wrap LanguageTags type in new AnyOrSome type to support wildcards (#2480)

CHANGES.md

@@ -1,6 +1,17 @@
 # Changes
 
 ## Unreleased - 2021-xx-xx
+### Added
+* Methods on `AcceptLanguage`: `ranked` and `preference`. [#2480]
+
+### Changed
+* Rename `Accept::{mime_precedence => ranked}`. [#2480]
+* Rename `Accept::{mime_preference => preference}`. [#2480]
+
+### Fixed
+* Accept wildcard `*` items in `AcceptLanguage`. [#2480]
+
+[#2480]: https://github.com/actix/actix-web/pull/2480
 
 
 ## 4.0.0-beta.13 - 2021-11-30

actix-http/src/header/mod.rs

@@ -55,7 +55,7 @@ pub trait Header: IntoHeaderValue {
     fn name() -> HeaderName;
 
     /// Parse a header
-    fn parse<T: HttpMessage>(msg: &T) -> Result<Self, ParseError>;
+    fn parse<M: HttpMessage>(msg: &M) -> Result<Self, ParseError>;
 }
 
 /// Convert `http::HeaderMap` to our `HeaderMap`.

actix-http/src/header/shared/quality_item.rs

@@ -1,8 +1,7 @@
 use std::{
     cmp,
     convert::{TryFrom, TryInto},
-    fmt,
+    fmt, str,
-    str::{self, FromStr},
 };
 
 use derive_more::{Display, Error};
@@ -83,16 +82,17 @@ impl TryFrom<f32> for Quality {
 /// in [RFC 7231 §5.3.1](https://datatracker.ietf.org/doc/html/rfc7231#section-5.3.1).
 #[derive(Clone, PartialEq, Debug)]
 pub struct QualityItem<T> {
-    /// The actual contents of the field.
+    /// The wrapped contents of the field.
     pub item: T,
+
     /// The quality (client or server preference) for the value.
     pub quality: Quality,
 }
 
 impl<T> QualityItem<T> {
-    /// Creates a new `QualityItem` from an item and a quality.
+    /// Constructs a new `QualityItem` from an item and a quality value.
-    /// The item can be of any type.
+    ///
-    /// The quality should be a value in the range [0, 1].
+    /// The item can be of any type. The quality should be a value in the range [0, 1].
     pub fn new(item: T, quality: Quality) -> QualityItem<T> {
         QualityItem { item, quality }
     }
@@ -116,7 +116,7 @@ impl<T: fmt::Display> fmt::Display for QualityItem<T> {
     }
 }
 
-impl<T: FromStr> FromStr for QualityItem<T> {
+impl<T: str::FromStr> str::FromStr for QualityItem<T> {
     type Err = ParseError;
 
     fn from_str(qitem_str: &str) -> Result<Self, Self::Err> {
@@ -128,6 +128,7 @@ impl<T: FromStr> FromStr for QualityItem<T> {
         let mut raw_item = qitem_str;
         let mut quality = 1f32;
 
+        // TODO: MSRV(1.52): use rsplit_once
         let parts: Vec<_> = qitem_str.rsplitn(2, ';').map(str::trim).collect();
 
         if parts.len() == 2 {

actix-http/src/header/utils.rs

@@ -12,7 +12,8 @@ where
     I: Iterator<Item = &'a HeaderValue> + 'a,
     T: FromStr,
 {
-    let mut result = Vec::new();
+    let size_guess = all.size_hint().1.unwrap_or(2);
+    let mut result = Vec::with_capacity(size_guess);
 
     for h in all {
         let s = h.to_str().map_err(|_| ParseError::Header)?;
@@ -26,6 +27,7 @@ where
                 .filter_map(|x| x.trim().parse().ok()),
         )
     }
+
     Ok(result)
 }
 
@@ -34,10 +36,12 @@ where
 pub fn from_one_raw_str<T: FromStr>(val: Option<&HeaderValue>) -> Result<T, ParseError> {
     if let Some(line) = val {
         let line = line.to_str().map_err(|_| ParseError::Header)?;
+
         if !line.is_empty() {
             return T::from_str(line).or(Err(ParseError::Header));
         }
     }
+
     Err(ParseError::Header)
 }
 
@@ -48,13 +52,16 @@ where
     T: fmt::Display,
 {
     let mut iter = parts.iter();
+
     if let Some(part) = iter.next() {
         fmt::Display::fmt(part, f)?;
     }
+
     for part in iter {
         f.write_str(", ")?;
         fmt::Display::fmt(part, f)?;
     }
+
     Ok(())
 }
 
