Add subshell to hide resource monitor (#5091)

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

src/toil/test/wdl/testfiles/wait.wdl

@@ -0,0 +1,34 @@
+version 1.0
+
+workflow wait {
+    input {
+    }
+
+    call waiter_task {
+    input:
+    }
+
+    output {
+        String result = read_lines(waiter_task.out)[0]
+    }
+}
+
+task waiter_task {
+    input {
+    }
+
+    command <<<
+        sleep 10 &
+        sleep 2 &
+        wait
+        echo "waited"
+    >>>
+
+    output {
+        File out = stdout()
+    }
+
+    runtime {
+        docker: "ubuntu:22.04"
+    }
+}

src/toil/test/wdl/wdltoil_test.py

@@ -17,6 +17,7 @@
 from toil.fileStores import FileID
 from toil.provisioners import cluster_factory
 from toil.test import (ToilTest,
+                       needs_docker,
                        needs_docker_cuda,
                        needs_google_storage,
                        needs_singularity_or_docker,
@@ -165,6 +166,21 @@ def test_url_to_file(self):
         assert 'url_to_file.first_line' in result
         assert isinstance(result['url_to_file.first_line'], str)
         self.assertEqual(result['url_to_file.first_line'], 'chr1\t248387328')
+
+    @needs_docker
+    def test_wait(self):
+        """
+        Test if Bash "wait" works in WDL scripts.
+        """
+        wdl = os.path.abspath('src/toil/test/wdl/testfiles/wait.wdl')
+
+        result_json = subprocess.check_output(
+            self.base_command + [wdl, '-o', self.output_dir, '--logInfo', '--retryCount=0', '--wdlContainer=docker'])
+        result = json.loads(result_json)
+
+        assert 'wait.result' in result
+        assert isinstance(result['wait.result'], str)
+        self.assertEqual(result['wait.result'], 'waited')
 
     def test_url_to_optional_file(self):
         """

src/toil/wdl/wdltoil.py

@@ -2089,7 +2089,8 @@ def add_injections(self, command_string: str, task_container: TaskContainer) ->
                 }
                 """)
             parts.append(script)
-            parts.append(f"_toil_resource_monitor {self.INJECTED_MESSAGE_DIR} &")
+            # Launch in a subshell so that it doesn't interfere with Bash "wait" in the main shell
+            parts.append(f"(_toil_resource_monitor {self.INJECTED_MESSAGE_DIR} &)")
 
         if isinstance(task_container, SwarmContainer) and platform.system() == "Darwin":
             # With gRPC FUSE file sharing, files immediately downloaded before