Make tests and code agree on missing version behavior

src/toil/lib/trs.py

@@ -106,6 +106,8 @@ def find_workflow(workflow: str, supported_languages: Optional[set[str]] = None)
     TODO: Needs to handle multi-workflow files if Dockstore can.
 
     :raises FileNotFoundError: if the workflow or version doesn't exist.
+    :raises ValueError: if the version is not specified but cannot be
+        automatically determined. 
     """
 
     if supported_languages is not None and len(supported_languages) == 0:
@@ -172,6 +174,7 @@ def find_workflow(workflow: str, supported_languages: Optional[set[str]] = None)
     problem_type: type[Exception] = RuntimeError
     if trs_version is None:
         problems.append(f"Workflow {workflow} does not specify a version")
+        problem_type = ValueError
     elif trs_version not in workflow_versions:
         problems.append(f"Workflow version {trs_version} from {workflow} does not exist")
         problem_type = FileNotFoundError

src/toil/test/lib/test_trs.py

@@ -61,14 +61,26 @@ def test_lookup_from_page_url(self) -> None:
         self.assertEqual(trs_version, "master")
         self.assertEqual(language, "WDL")
 
-    def test_lookup_from_trs(self) -> None:
+    def test_lookup_from_trs_with_version(self) -> None:
         TRS_ID = "#workflow/github.com/dockstore-testing/md5sum-checker"
-        trs_id, trs_version, language = find_workflow(TRS_ID)
+        TRS_VERSION = "master"
+        trs_id, trs_version, language = find_workflow(f"{TRS_ID}:{TRS_VERSION}")
 
         self.assertEqual(trs_id, TRS_ID)
-        self.assertEqual(trs_version, "master")
+        self.assertEqual(trs_version, TRS_VERSION)
         self.assertEqual(language, "CWL")
 
+    def test_lookup_from_trs_no_version(self) -> None:
+        TRS_ID = "#workflow/github.com/dockstore-testing/md5sum-checker"
+        with pytest.raises(ValueError):
+            # We don't yet have a way to read Dockstore's default version info,
+            # so it's not safe to apply any default version when multiple
+            # versions exist.
+            trs_id, trs_version, language = find_workflow(TRS_ID)
+
+    # TODO: Add a test with a workflow that we know has and will only ever
+    # have one version, to test version auto-detection in that case.
+
     def test_get(self) -> None:
         TRS_ID = "#workflow/github.com/dockstore-testing/md5sum-checker"
         TRS_VERSION = "master"