fix: don't increment registry keys unless {incr} is present

beet/toolchain/generator.py

@@ -44,18 +44,20 @@ def get_prefix(self, separator: str = ".") -> str:
             if part and isinstance(part, str)
         )
 
-    def format(self, fmt: str, hash: Optional[StableHashable] = None) -> str:
-        """Generate a unique key depending on the given template."""
-        key = (self.ctx.project_name, *self.scope, fmt)
-
+    def get_increment(self, *key: Any) -> int:
+        """Return the current value for the given key and increment it."""
+        key = (self.ctx.project_name, *self.scope, *key)
         count = self.registry[key]
         self.registry[key] += 1
+        return count
 
+    def format(self, fmt: str, hash: Optional[StableHashable] = None) -> str:
+        """Generate a unique key depending on the given template."""
         env = {
             "namespace": self.ctx.meta.get("generate_namespace", self.ctx.project_name),
             "path": LazyFormat(lambda: self.get_prefix("/")),
             "scope": LazyFormat(lambda: self.get_prefix()),
-            "incr": count,
+            "incr": LazyFormat(lambda: self.get_increment(fmt)),
         }
 
         if hash is not None: