cdk deployment error: RuntimeError: Cannot read properties of undefined (reading 'bindToGraph')

Question

I am trying to do a cdk deployment, where I am just copying the example from the documentation. See example below (https://docs.aws.amazon.com/cdk/api/v2/python/aws_cdk.aws_stepfunctions/StateMachineFragment.html#aws_cdk.aws_stepfunctions.StateMachineFragment)

```
 from aws_cdk import (
    # Duration,
    Stack,
    aws_stepfunctions as sfn,
    aws_stepfunctions_tasks as tasks,
 )
 from constructs import Construct

class MyJob(sfn.StateMachineFragment):

def __init__(self, parent, id, *, job_flavor):
        super().__init__(parent, id)

choice = sfn.Choice(self, "Choice").when(sfn.Condition.string_equals("$.branch", "left"), sfn.Pass(self, "Left Branch")).when(sfn.Condition.string_equals("$.branch", "right"), sfn.Pass(self, "Right Branch"))

# ...

self.start_state = choice
        self.end_states = choice.afterwards().end_states
      
    def start_state(self):
        return self._start_state

def end_states(self):
        return self._end_states

class CdkStateMachineFragmentStack(Stack):
    def __init__(self, scope, id):
        super().__init__(scope, id)
        # Do 3 different variants of MyJob in parallel
        parallel = sfn.Parallel(self, "All jobs").branch(MyJob(self, "Quick", job_flavor="quick").prefix_states()).branch(MyJob(self, "Medium", job_flavor="medium").prefix_states()).branch(MyJob(self, "Slow", job_flavor="slow").prefix_states())

sfn.StateMachine(self, "MyStateMachineFragmentTest",
            definition=parallel
        )
```

When deploying, I get the following error:

Traceback (most recent call last):
  File "app.py", line 10, in 
    CdkStateMachineFragmentStack(app, "CdkStateMachineFragmentStack",
  File "/home/workspace/development/cdk/cdk_test/cdk_state_machine_fragment/.venv/lib/python3.8/site-packages/jsii/_runtime.py", line 111, in __call__
    inst = super().__call__(*args, **kwargs)
  File "/home/workspace/development/cdk/cdk_test/cdk_state_machine_fragment/cdk_state_machine_fragment/cdk_state_machine_fragment_stack.py", line 34, in __init__
    sfn.StateMachine(self, "MyStateMachineFragmentTest",
  File "/home/workspace/development/cdk/cdk_test/cdk_state_machine_fragment/.venv/lib/python3.8/site-packages/jsii/_runtime.py", line 111, in __call__
    inst = super().__call__(*args, **kwargs)
  File "/home/workspace/development/cdk/cdk_test/cdk_state_machine_fragment/.venv/lib/python3.8/site-packages/aws_cdk/aws_stepfunctions/__init__.py", line 6871, in __init__
    jsii.create(self.__class__, self, [scope, id, props])
  File "/home/workspace/development/cdk/cdk_test/cdk_state_machine_fragment/.venv/lib/python3.8/site-packages/jsii/_kernel/__init__.py", line 336, in create
    response = self.provider.create(
  File "/home/workspace/development/cdk/cdk_test/cdk_state_machine_fragment/.venv/lib/python3.8/site-packages/jsii/_kernel/providers/process.py", line 363, in create
    return self._process.send(request, CreateResponse)
  File "/home/workspace/development/cdk/cdk_test/cdk_state_machine_fragment/.venv/lib/python3.8/site-packages/jsii/_kernel/providers/process.py", line 340, in send
    raise RuntimeError(resp.error) from JavaScriptError(resp.stack)
RuntimeError: Cannot read properties of undefined (reading 'bindToGraph')

I tried already what is suggested in the following stack overflow post [https://stackoverflow.com/questions/70553737/cannot-read-properties-of-undefined-reading-bindtograph] getting a different error:

Traceback (most recent call last):
  File "app.py", line 10, in 
    CdkStateMachineFragmentStack(app, "CdkStateMachineFragmentStack",
  File "/home/workspace/development/cdk/cdk_test/cdk_state_machine_fragment/.venv/lib/python3.8/site-packages/jsii/_runtime.py", line 111, in __call__
    inst = super().__call__(*args, **kwargs)
  File "/home/workspace/development/cdk/cdk_test/cdk_state_machine_fragment/cdk_state_machine_fragment/cdk_state_machine_fragment_stack.py", line 34, in __init__
    parallel = sfn.Parallel(self, "All jobs").branch(MyJob(self, "Quick", job_flavor="quick").prefix_states()).branch(MyJob(self, "Medium", job_flavor="medium").prefix_states()).branch(MyJob(self, "Slow", job_flavor="slow").prefix_states())
  File "/home/workspace/development/cdk/cdk_test/cdk_state_machine_fragment/.venv/lib/python3.8/site-packages/jsii/_runtime.py", line 111, in __call__
    inst = super().__call__(*args, **kwargs)
  File "/home/workspace/development/cdk/cdk_test/cdk_state_machine_fragment/cdk_state_machine_fragment/cdk_state_machine_fragment_stack.py", line 18, in __init__
    self.start_state = choice
AttributeError: can't set attribute

Could you support me?

Thanks,
Pablo

Maha_E · Answer

The error message "RuntimeError: Cannot read properties of undefined" is typically encountered when trying to access a property or method of a variable that has not been defined. In order to resolve this issue, you can add the @property decorator above the start_state and end_states methods, this will ensure that the methods are treated as properties and can be accessed without encountering the undefined error.

The second error message "AttributeError: can't set attribute" occurred because you had defined methods and attributes with the same name, namely "start_state" and "end_states". In Python, methods are attributes too, and having an attribute and method with the same name can cause naming conflicts. To fix this issue, you can simply rename the attributes to something else, you could use "_start_state" and "_end_states".

You can find both fixes below, these changes will ensure that your code runs smoothly:

```
from aws_cdk import (
    # Duration,
    Stack,
    aws_stepfunctions as sfn,
    aws_stepfunctions_tasks as tasks,
 )
from constructs import Construct