@@ -65,3 +72,25 @@ pub fn http_percent_encode(f: &mut fmt::Formatter<'_>, bytes: &[u8]) -> fmt::Res
     let encoded = percent_encoding::percent_encode(bytes, HTTP_VALUE);
     fmt::Display::fmt(&encoded, f)
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn comma_delimited_parsing() {
+        let headers = vec![];
+        let res: Vec<usize> = from_comma_delimited(headers.iter()).unwrap();
+        assert_eq!(res, vec![0; 0]);
+
+        let headers = vec![
+            HeaderValue::from_static(""),
+            HeaderValue::from_static(","),
+            HeaderValue::from_static("  "),
+            HeaderValue::from_static("1    ,"),
+            HeaderValue::from_static(""),
+        ];
+        let res: Vec<usize> = from_comma_delimited(headers.iter()).unwrap();
+        assert_eq!(res, vec![1]);
+    }
+}

src/http/header/accept.rs

@@ -77,7 +77,7 @@ crate::http::header::common_header! {
     ///     ])
     /// );
     /// ```
-    (Accept, header::ACCEPT) => (QualityItem<Mime>)+
+    (Accept, header::ACCEPT) => (QualityItem<Mime>)*
 
     test_parse_and_format {
         // Tests from the RFC
@@ -88,6 +88,7 @@ crate::http::header::common_header! {
                 QualityItem::new("audio/*".parse().unwrap(), q(200)),
                 qitem("audio/basic".parse().unwrap()),
                 ])));
+
         crate::http::header::common_header_test!(
             test2,
             vec![b"text/plain; q=0.5, text/html, text/x-dvi; q=0.8, text/x-c"],
@@ -99,6 +100,7 @@ crate::http::header::common_header! {
                     q(800)),
                 qitem("text/x-c".parse().unwrap()),
                 ])));
+
         // Custom tests
         crate::http::header::common_header_test!(
             test3,
@@ -154,7 +156,11 @@ impl Accept {
     /// [q-factor weighting] and specificity.
     ///
     /// [q-factor weighting]: https://datatracker.ietf.org/doc/html/rfc7231#section-5.3.2
-    pub fn mime_precedence(&self) -> Vec<Mime> {
+    pub fn ranked(&self) -> Vec<Mime> {
+        if self.is_empty() {
+            return vec![];
+        }
+
         let mut types = self.0.clone();
 
         // use stable sort so items with equal q-factor and specificity retain listed order
@@ -201,12 +207,29 @@ impl Accept {
     /// If no q-factors are provided, the first mime type is chosen. Note that items without
     /// q-factors are given the maximum preference value.
     ///
-    /// Returns `None` if contained list is empty.
+    /// As per the spec, will return [`Mime::STAR_STAR`] (indicating no preference) if the contained
+    /// list is empty.
     ///
     /// [q-factor weighting]: https://datatracker.ietf.org/doc/html/rfc7231#section-5.3.2
-    pub fn mime_preference(&self) -> Option<Mime> {
+    pub fn preference(&self) -> Mime {
-        let types = self.mime_precedence();
+        use actix_http::header::q;
-        types.first().cloned()
+
+        let mut max_item = None;
+        let mut max_pref = q(0);
+
+        // uses manual max lookup loop since we want the first occurrence in the case of same
+        // preference but `Iterator::max_by_key` would give us the last occurrence
+
+        for pref in &self.0 {
+            // only change if strictly greater
+            // equal items, even while unsorted, still have higher preference if they appear first
+            if pref.quality > max_pref {
+                max_pref = pref.quality;
+                max_item = Some(pref.item.clone());
+            }
+        }
+
+        max_item.unwrap_or(mime::STAR_STAR)
     }
 }
 
@@ -216,12 +239,12 @@ mod tests {
     use crate::http::header::q;
 
     #[test]
-    fn test_mime_precedence() {
+    fn ranking_precedence() {
         let test = Accept(vec![]);
-        assert!(test.mime_precedence().is_empty());
+        assert!(test.ranked().is_empty());
 
         let test = Accept(vec![qitem(mime::APPLICATION_JSON)]);
-        assert_eq!(test.mime_precedence(), vec!(mime::APPLICATION_JSON));
+        assert_eq!(test.ranked(), vec!(mime::APPLICATION_JSON));
 
         let test = Accept(vec![
             qitem(mime::TEXT_HTML),
@@ -230,7 +253,7 @@ mod tests {
             QualityItem::new(mime::STAR_STAR, q(0.8)),
         ]);
         assert_eq!(
-            test.mime_precedence(),
+            test.ranked(),
             vec![
                 mime::TEXT_HTML,
                 "application/xhtml+xml".parse().unwrap(),
@@ -245,20 +268,20 @@ mod tests {
             qitem(mime::IMAGE_PNG),
         ]);
         assert_eq!(
-            test.mime_precedence(),
+            test.ranked(),
             vec![mime::IMAGE_PNG, mime::IMAGE_STAR, mime::STAR_STAR]
         );
     }
 
