Fix NodeJS retrieval when Docker is unavailable

Fix #1053 by adding `_get_container_engine()` to detect the available
container runtime by probing `docker`, `singularity`, `podman`, and
`udocker` in order, caching the result with `@cached(FIFOCache(1))`
from `cachebox`. The detected engine is passed as `container_engine`
to `cwl_utils.expression.interpolate()` in `eval_expression()`,
fixing CWL JavaScript expression evaluation on systems without Docker.

Author: GlassOfWhiskey

streamflow/cwl/utils.py

@@ -8,13 +8,15 @@
 from collections.abc import MutableMapping, MutableSequence
 from enum import Enum
 from pathlib import PurePath
+from shutil import which
 from types import ModuleType
 from typing import Any, cast
 
 import cwl_utils.expression
 import cwl_utils.parser
 import cwl_utils.parser.utils
 import cwl_utils.types
+from cachebox import FIFOCache, cached
 from cwl_utils.parser.cwl_v1_2_utils import CONTENT_LIMIT
 from typing_extensions import Self, TypeIs
 
@@ -113,6 +115,14 @@ async def _create_remote_directory(
         )
 
 
+@cached(cache=FIFOCache(1))
+def _get_container_engine() -> str:
+    for engine in ("docker", "singularity", "podman", "udocker"):
+        if which(engine) is not None:
+            return engine
+    return "docker"
+
+
 async def _get_contents(
     path: StreamFlowPath,
     size: int,
@@ -740,6 +750,7 @@ def eval_expression(
             fullJS=full_js,
             strip_whitespace=strip_whitespace,
             timeout=timeout,
+            container_engine=_get_container_engine(),
         )
         if is_expression(expression)
         else expression