launch: include validation warnings in returned message

In case some warnings are issued when launching a workflow, the `launch`
endpoint will now include them in the returned `message`.
Closes reanahub/reana-client#660.

reana_server/rest/launch.py

@@ -180,7 +180,7 @@ def launch(user, url, name="", parameters="{}", specification=None):
         with load_reana_spec_lock:
             reana_yaml = load_reana_spec(spec_path, workspace_path=tmpdir)
         input_parameters = json.loads(parameters)
-        validate_workflow(reana_yaml, input_parameters)
+        validation_warnings = validate_workflow(reana_yaml, input_parameters)
 
         # Keep only files and directories listed as workflow's inputs
         filter_input_files(tmpdir, reana_yaml)
@@ -218,10 +218,18 @@ def launch(user, url, name="", parameters="{}", specification=None):
         # Start the workflow
         parameters = {"input_parameters": input_parameters}
         publish_workflow_submission(workflow, user.id_, parameters)
+        if validation_warnings:
+            message = (
+                "The workflow has been successfully submitted, but some "
+                "warnings were found during validation. "
+                f"{' '.join([x.message for x in validation_warnings])}"
+            )
+        else:
+            message = "The workflow has been successfully submitted."
         response_data = {
             "workflow_id": workflow.id_,
             "workflow_name": workflow.name,
-            "message": "The workflow has been successfully submitted.",
+            "message": message,
         }
         return LaunchSchema().dump(response_data)
     except HTTPError as e:

reana_server/validation.py

@@ -10,7 +10,7 @@
 
 import itertools
 import pathlib
-from typing import Dict
+from typing import Dict, List
 
 from reana_commons.config import WORKSPACE_PATHS
 from reana_commons.errors import REANAValidationError
@@ -107,7 +107,7 @@ def validate_inputs(reana_yaml: Dict) -> None:
             )
 
 
-def validate_workflow(reana_yaml: Dict, input_parameters: Dict) -> None:
+def validate_workflow(reana_yaml: Dict, input_parameters: Dict) -> List[Exception]:
     """Validate REANA workflow specification by calling all the validation utilities.
 
     :param reana_yaml: dictionary which represents REANA specification file.
@@ -119,12 +119,13 @@ def validate_workflow(reana_yaml: Dict, input_parameters: Dict) -> None:
     operational_options = reana_yaml.get("inputs", {}).get("options", {})
     original_parameters = reana_yaml.get("inputs", {}).get("parameters", {})
 
-    validate_reana_yaml(reana_yaml)
+    reana_yaml_warnings = validate_reana_yaml(reana_yaml)
     validate_operational_options(workflow_type, operational_options)
     validate_input_parameters(input_parameters, original_parameters)
     validate_compute_backends(reana_yaml)
     validate_workspace_path(reana_yaml)
     validate_inputs(reana_yaml)
+    return reana_yaml_warnings
 
 
 def validate_retention_rule(rule: str, days: int) -> None: