Change pydantic conversion to not load field data unless requested

[Mark90]

Changes the Pydantic model conversion so that it doesn't retrieve data for fields that aren't going to be used.

Description

It's been 8 months since I manually patched this in our own codebase, I wanted to create a PR here after some time when I was sure it didn't cause any regressions.

Without this patch I observed unnecessary requests (lazyloading through our ORM) being made which originated from fields on "Pydantic strawberry types" that weren't requested in the query. Moving these lines inside the if field.init: section appeared sufficient to fix this.

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Documentation

Issues Fixed or Closed by This PR

Checklist

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).

Summary by Sourcery

Enhancements:

• Improve performance by avoiding unnecessary data loading for Pydantic fields not requested in the query.

[sourcery-ai]

Reviewer's Guide by Sourcery

This pull request modifies the Pydantic model conversion to avoid unnecessary data retrieval for unrequested fields. The changes involve moving data retrieval logic inside a conditional block that checks if the field is initialized.

No diagrams generated as the changes look simple and do not need a visual representation.

File-Level Changes

Change	Details	Files
Modified the Pydantic model conversion logic to only retrieve data for fields that are used.	Moved the data retrieval logic for data_from_extra and data_from_model inside the if field.init: block. Added a release note to RELEASE.md.	strawberry/experimental/pydantic/conversion.py RELEASE.md

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[sourcery-ai]

Hey @Mark90 - I've reviewed your changes - here's some feedback:

Overall Comments:

• It would be helpful to add a test case that specifically demonstrates the performance improvement from this change.

Here's what I looked at during the review

• 🟢 General issues: all looks good
• 🟢 Security: all looks good
• 🟢 Testing: all looks good
• 🟢 Complexity: all looks good
• 🟢 Documentation: all looks good

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[botberry]

Thanks for adding the RELEASE.md file!

Here's a preview of the changelog:

---

Change pydantic conversion to not load field data unless requested

Here's the tweet text:

🆕 Release (next) is out! Thanks to Mark Moes for the PR 👏

Get it here 👉 https://strawberry.rocks/release/(next)

[Mark90]

If tests to measure the performance difference are required I'll be happy to supply them; I haven't delved into the testsuite deep enough yet to know how you typically do this.

I just wanted to get this PR up before I forget to do so again. :)

[patrick91]

@Mark90 thanks!

If tests to measure the performance difference are required I'll be happy to supply them; I haven't delved into the testsuite deep enough yet to know how you typically do this.

They aren't really needed, unless you think there was a big change!

[patrick91]

@Mark90 but it would be nice to have some test to check the behaviour is what we expect now 😄

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.23%. Comparing base (7d4ba10) to head (9027fb3).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3812   +/-   ##
=======================================
  Coverage   97.23%   97.23%           
=======================================
  Files         503      503           
  Lines       33580    33580           
  Branches     1717     1717           
=======================================
  Hits        32653    32653           
  Misses        708      708           
  Partials      219      219           

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[codspeed-hq]

CodSpeed Performance Report

Merging #3812 will not alter performance

_{Comparing Mark90:pydantic-load-data-when-needed (9027fb3) with main (7d4ba10)}

Summary

✅ 21 untouched benchmarks

[Mark90]

@Mark90 but it would be nice to have some test to check the behaviour is what we expect now 😄

Done!

The added test fails without the change in conversion.py, and passes with the change.

The test uses root._original_model.name in the resolver, which is probably not recommended usage, but this is not even necessary to reproduce the problem. E.g. if the get_name() resolver is changed to return "foo" and the change in conversion.py reverted, then the name computed_field is still accessed somewhere during the conversion.