only allow valid python identifiers as resource names

See #436

cate/core/workspace.py

@@ -486,6 +486,7 @@ def delete_resource(self, res_name: str):
                 del self._resource_cache[res_name]
 
     def rename_resource(self, res_name: str, new_res_name: str) -> None:
+        Workspace._validate_res_name(new_res_name)
         with self._lock:
             res_step = self.workflow.find_node(res_name)
             if res_step is None:
@@ -533,6 +534,7 @@ def set_resource(self,
                 default_res_pattern = conf.get_default_res_pattern()
                 res_pattern = op.op_meta_info.header.get('res_pattern', default_res_pattern)
                 res_name = self._new_resource_name(res_pattern)
+            Workspace._validate_res_name(res_name)
 
             new_step = OpStep(op, node_id=res_name)
 
@@ -656,6 +658,15 @@ def _assert_open(self):
     def _new_resource_name(self, res_pattern):
         return new_indexed_name({step.id for step in self.workflow.steps}, res_pattern)
 
+    @staticmethod
+    def _validate_res_name(res_name: str):
+        if not res_name.isidentifier():
+            raise WorkspaceError(
+                "Resource name '%s' is not valid. "
+                "The name must only contain the uppercase and lowercase letters A through Z, the underscore _ and, "
+                "except for the first character, the digits 0 through 9." % res_name)
+
+
 
 # noinspection PyArgumentList
 class WorkspaceError(Exception):

test/core/test_workspace.py

@@ -8,7 +8,7 @@
 import xarray as xr
 
 from cate.core.workflow import Workflow, OpStep
-from cate.core.workspace import Workspace, mk_op_arg, mk_op_args, mk_op_kwargs
+from cate.core.workspace import Workspace, WorkspaceError, mk_op_arg, mk_op_args, mk_op_kwargs
 from cate.util import UNDEFINED
 from cate.util.opmetainf import OpMetaInfo
 
@@ -304,6 +304,23 @@ def set_resource_and_execute():
         expected_res_names = {'res_%s' % (i + 1) for i in range(num_res)}
         self.assertEqual(actual_res_names, expected_res_names)
 
+    def test_validate_res_name(self):
+        Workspace._validate_res_name("a")
+        Workspace._validate_res_name("A")
+        Workspace._validate_res_name("abc_42")
+        Workspace._validate_res_name("abc42")
+        Workspace._validate_res_name("_abc42")
+        # with self.assertRaises(WorkspaceError):
+        #     Workspace._validate_res_name("0")
+        with self.assertRaises(WorkspaceError):
+            Workspace._validate_res_name("a-b")
+        with self.assertRaises(WorkspaceError):
+            Workspace._validate_res_name("a+b")
+        with self.assertRaises(WorkspaceError):
+            Workspace._validate_res_name("a.b")
+        with self.assertRaises(WorkspaceError):
+            Workspace._validate_res_name("file://path")
+
     def test_example(self):
         expected_json_text = """{
             "schema_version": 1,