Type serialization/deserialization failure with PEP-585 generics

[mikebellerU]

Describe the bug

I receive a PipelineConnect error if I try to deserialize a pipeline containing a
component with output type list[Document]. If I change to List[Document], the error
goes away.

Error message
Error that was thrown (if available)

haystack.core.errors.PipelineConnectError: Cannot connect 'mux.value' with 'paris_router.documents': their declared input and output types do not match.
'mux':
 - value: list
'paris_router':
 - documents: List[Document] (available)

Expected behavior

Expected no error. Per PEP-585 (implemented originally in Python 3.9)

Additional context

It's possible one could view this as a documentation problem -- in that it is not documented
that list[X] and List[X] are not treated the same by the deserialization mechanism, but it
seems a bit of a "gotcha" to me.

To Reproduce

Example:

Run the following code:

from haystack import Document, Pipeline
from haystack.components.others import Multiplexer
from haystack.components.routers import MetadataRouter

p = Pipeline()
p.add_component("mux", Multiplexer(list[Document]))
p.add_component("paris_router", MetadataRouter(
    rules={"city": {"field": "meta.city", "operator": "==", "value": "Paris"}}))
p.connect("mux.value", "paris_router.documents")
s = p.dumps()
print(s)
p2 = Pipeline.loads(s)

To work around, just replace list[Document] with List[Document] (and import List from typing module obvi)

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System:

• OS: Linux Ubuntu 22.04
• GPU/CPU: Intel
• Haystack version (commit or version number): both 2.0.1, and tested also with 8d04e53
• DocumentStore: none
• Reader: none
• Retriever: none

[mrm1001]

Hi there, thanks for writing such a detailed issue, we are looking into it! I am the product manager of the library and I like to reach out to users to get feedback and see how we could help. Let me know if you would be available some time this week for a 15 min chat (calendly).

[mikebellerU]

Hi Deepset-Ai/Haystack -- happy to chat with you. Pretty tied up this week. How about sometime next week? Mike

…

On Mon, May 13, 2024 at 6:37 AM mrm1001 ***@***.***> wrote: Hi there, thanks for writing such a detailed issue, we are looking into it! I am the product manager of the library and I like to reach out to users to get feedback and see how we could help. Let me know if you would be available some time this week for a 15 min chat (calendly <https://calendly.com/maria-mestre-ugu/haystack-catch-up>). — Reply to this email directly, view it on GitHub <#7609 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/BANYT3JJCX4DEDLI6XS5QS3ZCCJXJAVCNFSM6AAAAABG5AC6V2VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDCMBXGIZDSMJXGE> . You are receiving this because you authored the thread.Message ID: ***@***.***>