     #[test]
-    fn test_mime_preference() {
+    fn preference_selection() {
         let test = Accept(vec![
             qitem(mime::TEXT_HTML),
             "application/xhtml+xml".parse().unwrap(),
             QualityItem::new("application/xml".parse().unwrap(), q(0.9)),
             QualityItem::new(mime::STAR_STAR, q(0.8)),
         ]);
-        assert_eq!(test.mime_preference(), Some(mime::TEXT_HTML));
+        assert_eq!(test.preference(), mime::TEXT_HTML);
 
         let test = Accept(vec![
             QualityItem::new("video/*".parse().unwrap(), q(0.8)),
@@ -267,6 +290,6 @@ mod tests {
             qitem(mime::IMAGE_SVG),
             QualityItem::new(mime::IMAGE_STAR, q(0.8)),
         ]);
-        assert_eq!(test.mime_preference(), Some(mime::IMAGE_PNG));
+        assert_eq!(test.preference(), mime::IMAGE_PNG);
     }
 }

src/http/header/accept_language.rs

@@ -1,66 +1,224 @@
 use language_tags::LanguageTag;
 
-use super::{QualityItem, ACCEPT_LANGUAGE};
+use super::{common_header, Preference, QualityItem};
+use crate::http::header;
 
-crate::http::header::common_header! {
+common_header! {
     /// `Accept-Language` header, defined
     /// in [RFC 7231 §5.3.5](https://datatracker.ietf.org/doc/html/rfc7231#section-5.3.5)
     ///
-    /// The `Accept-Language` header field can be used by user agents to
+    /// The `Accept-Language` header field can be used by user agents to indicate the set of natural
-    /// indicate the set of natural languages that are preferred in the
+    /// languages that are preferred in the response.
-    /// response.
+    ///
+    /// The `Accept-Language` header is defined in
+    /// [RFC 7231 §5.3.5](https://datatracker.ietf.org/doc/html/rfc7231#section-5.3.5) using language
+    /// ranges defined in [RFC 4647 §2.1](https://datatracker.ietf.org/doc/html/rfc4647#section-2.1).
     ///
     /// # ABNF
-    ///
     /// ```text
     /// Accept-Language = 1#( language-range [ weight ] )
-    /// language-range  = <language-range, see [RFC4647], Section 2.1>
+    /// language-range  = (1*8ALPHA *("-" 1*8alphanum)) / "*"
+    /// alphanum        = ALPHA / DIGIT
+    /// weight          = OWS ";" OWS "q=" qvalue
+    /// qvalue          = ( "0" [ "." 0*3DIGIT ] )
+    ///                 / ( "1" [ "." 0*3("0") ] )
     /// ```
     ///
-    /// # Example values
+    /// # Example Values
-    /// * `da, en-gb;q=0.8, en;q=0.7`
+    /// - `da, en-gb;q=0.8, en;q=0.7`
-    /// * `en-us;q=1.0, en;q=0.5, fr`
+    /// - `en-us;q=1.0, en;q=0.5, fr`
+    /// - `fr-CH, fr;q=0.9, en;q=0.8, de;q=0.7, *;q=0.5`
     ///
     /// # Examples
-    ///
     /// ```
     /// use actix_web::HttpResponse;
-    /// use actix_web::http::header::{AcceptLanguage, LanguageTag, qitem};
+    /// use actix_web::http::header::{AcceptLanguage, qitem};
     ///
     /// let mut builder = HttpResponse::Ok();
-    /// let langtag = LanguageTag::parse("en-US").unwrap();
     /// builder.insert_header(
     ///     AcceptLanguage(vec![
-    ///         qitem(langtag),
+    ///         qitem("en-US".parse().unwrap())
     ///     ])
     /// );
     /// ```
     ///
     /// ```
     /// use actix_web::HttpResponse;
-    /// use actix_web::http::header::{AcceptLanguage, LanguageTag, QualityItem, q, qitem};
+    /// use actix_web::http::header::{AcceptLanguage, QualityItem, q, qitem};
     ///
     /// let mut builder = HttpResponse::Ok();
     /// builder.insert_header(
     ///     AcceptLanguage(vec![
-    ///         qitem(LanguageTag::parse("da").unwrap()),
+    ///         qitem("da".parse().unwrap()),
-    ///         QualityItem::new(LanguageTag::parse("en-GB").unwrap(), q(800)),
+    ///         QualityItem::new("en-GB".parse().unwrap(), q(800)),
-    ///         QualityItem::new(LanguageTag::parse("en").unwrap(), q(700)),
+    ///         QualityItem::new("en".parse().unwrap(), q(700)),
     ///     ])
     /// );
     /// ```
-    (AcceptLanguage, ACCEPT_LANGUAGE) => (QualityItem<LanguageTag>)+
+    (AcceptLanguage, header::ACCEPT_LANGUAGE) => (QualityItem<Preference<LanguageTag>>)*
 
