fix: use bash parameter expansion for SFN resume CLI opts

The $(if ...) construct with double-quoted variables caused
shlex.split in batch.py's _command() to split the bash -c
string incorrectly, breaking all SFN deployer runs.

Switch to ${VAR:+...} parameter expansion (matching the Argo
implementation) to avoid quoting issues.

Author: Nissan Pow

metaflow/plugins/aws/step_functions/step_functions.py

@@ -1064,7 +1064,18 @@ def _step_cli(self, node, paths, code_package_url, user_code_retries):
             step.extend("--tag %s" % tag for tag in self.tags)
         if self.namespace is not None:
             step.append("--namespace=%s" % self.namespace)
-        cmds.append(" ".join(entrypoint + top_level + step))
+        # Build the step command, then append resume options that are only
+        # included when the env vars are non-empty (normal triggers set them
+        # to empty strings).  We use bash parameter expansion ${VAR:+...}
+        # instead of $(if ...) to avoid double-quote issues with shlex.split
+        # in batch.py's _command().
+        step_cmd = " ".join(entrypoint + top_level + step)
+        resume_opts = (
+            "${METAFLOW_RESUME_ORIGIN_RUN_ID:+"
+            "--resume-origin-run-id $METAFLOW_RESUME_ORIGIN_RUN_ID "
+            "--resume-steps-to-rerun $METAFLOW_RESUME_STEPS_TO_RERUN}"
+        )
+        cmds.append("%s %s" % (step_cmd, resume_opts))
         return " && ".join(cmds)