Core: Reject an unknown map type instead of silently emitting a hash map

process_bpf_map logged a warning and fell back to process_hash_map for any map
type it did not recognise. That turns a typo into an object file that compiles
cleanly, carries the wrong BPF_MAP_TYPE, skips the intended map type's
parameter validation entirely, and is only rejected once it reaches the kernel
-- as tests/passing_tests/ringbuf.py was, with 'failed to create: -EINVAL'.

A warning was not enough to surface it either: the test framework only fails a
test on logging.ERROR records.

Raise instead, naming the registered map types so the fix is obvious:

    ValueError: Unknown map type 'RingBuf' returned by 'm'.
    Known map types: HashMap, PerfEventArray, RingBuffer

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: r41k0u

pythonbpf/maps/maps_pass.py

@@ -175,10 +175,16 @@ def process_bpf_map(func_node, compilation_context):
 
     if isinstance(rval, ast.Call) and isinstance(rval.func, ast.Name):
         handler = MapProcessorRegistry.get_processor(rval.func.id)
-        if handler:
-            return handler(map_name, rval, compilation_context)
-        else:
-            logger.warning(f"Unknown map type {rval.func.id}, defaulting to HashMap")
-            return process_hash_map(map_name, rval, compilation_context)
+        if handler is None:
+            # Falling back to a hash map here used to produce an object that
+            # compiled cleanly and was then rejected by the kernel, because the
+            # map carried the wrong type and none of the real map type's
+            # validation ran. A misspelled map type is a program error.
+            known = ", ".join(sorted(MapProcessorRegistry.known_types()))
+            raise ValueError(
+                f"Unknown map type '{rval.func.id}' returned by '{map_name}'. "
+                f"Known map types: {known}"
+            )
+        return handler(map_name, rval, compilation_context)
     else:
         raise ValueError("Function under @map must return a map")

pythonbpf/maps/maps_utils.py

@@ -33,3 +33,8 @@ def decorator(func):
     def get_processor(cls, map_type_name):
         """Get the processor function for a map type"""
         return cls._processors.get(map_type_name)
+
+    @classmethod
+    def known_types(cls):
+        """Names of every registered map type, for error messages"""
+        return list(cls._processors)