-    test_accept_language {
+    parse_and_fmt_tests {
-        // From the RFC
+        common_header_test!(no_headers, vec![b""; 0], Some(AcceptLanguage(vec![])));
-        crate::http::header::common_header_test!(test1, vec![b"da, en-gb;q=0.8, en;q=0.7"]);
+
-        // Own test
+        common_header_test!(empty_header, vec![b""; 1], Some(AcceptLanguage(vec![])));
-        crate::http::header::common_header_test!(
+
-            test2, vec![b"en-US, en; q=0.5, fr"],
+        common_header_test!(
+            example_from_rfc,
+            vec![b"da, en-gb;q=0.8, en;q=0.7"]
+        );
+
+        common_header_test!(
+            not_ordered_by_weight,
+            vec![b"en-US, en; q=0.5, fr"],
             Some(AcceptLanguage(vec![
                 qitem("en-US".parse().unwrap()),
                 QualityItem::new("en".parse().unwrap(), q(500)),
                 qitem("fr".parse().unwrap()),
-        ])));
+            ]))
+        );
+
+        common_header_test!(
+            has_wildcard,
+            vec![b"fr-CH, fr; q=0.9, en; q=0.8, de; q=0.7, *; q=0.5"],
+            Some(AcceptLanguage(vec![
+                qitem("fr-CH".parse().unwrap()),
+                QualityItem::new("fr".parse().unwrap(), q(900)),
+                QualityItem::new("en".parse().unwrap(), q(800)),
+                QualityItem::new("de".parse().unwrap(), q(700)),
+                QualityItem::new("*".parse().unwrap(), q(500)),
+            ]))
+        );
+    }
+}
+
+impl AcceptLanguage {
+    /// Returns a sorted list of languages from highest to lowest precedence, accounting
+    /// for [q-factor weighting].
+    ///
+    /// [q-factor weighting]: https://datatracker.ietf.org/doc/html/rfc7231#section-5.3.2
+    pub fn ranked(&self) -> Vec<Preference<LanguageTag>> {
+        if self.0.is_empty() {
+            return vec![];
+        }
+
+        let mut types = self.0.clone();
+
+        // use stable sort so items with equal q-factor retain listed order
+        types.sort_by(|a, b| {
+            // sort by q-factor descending
+            b.quality.cmp(&a.quality)
+        });
+
+        types.into_iter().map(|qitem| qitem.item).collect()
+    }
+
+    /// Extracts the most preferable language, accounting for [q-factor weighting].
+    ///
+    /// If no q-factors are provided, the first language is chosen. Note that items without
+    /// q-factors are given the maximum preference value.
+    ///
+    /// As per the spec, returns [`Preference::Any`] if contained list is empty.
+    ///
+    /// [q-factor weighting]: https://datatracker.ietf.org/doc/html/rfc7231#section-5.3.2
+    pub fn preference(&self) -> Preference<LanguageTag> {
+        use actix_http::header::q;
+
+        let mut max_item = None;
+        let mut max_pref = q(0);
+
+        // uses manual max lookup loop since we want the first occurrence in the case of same
+        // preference but `Iterator::max_by_key` would give us the last occurrence
+
+        for pref in &self.0 {
+            // only change if strictly greater
+            // equal items, even while unsorted, still have higher preference if they appear first
+            if pref.quality > max_pref {
+                max_pref = pref.quality;
+                max_item = Some(pref.item.clone());
+            }
+        }
+
+        max_item.unwrap_or(Preference::Any)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::http::header::*;
+
+    #[test]
+    fn ranking_precedence() {
+        let test = AcceptLanguage(vec![]);
+        assert!(test.ranked().is_empty());
+
+        let test = AcceptLanguage(vec![qitem("fr-CH".parse().unwrap())]);
+        assert_eq!(test.ranked(), vec!("fr-CH".parse().unwrap()));
+
+        let test = AcceptLanguage(vec![
+            QualityItem::new("fr".parse().unwrap(), q(900)),
+            QualityItem::new("fr-CH".parse().unwrap(), q(1000)),
+            QualityItem::new("en".parse().unwrap(), q(800)),
+            QualityItem::new("*".parse().unwrap(), q(500)),
+            QualityItem::new("de".parse().unwrap(), q(700)),
+        ]);
+        assert_eq!(
+            test.ranked(),
+            vec![
+                "fr-CH".parse().unwrap(),
+                "fr".parse().unwrap(),
+                "en".parse().unwrap(),
+                "de".parse().unwrap(),
+                "*".parse().unwrap(),
+            ]
+        );
+
+        let test = AcceptLanguage(vec![
+            qitem("fr".parse().unwrap()),
+            qitem("fr-CH".parse().unwrap()),
+            qitem("en".parse().unwrap()),
+            qitem("*".parse().unwrap()),
+            qitem("de".parse().unwrap()),
+        ]);
+        assert_eq!(
+            test.ranked(),
+            vec![
+                "fr".parse().unwrap(),
+                "fr-CH".parse().unwrap(),
+                "en".parse().unwrap(),
+                "*".parse().unwrap(),
+                "de".parse().unwrap(),
+            ]
+        );
+    }
+
+    #[test]
+    fn preference_selection() {
+        let test = AcceptLanguage(vec![
+            QualityItem::new("fr".parse().unwrap(), q(900)),
+            QualityItem::new("fr-CH".parse().unwrap(), q(1000)),
+            QualityItem::new("en".parse().unwrap(), q(800)),
+            QualityItem::new("*".parse().unwrap(), q(500)),
+            QualityItem::new("de".parse().unwrap(), q(700)),
+        ]);
+        assert_eq!(
+            test.preference(),
+            Preference::Specific("fr-CH".parse().unwrap())
+        );
+
+        let test = AcceptLanguage(vec![
+            qitem("fr".parse().unwrap()),
+            qitem("fr-CH".parse().unwrap()),
+            qitem("en".parse().unwrap()),
+            qitem("*".parse().unwrap()),
+            qitem("de".parse().unwrap()),
+        ]);
+        assert_eq!(
+            test.preference(),
+            Preference::Specific("fr".parse().unwrap())
+        );
+
+        let test = AcceptLanguage(vec![]);
+        assert_eq!(test.preference(), Preference::Any);
     }
 }

