from typing import Optional
 
 from .server import capability, request
+from .sources import decode_source
 from .startup import in_gdb_thread, send_gdb_with_response
 
 
 @in_gdb_thread
-def _find_lines(filename, start_line, end_line):
+def _find_lines(source, start_line, end_line):
+    filename = decode_source(source)
     lines = set()
     for entry in gdb.execute_mi("-symbol-list-lines", filename)["lines"]:
         line = entry["line"]
 def breakpoint_locations(*, source, line: int, endLine: Optional[int] = None, **extra):
     if endLine is None:
         endLine = line
-    if "path" in source:
-        filename = source["path"]
-    elif "name" in source:
-        filename = source["name"]
-    else:
-        raise Exception("")
-    return send_gdb_with_response(lambda: _find_lines(filename, line, endLine))
+    return send_gdb_with_response(lambda: _find_lines(source, line, endLine))
 
     return result
 
 
+@in_gdb_thread
+def decode_source(source):
+    """Decode a Source object.
+
+    Finds and returns the filename of a given Source object."""
+    if "path" in source:
+        return source["path"]
+    if "sourceReference" not in source:
+        raise Exception("either 'path' or 'sourceReference' must appear in Source")
+    ref = source["sourceReference"]
+    global _id_map
+    if ref not in _id_map:
+        raise Exception("no sourceReference " + str(ref))
+    return _id_map[ref]["path"]
+
+
 @in_gdb_thread
 def _sources():
     result = []