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🐛 Fix validation error when File is declared after Form parameter #11194

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tiangolo merged 4 commits into from
Sep 20, 2025
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🐛 Fix validation error when File is declared after Form parameter #11194

tiangolo merged 4 commits into from
Sep 20, 2025
+93 −4

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@thomasleveil
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@thomasleveil thomasleveil commented Feb 25, 2024

This PR updates the fix (6185a92) from @jsg921019 so that tests pass with the latest FastAPI code (0.110.0).
It also adds a test to cover the case with multiple files, and another to ensure the order of parameters in an endpoint definition does not affect the way FastAPI handles the request.

Problem
When declaring an endpoint which accepts a File but also a Form parameter, the File parameter must be declared first or the endpoint would respond with error 422.

Context

@thomasleveil thomasleveil force-pushed the fix-9116-form-and-file-order branch from 1763ed4 to dcd2e69 Compare February 25, 2024 15:11
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@thomasleveil thomasleveil force-pushed the fix-9116-form-and-file-order branch from 7e97f62 to 0a1e865 Compare February 25, 2024 16:07
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thomasleveil commented Feb 25, 2024

Thank you for the feed back. I pushed force with your suggested changes. Let me know if anything else can be improved.

@thomasleveil thomasleveil changed the title Fix #9116 form and file order 🐛 Fix #9116 form and file order Feb 25, 2024
@thomasleveil thomasleveil changed the title 🐛 Fix #9116 form and file order 🐛 Fix #9116 Form and File parameters order should not matter Feb 25, 2024
YuriiMotov
YuriiMotov approved these changes Feb 25, 2024
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The solution works.
Tests cover the issue. Tests fail before changes and pass after

@thomasleveil thomasleveil mentioned this pull request Feb 25, 2024
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@tiangolo tiangolo added bug Something isn't working p2 labels Mar 13, 2024
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cfreksen commented Nov 22, 2024 •
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I am wondering if this PR has been forgotten?

I am not that familiar with the workflow in this repository, so excuse me if these things just take time or if this has low priority and there have been more important things to spend your time on.

However, I was affected by #9116 which led me to this PR, and since it has some approvals and it hasn't been touched in 9 months, I thought it would be ok to "bump" it.

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carl-sauter commented Jun 20, 2025

Hey what about this pr? At least there should be a better error message. Wasted my time only for finding this.

@YuriiMotov YuriiMotov self-requested a review June 21, 2025 17:05
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@thomasleveil thomasleveil force-pushed the fix-9116-form-and-file-order branch from 0a1e865 to 4b6e747 Compare June 22, 2025 17:21
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@thomasleveil thomasleveil force-pushed the fix-9116-form-and-file-order branch from 577dce8 to 150fb07 Compare June 22, 2025 17:27
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@thomasleveil thomasleveil force-pushed the fix-9116-form-and-file-order branch 2 times, most recently from 50b9f22 to e34c53c Compare June 23, 2025 12:32
@thomasleveil
✅ add tests for using Form and File in the same endpoint
7e92b2b
@thomasleveil
🐛 Fix handling uploaded file data correctly when not in the first par…
6e0abe9 
…t of a multipart/form-data request body

The HTTP specification for multipart/form-data, defined in RFC 7578, allows both form data and uploaded files in a single request. It does not require files to be before or after form fields.

As such, no specific care is to be given to the first field.

References:
- [RFC 7578](https://datatracker.ietf.org/doc/html/rfc7578)
- [FastAPI issue 9116](fastapi#9116)

Close fastapi#9116
@thomasleveil thomasleveil force-pushed the fix-9116-form-and-file-order branch from bb07937 to 6e0abe9 Compare June 23, 2025 12:55
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thomasleveil commented Jun 23, 2025

@YuriiMotov here you go.

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LGTM!

@YuriiMotov YuriiMotov changed the title 🐛 Fix #9116 Form and File parameters order should not matter 🐛 Fix validation error when File is declared after Form parameter Jun 23, 2025
tiangolo
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Great, thank you! 🚀 🙌

@tiangolo tiangolo merged commit 44fc676 into fastapi:master Sep 20, 2025
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@thomasleveil thomasleveil deleted the fix-9116-form-and-file-order branch September 26, 2025 08:08
@YuriiMotov YuriiMotov mentioned this pull request Nov 2, 2025
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@tiangolo tiangolo tiangolo approved these changes

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