src/http/header/macros.rs

@@ -1,33 +1,36 @@
+// TODO: replace with derive_more impl
 macro_rules! common_header_deref {
     ($from:ty => $to:ty) => {
-        impl ::std::ops::Deref for $from {
+        impl ::core::ops::Deref for $from {
             type Target = $to;
 
             #[inline]
-            fn deref(&self) -> &$to {
+            fn deref(&self) -> &Self::Target {
                 &self.0
             }
         }
 
-        impl ::std::ops::DerefMut for $from {
+        impl ::core::ops::DerefMut for $from {
             #[inline]
-            fn deref_mut(&mut self) -> &mut $to {
+            fn deref_mut(&mut self) -> &mut Self::Target {
                 &mut self.0
             }
         }
     };
 }
 
+/// Sets up a test module with some useful imports for use with [`common_header_test!`].
 macro_rules! common_header_test_module {
     ($id:ident, $tm:ident{$($tf:item)*}) => {
-        #[allow(unused_imports)]
         #[cfg(test)]
         mod $tm {
+            #![allow(unused_imports)]
+
             use std::str;
             use actix_http::http::Method;
             use mime::*;
             use $crate::http::header::*;
-            use super::$id as HeaderField;
+            use super::{$id as HeaderField, *};
             $($tf)*
         }
     }
@@ -42,14 +45,19 @@ macro_rules! common_header_test {
 
