Add GK check to see if we should allow preempting

Summary:
The previous diff added logic around figuring out if we should retry a type check if it was preempted.

With that logic present, this diff adds logic to check a gatekeeper and see if we should allow the preemptible flag to be passed to the subprocess call.

Along with that, we need to make sure any time we type check in the default isolation directory, we **always** use the preemptible flag. We should never block user buck operations because of an IDE type check. This should be handled by the GK,  but there's also going to be an extra check here to make sure we don't accidentally mess this up and cause issues.

Reviewed By: grievejia

Differential Revision: D64979502

fbshipit-source-id: 600e6b510740f6d65a48fcd004f5628a0c2b246e

client/commands/pyre_language_server.py

@@ -730,14 +730,20 @@ async def _query_buck_for_type_errors(
                 file=argfile,
             )
             argfile.flush()
+            if (
+                self.get_language_server_features().type_errors_preemptible.is_enabled()
+                or self.get_language_server_features().per_target_isolation_dir.is_disabled()
+            ):
+                preemptible = [
+                    "--preemptible=ondifferentstate",
+                ]
+            else:
+                preemptible = []
             if self.get_language_server_features().per_target_isolation_dir.is_enabled():
                 isolation_dir = [f"--isolation-dir={PTT_ISOLATION_PREFIX}"]
-                preemptible = []
             else:
                 isolation_dir = []
-                preemptible = [
-                    "--preemptible=ondifferentstate",
-                ]
+
             type_check_parameters = [
                 "buck2",
                 *isolation_dir,
@@ -1016,6 +1022,10 @@ async def handle_overlay_type_errors(
                     "new_file_loaded": new_file_loaded,
                     "isolation_dir": isolation_dir,
                     "sharding_enabled": self.get_language_server_features().type_error_sharding.is_enabled(),
+                    "preemptible": (
+                        self.get_language_server_features().type_errors_preemptible.is_enabled()
+                        or self.get_language_server_features().per_target_isolation_dir.is_disabled()
+                    ),
                 },
                 **daemon_status_before.as_telemetry_dict(),
             },

client/language_server/features.py

@@ -100,6 +100,7 @@ def is_disabled(self) -> bool:
 PerTargetTypeErrorsAvailability = CustomAvailability
 PerTargetIsolationDirAvailability = CustomAvailability
 TypeErrorShardingAvailability = CustomAvailability
+TypeErrorsPreemptibleAvailability = CustomAvailability
 PythonAutoTargetsAvailability = CustomAvailability
 SystemPyAutoTargetsAvailability = CustomAvailability
 # TODO: T204372341 remove this once we have rolled out addition and removal features
@@ -127,6 +128,9 @@ class LanguageServerFeatures:
     type_error_sharding: TypeErrorShardingAvailability = (
         TypeErrorShardingAvailability.from_enabled(False)
     )
+    type_errors_preemptible: TypeErrorsPreemptibleAvailability = (
+        TypeErrorsPreemptibleAvailability.from_enabled(False)
+    )
     unsaved_changes: UnsavedChangesAvailability = UnsavedChangesAvailability.DISABLED
     telemetry: TelemetryAvailability = TelemetryAvailability.DISABLED
     completion: CompletionAvailability = CompletionAvailability.DISABLED