refactor(headers): Introduce header!() macro, improve documentation

The new macro handles single value headers, list headers, and list
headers with at least one item.
It creates the item for the header and contains its documentation. The
new macro allows handling
more header cases in the future, it will also be possible to include
tests inside the macro.

BREAKING CHANGE: Removed impl_header!() and impl_list_header!() macros,
use new header!() macro.

src/header/common/mod.rs

@@ -89,64 +89,91 @@ macro_rules! deref(
 );
 
 #[macro_export]
-macro_rules! impl_list_header(
-    ($from:ident, $name:expr, $item:ty) => {
-        deref!($from => $item);
+macro_rules! header {
+    // $a:meta: Attributes associated with the header item (usually docs)
+    // $id:ident: Identifier of the header
+    // $n:expr: Lowercase name of the header
+    // $nn:expr: Nice name of the header
 
-        impl $crate::header::Header for $from {
+    // List header, zero or more items
+    ($(#[$a:meta])*($id:ident, $n:expr) => ($item:ty)*) => {
+        $(#[$a])*
+        #[derive(Clone, Debug, PartialEq)]
+        pub struct $id(pub Vec<$item>);
+        deref!($id => Vec<$item>);
+        impl $crate::header::Header for $id {
             fn header_name() -> &'static str {
-                $name
+                $n
             }
-
-            fn parse_header(raw: &[Vec<u8>]) -> Option<$from> {
-                $crate::header::parsing::from_comma_delimited(raw).map($from)
+            fn parse_header(raw: &[Vec<u8>]) -> Option<Self> {
+                $crate::header::parsing::from_comma_delimited(raw).map($id)
             }
         }
-
-        impl $crate::header::HeaderFormat for $from {
-            fn fmt_header(&self, fmt: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
-                $crate::header::parsing::fmt_comma_delimited(fmt, &self[..])
+        impl $crate::header::HeaderFormat for $id {
+            fn fmt_header(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+                $crate::header::parsing::fmt_comma_delimited(f, &self.0[..])
             }
         }
-
-        impl ::std::fmt::Display for $from {
+        impl ::std::fmt::Display for $id {
             fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
                 use $crate::header::HeaderFormat;
                 self.fmt_header(f)
             }
         }
-    }
-);
 
-#[macro_export]
-macro_rules! impl_header(
-    ($from:ident, $name:expr, $item:ty) => {
-        deref!($from => $item);
-
-        impl $crate::header::Header for $from {
+    };
+    // List header, one or more items
+    ($(#[$a:meta])*($id:ident, $n:expr) => ($item:ty)+) => {
+        $(#[$a])*
+        #[derive(Clone, Debug, PartialEq)]
+        pub struct $id(pub Vec<$item>);
+        deref!($id => Vec<$item>);
+        impl $crate::header::Header for $id {
             fn header_name() -> &'static str {
-                $name
+                $n
             }
-
-            fn parse_header(raw: &[Vec<u8>]) -> Option<$from> {
-                $crate::header::parsing::from_one_raw_str(raw).map($from)
+            fn parse_header(raw: &[Vec<u8>]) -> Option<Self> {
+                $crate::header::parsing::from_comma_delimited(raw).map($id)
             }
         }
-
-        impl $crate::header::HeaderFormat for $from {
+        impl $crate::header::HeaderFormat for $id {
+            fn fmt_header(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+                $crate::header::parsing::fmt_comma_delimited(f, &self.0[..])
+            }
+        }
+        impl ::std::fmt::Display for $id {
+            fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
+                use $crate::header::HeaderFormat;
+                self.fmt_header(f)
+            }
+        }
+    };
+    // Single value header
+    ($(#[$a:meta])*($id:ident, $n:expr) => [$value:ty]) => {
+        $(#[$a])*
+        #[derive(Clone, Debug, PartialEq)]
+        pub struct $id(pub $value);
+        deref!($id => $value);
+        impl $crate::header::Header for $id {
+            fn header_name() -> &'static str {
+                $n
+            }
+            fn parse_header(raw: &[Vec<u8>]) -> Option<Self> {
+                $crate::header::parsing::from_one_raw_str(raw).map($id)
+            }
+        }
+        impl $crate::header::HeaderFormat for $id {
             fn fmt_header(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
                 ::std::fmt::Display::fmt(&**self, f)
             }
         }
-
-        impl ::std::fmt::Display for $from {
+        impl ::std::fmt::Display for $id {
             fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
-                use $crate::header::HeaderFormat;
-                self.fmt_header(f)
+                ::std::fmt::Display::fmt(&**self, f)
             }
         }
-    }
-);
+    };
+}
 
 mod access_control;
 mod accept;