Whitespaces around character entities

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#900 3 comentarios 2 reacciones 0 asignados Ver en GitHub

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Evaluación

Dificultad
4/5
Tiempo estimado
3-5 días
Aptitud para principiantes
35/100
Tipo de issue
Nueva funcionalidad
Claridad
Bastante claro
Estado de actividad
Estancado
Stack tecnológico
rust
Área
backend

Línea de trabajo

Start by reading the Config::trim_text behavior and the deserializer path that handles text and decoded character entities; the report includes a reproducer using NsReader and quick_xml::de::Deserializer::borrowing. Check existing tests for trimming and entity decoding, then determine whether a configuration option can preserve spaces around entities while trimming only leading and trailing text. Done means the reproducer retains those internal spaces without losing global edge trimming.

Escrito por el modelo de indexación a partir del texto del issue.

Descripción

help wanted serde

I maintain a large codebase that used quick-xml for years across hundreds of structs.

After switching from 0.37.5 to 0.38, I hit the already well-known whitespace issues. 0.38.1 introduced Config::trim_text which saved me from touching thousands of fields, but now I found the next caveat: XML character entities make trim_text(true) trim more than needed:

#!/usr/bin/env cargo
---
[dependencies]
serde = { version = "1", features = ["derive"] }
quick-xml = { version = "0.38", features = ["serialize"] }
quick-xml-old = { package = "quick-xml", version = "0.37", features = ["serialize"] }
---

use quick_xml::reader::NsReader;
use serde::Deserialize;
use std::result::Result;

#[derive(Debug, Deserialize)]
struct Root {
    bar: String,
}

pub fn from_str_trim_text<'de, T>(s: &'de str) -> Result<T, Box<dyn std::error::Error>>
where
    T: Deserialize<'de>,
{
    let mut reader = NsReader::from_str(s);
    let config = reader.config_mut();

    config.trim_text(true); // Trims also spaces around decoded &amp;
    config.expand_empty_elements = true;

    let mut de = quick_xml::de::Deserializer::borrowing(reader);
    Ok(T::deserialize(&mut de)?)
}

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let xml = r#"
    <root>
        <bar>
            Foo &amp; Bar  &amp;  Baz Qux   Quux
        </bar>
    </root>"#;

    let old: Root = quick_xml_old::de::from_str(xml)?;
    let new: Root = quick_xml::de::from_str(xml)?;
    let new_trimming: Root = from_str_trim_text(xml)?;

    println!("Old: {}", old.bar); // "Foo & Bar  &  Baz Qux   Quux"
    println!("New: {}", new.bar); // "\n            Foo & Bar  &  Baz Qux   Quux\n        "
    println!("New trimming: {}", new_trimming.bar); // "Foo&Bar&Baz Qux   Quux"

    Ok(())
}

(cargo +nightly -Zscript example.rs)

I know this is documented behavior (thank you), so I'm not calling it a bug. I’m looking for a solution to preserve "internal" spaces (e.g, around the decoded entities) while still trimming leading/trailing whitespace globally.

The only workaround that comes to my mind atm is either introducing a newtype or using deserialize_with, which are both rather error-prone in a mature codebase like mine and require tons of work.

If there is no existing solution right now, I could try to implement a feature (e.g., a new config option?) if the maintainers think it is a good idea.

Lenguaje dominante
Rust
Estrellas
1.6k
Forks
299
Merge medio
2 d 4 h
PR fusionados (30 d)
9

Preparar el entorno

Primeros pasos

  1. Lee el issue completo y luego la guía de contribución del proyecto.
  2. Comenta en el issue que vas a ocuparte — evita que dos personas hagan lo mismo.
  3. Haz un fork del repositorio y trabaja en una rama.
  4. Abre un pull request que haga referencia al número del issue.

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