chore: Add a way to extract Fluent launch command and subprocess arguments from StandaloneLauncher

doc/changelog.d/4028.maintenance.md

@@ -0,0 +1 @@
+Add a way to extract Fluent launch command and subprocess arguments from StandaloneLauncher

src/ansys/fluent/core/launcher/launcher.py

@@ -312,8 +312,6 @@ def launch_fluent(
     The allocated machines and core counts are queried from the scheduler environment and
     passed to Fluent.
     """
-    if env is None:
-        env = {}
 
     def _mode_to_launcher_type(fluent_launch_mode: LaunchMode):
         launcher_mode_type = {

src/ansys/fluent/core/launcher/slurm_launcher.py

@@ -416,6 +416,7 @@ def __init__(
         """
         if not _SlurmWrapper.is_available():
             raise RuntimeError("Slurm is not available.")
+        env = env or {}
         locals_ = locals().copy()
         argvals = {
             arg: locals_.get(arg)

src/ansys/fluent/core/launcher/standalone_launcher.py

@@ -40,7 +40,7 @@
 import os
 from pathlib import Path
 import subprocess
-from typing import Any, Dict
+from typing import Any
 
 from ansys.fluent.core.launcher.error_handler import (
     LaunchFluentError,
@@ -91,7 +91,7 @@ def __init__(
         journal_file_names: None | str | list[str] = None,
         start_timeout: int = 60,
         additional_arguments: str = "",
-        env: Dict[str, Any] | None = None,
+        env: dict[str, Any] | None = None,
         cleanup_on_exit: bool = True,
         dry_run: bool = False,
         start_transcript: bool = True,
@@ -184,7 +184,7 @@ def __init__(
         In job scheduler environments (e.g., SLURM, LSF, PBS), resources and compute nodes are allocated,
         and core counts are queried from these environments before being passed to Fluent.
         """
-        import ansys.fluent.core as pyfluent
+        env = env or {}
 
         locals_ = locals().copy()
         argvals = {
@@ -234,6 +234,8 @@ def __init__(
         )
 
         if is_windows():
+            import ansys.fluent.core as pyfluent
+
             if pyfluent.LAUNCH_FLUENT_STDOUT or pyfluent.LAUNCH_FLUENT_STDERR:
                 self._launch_cmd = self._launch_string
             else:
@@ -246,6 +248,16 @@ def __init__(
             else:
                 self._launch_cmd = self._launch_string
 
+    @property
+    def command(self) -> str:
+        """Return the command for launching Fluent."""
+        return self._launch_string
+
+    @property
+    def subprocess_keywords(self) -> dict[str, Any]:
+        """Return the keyword arguments for launching Fluent via Python subprocess."""
+        return self._kwargs
+
     def __call__(self):
         if self.argvals["dry_run"]:
             print(f"Fluent launch string: {self._launch_string}")