a295c38ba3
This is intended to be used by other crates which provide their own proc macros and use serde internally. Today there's no consistent way to put `#[derive(Deserialize)]` on a struct that consistently works, since crates may be using either `features = ["derive"]` or relying on `serde_derive` separately. Even if we assume that everyone is using `features = ["derive"]`, without this commit, any crate which generates `#[derive(serde::Deserialize)]` forces its consumers to put `serde` in their `Cargo.toml`, even if they aren't otherwise using serde for anything. Examples of crates which suffer from this in the real world are tower-web and swirl. With this feature, it's expected that these crates would have `pub extern crate serde;` in some accessible path, and add `#[serde(serde_path = "that_crate::wherever::serde")]` anywhere they place serde's derives. Those crates would also have to derive `that_crate::whatever::serde::Deserialize`, or `use` the macros explicitly beforehand. The test for this is a little funky, as it's testing this in a way that is not the intended use case, or even one we want to support. It has its own module which re-exports all of serde, but defines its own `Serialize` and `Deserialize` traits. We then test that we generated impls for those traits, instead of serde's. The only other way to test this would be to create a new test crate which does not depend on serde, but instead depends on `serde_derive` and a third crate which publicly re-exports serde. This feels like way too much overhead for a single test case, hence the funky test given. I didn't see anywhere in this repo to document this attribute, so I assume the docs will have to be done as a separate PR to a separate repo. Fixes #1487
40 lines
1016 B
Rust
40 lines
1016 B
Rust
#[test]
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fn test_gen_custom_serde() {
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#[derive(serde::Serialize, serde::Deserialize)]
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#[serde(serde_path = "fake_serde")]
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struct Foo;
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// Would be overlapping if serde::Serialize were implemented
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impl AssertNotSerdeSerialize for Foo {}
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// Would be overlapping if serde::Deserialize were implemented
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impl<'a> AssertNotSerdeDeserialize<'a> for Foo {}
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fake_serde::assert::<Foo>();
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}
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mod fake_serde {
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pub use serde::*;
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pub fn assert<T>()
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where
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T: Serialize,
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T: for<'a> Deserialize<'a>,
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{}
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pub trait Serialize {
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fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error>;
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}
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pub trait Deserialize<'a>: Sized {
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fn deserialize<D: Deserializer<'a>>(deserializer: D) -> Result<Self, D::Error>;
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}
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}
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trait AssertNotSerdeSerialize {}
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impl<T: serde::Serialize> AssertNotSerdeSerialize for T {}
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trait AssertNotSerdeDeserialize<'a> {}
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impl<'a, T: serde::Deserialize<'a>> AssertNotSerdeDeserialize<'a> for T {}
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