From 67ca47902d111fae418801d753c7ce232c25c6ec Mon Sep 17 00:00:00 2001
From: christailu <44705085+christailu@users.noreply.github.com>
Date: Mon, 18 Mar 2024 08:10:21 -0500
Subject: [PATCH] Issue warning if SimpleLauncher is used with multiple nodes
 per block (#3177)

This addresses the issue where users could inadvertently attempt to use the SimpleLauncher with multiple nodes per block, which could lead to confusion and unexpected behavior. This enhancement ensures that a warning is raised when users try to use the SimpleLauncher with more than one node per block, unless explicitly permitted.
---
 parsl/launchers/launchers.py | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/parsl/launchers/launchers.py b/parsl/launchers/launchers.py
index 1677325fac..4845284376 100644
--- a/parsl/launchers/launchers.py
+++ b/parsl/launchers/launchers.py
@@ -8,16 +8,14 @@
 class SimpleLauncher(Launcher):
     """ Does no wrapping. Just returns the command as-is
     """
-    def __init_(self, debug: bool = True) -> None:
+    def __init__(self, debug: bool = True) -> None:
         super().__init__(debug=debug)
 
-    def __call__(self, command: str, tasks_per_node: int, nodes_per_block: int) -> str:
-        """
-        Args:
-        - command (string): The command string to be launched
-        - task_block (string) : bash evaluated string.
+    def __call__(self, command: str, tasks_per_node: int, nodes_per_block: int, permit_multiple_nodes: bool = False) -> str:
 
-        """
+        if nodes_per_block > 1 and not permit_multiple_nodes:
+            logger.warning("SimpleLauncher only supports 1 node per block. "
+                           "Set permit_multiple_nodes=True to allow multiple nodes per block.")
         return command