             let raw = $raw;
             let a: Vec<Vec<u8>> = raw.iter().map(|x| x.to_vec()).collect();
+
             let mut req = test::TestRequest::default();
+
             for item in a {
                 req = req.insert_header((HeaderField::name(), item)).take();
             }
+
             let req = req.finish();
             let value = HeaderField::parse(&req);
+
             let result = format!("{}", value.unwrap());
             let expected = String::from_utf8(raw[0].to_vec()).unwrap();
+
             let result_cmp: Vec<String> = result
                 .to_ascii_lowercase()
                 .split(' ')
@@ -60,10 +68,12 @@ macro_rules! common_header_test {
                 .split(' ')
                 .map(|x| x.to_owned())
                 .collect();
+
             assert_eq!(result_cmp.concat(), expected_cmp.concat());
         }
     };
-    ($id:ident, $raw:expr, $typed:expr) => {
+
+    ($id:ident, $raw:expr, $exp:expr) => {
         #[test]
         fn $id() {
             use actix_http::test;
@@ -75,26 +85,35 @@ macro_rules! common_header_test {
             }
             let req = req.finish();
             let val = HeaderField::parse(&req);
-            let typed: Option<HeaderField> = $typed;
+            let exp: Option<HeaderField> = $exp;
-            // Test parsing
+
-            assert_eq!(val.ok(), typed);
+            println!("req: {:?}", &req);
-            // Test formatting
+            println!("val: {:?}", &val);
-            if typed.is_some() {
+            println!("exp: {:?}", &exp);
+
+            // test parsing
+            assert_eq!(val.ok(), exp);
+
+            // test formatting
+            if let Some(exp) = exp {
                 let raw = &($raw)[..];
                 let mut iter = raw.iter().map(|b| str::from_utf8(&b[..]).unwrap());
                 let mut joined = String::new();
-                joined.push_str(iter.next().unwrap());
+                if let Some(s) = iter.next() {
-                for s in iter {
-                    joined.push_str(", ");
                     joined.push_str(s);
+                    for s in iter {
+                        joined.push_str(", ");
+                        joined.push_str(s);
+                    }
                 }
-                assert_eq!(format!("{}", typed.unwrap()), joined);
+                assert_eq!(format!("{}", exp), joined);
             }
         }
     };
 }
 
 macro_rules! common_header {
+    // TODO: these docs are wrong, there's no $n or $nn
     // $a:meta: Attributes associated with the header item (usually docs)
     // $id:ident: Identifier of the header
     // $n:expr: Lowercase name of the header
@@ -111,92 +130,100 @@ macro_rules! common_header {
             fn name() -> $crate::http::header::HeaderName {
                 $name
             }
+
             #[inline]
-            fn parse<T>(msg: &T) -> Result<Self, $crate::error::ParseError>
+            fn parse<M: $crate::HttpMessage>(msg: &M) -> Result<Self, $crate::error::ParseError> {
-                where T: $crate::HttpMessage
+                let headers = msg.headers().get_all(Self::name());
-            {
+                $crate::http::header::from_comma_delimited(headers).map($id)
-                $crate::http::header::from_comma_delimited(
-                    msg.headers().get_all(Self::name())).map($id)
             }
         }
-        impl std::fmt::Display for $id {
+
+        impl ::core::fmt::Display for $id {
             #[inline]
-            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> ::std::fmt::Result {
+            fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
                 $crate::http::header::fmt_comma_delimited(f, &self.0[..])
             }
         }
+
         impl $crate::http::header::IntoHeaderValue for $id {
             type Error = $crate::http::header::InvalidHeaderValue;
 
             fn try_into_value(self) -> Result<$crate::http::header::HeaderValue, Self::Error> {
-                use std::fmt::Write;
+                use ::core::fmt::Write;
                 let mut writer = $crate::http::header::Writer::new();
                 let _ = write!(&mut writer, "{}", self);
                 $crate::http::header::HeaderValue::from_maybe_shared(writer.take())
             }
         }
     };
+
     // List header, one or more items
     ($(#[$a:meta])*($id:ident, $name:expr) => ($item:ty)+) => {
         $(#[$a])*
         #[derive(Clone, Debug, PartialEq)]
         pub struct $id(pub Vec<$item>);
+
         crate::http::header::common_header_deref!($id => Vec<$item>);
+
         impl $crate::http::header::Header for $id {
             #[inline]
             fn name() -> $crate::http::header::HeaderName {
                 $name
             }
             #[inline]
-            fn parse<T>(msg: &T) -> Result<Self, $crate::error::ParseError>
+            fn parse<M: $crate::HttpMessage>(msg: &M) -> Result<Self, $crate::error::ParseError> {
-                where T: $crate::HttpMessage
-            {
                 $crate::http::header::from_comma_delimited(
                     msg.headers().get_all(Self::name())).map($id)
             }
         }
-        impl std::fmt::Display for $id {
+
+        impl ::core::fmt::Display for $id {
             #[inline]
-            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
                 $crate::http::header::fmt_comma_delimited(f, &self.0[..])
             }
         }
+
         impl $crate::http::header::IntoHeaderValue for $id {
             type Error = $crate::http::header::InvalidHeaderValue;
 
