support multipart/digest parsing

README.md

@@ -37,7 +37,7 @@ This library does not aim at implementing a specific RFC, but to be a swiss-army
 - Maintainability - modifying the code does not create regression and is possible for someone exterior to the project.
 - Compatibility - always try to parse something, do not panic or return an error.
 - Exhaustivity - serve as a common project to encode knowledge about emails (existing mime types, existing headers, etc.).
-- Type safe - do not manipulate only strings/bytes but leverage Rust type system instead so you benefit of its safety checks at compile time.
+- Type safe - do not manipulate only strings/bytes but leverage Rust type system instead so you benefit from its safety checks at compile time.
 
 [See more about this library goals in the doc/ folder](./doc/goals.md)
 

src/mime/field.rs

@@ -8,7 +8,7 @@ use nom::{
 use crate::header::{field_name, CompFieldList};
 use crate::imf::identification::{msg_id, MessageID};
 use crate::mime::mechanism::{mechanism, Mechanism};
-use crate::mime::AnyMIME;
+use crate::mime::{AnyMIMEWithDefault, WithDefaultType};
 use crate::mime::r#type::{naive_type, NaiveType};
 use crate::text::misc_token::{unstructured, Unstructured};
 use crate::text::whitespace::obs_crlf;
@@ -49,8 +49,8 @@ impl<'a> Content<'a> {
 }
 
 impl<'a> CompFieldList<'a, Content<'a>> {
-    pub fn to_mime(self) -> AnyMIME<'a> {
-        self.known().into_iter().collect::<AnyMIME>()
+    pub fn to_mime<T: WithDefaultType> (self) -> AnyMIMEWithDefault<'a, T> {
+        self.known().into_iter().collect::<AnyMIMEWithDefault<T>>()
     }
 }
 

src/mime/mod.rs

@@ -10,6 +10,8 @@ pub mod mechanism;
 /// Content-Type representation
 pub mod r#type;
 
+use std::marker::PhantomData;
+
 use crate::imf::identification::MessageID;
 use crate::mime::field::Content;
 use crate::mime::mechanism::Mechanism;
@@ -47,10 +49,43 @@ impl<'a> AnyMIME<'a> {
     }
 }
 
-impl<'a> FromIterator<Content<'a>> for AnyMIME<'a> {
+impl<'a, T: WithDefaultType> From<AnyMIMEWithDefault<'a, T>> for AnyMIME<'a> {
+    fn from(a: AnyMIMEWithDefault<'a, T>) -> Self {
+        a.0
+    }
+}
+
+#[derive(Debug, PartialEq, Default, Clone)]
+pub struct Generic<'a> {
+    pub transfer_encoding: Mechanism<'a>,
+    pub id: Option<MessageID<'a>>,
+    pub description: Option<Unstructured<'a>>,
+}
+
+pub trait WithDefaultType {
+    fn default_type() -> AnyType;
+}
+
+pub struct WithGenericDefault {}
+impl WithDefaultType for WithGenericDefault {
+    fn default_type() -> AnyType {
+        AnyType::Text(r#type::Text::default())
+    }
+}
+pub struct WithDigestDefault {}
+impl WithDefaultType for WithDigestDefault {
+    fn default_type() -> AnyType {
+        AnyType::Message(r#type::Message::default())
+    }
+}
+
+#[derive(Debug, PartialEq)]
+pub struct AnyMIMEWithDefault<'a, T: WithDefaultType>(pub AnyMIME<'a>, PhantomData<T>);
+
+impl<'a, T: WithDefaultType> FromIterator<Content<'a>> for AnyMIMEWithDefault<'a, T> {
     fn from_iter<I: IntoIterator<Item = Content<'a>>>(it: I) -> Self {
         let (at, gen) = it.into_iter().fold(
-            (AnyType::default(), Generic::default()),
+            (T::default_type(), Generic::default()),
             |(mut at, mut section), field| {
                 match field {
                     Content::Type(v) => at = v.to_type(),
@@ -62,13 +97,6 @@ impl<'a> FromIterator<Content<'a>> for AnyMIME<'a> {
             },
         );
 
-        Self::from_pair(at, gen)
+        Self(AnyMIME::from_pair(at, gen), PhantomData)
     }
 }
-
-#[derive(Debug, PartialEq, Default, Clone)]
-pub struct Generic<'a> {
-    pub transfer_encoding: Mechanism<'a>,
-    pub id: Option<MessageID<'a>>,
-    pub description: Option<Unstructured<'a>>,
-}

src/mime/type.rs

@@ -57,17 +57,12 @@ pub enum AnyType {
     Binary(Binary),
 }
 
-impl Default for AnyType {
-    fn default() -> Self {
-        Self::Text(Text::default())
-    }
-}
 impl<'a> From<&'a NaiveType<'a>> for AnyType {
     fn from(nt: &'a NaiveType<'a>) -> Self {
         match nt.main.to_ascii_lowercase().as_slice() {
             b"multipart" => Multipart::try_from(nt)
                 .map(Self::Multipart)
-                .unwrap_or(Self::default()),
+                .unwrap_or(Self::Text(Text::default())),
             b"message" => Self::Message(Message::from(nt)),
             b"text" => Self::Text(Text::from(nt)),
             _ => Self::Binary(Binary::default()),

src/part/composite.rs

@@ -47,7 +47,10 @@ pub fn multipart<'a>(
 
             // parse mime headers
             let (input, fields) = header(mime::field::content)(input)?;
-            let mime = fields.to_mime();
+            let mime = match m.0.subtype {
+                mime::r#type::MultipartSubtype::Digest => fields.to_mime::<mime::WithDigestDefault>().into(),
+                _ => fields.to_mime::<mime::WithGenericDefault>().into(),
+            };
 
             // parse raw part
             let (input, rpart) = part::part_raw(bound)(input)?;
@@ -75,7 +78,7 @@ pub fn message<'a>(
     move |input: &[u8]| {
         let (input, fields): (_, CompFieldList<part::field::MixedField>) =
             header(part::field::mixed_field)(input)?;
-        let (in_mime, imf) = fields.sections();
+        let (in_mime, imf) = fields.sections::<mime::WithGenericDefault>();
 
         let part = part::to_anypart(in_mime, input);
 

src/part/field.rs

@@ -36,19 +36,19 @@ impl<'a> MixedField<'a> {
     }
 }
 impl<'a> CompFieldList<'a, MixedField<'a>> {
-    pub fn sections(self) -> (mime::AnyMIME<'a>, imf::Imf<'a>) {
+    pub fn sections<T: mime::WithDefaultType>(self) -> (mime::AnyMIME<'a>, imf::Imf<'a>) {
         let k = self.known();
         let (v1, v2): (Vec<MixedField>, Vec<MixedField>) =
             k.into_iter().partition(|v| v.mime().is_some());
         let mime = v1
             .into_iter()
             .filter_map(|v| v.to_mime())
-            .collect::<mime::AnyMIME>();
+            .collect::<mime::AnyMIMEWithDefault<T>>();
         let imf = v2
             .into_iter()
             .filter_map(|v| v.to_imf())
             .collect::<imf::Imf>();
-        (mime, imf)
+        (mime.into(), imf)
     }
 }
 pub fn mixed_field(input: &[u8]) -> IResult<&[u8], MixedField> {