From 7ff013c5bbf45b3eccd2cafe2295d2b28c1fc7f9 Mon Sep 17 00:00:00 2001
From: Aaron O'Mullan <aaron.omullan@gmail.com>
Date: Thu, 29 Apr 2021 01:26:56 +0200
Subject: [PATCH] refactor(extensions): reintroduce declare_ops!() macro

This implementation is both cleaner and more flexible than the original prototype in #9800
---
 core/extensions.rs | 62 ++++++++++++++++++++++++++++++++++++++++++++++
 core/lib.rs        |  2 +-
 2 files changed, 63 insertions(+), 1 deletion(-)

diff --git a/core/extensions.rs b/core/extensions.rs
index 134aab5d41c79b..7043ed484fa0a6 100644
--- a/core/extensions.rs
+++ b/core/extensions.rs
@@ -126,3 +126,65 @@ macro_rules! include_js_files {
     ]
   };
 }
+
+// declare_ops! helps declare ops for an extension.
+// Example:
+// ```
+// declare_ops!(
+//   sync[
+//     op_foo,
+//     op_bar,
+//   ],
+//   async[
+//     op_write,
+//     op_read,
+//   ],
+// )
+// ```
+#[macro_export]
+macro_rules! declare_ops {
+  // A flattened group of async[] & sync[] subgroups
+  ($($wrapper:ident[$($opfn:expr,)+],)+) => {
+    vec![
+      $(declare_ops!($wrapper[$($opfn,)+]),)+
+    ].into_iter().flatten().collect()
+  };
+
+  // Async group
+  (async[$($opfn:expr,)+]) => {
+    vec![$((
+      $crate::extensions::op_ident(stringify!($opfn)),
+      $crate::op_async($opfn),
+    ),)+]
+  };
+
+  // Sync group
+  (sync[$($opfn:expr,)+]) => {
+    vec![$((
+      $crate::extensions::op_ident(stringify!($opfn)),
+      $crate::op_sync($opfn),
+    ),)+]
+  };
+}
+
+/// transforms a stringified identifier path into an op_name
+/// it also enforces that all op_names must start with "op_"
+/// ```
+/// stringify!(foo::op_bar<X>) => "foo :: op_bar < X >"
+/// op_ident(stringify!(foo::op_bar<X>)) => "op_bar"
+/// ```
+pub fn op_ident(ident_path: &'static str) -> &'static str {
+  let end = ident_path.rfind("::<").unwrap_or_else(|| ident_path.len());
+  let ident_path = ident_path.get(0..end).unwrap();
+  let start = ident_path.rfind("::").unwrap_or(0);
+  let name = ident_path.get(start..ident_path.len()).unwrap();
+
+  // Assert op_ prefix
+  assert!(
+    name.starts_with("op_"),
+    "Op '{}' missing 'op_' prefix",
+    name
+  );
+
+  name
+}
diff --git a/core/lib.rs b/core/lib.rs
index 37055bcc8d7095..85d14d92c3e7de 100644
--- a/core/lib.rs
+++ b/core/lib.rs
@@ -3,7 +3,7 @@ mod async_cancel;
 mod async_cell;
 mod bindings;
 pub mod error;
-mod extensions;
+pub mod extensions;
 mod flags;
 mod gotham_state;
 mod module_specifier;