142 lines
3.9 KiB
Rust
142 lines
3.9 KiB
Rust
//! Serde helpers.
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use serde::{Deserialize, Deserializer};
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/// This helper function enables successful deserialization of versioned structs; new structs may
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/// include additional fields if they impl Default and are added to the end of the struct. Right
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/// now, this function is targeted at `bincode` deserialization; the error match may need to be
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/// updated if another package needs to be used in the future.
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pub fn default_on_eof<'de, T, D>(d: D) -> Result<T, D::Error>
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where
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D: Deserializer<'de>,
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T: Deserialize<'de> + Default,
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{
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let result = T::deserialize(d);
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ignore_eof_error::<'de, T, D::Error>(result)
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}
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pub fn ignore_eof_error<'de, T, D>(result: Result<T, D>) -> Result<T, D>
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where
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T: Deserialize<'de> + Default,
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D: std::fmt::Display,
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{
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match result {
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Err(err) if err.to_string() == "io error: unexpected end of file" => Ok(T::default()),
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Err(err) if err.to_string() == "io error: failed to fill whole buffer" => Ok(T::default()),
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result => result,
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}
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}
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#[cfg(test)]
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pub mod tests {
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use {super::*, bincode::deserialize};
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#[test]
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fn test_default_on_eof() {
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#[derive(Serialize, Deserialize, Debug, PartialEq, Eq)]
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struct Foo {
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bar: u16,
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#[serde(deserialize_with = "default_on_eof")]
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baz: Option<u16>,
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#[serde(deserialize_with = "default_on_eof")]
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quz: String,
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}
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let data = vec![1, 0];
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assert_eq!(
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Foo {
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bar: 1,
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baz: None,
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quz: "".to_string(),
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},
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deserialize(&data).unwrap()
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);
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let data = vec![1, 0, 0];
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assert_eq!(
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Foo {
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bar: 1,
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baz: None,
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quz: "".to_string(),
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},
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deserialize(&data).unwrap()
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);
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let data = vec![1, 0, 1];
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assert_eq!(
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Foo {
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bar: 1,
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baz: None,
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quz: "".to_string(),
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},
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deserialize(&data).unwrap()
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);
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let data = vec![1, 0, 1, 0];
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assert_eq!(
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Foo {
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bar: 1,
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baz: None,
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quz: "".to_string(),
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},
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deserialize(&data).unwrap()
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);
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let data = vec![1, 0, 1, 0, 0, 1];
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assert_eq!(
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Foo {
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bar: 1,
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baz: Some(0),
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quz: "".to_string(),
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},
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deserialize(&data).unwrap()
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);
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let data = vec![1, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 116];
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assert_eq!(
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Foo {
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bar: 1,
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baz: Some(0),
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quz: "t".to_string(),
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},
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deserialize(&data).unwrap()
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);
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}
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#[test]
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#[should_panic]
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fn test_default_on_eof_additional_untagged_fields() {
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// If later fields are not tagged `deserialize_with = "default_on_eof"`, deserialization
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// will panic on any missing fields/data
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#[derive(Serialize, Deserialize, Debug, PartialEq, Eq)]
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struct Foo {
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bar: u16,
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#[serde(deserialize_with = "default_on_eof")]
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baz: Option<u16>,
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quz: String,
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}
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// Fully populated struct will deserialize
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let data = vec![1, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 116];
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assert_eq!(
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Foo {
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bar: 1,
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baz: Some(0),
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quz: "t".to_string(),
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},
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deserialize(&data).unwrap()
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);
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// Will panic because `quz` is missing, even though `baz` is tagged
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let data = vec![1, 0, 1, 0];
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assert_eq!(
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Foo {
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bar: 1,
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baz: None,
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quz: "".to_string(),
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},
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deserialize(&data).unwrap()
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);
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}
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}
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