Common mistakes docs section

[sydney-runkle]

Many of the issues we get are repeats of the same common questions / mistakes. We should create a small docs section logging said common mistakes and their solutions :).

[SohamG934]

Hello, I would like to work on this issue!

[sydney-runkle]

@SohamG934,

Great! Feel free to submit a PR and I'll review. A few common mistakes I can think of:

• Mixing up how use_enum_values is used (we have an example in the API docs)
• Mixing up how to add annotations to compound types (see Implement more clear warning/error when using constraints on compound types #8362)

I'm sure there are many more that we could include - you could search on duplicate tags to see what issues have been reported the most frequently!

[SohamG934]

Hello, shall i make a single doc mentioning the title of the issue and then linking the closed issue solution link for reference? If not, how do you propose I solve this?

…

On Sat, 16 Dec 2023 at 18:14, Sydney Runkle ***@***.***> wrote: @SohamG934 <https://github.com/SohamG934>, Great! Feel free to submit a PR and I'll review. A few common mistakes I can think of: - Mixing up how use_enum_values is used (we have an example in the API docs) - Mixing up how to add annotations to compound types (see #8362 <#8362>) I'm sure there are many more that we could include - you could search on duplicate tags to see what issues have been reported the most frequently! — Reply to this email directly, view it on GitHub <#8380 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AX3DW7QYWWTQYI6HN76IIMLYJWJRHAVCNFSM6AAAAABAW4NJDOVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMYTQNJYHAYTAMBUGE> . You are receiving this because you were mentioned.Message ID: ***@***.***>

[sydney-runkle]

Hi @SohamG934,

I think we should create a new page for our documentation site that has various examples of common mistakes and ways to correct said mistakes. I don't see a reason to reference issues for the most part. You can create a fork of the pydantic repo and submit a PR with your changes 👍

[bL34cHig0]

Hi @SohamG934,

I think we should create a new page for our documentation site that has various examples of common mistakes and ways to correct said mistakes. I don't see a reason to reference issues for the most part. You can create a fork of the pydantic repo and submit a PR with your changes 👍

Hi @sydney-runkle, is @SohamG934 still working on this issue?

If not, I'd like to work on it. Thank you

[sydney-runkle]

@bL34cHig0,

I haven't seen a PR yet, so feel free to get started on this :). Thanks!

[sydney-runkle]

@bL34cHig0,

I've assigned you to this issue :)

[bL34cHig0]

@sydney-runkle

Thank you for assigning me this issue. Just a couple questions:

• Under which section of the docs, do you want the page to be added?
• Is there a template I can use?

[sydney-runkle]

@bL34cHig0,

There's no template at the moment - I'd recommend combing through issues listed as duplicates to see what kind of issues come up often.
Could you please add this section to the examples section on a new page for now? Thanks!

[bL34cHig0]

@sydney-runkle

I have started working on documenting the common mistakes / questions. So I wanted to ask if I am on the right track.

Please see screenshot below. Thanks :)

Work done so far:

• Created a new branch called common-mistakes-doc
• Created a new page titled common_mistakes.md under the examples section.
• Wrote the first common question / mistake.

Please kindly review it and let me know if this structure is okay or not. Thanks again

[sydney-runkle]

@bL34cHig0,

The structure looks great. Nice work so far!

[sydney-runkle]

Here's another I think should be included: #8708

[sydney-runkle]

See #8759 (comment) as the reason for closing this issue. I think this collection is more helpful to have as an issue than as an official docs page, despite my initial motivations for filing this issue.

A helpful collection of recommendations, thanks to @bL34cHig0: #8759

[sydney-runkle]

Below shows the relevant docs sections for explaining each of these questions:

How to implement custom error messages?

https://docs.pydantic.dev/latest/errors/errors/#customize-error-messages

Cannot use v1 model as type parameter in v2 generic model

https://docs.pydantic.dev/latest/migration/#changes-to-pydanticgenericsgenericmodel

AnyUrl adds trailing slash (/) in URL validation

https://docs.pydantic.dev/latest/migration/#url-and-dsn-types-in-pydanticnetworks-no-longer-inherit-from-str
See updates here: #7186

TypeError occurs when using Pydantic's Constraint Types

This one makes more sense to have reported + documented as an issue, which is explained well here:

This error occurs if you are using Python 3.9.7. To prevent this, upgrade to Python 3.9.8 or higher as there is a
bug in version 3.9.7. Also, it is discouraged to use some of the
con functions because they will be deprecated
in Pydantic 3.0. So check out the Discouraged warning for alternative solution.

validate_call decorator raises "AttributeError" when applied to an instance method of a class with __slots__

No longer an issue

Two validators consecutively do not report all errors

Pydantic does not currently support exhaustive validation, so it stops after the first error on a given field and
reports that validation error. Relevant feature request, for tracking: #7476

Can not use ValidationError __init__ method

https://docs.pydantic.dev/latest/api/pydantic_core/#pydantic_core.ValidationError provides info on helpful static methods

Pydantic does not allow Literal enum value discriminator to be initialized by string

A simple solution to this is to allow your class to inherit from both str and Enum. This is the one case where I do think we could use a docs update in the relevant section of the docs :).

https://docs.pydantic.dev/latest/api/standard_library_types/#enum