Error using "DynamoEventSource" for a imported table on Python

[jpenalber]

When trying to create a DynamoDB source for my lambda there is some kind type conflict. I believe there is some kind of bug on the type error on handling the table since the return is an ITABLE

Reproduction Steps

table = aws_dynamodb.Table.from_table_attributes(self, "Name",table_name="<table-name>")

event = aws_lambda_event_sources.DynamoEventSource(table, starting_position=aws_lambda.StartingPosition.TRIM_HORIZON)

Error Log

jsii.errors.JavaScriptError: 
  Error: Object of type @aws-cdk/core.Resource is not convertible to @aws-cdk/aws-dynamodb.Table
      at Object.deserialize (/usr/local/lib/python3.6/site-packages/jsii/_embedded/jsii/jsii-runtime.js:6964:27)
      at Kernel._toSandbox (/usr/local/lib/python3.6/site-packages/jsii/_embedded/jsii/jsii-runtime.js:8207:61)
      at xs.map (/usr/local/lib/python3.6/site-packages/jsii/_embedded/jsii/jsii-runtime.js:8260:33)
      at Array.map (<anonymous>)
      at Kernel._boxUnboxParameters (/usr/local/lib/python3.6/site-packages/jsii/_embedded/jsii/jsii-runtime.js:8260:19)
      at Kernel._toSandboxValues (/usr/local/lib/python3.6/site-packages/jsii/_embedded/jsii/jsii-runtime.js:8245:21)
      at obj._wrapSandboxCode (/usr/local/lib/python3.6/site-packages/jsii/_embedded/jsii/jsii-runtime.js:7838:66)
      at Kernel._wrapSandboxCode (/usr/local/lib/python3.6/site-packages/jsii/_embedded/jsii/jsii-runtime.js:8301:19)
      at Kernel._create (/usr/local/lib/python3.6/site-packages/jsii/_embedded/jsii/jsii-runtime.js:7838:26)
      at Kernel.create (/usr/local/lib/python3.6/site-packages/jsii/_embedded/jsii/jsii-runtime.js:7585:21)
      at KernelHost.processRequest (/usr/local/lib/python3.6/site-packages/jsii/_embedded/jsii/jsii-runtime.js:7372:28)
      at KernelHost.run (/usr/local/lib/python3.6/site-packages/jsii/_embedded/jsii/jsii-runtime.js:7312:14)
      at Immediate.setImmediate [as _onImmediate] (/usr/local/lib/python3.6/site-packages/jsii/_embedded/jsii/jsii-runtime.js:7315:37)
      at runCallback (timers.js:705:18)
      at tryOnImmediate (timers.js:676:5)
      at processImmediate (timers.js:658:5)

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "app.py", line 9, in <module>
    WorkflowStackStack(app, "workflow-stack")
  File "/usr/local/lib/python3.6/site-packages/jsii/_runtime.py", line 66, in __call__
    inst = super().__call__(*args, **kwargs)
  File "/home/ec2-user/environment/workflow-stack/workflow_stack/workflow_stack_stack.py", line 60, in __init__
    event = aws_lambda_event_sources.DynamoEventSource(table, starting_position=aws_lambda.StartingPosition.TRIM_HORIZON)
  File "/usr/local/lib/python3.6/site-packages/jsii/_runtime.py", line 66, in __call__
    inst = super().__call__(*args, **kwargs)
  File "/usr/local/lib/python3.6/site-packages/aws_cdk/aws_lambda_event_sources/__init__.py", line 443, in __init__
    jsii.create(DynamoEventSource, self, [table, props])
  File "/usr/local/lib/python3.6/site-packages/jsii/_kernel/__init__.py", line 229, in create
    interfaces=[iface.__jsii_type__ for iface in getattr(klass, "__jsii_ifaces__", [])],
  File "/usr/local/lib/python3.6/site-packages/jsii/_kernel/providers/process.py", line 333, in create
    return self._process.send(request, CreateResponse)
  File "/usr/local/lib/python3.6/site-packages/jsii/_kernel/providers/process.py", line 318, in send
    raise JSIIError(resp.error) from JavaScriptError(resp.stack)
jsii.errors.JSIIError: Object of type @aws-cdk/core.Resource is not convertible to @aws-cdk/aws-dynamodb.Table
Subprocess exited with error 1

Environment

• CLI Version : aws-cli/1.17.17
• Framework Version:1.24.0
• OS :Amazon cloud9
• Language :Python3.6

---

This is 🐛 Bug Report

[glitchedcat]

Can confirm this is an issue for me too.
Environment
CLI Version : aws-cli/1.17.11
Framework Version:1.27.0
OS : Macos Catalina
Language :Python3.7

[RomainMuller]

The problem seems to be that DynamoEventSource's first parameters is typed as aws_dynamodb.Table, but the result of aws_dynamodb.Table.from_table_attributes is actually an aws_dynamodb.ITable.

So technically, your code is violating the type requirements for DynamoEventSource. Unfortunately, right now you get an error message that's not great (we are looking to improve this in aws/jsii#1321).

A secondary issue here is that you cannot currently use a "non-owned" (i.e: not created as part of the same CDK app) table with DynamoEventSource. That's arguably not a bug, but a feature gap... Regardless, I've prepared a PR to address this particular quirk at: #6635.

⚠️ Note however that in order to use this, you will need to provide the table_stream_arn property to from_table_attributes, as this is required in order to create the event source.