radicle-cob: simplify trailers module

The macro in the trailers module existed since there were multiple
trailers before the refactoring, so it minimised boilerplate code.

After the refactoring of the code there was only one trailer
left. Remove the macro generation code and replace it with just the
necessary code for the ResourceCommitTrailer.

Signed-off-by: Fintan Halpenny <fintan.halpenny@gmail.com>
X-Clacks-Overhead: GNU Terry Pratchett

radicle-cob/src/trailers.rs

@@ -3,108 +3,79 @@
 // This file is part of radicle-link, distributed under the GPLv3 with Radicle
 // Linking Exception. For full terms see the included LICENSE file.
 
-mod resource_identity {
-    super::oid_trailer! {ResourceCommitTrailer, "Rad-Resource"}
-}
-
-pub mod error {
-    pub use super::resource_identity::Error as InvalidResourceTrailer;
-}
-
-pub use resource_identity::ResourceCommitTrailer;
-
-/// A macro for generating boilerplate From and TryFrom impls for trailers which
-/// have git object IDs as their values
-#[macro_export]
-macro_rules! oid_trailer {
-    ($typename:ident, $trailer:literal) => {
 use git_trailers::{OwnedTrailer, Token, Trailer};
 use radicle_git_ext as ext;
 
-        use std::convert::{TryFrom, TryInto};
+pub mod error {
+    use thiserror::Error;
 
-        #[derive(Debug)]
+    #[derive(Debug, Error)]
-        pub enum Error {
+    pub enum InvalidResourceTrailer {
+        #[error("found wrong token for Rad-Resource tailer")]
         WrongToken,
+        #[error("no Rad-Resource")]
         NoTrailer,
+        #[error("no value for Rad-Resource")]
         NoValue,
+        #[error("invalid git OID")]
         InvalidOid,
     }
-
-        // We can't use `derive(thiserror::Error)` as we need to concat strings with
-        // $trailer and macros are not allowed in non-key-value attributes
-        impl std::fmt::Display for Error {
-            fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-                match self {
-                    Self::WrongToken => {
-                        write!(f, concat!("found wrong token for ", $trailer, " trailer"))
-                    }
-                    Self::NoTrailer => write!(f, concat!("no ", $trailer)),
-                    Self::NoValue => write!(f, concat!("no value for ", $trailer, " trailer")),
-                    Self::InvalidOid => write!(f, "invalid git OID"),
-                }
-            }
 }
 
-        impl std::error::Error for Error {}
+pub struct ResourceCommitTrailer(git2::Oid);
 
-        pub struct $typename(git2::Oid);
+impl ResourceCommitTrailer {
-
-        impl $typename {
     pub fn oid(&self) -> git2::Oid {
         self.0
     }
 }
 
-        impl From<git2::Oid> for $typename {
+impl TryFrom<&Trailer<'_>> for ResourceCommitTrailer {
-            fn from(oid: git2::Oid) -> Self {
+    type Error = error::InvalidResourceTrailer;
-                $typename(oid)
+
+    fn try_from(Trailer { values, token }: &Trailer<'_>) -> Result<Self, Self::Error> {
+        let val = values.first().ok_or(Self::Error::NoValue)?;
+        let ext_oid =
+            radicle_git_ext::Oid::try_from(val.as_ref()).map_err(|_| Self::Error::InvalidOid)?;
+        if Some(token) == Token::try_from("Rad-Resource").ok().as_ref() {
+            Ok(ResourceCommitTrailer(ext_oid.into()))
+        } else {
+            Err(Self::Error::WrongToken)
+        }
     }
 }
 
-        impl From<$typename> for Trailer<'_> {
+impl TryFrom<&OwnedTrailer> for ResourceCommitTrailer {
-            fn from(containing: $typename) -> Self {
+    type Error = error::InvalidResourceTrailer;
+
+    fn try_from(trailer: &OwnedTrailer) -> Result<Self, Self::Error> {
+        Self::try_from(&Trailer::from(trailer))
+    }
+}
+
+impl From<git2::Oid> for ResourceCommitTrailer {
+    fn from(oid: git2::Oid) -> Self {
+        Self(oid)
+    }
+}
+
+impl From<ResourceCommitTrailer> for Trailer<'_> {
+    fn from(containing: ResourceCommitTrailer) -> Self {
         Trailer {
-                    token: Token::try_from($trailer).unwrap(),
+            token: Token::try_from("Rad-Resource").unwrap(),
             values: vec![containing.0.to_string().into()],
         }
     }
 }
 
-        impl From<$typename> for OwnedTrailer {
+impl From<ResourceCommitTrailer> for OwnedTrailer {
-            fn from(containing: $typename) -> Self {
+    fn from(containing: ResourceCommitTrailer) -> Self {
         Trailer::from(containing).to_owned()
     }
 }
 
-        impl TryFrom<&Trailer<'_>> for $typename {
+impl From<ext::Oid> for ResourceCommitTrailer {
-            type Error = Error;
-
-            fn try_from(Trailer { values, token }: &Trailer<'_>) -> Result<Self, Self::Error> {
-                let val = values.first().ok_or(Error::NoValue)?;
-                let ext_oid =
-                    radicle_git_ext::Oid::try_from(val.as_ref()).map_err(|_| Error::InvalidOid)?;
-                if Some(token) == Token::try_from($trailer).ok().as_ref() {
-                    Ok($typename(ext_oid.into()))
-                } else {
-                    Err(Error::WrongToken)
-                }
-            }
-        }
-
-        impl TryFrom<&OwnedTrailer> for $typename {
-            type Error = Error;
-
-            fn try_from(trailer: &OwnedTrailer) -> Result<Self, Self::Error> {
-                (&Trailer::from(trailer)).try_into()
-            }
-        }
-
-        impl From<ext::Oid> for $typename {
     fn from(oid: ext::Oid) -> Self {
-                $typename(oid.into())
+        Self(oid.into())
     }
 }
-    };
-}
-pub(crate) use oid_trailer;