[][src]Struct serde_with::DefaultOnError

pub struct DefaultOnError<T = Same>(_);

Deserialize value and return Default on error

The main use case is ignoring error while deserializing. Instead of erroring, it simply deserializes the Default variant of the type. It is not possible to find the error location, i.e., which field had a deserialization error, with this method. During serialization this wrapper does nothing. The serialization behavior of the underlying type is preserved. The type must implement Default for this conversion to work.

The same functionality is also available as serde_with::rust::default_on_error compatible with serde's with-annotation.


#[derive(Deserialize,  Debug)]
struct A {
    #[serde_as(deserialize_as = "DefaultOnError")]
    value: u32,

let a: A = serde_json::from_str(r#"{"value": 123}"#).unwrap();
assert_eq!(123, a.value);

// null is of invalid type
let a: A = serde_json::from_str(r#"{"value": null}"#).unwrap();
assert_eq!(0, a.value);

// String is of invalid type
let a: A = serde_json::from_str(r#"{"value": "123"}"#).unwrap();
assert_eq!(0, a.value);

// Map is of invalid type
let a: A = dbg!(serde_json::from_str(r#"{"value": {}}"#)).unwrap();
assert_eq!(0, a.value);

// Missing entries still cause errors
assert!(serde_json::from_str::<A>(r#"{  }"#).is_err());

Deserializing missing values can be supported by adding the default field attribute:

struct B {
    #[serde_as(deserialize_as = "DefaultOnError")]
    value: u32,

let b: B = serde_json::from_str(r#"{  }"#).unwrap();
assert_eq!(0, b.value);

DefaultOnError can be combined with other conversion methods. In this example we deserialize a Vec, each element is deserialized from a string. If the string does not parse as a number, then we get the default value of 0.

#[derive(Serialize, Deserialize)]
struct C {
    #[serde_as(as = "Vec<DefaultOnError<DisplayFromStr>>")]
    value: Vec<u32>,

let c: C = serde_json::from_value(json!({
    "value": ["1", "2", "a3", "", {}, "6"]
assert_eq!(vec![1, 2, 0, 0, 0, 6], c.value);

Trait Implementations

impl<T: Clone> Clone for DefaultOnError<T>[src]

impl<T: Copy> Copy for DefaultOnError<T>[src]

impl<T: Debug> Debug for DefaultOnError<T>[src]

impl<T: Default> Default for DefaultOnError<T>[src]

impl<'de, T, TAs> DeserializeAs<'de, T> for DefaultOnError<TAs> where
    TAs: DeserializeAs<'de, T>,
    T: Default

impl<T, TAs> SerializeAs<T> for DefaultOnError<TAs> where
    TAs: SerializeAs<T>, 

Auto Trait Implementations

impl<T> RefUnwindSafe for DefaultOnError<T> where
    T: RefUnwindSafe

impl<T> Send for DefaultOnError<T> where
    T: Send

impl<T> Sync for DefaultOnError<T> where
    T: Sync

impl<T> Unpin for DefaultOnError<T> where
    T: Unpin

impl<T> UnwindSafe for DefaultOnError<T> where
    T: UnwindSafe

Blanket Implementations

impl<T> Any for T where
    T: 'static + ?Sized

impl<T> Borrow<T> for T where
    T: ?Sized

impl<T> BorrowMut<T> for T where
    T: ?Sized

impl<T> From<T> for T[src]

impl<T, U> Into<U> for T where
    U: From<T>, 

impl<T> ToOwned for T where
    T: Clone

type Owned = T

The resulting type after obtaining ownership.

impl<T, U> TryFrom<U> for T where
    U: Into<T>, 

type Error = Infallible

The type returned in the event of a conversion error.

impl<T, U> TryInto<U> for T where
    U: TryFrom<T>, 

type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.