Tuple value for blocks argument does not work for Web API calls

[tommasobertoni]

Both WebClient and AsyncWebClient accept a sequence of blocks (and attachments) but _parse_web_class_objects fails to serialize the objects into dictionaries since it only checks for lists via isinstance(blocks, list), therefore disagreeing with the clients' signature.

Impact on:

• both sync and async clients
• chat_postEphemeral, chat_postMessage, chat_scheduleMessage, chat_unfurl, chat_update
• both Block and Attachment

Reproducible in:

The Slack SDK version

slack-sdk=3.18.1

Python runtime version

Python 3.10.3

OS info

ProductName:	macOS
ProductVersion:	12.5.1
BuildVersion:	21G83
Darwin Kernel Version 21.6.0: Wed Aug 10 14:28:23 PDT 2022; root:xnu-8020.141.5~2/RELEASE_ARM64_T6000

Steps to reproduce:

client = WebClient(token="token")

# a tuple of blocks
blocks: Sequence[Block] = (
    SectionBlock(text="foo"),
    SectionBlock(text="bar"),
)

# works
client.chat_postMessage(channel="#channel", blocks=list(blocks))

# raises: Object of type SectionBlock is not JSON serializable
client.chat_postMessage(channel="#channel", blocks=blocks)

Expected result:

Since both clients accept a Sequence, one should be able to pass both a list or a tuple.

Actual result:

TypeError: Object of type SectionBlock is not JSON serializable since the blocks weren't serialized into dicts.

[seratch]

Hi @tommasobertoni, thanks for taking the time to report this issue!

You are right that blocks can be a tuple, but the current implementation does not work with the type. This issue can be resolved similarly to #1206 We will fix it in future versions. Until then, please consider going with list objects instead.

[tommasobertoni]

Hi @seratch, I'm working on a PR for solving this issue, would that be ok?

[seratch]

@tommasobertoni As long as you are fine with 1) signing our Contributor License Agreement, and 2) writing some unit tests covering the patterns, your contributions are welcomed!