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#[serde(flatten)] doesn't work with #[serde(default)] for externally tagged enums #1626

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slckl opened this issue Sep 9, 2019 · 6 comments · May be fixed by #2687
Open

#[serde(flatten)] doesn't work with #[serde(default)] for externally tagged enums #1626

slckl opened this issue Sep 9, 2019 · 6 comments · May be fixed by #2687
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@slckl
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slckl commented Sep 9, 2019

Given this:

#[derive(Deserialize, Debug)]
enum SomeEnum {
    A(u32),
    B(u32),
}

impl Default for SomeEnum {
    fn default() -> Self {
        SomeEnum::B(1)
    }
}

#[derive(Deserialize, Debug)]
struct SomeStruct {
    filler: u32,
    #[serde(default)]
    #[serde(flatten)]
    some_enum: SomeEnum,
}

trying to deserialize this yaml:

filler: 1

into SomeStruct panics with a message:

no variant of enum SomeEnum found in flattened data

I hoped it would pick up the default value specified for SomeEnum instead...

Playground example.

Is this a bug or is this not supported?
Docs don't cover this, I tried searching issues, but couldn't find anything quite like this.
@dtolnay dtolnay added the derive label Sep 9, 2019
@dtolnay
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dtolnay commented Sep 9, 2019

Thanks, I would accept a PR to make this work.

@slckl
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slckl commented Sep 9, 2019

Happy to give it a try, but I haven't dug too much into Serde's internals. Any pointers on where to start?

@Ploppz
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Ploppz commented Sep 13, 2019 •
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I need the same behaviour, but with internal tagging. My example: https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=3dcd2fca7a231d6c1d7d41ff830e8d2e
Edit: never mind, I realize my problem can easily be solved by using external tagging and renaming the ty field to type.

@heftig
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heftig commented Mar 27, 2020

FTR, the issue isn't restricted to external tagging; other forms of tagging don't make it work, either.

@mkatychev mkatychev mentioned this issue Mar 25, 2021
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@veeg
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veeg commented May 20, 2021

I encounter the same issue when using #[serde(other)] for the externally tagged enum, e.g.,:

#[derive(Deserialize, Debug)]
enum SomeEnum {
    A(u32),
    B(u32),
    #[serde(other)]
    C,
}

#[derive(Deserialize, Debug)]
struct SomeStruct {
    filler: u32,
    #[serde(flatten)]
    some_enum: SomeEnum,
}

My use-case specifically is to still be able to deserialize a collection of SomeStruct after the sender may have added another SomeEnum variant. I am interested in the SomeStructs existence, and shared metadata, without necessarily knowing all variants and details of SomeEnum that exist.

@josojo josojo mentioned this issue Aug 7, 2022
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@gamife

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@Mingun Mingun mentioned this issue Aug 11, 2023
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@evenyag evenyag mentioned this issue Sep 18, 2023
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@fleupold fleupold mentioned this issue Dec 23, 2023
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mfw78 pushed a commit to cowprotocol/services that referenced this issue Dec 25, 2023
@fleupold
[Easy] Make legacy solver competition data parseable (#2209)
d8ab692 
# Description
We've been seeing error message alerts when loading very competition
data from the db. This is expected (cf. #2143) however it is pertubating
on-call. The alternative would be to downgrade the warning to an error,
however I feel we may be losing signal of future breakages in this case.

# Changes
<!-- List of detailed changes (how the change is accomplished) -->

- [x] use serde[(default)] where possible
- [x] for score, which is a flattened enum that doesn't support defaults
(cf. this [open issue](serde-rs/serde#1626)),
we go back to making it an optional. This is fine since with
rank-by-surplus we likely no longer need mandatory score anymore
anyways.

## How to test
Unit test for old transactions data
flavio added a commit to flavio/kube that referenced this issue Jan 25, 2024
@flavio
fix: ObjectList handle missing apiVersion and kind during deserializa…
4b97295 
…tion

The `serde` crate has a bug that prevents the proper deserialization of
attributes that are using the `flatten` and `default` directives.
See [1] and [2].

This bug affects the freshly introduced `ObjectList.types` attribute.
It's not possible to deserialize an `ObjectList` that is missing the
`apiVersion` and/or the `kind` values.

This commit introduces a custom deserializer for the `types` attribute
of `ObjectList`.

On top of handling the deserialization case, the custom deserializer
provides better default values compared to the ones of the stock
`TypeMeta`.
The `TypeMeta` struct has empty strings as default values. However, in the
context of `ObjectList`, proper default values should be `v1` and `List`
instead.

[1] serde-rs/serde#1626
[2] serde-rs/serde#1879

Signed-off-by: Flavio Castelli <[email protected]>
@flavio flavio mentioned this issue Jan 25, 2024
Merged
clux pushed a commit to kube-rs/kube that referenced this issue Jan 26, 2024
@flavio
Minor fixes to ObjectList (#1398)
b700529 
* fix: ObjectList handle missing apiVersion and kind during deserialization

The `serde` crate has a bug that prevents the proper deserialization of
attributes that are using the `flatten` and `default` directives.
See [1] and [2].

This bug affects the freshly introduced `ObjectList.types` attribute.
It's not possible to deserialize an `ObjectList` that is missing the
`apiVersion` and/or the `kind` values.

This commit introduces a custom deserializer for the `types` attribute
of `ObjectList`.

On top of handling the deserialization case, the custom deserializer
provides better default values compared to the ones of the stock
`TypeMeta`.
The `TypeMeta` struct has empty strings as default values. However, in the
context of `ObjectList`, proper default values should be `v1` and `List`
instead.

[1] serde-rs/serde#1626
[2] serde-rs/serde#1879

Signed-off-by: Flavio Castelli <[email protected]>

* ObjectList: derive the `Clone` trait

Ensure `ObjectList` derive the `Clone` trait.

Signed-off-by: Flavio Castelli <[email protected]>

* chore: fix rustfmt warning

Signed-off-by: Flavio Castelli <[email protected]>

---------

Signed-off-by: Flavio Castelli <[email protected]>
@andrewtoth andrewtoth linked a pull request Feb 2, 2024 that will close this issue
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Support flattened externally tagged enums with default attributes andrewtoth/serde
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@heftig @dtolnay @veeg @Ploppz @slckl @gamife