             fn try_into_value(self) -> Result<$crate::http::header::HeaderValue, Self::Error> {
-                use std::fmt::Write;
+                use ::core::fmt::Write;
                 let mut writer = $crate::http::header::Writer::new();
                 let _ = write!(&mut writer, "{}", self);
                 $crate::http::header::HeaderValue::from_maybe_shared(writer.take())
             }
         }
     };
+
     // Single value header
     ($(#[$a:meta])*($id:ident, $name:expr) => [$value:ty]) => {
         $(#[$a])*
         #[derive(Clone, Debug, PartialEq)]
         pub struct $id(pub $value);
+
         crate::http::header::common_header_deref!($id => $value);
+
         impl $crate::http::header::Header for $id {
             #[inline]
             fn name() -> $crate::http::header::HeaderName {
                 $name
             }
+
             #[inline]
-            fn parse<T>(msg: &T) -> Result<Self, $crate::error::ParseError>
+            fn parse<M: $crate::HttpMessage>(msg: &M) -> Result<Self, $crate::error::ParseError> {
-                where T: $crate::HttpMessage
+                let header = msg.headers().get(Self::name());
-            {
+                $crate::http::header::from_one_raw_str(header).map($id)
-                $crate::http::header::from_one_raw_str(
-                    msg.headers().get(Self::name())).map($id)
             }
         }
-        impl std::fmt::Display for $id {
+
+        impl ::core::fmt::Display for $id {
             #[inline]
-            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
-                std::fmt::Display::fmt(&self.0, f)
+                ::core::fmt::Display::fmt(&self.0, f)
             }
         }
+
         impl $crate::http::header::IntoHeaderValue for $id {
             type Error = $crate::http::header::InvalidHeaderValue;
 
@@ -205,6 +232,7 @@ macro_rules! common_header {
             }
         }
     };
+
     // List header, one or more items with "*" option
     ($(#[$a:meta])*($id:ident, $name:expr) => {Any / ($item:ty)+}) => {
         $(#[$a])*
@@ -215,42 +243,46 @@ macro_rules! common_header {
             /// Only the listed items are a match
             Items(Vec<$item>),
         }
+
         impl $crate::http::header::Header for $id {
             #[inline]
             fn name() -> $crate::http::header::HeaderName {
                 $name
             }
-            #[inline]
-            fn parse<T>(msg: &T) -> Result<Self, $crate::error::ParseError>
-                where T: $crate::HttpMessage
-            {
-                let any = msg.headers().get(Self::name()).and_then(|hdr| {
-                    hdr.to_str().ok().and_then(|hdr| Some(hdr.trim() == "*"))});
 
-                if let Some(true) = any {
+            #[inline]
+            fn parse<M: $crate::HttpMessage>(msg: &M) -> Result<Self, $crate::error::ParseError> {
+                let is_any = msg
+                    .headers()
+                    .get(Self::name())
+                    .and_then(|hdr| hdr.to_str().ok())
+                    .map(|hdr| hdr.trim() == "*");
+
+                if let Some(true) = is_any {
                     Ok($id::Any)
                 } else {
-                    Ok($id::Items(
+                    let headers = msg.headers().get_all(Self::name());
-                        $crate::http::header::from_comma_delimited(
+                    Ok($id::Items($crate::http::header::from_comma_delimited(headers)?))
-                            msg.headers().get_all(Self::name()))?))
                 }
             }
         }
-        impl std::fmt::Display for $id {
+
+        impl ::core::fmt::Display for $id {
             #[inline]
-            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+            fn fmt(&self, f: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
                 match *self {
                     $id::Any => f.write_str("*"),
-                    $id::Items(ref fields) => $crate::http::header::fmt_comma_delimited(
+                    $id::Items(ref fields) =>
-                        f, &fields[..])
+                        $crate::http::header::fmt_comma_delimited(f, &fields[..])
                 }
             }
         }
+
         impl $crate::http::header::IntoHeaderValue for $id {
             type Error = $crate::http::header::InvalidHeaderValue;
 
             fn try_into_value(self) -> Result<$crate::http::header::HeaderValue, Self::Error> {
-                use std::fmt::Write;
+                use ::core::fmt::Write;
                 let mut writer = $crate::http::header::Writer::new();
                 let _ = write!(&mut writer, "{}", self);
                 $crate::http::header::HeaderValue::from_maybe_shared(writer.take())

src/http/header/mod.rs

@@ -1,15 +1,52 @@
 //! A Collection of Header implementations for common HTTP Headers.
 //!
-//! ## Mime
+//! ## Mime Types
-//!
 //! Several header fields use MIME values for their contents. Keeping with the strongly-typed theme,
 //! the [mime] crate is used in such headers as [`ContentType`] and [`Accept`].
 
