Implement DAP loadedSources request

This implements the DAP loadedSources request, using gdb.execute_mi to
avoid having to write another custom Python API.

gdb/python/lib/gdb/dap/__init__.py

@@ -29,6 +29,7 @@ from . import memory
 from . import next
 from . import pause
 from . import scopes
+from . import sources
 from . import threads
 
 from .server import Server

gdb/python/lib/gdb/dap/sources.py

@@ -0,0 +1,40 @@
+# Copyright 2023 Free Software Foundation, Inc.
+
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import gdb
+
+from .server import request, capability
+from .startup import send_gdb_with_response, in_gdb_thread
+
+
+@in_gdb_thread
+def _sources():
+    result = []
+    for elt in gdb.execute_mi("-file-list-exec-source-files")["files"]:
+        result.append(
+            {
+                "name": elt["file"],
+                "path": elt["fullname"],
+            }
+        )
+    return {
+        "sources": result,
+    }
+
+
+@request("loadedSources")
+@capability("supportsLoadedSourcesRequest")
+def sources(**extra):
+    return send_gdb_with_response(_sources)