Enum MimePart 

pub enum MimePart {
    Leaf {
        content_type: ContentType,
        content_transfer_encoding: Option<ContentTransferEncoding>,
        content_disposition: Option<ContentDisposition>,
        body: Vec<u8>,
    },
    Multipart {
        content_type: ContentType,
        boundary: Option<String>,
        parts: Vec<Self>,
    },
}

Low-level MIME tree node, gated behind the mime Cargo feature.

MimePart is the kernel’s escape hatch for callers building exotic MIME structures (custom multipart shapes, hand-rolled transfer-encoding choices, etc.). High-level paths through Body::Text / Body::Html / Body::TextAndHtml cover the common cases and apply byte-discipline (auto-promote non-ASCII text to base64, etc.) on the caller’s behalf.

Body byte-discipline is the caller’s responsibility

Constructing MimePart::Leaf directly bypasses the kernel’s auto-promotion path. The wire renderer enforces header invariants strictly (rejects raw CR / LF / NUL / non-tab control chars in any header value, regardless of Content-Transfer-Encoding), but it trusts the caller’s bytes for body content under any transfer encoding other than base64 / quoted-printable. That includes 7bit, 8bit, binary, and any Other(...) value: the renderer emits the body verbatim. RFC 2045 §6.2 forbids bytes > 127 under 7bit and forbids bare CR / LF under both 7bit and 8bit; callers building MimePart::Leaf with a non-base64 / non-QP encoding must satisfy those invariants themselves, or downstream MTAs may reject the message.

Variant set

Deliberately not #[non_exhaustive]. RFC 2046 closes MIME parts to exactly discrete (Leaf) and composite (Multipart); the kernel cannot honestly add a third variant without an RFC update. The exhaustive match shape lets downstream callers type-cover both arms without an _ => clause.

Untrusted-deserialize caveat

MimePart::Multipart { parts: Vec<Self> } is recursive: any caller deserializing a MimePart (or a Body containing one) from untrusted input must pre-bound the input length and the recursion depth. serde_json defaults to a 128-frame recursion limit which is safe; other formats (e.g. serde_yaml, bincode, rmp-serde, serde_cbor) may not, and a deeply nested attacker payload yields a MimePart value of arbitrary depth. The wire renderer (email_message_wire::render_rfc822) enforces a MAX_MULTIPART_DEPTH cap on outbound trees, including up to two frames of attachment-wrapping when inline and/or regular attachments are present, but other consumers of a deserialized MimePart (e.g. arbitrary caller code that walks the tree) must defend themselves.

Variants

Leaf

Fields

content_type: ContentType

content_transfer_encoding: Option<ContentTransferEncoding>

content_disposition: Option<ContentDisposition>

body: Vec<u8>

Multipart

Fields

content_type: ContentType

boundary: Option<String>

parts: Vec<Self>

Trait Implementations

impl<'arbitrary> Arbitrary<'arbitrary> for MimePart

fn arbitrary(u: &mut Unstructured<'arbitrary>) -> Result<Self>

Generate an arbitrary value of Self from the given unstructured data.

fn arbitrary_take_rest(u: Unstructured<'arbitrary>) -> Result<Self>

Generate an arbitrary value of Self from the entirety of the given unstructured data.

fn size_hint(depth: usize) -> (usize, Option<usize>)

Get a size hint for how many bytes out of an Unstructured this type needs to construct itself.

fn try_size_hint( depth: usize, ) -> Result<(usize, Option<usize>), MaxRecursionReached>

Get a size hint for how many bytes out of an Unstructured this type needs to construct itself.

impl Clone for MimePart

fn clone(&self) -> MimePart

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for MimePart

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

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for MimePart

Available on crate features mime and serde only.

fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl JsonSchema for MimePart

Available on crate features mime and schemars only.

fn json_schema(generator: &mut SchemaGenerator) -> Schema

MIME parts have no RFC 5322 string form, so this schema is not wrapped in an rfc5322-string-compat oneOf: [object, string] the way Mailbox / Group / Address are. The asymmetry is deliberate: there is no producer-side wire shape for “MIME part as a header-like string” to migrate from.

fn schema_name() -> Cow<'static, str>

The name of the generated JSON Schema.

fn schema_id() -> Cow<'static, str>

Returns a string that uniquely identifies the schema produced by this type.

fn inline_schema() -> bool

Whether JSON Schemas generated for this type should be included directly in parent schemas, rather than being re-used where possible using the $ref keyword.

impl PartialEq for MimePart

fn eq(&self, other: &MimePart) -> 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 Serialize for MimePart

Available on crate features mime and serde only.

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

where S: Serializer,

Serialize this value into the given Serde serializer.

impl Eq for MimePart

impl StructuralPartialEq for MimePart