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社区首页 >问答首页 >难以使用Rust和Serde反序列化XML，其中文档具有可选的子元素

问难以使用Rust和Serde反序列化XML，其中文档具有可选的子元素
EN

Stack Overflow用户
提问于 2019-12-23 08:31:24
回答 1查看 2K关注 0票数 2

我对锈病很陌生，而且还在努力掌握使用它的诀窍。这很酷，但我显然错过了一些我给自己做的练习。作为参考，我使用的是rustc 1.39.0。

我想尝试编写一个简单的程序，从MSBuild的代码分析中读取XML，后者输出一些相当简单的XML。我认为的问题是，有一个元素(PATH)通常是空的，但有时可以在它下面包含元素。更大的问题是，我对Rust (而且我通常不处理XML)很感兴趣，而且我也不知道如何正确设置反序列化所需的结构。我用的是Serde和quick_xml。当我将PATH设置为字符串并使用路径下没有SFA元素的XML时，我的测试就成功了。但是，一旦我知道了应该如何使用该标记并相应地更新了我的结构，我就会不断地得到错误：

代码语言：javascript
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thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Custom("missing field `FILEPATH`")', src\libcore\result.rs:1165:5

...even如果测试XML文件中的所有缺陷在PATH下都有SFA元素。

我处理的所有XML文件都如下所示：

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<?xml version="1.0" encoding="utf-8"?>
<DEFECTS>
  <DEFECT>
    <SFA>
      <FILEPATH>c:\projects\source\repos\defecttest\defecttest</FILEPATH>
      <FILENAME>source.cpp</FILENAME>
      <LINE>8</LINE>
      <COLUMN>5</COLUMN>
    </SFA>
    <DEFECTCODE>26496</DEFECTCODE>
    <DESCRIPTION>The variable 'y' is assigned only once, mark it as const (con.4).</DESCRIPTION>
    <FUNCTION>main</FUNCTION>
    <DECORATED>main</DECORATED>
    <FUNCLINE>6</FUNCLINE>
    <PATH></PATH>
  </DEFECT>
  <DEFECT>
    <SFA>
      <FILEPATH>c:\projects\source\repos\defecttest\defecttest</FILEPATH>
      <FILENAME>source.cpp</FILENAME>
      <LINE>9</LINE>
      <COLUMN>5</COLUMN>
    </SFA>
    <DEFECTCODE>26496</DEFECTCODE>
    <DESCRIPTION>The variable 'z' is assigned only once, mark it as const (con.4).</DESCRIPTION>
    <FUNCTION>main</FUNCTION>
    <DECORATED>main</DECORATED>
    <FUNCLINE>6</FUNCLINE>
    <PATH></PATH>
  </DEFECT>
</DEFECTS>

在许多情况下，PATH是空的，但在有些情况下，它包含自己的SFA元素：

代码语言：javascript
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  <DEFECT>
    <SFA>
      <FILEPATH>c:\projects\source\repos\defecttest\defecttest</FILEPATH>
      <FILENAME>source.cpp</FILENAME>
      <LINE>9</LINE>
      <COLUMN>5</COLUMN>
    </SFA>
    <DEFECTCODE>26496</DEFECTCODE>
    <DESCRIPTION>The variable 'z' is assigned only once, mark it as const (con.4).</DESCRIPTION>
    <FUNCTION>main</FUNCTION>
    <DECORATED>main</DECORATED>
    <FUNCLINE>6</FUNCLINE>
    <PATH>
      <SFA>
        <FILEPATH>c:\projects\source\repos\defecttest\defecttest</FILEPATH>
        <FILENAME>source.cpp</FILENAME>
        <LINE>12</LINE>
        <COLUMN>3</COLUMN>
      </SFA>
    </PATH>
  </DEFECT>

在我意识到这一点之前，缺陷结构中的所有字段都被设置为String。这是正确的，假设XML文件中的任何缺陷都没有子元素在PATH下。当我将它改为SFA而不是String时，它会给出上面提到的丢失字段错误。我正在测试的代码示例：

main.rs

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extern crate quick_xml;
extern crate serde;

use std::default::Default;
use std::env;
use std::vec::Vec;

use quick_xml::de::from_str;
use serde::{Serialize, Deserialize};

