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Deriving Serialize for a struct from external crate which uses generics #2327

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AntoineBalaine opened this issue Nov 27, 2022 · 3 comments · Fixed by #2330
Closed

Deriving Serialize for a struct from external crate which uses generics #2327

AntoineBalaine opened this issue Nov 27, 2022 · 3 comments · Fixed by #2330

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@AntoineBalaine
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AntoineBalaine commented Nov 27, 2022

Hello,
I'm trying to implement Serialize for nom_locate's LocatedSpan. It's a struct that encapsulates a token with some location information. can't figure out how to implement Serialize for it.

I created a WrappedSpan to build the bridge with LocatedSpan, but the derive macro doesn't chew up the passed-in generic. Is there a way around this?

#[derive(Serialize, Deserialize)]
#[serde(remote = "LocatedSpan<T>")] // <= This <T> produces an un-parseable token
struct WrappedSpan<T: AsBytes>{
    #[serde(getter = "LocatedSpan::location_offset")]
    offset: usize,
    #[serde(getter = "LocatedSpan::location_line")]
    line: u32,
    #[serde(getter = "LocatedSpan::fragment")]
    fragment: T,
};

// Provide a conversion to construct the remote type.
impl <T: AsBytes>From<WrappedSpan<T>> for LocatedSpan<T> {
    fn from(def: WrappedSpan<T>) -> LocatedSpan<T> {
        LocatedSpan{
            offset: def.offset,
            line: def.line,
            fragment: def.fragment,
            extra: (),
        }
    }
}
@AntoineBalaine
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Thank you for this update!

@dtolnay
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dtolnay commented Nov 28, 2022

Fixed in serde_derive 1.0.148. You need to use serde(remote = "LocatedSpan").

@AntoineBalaine
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AntoineBalaine commented Nov 28, 2022

Could you be a bit more specific ? I can't seem to figure it out with the update:

#[derive(Serialize, Deserialize, PartialEq, Eq)]
#[serde(remote = "LocatedSpan")]
struct WrappedSpan<T: AsBytes> {
    #[serde(getter = "LocatedSpan::location_offset")]
    offset: usize,
    #[serde(getter = "LocatedSpan::location_line")]
    line: u32,
    #[serde(getter = "LocatedSpan::fragment")]
    fragment: T,
}

impl<T: AsBytes> From<WrappedSpan<T>> for LocatedSpan<T> {
    fn from(def: WrappedSpan<T>) -> LocatedSpan<T> {
        LocatedSpan::new(def.fragment)
    }
}

#[test]
fn serialize_located_span() {
    let input = LocatedSpan::new("");
    let serialized = serde_json::to_string(&input).unwrap(); //<= the trait bound `LocatedSpan<&str>: Serialize` is not satisfied
    let converted = "{\"offset\":0,\"line\":1,\"fragment\":\"\",\"column\":1}";
    assert_eq!(serialized, converted)
}

crapStone added a commit to Calciumdibromid/CaBr2 that referenced this issue Dec 1, 2022
This PR contains the following updates:

| Package | Type | Update | Change |
|---|---|---|---|
| [serde](https://serde.rs) ([source](https://github.com/serde-rs/serde)) | dependencies | patch | `1.0.147` -> `1.0.148` |

---

### Release Notes

<details>
<summary>serde-rs/serde</summary>

### [`v1.0.148`](https://github.com/serde-rs/serde/releases/tag/v1.0.148)

[Compare Source](serde-rs/serde@v1.0.147...v1.0.148)

-   Support `remote` derive for generic types that have private fields ([#&#8203;2327](serde-rs/serde#2327))

</details>

---

### Configuration

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🚦 **Automerge**: Disabled by config. Please merge this manually once you are satisfied.

 **Rebasing**: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 **Ignore**: Close this PR and you won't be reminded about this update again.

---

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---

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Co-authored-by: cabr2-bot <cabr2.help@gmail.com>
Co-authored-by: crapStone <crapstone01@gmail.com>
Reviewed-on: https://codeberg.org/Calciumdibromid/CaBr2/pulls/1657
Reviewed-by: crapStone <crapstone@noreply.codeberg.org>
Co-authored-by: Calciumdibromid Bot <cabr2_bot@noreply.codeberg.org>
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