Enum Patch 

pub enum Patch<T> {
    Keep,
    Set(T),
    Clear,
}

Three-way patch value for nullable JMAP fields.

• Keep (default): the field is omitted from the patch — server leaves it unchanged.
• Set(v): the field is included with value v.
• Clear: the field is included as JSON null (clears the server-side value).

Use Patch::from(v) to construct Set(v). Use Default::default() or Patch::Keep to leave the field unchanged. Use Patch::Clear to set a nullable field to null explicitly.

Serde usage

Fields of type Patch<T> must carry both attributes:

#[serde(default, skip_serializing_if = "Patch::is_keep")]
pub my_field: Patch<String>,

• default: absent JSON key → Patch::Keep (no change).
• skip_serializing_if: omits the key from the output when the value is Keep.

Without skip_serializing_if, Patch::Keep serializes as a runtime error.

Deserialization

Patch::Keep is not reachable from JSON deserialization. The custom Deserialize impl maps JSON null → Clear and a JSON value → Set(v). An absent key (via #[serde(default)]) produces Keep via Default.

Variants

Keep

Omit the field from the patch — server leaves it unchanged.

Set(T)

Include the field with value T.

Clear

Include the field as JSON null (clears the server-side value).

Implementations

impl<T> Patch<T>

pub fn is_keep(&self) -> bool

Returns true if this is Patch::Keep (field should be omitted from serialization).

impl<T: Serialize> Patch<T>

pub fn map_entry(&self) -> Result<Option<Value>, Error>

Returns None when Keep (omit key from patch), Some(Value::Null) when Clear, or Some(serialized_value) when Set.

Trait Implementations

impl<T: Clone> Clone for Patch<T>

fn clone(&self) -> Patch<T>

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Debug> Debug for Patch<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T> Default for Patch<T>

fn default() -> Patch<T>

Returns the “default value” for a type.

impl<'de, T: Deserialize<'de>> Deserialize<'de> for Patch<T>

fn deserialize<D: Deserializer<'de>>(d: D) -> Result<Self, D::Error>

Deserialize this value from the given Serde deserializer.

impl<T> From<T> for Patch<T>

fn from(v: T) -> Self

Converts to this type from the input type.

impl<T: PartialEq> PartialEq for Patch<T>

fn eq(&self, other: &Patch<T>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T: Serialize> Serialize for Patch<T>

fn serialize<S: Serializer>(&self, s: S) -> Result<S::Ok, S::Error>

Serialize this value into the given Serde serializer.

impl<T> StructuralPartialEq for Patch<T>