From 339d7fc097d2c3c256345e551479b1817bed7821 Mon Sep 17 00:00:00 2001
From: Fintan Halpenny <fintan.halpenny@gmail.com>
Date: Wed, 12 Oct 2022 16:56:40 +0100
Subject: [PATCH] git-ref-format: qualified macro

Add a `qualified!` macro to the set of git-ref-format macros. This
allows the construction of a `refs/<cat>/<name>` reference from a
string literal.

Signed-off-by: Fintan Halpenny <fintan.halpenny@gmail.com>
---
 git-ref-format/macro/src/lib.rs | 48 ++++++++++++++++++++++++++++++++-
 git-ref-format/src/lib.rs       |  2 ++
 git-ref-format/t/src/tests.rs   | 17 +++++++++++-
 3 files changed, 65 insertions(+), 2 deletions(-)

diff --git a/git-ref-format/macro/src/lib.rs b/git-ref-format/macro/src/lib.rs
index cffbdbd..4b617df 100644
--- a/git-ref-format/macro/src/lib.rs
+++ b/git-ref-format/macro/src/lib.rs
@@ -13,7 +13,7 @@ use proc_macro_error::abort;
 use quote::quote;
 use syn::{parse_macro_input, LitStr};
 
-use git_ref_format_core::{refspec::PatternStr, Component, Error, RefStr};
+use git_ref_format_core::{refspec::PatternStr, Component, Error, Qualified, RefStr};
 
 /// Create a [`git_ref_format_core::RefString`] from a string literal.
 ///
@@ -46,6 +46,52 @@ pub fn refname(input: TokenStream) -> TokenStream {
     }
 }
 
+/// Create a [`git_ref_format_core::Qualified`] from a string literal.
+///
+/// The string is validated at compile time, and an unsafe conversion is
+/// emitted.
+#[proc_macro_error]
+#[proc_macro]
+pub fn qualified(input: TokenStream) -> TokenStream {
+    let lit = parse_macro_input!(input as LitStr);
+    let val = lit.value();
+
+    let parsed: Result<&RefStr, Error> = val.as_str().try_into();
+    match parsed {
+        Ok(name) => {
+            let qualified: Option<Qualified> = Qualified::from_refstr(name);
+            match qualified {
+                Some(safe) => {
+                    let safe: &str = safe.as_str();
+                    let expand = quote! {
+                        unsafe {
+                            use ::std::{borrow::Cow, mem::transmute};
+                            use ::git_ref_format::{Component, RefStr, RefString};
+
+                            let inner: RefString = transmute(#safe.to_owned());
+                            let cow: Cow<'static, RefStr> = Cow::Owned(inner);
+                            transmute::<_, Qualified>(cow)
+                        }
+                    };
+
+                    TokenStream::from(expand)
+                },
+
+                None => {
+                    abort!(
+                        lit.span(),
+                        "refname is not of the form 'refs/<category>/<name>'"
+                    );
+                },
+            }
+        },
+
+        Err(e) => {
+            abort!(lit.span(), "invalid refname literal: {}", e);
+        },
+    }
+}
+
 /// Create a [`git_ref_format_core::Component`] from a string literal.
 ///
 /// The string is validated at compile time, and an unsafe conversion is
diff --git a/git-ref-format/src/lib.rs b/git-ref-format/src/lib.rs
index 78a536f..a0dad0f 100644
--- a/git-ref-format/src/lib.rs
+++ b/git-ref-format/src/lib.rs
@@ -144,6 +144,8 @@ pub mod name {
     pub use git_ref_format_macro::component;
 }
 
+#[cfg(any(feature = "macro", feature = "git-ref-format-macro"))]
+pub use git_ref_format_macro::qualified;
 #[cfg(any(feature = "macro", feature = "git-ref-format-macro"))]
 pub use git_ref_format_macro::refname;
 
diff --git a/git-ref-format/t/src/tests.rs b/git-ref-format/t/src/tests.rs
index 48e4b7b..d021305 100644
--- a/git-ref-format/t/src/tests.rs
+++ b/git-ref-format/t/src/tests.rs
@@ -1,13 +1,28 @@
 // Copyright © 2022 The Radicle Link Contributors
 // SPDX-License-Identifier: GPL-3.0-or-later
 
-use git_ref_format::{component, name, refname, refspec, Error, Qualified, RefStr, RefString};
+use git_ref_format::{
+    component,
+    name,
+    qualified,
+    refname,
+    refspec,
+    Error,
+    Qualified,
+    RefStr,
+    RefString,
+};
 
 #[test]
 fn refname_macro_works() {
     assert_eq!("refs/heads/main", refname!("refs/heads/main").as_str())
 }
 
+#[test]
+fn qualified_macro_works() {
+    assert_eq!("refs/heads/main", qualified!("refs/heads/main").as_str())
+}
+
 #[test]
 fn component_macro_works() {
     assert_eq!("self", name::component!("self").as_str())