reword error message for unresolved template values + add dedicated t…

…est to check on resolving of template values

easybuild/framework/easyconfig/easyconfig.py

@@ -2075,8 +2075,8 @@ def resolve_template(value, tmpl_dict, expect_resolved=True):
                                             ver)
                 except KeyError:
                     if expect_resolved:
-                        msg = ('Failed to resolve template value %s with dict %s. ' % (value, tmpl_dict) +
-                               'This might cause failures or unexpected behavior, ' +
+                        msg = (f'Failed to resolve all templates in "{value}" using template dictionary: {tmpl_dict}. '
+                               'This might cause failures or unexpected behavior, '
                                'check for correct escaping if this is intended!')
                         if build_option('allow_unresolved_templates'):
                             print_warning(msg)

test/framework/easyconfig.py

@@ -5148,6 +5148,43 @@ def test_easyconfigs_caches(self):
         regex = re.compile(r"libtoy/0\.0 is already installed", re.M)
         self.assertTrue(regex.search(stdout), "Pattern '%s' should be found in: %s" % (regex.pattern, stdout))
 
+    def test_templates(self):
+        """
+        Test use of template values like %(version)s
+        """
+        test_ecs_dir = os.path.join(os.path.dirname(os.path.abspath(__file__)), 'easyconfigs', 'test_ecs')
+        toy_ec = os.path.join(test_ecs_dir, 't', 'toy', 'toy-0.0.eb')
+
+        test_ec_txt = read_file(toy_ec)
+        test_ec_txt += '\ndescription = "name: %(name)s, version: %(version)s"'
+
+        test_ec = os.path.join(self.test_prefix, 'test.eb')
+        write_file(test_ec, test_ec_txt)
+        ec = EasyConfig(test_ec)
+
+        # get_ref provides access to non-templated raw value
+        self.assertEqual(ec.get_ref('description'), "name: %(name)s, version: %(version)s")
+        self.assertEqual(ec['description'], "name: toy, version: 0.0")
+
+        # error when using wrong template value or using template value that can not be resolved yet too early
+        test_ec_txt += '\ndescription = "name: %(name)s, version: %(version)s, pyshortver: %(pyshortver)s"'
+        write_file(test_ec, test_ec_txt)
+        ec = EasyConfig(test_ec)
+
+        self.assertEqual(ec.get_ref('description'), "name: %(name)s, version: %(version)s, pyshortver: %(pyshortver)s")
+        error_pattern = "Failed to resolve all templates in.* %\(pyshortver\)s.* using template dictionary:"
+        self.assertErrorRegex(EasyBuildError, error_pattern, ec.__getitem__, 'description')
+
+        # EasyBuild can be configured to allow unresolved templates
+        update_build_option('allow_unresolved_templates', True)
+        self.assertEqual(ec.get_ref('description'), "name: %(name)s, version: %(version)s, pyshortver: %(pyshortver)s")
+        with self.mocked_stdout_stderr() as (stdout, stderr):
+            self.assertEqual(ec['description'], "name: %(name)s, version: %(version)s, pyshortver: %(pyshortver)s")
+
+            self.assertFalse(stdout.getvalue())
+            regex = re.compile(r"WARNING: Failed to resolve all templates.* %\(pyshortver\)s", re.M)
+            self.assertRegex(stderr.getvalue(), regex)
+
 
 def suite():
     """ returns all the testcases in this module """