From 2475a2b7254274cf75444d0cf4587b023d31bfb4 Mon Sep 17 00:00:00 2001
From: mulhern <amulhern@redhat.com>
Date: Mon, 9 Sep 2024 10:38:50 -0400
Subject: [PATCH] Panic if more than one attribute found

In stratisd, we always expect exactly one. If that changes, we'll
probably have to enrich this method somehow.

Signed-off-by: mulhern <amulhern@redhat.com>
---
 stratisd_proc_macros/src/lib.rs | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/stratisd_proc_macros/src/lib.rs b/stratisd_proc_macros/src/lib.rs
index 31c831a5f3..700605f5c6 100644
--- a/stratisd_proc_macros/src/lib.rs
+++ b/stratisd_proc_macros/src/lib.rs
@@ -228,16 +228,23 @@ fn get_attr_level(attrs: &mut Vec<Attribute>) -> Option<Ident> {
 
 /// Determine whether a method has the given attribute.
 fn has_attribute(attrs: &mut Vec<Attribute>, attribute: &str) -> bool {
-    if let Some((index, _)) = attrs
+    let matching_attrs = attrs
         .iter()
         .enumerate()
         .filter(|(_, a)| a.path().is_ident(attribute))
-        .last()
-    {
-        attrs.remove(index);
-        true
-    } else {
-        false
+        .collect::<Vec<_>>();
+
+    match matching_attrs.len() {
+        0 => false,
+        1 => {
+            let (index, _) = matching_attrs[0];
+            attrs.remove(index);
+            true
+        }
+        _ => panic!(
+            "More than 1 {} attribute specified for the same syntactic entity.",
+            attribute
+        ),
     }
 }