Parse and apply "python" / "pythonPath" in the adapter rather than in…

… the launcher.

Fix errors with missing "args".

Add test for "pythonPath".

src/debugpy/adapter/clients.py

@@ -9,7 +9,7 @@
 
 import debugpy
 from debugpy import adapter, launcher
-from debugpy.common import fmt, json, log, messaging, sockets
+from debugpy.common import compat, fmt, json, log, messaging, sockets
 from debugpy.common.compat import unicode
 from debugpy.adapter import components, servers, sessions
 
@@ -272,6 +272,21 @@ def property_or_debug_option(prop_name, flag_name):
 
             return value
 
+        # "pythonPath" is a deprecated legacy spelling. If "python" is missing, then try
+        # the alternative. But if both are missing, the error message should say "python".
+        python_key = "python"
+        if python_key in request:
+            if "pythonPath" in request:
+                raise request.isnt_valid(
+                    '"pythonPath" is not valid if "python" is specified'
+                )
+        elif "pythonPath" in request:
+            python_key = "pythonPath"
+        python = request(python_key, json.array(unicode, vectorize=True, size=(0,)))
+        if not len(python):
+            python = [compat.filename(sys.executable)]
+        request.arguments["pythonArgs"] = python[1:]
+
         program = module = code = ()
         if "program" in request:
             program = request("program", unicode)
@@ -300,7 +315,7 @@ def property_or_debug_option(prop_name, flag_name):
         args_expansion = request("argsExpansion", json.enum("shell", "none", optional=True))
         if args_expansion == "shell":
             args += request("args", json.array(unicode))
-            del request.arguments["args"]
+            request.arguments.pop("args", None)
 
         cwd = request("cwd", unicode, optional=True)
         if cwd == ():
@@ -330,6 +345,7 @@ def property_or_debug_option(prop_name, flag_name):
         launchers.spawn_debuggee(
             self.session,
             request,
+            python,
             launcher_path,
             adapter_host,
             args,
@@ -537,8 +553,9 @@ def notify_of_subprocess(self, conn):
         body["name"] = fmt("Subprocess {0}", conn.pid)
         body["request"] = "attach"
         body["subProcessId"] = conn.pid
-        body.pop("processName", None)
-        body.pop("args", None)
+
+        for key in "args", "processName", "pythonArgs":
+            body.pop(key, None)
 
         host = body.pop("host", None)
         port = body.pop("port", None)

src/debugpy/adapter/launchers.py

@@ -68,6 +68,7 @@ def terminate_debuggee(self):
 def spawn_debuggee(
     session,
     start_request,
+    python,
     launcher_path,
     adapter_host,
     args,
@@ -79,7 +80,8 @@ def spawn_debuggee(
     # -E tells sudo to propagate environment variables to the target process - this
     # is necessary for launcher to get DEBUGPY_LAUNCHER_PORT and DEBUGPY_LOG_DIR.
     cmdline = ["sudo", "-E"] if sudo else []
-    cmdline += [sys.executable, launcher_path]
+    cmdline += python
+    cmdline += [launcher_path]
     env = {}
 
     arguments = dict(start_request.arguments)

src/debugpy/launcher/handlers.py

@@ -39,19 +39,8 @@ def property_or_debug_option(prop_name, flag_name):
 
         return value
 
-    # "pythonPath" is a deprecated legacy spelling. If "python" is missing, then try
-    # the alternative. But if both are missing, the error message should say "python".
-    python_key = "python"
-    if python_key in request:
-        if "pythonPath" in request:
-            raise request.isnt_valid(
-                '"pythonPath" is not valid if "python" is specified'
-            )
-    elif "pythonPath" in request:
-        python_key = "pythonPath"
-    cmdline = request(python_key, json.array(unicode, vectorize=True, size=(0,)))
-    if not len(cmdline):
-        cmdline = [compat.filename(sys.executable)]
+    python_args = request("pythonArgs", json.array(unicode, vectorize=True, size=(0,)))
+    cmdline = [compat.filename(sys.executable)] + python_args
 
     if not request("noDebug", json.default(False)):
         port = request("port", int)

tests/debug/runners.py

@@ -331,12 +331,9 @@ def spawn_debuggee(occ):
 attach_listen.host = "127.0.0.1"
 attach_listen.port = net.get_test_server_port(5478, 5600)
 
+all_launch_terminal = [launch["integratedTerminal"], launch["externalTerminal"]]
 
-all_launch = [
-    launch["internalConsole"],
-    launch["integratedTerminal"],
-    launch["externalTerminal"],
-]
+all_launch = [launch["internalConsole"]] + all_launch_terminal
 
 all_attach_listen = [attach_listen["api"], attach_listen["cli"]]
 

tests/debugpy/test_run.py

@@ -135,3 +135,30 @@ def code_to_debug():
         # The launcher, however, should use our dummy sudo to spawn the debuggee,
         # and the debuggee should report the environment variable accordingly.
         assert backchannel.receive() == "1"
+
+
+@pytest.mark.parametrize("run", runners.all_launch_terminal)
+def test_custom_python(pyfile, run, target):
+    @pyfile
+    def code_to_debug():
+        import sys
+        import debuggee
+        from debuggee import backchannel
+
+        debuggee.setup()
+        backchannel.send(sys.executable)
+
+    class Session(debug.Session):
+        def run_in_terminal(self, args, cwd, env):
+            assert args[:2] == ["CUSTOMPY", "-O"]
+            args[0] = sys.executable
+            return super(Session, self).run_in_terminal(args, cwd, env)
+
+    with Session() as session:
+        session.config["pythonPath"] = ["CUSTOMPY", "-O"]
+
+        backchannel = session.open_backchannel()
+        with run(session, target(code_to_debug)):
+            pass
+
+        assert backchannel.receive() == sys.executable