-use bytes::{Bytes, BytesMut};
 use std::fmt;
 
-pub use self::accept_charset::AcceptCharset;
+use bytes::{Bytes, BytesMut};
+
+// re-export from actix-http
+// - header name / value types
+// - relevant traits for converting to header name / value
+// - all const header names
+// - header map
+// - the few typed headers from actix-http
+// - header parsing utils
 pub use actix_http::http::header::*;
+
+mod accept_charset;
+// mod accept_encoding;
+mod accept;
+mod accept_language;
+mod allow;
+mod cache_control;
+mod content_disposition;
+mod content_language;
+mod content_range;
+mod content_type;
+mod date;
+mod encoding;
+mod entity;
+mod etag;
+mod expires;
+mod if_match;
+mod if_modified_since;
+mod if_none_match;
+mod if_range;
+mod if_unmodified_since;
+mod last_modified;
+mod macros;
+mod preference;
+// mod range;
+
+#[cfg(test)]
+pub(crate) use macros::common_header_test;
+pub(crate) use macros::{common_header, common_header_deref, common_header_test_module};
+
+pub use self::accept_charset::AcceptCharset;
 //pub use self::accept_encoding::AcceptEncoding;
 pub use self::accept::Accept;
 pub use self::accept_language::AcceptLanguage;
@@ -30,11 +67,10 @@ pub use self::if_none_match::IfNoneMatch;
 pub use self::if_range::IfRange;
 pub use self::if_unmodified_since::IfUnmodifiedSince;
 pub use self::last_modified::LastModified;
+pub use self::preference::Preference;
 //pub use self::range::{Range, ByteRangeSpec};
-pub(crate) use actix_http::http::header::{
-    fmt_comma_delimited, from_comma_delimited, from_one_raw_str,
-};
 
+/// Format writer ([`fmt::Write`]) for a [`BytesMut`].
 #[derive(Debug, Default)]
 struct Writer {
     buf: BytesMut,
@@ -62,30 +98,3 @@ impl fmt::Write for Writer {
         fmt::write(self, args)
     }
 }
-
-mod accept_charset;
-// mod accept_encoding;
-mod accept;
-mod accept_language;
-mod allow;
-mod cache_control;
-mod content_disposition;
-mod content_language;
-mod content_range;
-mod content_type;
-mod date;
-mod encoding;
-mod entity;
-mod etag;
-mod expires;
-mod if_match;
-mod if_modified_since;
-mod if_none_match;
-mod if_range;
-mod if_unmodified_since;
-mod last_modified;
-
-mod macros;
-#[cfg(test)]
-pub(crate) use macros::common_header_test;
-pub(crate) use macros::{common_header, common_header_deref, common_header_test_module};

src/http/header/preference.rs

@@ -0,0 +1,70 @@
+use std::{
+    fmt::{self, Write as _},
+    str,
+};
+
+/// A wrapper for types used in header values where wildcard (`*`) items are allowed but the
+/// underlying type does not support them.
+///
+/// For example, we use the `language-tags` crate for the [`AcceptLanguage`](super::AcceptLanguage)
+/// typed header but it does not parse `*` successfully. On the other hand, the `mime` crate, used
+/// for [`Accept`](super::Accept), has first-party support for wildcard items so this wrapper is not
+/// used in those header types.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Hash)]
+pub enum Preference<T> {
+    /// A wildcard value.
+    Any,
+
+    /// A valid `T`.
+    Specific(T),
+}
+
+impl<T> Preference<T> {
+    /// Returns true if preference is the any/wildcard (`*`) value.
+    pub fn is_any(&self) -> bool {
+        matches!(self, Self::Any)
+    }
+
+    /// Returns true if preference is the specific item (`T`) variant.
+    pub fn is_specific(&self) -> bool {
+        matches!(self, Self::Specific(_))
+    }
+
+    /// Returns reference to value in `Specific` variant, if it is set.
+    pub fn item(&self) -> Option<&T> {
+        match self {
+            Preference::Specific(ref item) => Some(item),
+            Preference::Any => None,
+        }
+    }
+
+    /// Consumes the container, returning the value in the `Specific` variant, if it is set.
+    pub fn into_item(self) -> Option<T> {
+        match self {
+            Preference::Specific(item) => Some(item),
+            Preference::Any => None,
+        }
+    }
+}
+
+impl<T: fmt::Display> fmt::Display for Preference<T> {
+    #[inline]
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Preference::Any => f.write_char('*'),
+            Preference::Specific(item) => fmt::Display::fmt(item, f),
+        }
+    }
+}
+
+impl<T: str::FromStr> str::FromStr for Preference<T> {
+    type Err = T::Err;
+
+    #[inline]
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        match s.trim() {
+            "*" => Ok(Self::Any),
+            other => other.parse().map(Preference::Specific),
+        }
+    }
+}