Fail the query with a helpful message if the variables defined do not match the expected values

CHANGES.md

@@ -48,6 +48,10 @@ compatibility, the `cylc run` command will automatically symlink an existing
 
 ### Enhancements
 
+[#3856](https://github.com/cylc/cylc-flow/pull/3856) - fail the GraphQL query
+with a helpful message if the variables defined do not match the expected
+values.
+
 [#3853](https://github.com/cylc/cylc-flow/pull/3853) - Update protobuf and
 pyzmq.
 

cylc/flow/network/graphql.py

@@ -150,12 +150,29 @@ def __init__(self, schema, document_ast, variable_values):
         for defn in document_ast.definitions:
             if isinstance(defn, ast.OperationDefinition):
                 root_type = get_operation_root_type(schema, defn)
+                definition_variables = defn.variable_definitions or []
+                if definition_variables:
+                    def_var_names = {
+                        v.variable.name.value
+                        for v in definition_variables
+                    }
+                    var_names_diff = def_var_names.difference({
+                        k
+                        for k in variable_values
+                        if k in def_var_names
+                    })
+                    # check if we are missing some of the definition variables
+                    if var_names_diff:
+                        msg = (f'Please check your query variables. The '
+                               f'following variables are missing: '
+                               f'[{", ".join(var_names_diff)}]')
+                        raise ValueError(msg)
                 self.operation_defs[getattr(defn.name, 'value', root_type)] = {
                     'definition': defn,
                     'parent_type': root_type,
                     'variables': get_variable_values(
                         schema,
-                        defn.variable_definitions or [],
+                        definition_variables,
                         variable_values
                     ),
                 }

tests/unit/network/test_graphql.py

@@ -0,0 +1,119 @@
+# THIS FILE IS PART OF THE CYLC SUITE ENGINE.
+# Copyright (C) NIWA & British Crown (Met Office) & Contributors.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from typing import Optional
+
+import pytest
+from graphql import parse
+
+from cylc.flow.network.graphql import AstDocArguments
+from cylc.flow.network.schema import schema
+
+
+@pytest.mark.parametrize(
+    'query,'
+    'variables,'
+    'expected_variables,'
+    'expected_error',
+    [
+        # a simple query with the correct variables
+        (
+            '''
+            query ($workflowID: ID) {
+                workflows (ids: [$workflowID]) {
+                    id
+                }
+            }
+            ''',
+            {
+                'workflowID': 'cylc|workflow'
+            },
+            {
+                'workflowID': 'cylc|workflow'
+            },
+            None
+        ),
+        # a query with a fragment and with the correct variables
+        (
+            '''
+            query ($workflowID: ID) {
+                ...WorkflowData
+            }
+            fragment WorkflowData on workflows {
+                workflows (ids: [$workflowID]) {
+                    id
+                }
+            }
+            ''',
+            {
+                'workflowID': 'cylc|workflow'
+            },
+            {
+                'workflowID': 'cylc|workflow'
+            },
+            None
+        ),
+        # a query with the right variable definition, but missing
+        # variable in the provided values
+        (
+            '''
+            query ($workflowID: ID) {
+                workflows (ids: [$workflowID]) {
+                    id
+                }
+            }
+            ''',
+            {
+                'workflowId': 'cylc|workflow'
+            },
+            None,
+            ValueError
+        )
+    ]
+)
+def test_query_variables(
+        query: str,
+        variables: dict,
+        expected_variables: Optional[dict],
+        expected_error: Optional[Exception]
+):
+    """Test that query variables are parsed correctly.
+
+    Args:
+        query (str): a valid GraphQL query (using our schema)
+        variables (dict): map with variable values for the query
+        expected_variables (dict): expected parsed variables
+        expected_error (Exception): expected error, if any
+    """
+    def test():
+        """Inner function to avoid duplication in if/else"""
+        document = parse(query)
+        document_arguments = AstDocArguments(
+            schema=schema,
+            document_ast=document,
+            variable_values=variables
+        )
+        parsed_variables = next(
+            iter(
+                document_arguments.operation_defs.values()
+            )
+        )['variables']
+        assert expected_variables == parsed_variables
+    if expected_error is not None:
+        with pytest.raises(expected_error):
+            test()
+    else:
+        test()