/*
 * Structs for the defect XML
 */

#[derive(Serialize, Deserialize, Debug)]
#[allow(non_snake_case)]
pub struct DEFECTS {
    #[serde(rename = "DEFECT", default)]
    pub defects: Vec<DEFECT>,
}

#[derive(Default, Serialize, Deserialize, Debug)]
#[allow(non_snake_case)]
pub struct DEFECT {
    #[serde(default)]
    pub SFA: SFA,
    pub DEFECTCODE: String,
    pub DESCRIPTION: String,
    pub FUNCTION: String,
    pub DECORATED: String,
    pub FUNCLINE: String,
    #[serde(default)]
    pub PATH: Vec<SFA>,
}

#[derive(Default, Serialize, Deserialize, Debug)]
#[allow(non_snake_case)]
pub struct SFA {
    pub FILEPATH: String,
    pub FILENAME: String,
    pub LINE: String,
    pub COLUMN: String,
}

/*
 * Main app code
 */

fn main() {
    // Expect the path to the XML file to be passed as the first and only argument
    let args: Vec<String> = env::args().collect();
    if args.len() != 2 {
        panic!("Invalid argument count. Specify a single file to process.");
    }

    let processing_file = &args[1];
    println!("Will attempt to process file: '{}'", &processing_file);

    // Try to load the contents of the file
    let file_content : String = match std::fs::read_to_string(&processing_file) {
        Ok(file_content) => file_content,
        Err(e) => {
            panic!("Failed to read file: '{}' -- {}", &processing_file, e);
        }
    };

    // Now, try to deserialize the XML we have in file_content
    let defect_list : DEFECTS = from_str(&file_content).unwrap();

    // Assuming the unwrap above didn't blow up, we should get a count here
    println!("Retrieved {} defects from file '{}'", defect_list.defects.len(), &processing_file);
}

Cargo.toml

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[package]
name = "rust_xml_test"
version = "0.1.0"
authors = ["fny82"]
edition = "2018"

[dependencies]
quick-xml = { version = "0.17", features = [ "serialize" ] }
serde = { version = "1.0", features = [ "derive" ] }

示例输出

代码语言：javascript
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C:\Development\RustXmlTest>cargo run -- "c:\development\rustxmltest\test3.xml"
   Compiling rust_xml_test v0.1.0 (C:\Development\RustXmlTest)
    Finished dev [unoptimized + debuginfo] target(s) in 1.56s
     Running `target\debug\rust_xml_test.exe c:\development\rustxmltest\test3.xml`
Will attempt to process file: 'c:\development\rustxmltest\test3.xml'
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: Custom("missing field `FILEPATH`")', src\libcore\result.rs:1165:5
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace.
error: process didn't exit successfully: `target\debug\rust_xml_test.exe c:\development\rustxmltest\test3.xml` (exit code: 101)

我肯定我在做一些愚蠢的事情，其中一部分原因可能是我在挑战的范围和我目前对使用Rust的理解程度上超越了我自己。有人能帮我找出我错过了什么，做错什么吗？

有些关联:从那以后，我了解到我可以使用rename属性来使我的结构符合Rust的命名约定，但现在我不想开始处理这个问题，直到底层功能开始工作为止。

--编辑--

请参阅@edwardw现在正在工作的代码中的更正：

代码语言：javascript
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extern crate quick_xml;
extern crate serde;

use std::default::Default;
use std::env;
use std::vec::Vec;

use quick_xml::de::from_str;
use serde::{Serialize, Deserialize};

/*
 * Structs for the defect XML
 */

#[derive(Serialize, Deserialize, Debug)]
#[allow(non_snake_case)]
pub struct DEFECTS {
    #[serde(rename = "DEFECT", default)]
    pub defects: Vec<DEFECT>,
}

#[derive(Default, Serialize, Deserialize, Debug)]
#[allow(non_snake_case)]
pub struct DEFECT {
    #[serde(default)]
    pub SFA: SFA,
    pub DEFECTCODE: String,
    pub DESCRIPTION: String,
    pub FUNCTION: String,
    pub DECORATED: String,
    pub FUNCLINE: String,
    pub PATH: PATH,
}

#[derive(Default, Serialize, Deserialize, Debug)]
#[allow(non_snake_case)]
pub struct SFA {
    pub FILEPATH: String,
    pub FILENAME: String,
    pub LINE: String,
    pub COLUMN: String,
}

#[derive(Default, Serialize, Deserialize, Debug)]
#[allow(non_snake_case)]
pub struct PATH {
    pub SFA: Option<SFA>,
}

/*
 * Main app code
 */

fn main() {
    // Expect the path to the XML file to be passed as the first and only argument
    let args: Vec<String> = env::args().collect();
    if args.len() != 2 {
        panic!("Invalid argument count. Specify a single file to process.");
    }

    let processing_file = &args[1];
    println!("Will attempt to process file: '{}'", &processing_file);

    // Try to load the contents of the file
    let file_content : String = match std::fs::read_to_string(&processing_file) {
        Ok(file_content) => file_content,
        Err(e) => {
            panic!("Failed to read file: '{}' -- {}", &processing_file, e);
        }
    };

    // Now, try to deserialize the XML we have in file_content
    let defect_list : DEFECTS = from_str(&file_content).unwrap();

    // Assuming the unwrap above didn't blow up, we should get a count here
    println!("Retrieved {} defects from file '{}'", defect_list.defects.len(), &processing_file);
}

示例：

代码语言：javascript
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C:\Development\RustXmlTest>cargo run -- "c:\development\rustxmltest\test1.xml"
   Compiling rust_xml_test v0.1.0 (C:\Development\RustXmlTest)
    Finished dev [unoptimized + debuginfo] target(s) in 1.66s
     Running `target\debug\rust_xml_test.exe c:\development\rustxmltest\test1.xml`
Will attempt to process file: 'c:\development\rustxmltest\test1.xml'
Retrieved 2 defects from file 'c:\development\rustxmltest\test1.xml'

其中test1.xml包含：

代码语言：javascript
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<?xml version="1.0" encoding="utf-8"?>
<DEFECTS>
  <DEFECT>
    <SFA>
      <FILEPATH>c:\projects\source\repos\defecttest\defecttest</FILEPATH>
      <FILENAME>source.cpp</FILENAME>
      <LINE>8</LINE>
      <COLUMN>5</COLUMN>
    </SFA>
    <DEFECTCODE>26496</DEFECTCODE>
    <DESCRIPTION>The variable 'y' is assigned only once, mark it as const (con.4).</DESCRIPTION>
    <FUNCTION>main</FUNCTION>
    <DECORATED>main</DECORATED>
    <FUNCLINE>6</FUNCLINE>
    <PATH></PATH>
  </DEFECT>
  <DEFECT>
    <SFA>
      <FILEPATH>c:\projects\source\repos\defecttest\defecttest</FILEPATH>
      <FILENAME>source.cpp</FILENAME>
      <LINE>9</LINE>
      <COLUMN>5</COLUMN>
    </SFA>
    <DEFECTCODE>26496</DEFECTCODE>
    <DESCRIPTION>The variable 'z' is assigned only once, mark it as const (con.4).</DESCRIPTION>
    <FUNCTION>main</FUNCTION>
    <DECORATED>main</DECORATED>
    <FUNCLINE>6</FUNCLINE>
    <PATH>
      <SFA>
        <FILEPATH>c:\projects\source\repos\defecttest\defecttest</FILEPATH>
        <FILENAME>source.cpp</FILENAME>
        <LINE>12</LINE>
        <COLUMN>3</COLUMN>
      </SFA>
    </PATH>
  </DEFECT>
</DEFECTS>
xml
rust
serde
EN

回答 1

Stack Overflow用户

回答已采纳

发布于 2019-12-23 09:55:22

PATH本身应该被建模为一个带有一个可选字段的结构。这样做是可行的：

代码语言：javascript
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#[derive(Default, Serialize, Deserialize, Debug)]
#[allow(non_snake_case)]
pub struct DEFECT {
    #[serde(default)]
    pub SFA: SFA,
    pub DEFECTCODE: String,
    pub DESCRIPTION: String,
    pub FUNCTION: String,
    pub DECORATED: String,
    pub FUNCLINE: String,
    pub PATH: PATH,
}

#[derive(Default, Serialize, Deserialize, Debug)]
#[allow(non_snake_case)]
pub struct PATH {
    SFA: Option<SFA>,
}
票数 2
EN
页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：

https://stackoverflow.com/questions/59452193

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