passed as the execution input to the associated state machine resource.
+
+        Unescapes single quotes such that it's valid JSON.
+
+        :param model.stepfunctions.resources.StepFunctionsStateMachine resource; the state machine
+                resource to which the Api event source must be associated
+
+        :returns: a body mapping request which passes the Api input to the state machine execution
+        :rtype: dict
+        """
+        request_templates = {
+            "application/json": fnSub(
+                # Need to unescape single quotes escaped by escapeJavaScript.
+                # Also the mapping template isn't valid JSON, so can't use json.dumps().
+                # See https://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-mapping-template-reference.html#util-template-reference
+                """{"input": "$util.escapeJavaScript($input.json('$')).replaceAll("\\\\'","'")", "stateMachineArn": "${"""
+                + resource.logical_id
+                + """}"}"""
+            )
+        }
+        return request_templates

tests/translator/input/state_machine_with_api.yaml

@@ -0,0 +1,35 @@
+Transform: AWS::Serverless-2016-10-31
+Resources:
+  MyApi:
+    Type: AWS::Serverless::Api
+    Properties:
+      StageName: Prod
+  HelloWorldFunction:
+    Type: AWS::Serverless::Function
+    Properties:
+      InlineCode: |
+        def handler(event, context):
+            print(event)
+            return "do nothing"
+      Handler: index.handler
+      Runtime: python3.8
+  Post:
+    Type: AWS::Serverless::StateMachine
+    Properties:
+      Policies:
+        - arn:aws:iam::aws:policy/AWSLambda_FullAccess
+      Definition:
+        StartAt: One
+        States:
+          One:
+            Type: Task
+            Resource: !GetAtt HelloWorldFunction.Arn
+            End: true
+      Events:
+        PostEcho:
+          Type: Api
+          Properties:
+            RestApiId: !Ref MyApi
+            Path: /echo
+            Method: POST
+            UnescapeMappingTemplate: true