Add "args" and "env" parameters to DAP launch request

This patch augments the DAP launch request with some optional new
parameters that let the client control the command-line arguments and
the environment of the inferior.

Reviewed-By: Andrew Burgess <aburgess@redhat.com>
Reviewed-By: Eli Zaretskii <eliz@gnu.org>

gdb/python/lib/gdb/dap/launch.py

@@ -13,20 +13,36 @@
 # 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 .events import ExecutionInvoker
 from .server import request, capability
-from .startup import send_gdb
+from .startup import send_gdb, in_gdb_thread
 
 
 _program = None
 
 
+@in_gdb_thread
+def _set_args_env(args, env):
+    inf = gdb.selected_inferior()
+    inf.arguments = args
+    if env is not None:
+        inf.clear_env()
+        for name, value in env.items():
+            inf.set_env(name, value)
+
+
+# Any parameters here are necessarily extensions -- DAP requires this
+# from implementations.  Any additions or changes here should be
+# documented in the gdb manual.
 @request("launch")
-def launch(*, program=None, **args):
+def launch(*, program=None, args=[], env=None, **extra):
     if program is not None:
         global _program
         _program = program
         send_gdb(f"file {_program}")
+    if len(args) > 0 or env is not None:
+        send_gdb(lambda: _set_args_env(args, env))
 
 
 @capability("supportsConfigurationDoneRequest")