make sure that specified easyblock can be used to install extensions (should derive from Extension class)

Author: boegel

easybuild/framework/easyblock.py

@@ -61,7 +61,7 @@
 from easybuild.framework.easyconfig.style import MAX_LINE_LENGTH
 from easybuild.framework.easyconfig.tools import get_paths_for
 from easybuild.framework.easyconfig.templates import TEMPLATE_NAMES_EASYBLOCK_RUN_STEP, template_constant_dict
-from easybuild.framework.extension import resolve_exts_filter_template
+from easybuild.framework.extension import Extension, resolve_exts_filter_template
 from easybuild.tools import config, run
 from easybuild.tools.build_details import get_build_stats
 from easybuild.tools.build_log import EasyBuildError, dry_run_msg, dry_run_warning, dry_run_set_dirs
@@ -2317,8 +2317,13 @@ def init_ext_instances(self):
                 # with a similar name (e.g., Perl Extension 'GO' vs 'Go' for which 'EB_Go' is available)
                 cls = get_easyblock_class(easyblock, name=ext_name, error_on_failed_import=False,
                                           error_on_missing_easyblock=False)
+
                 self.log.debug("Obtained class %s for extension %s", cls, ext_name)
                 if cls is not None:
+                    # make sure that this easyblock can be used to install extensions
+                    if not issubclass(cls, Extension):
+                        raise EasyBuildError("%s easyblock can not be used to install extensions!", cls.__name__)
+
                     inst = cls(self, ext)
             except (ImportError, NameError) as err:
                 self.log.debug("Failed to use extension-specific class for extension %s: %s", ext_name, err)

test/framework/easyblock.py

@@ -1017,6 +1017,18 @@ def test_init_extensions(self):
         ]
         self.assertEqual(ext_inst_class_names, expected)
 
+        # check what happen if we specify an easyblock that doesn't derive from Extension,
+        # and hence can't be used to install extensions...
+        test_ec = os.path.join(self.test_prefix, 'test_broken.eb')
+        test_ec_txt = test_ec_txt.replace('DummyExtension', 'ConfigureMake')
+        write_file(test_ec, test_ec_txt)
+        ec = process_easyconfig(test_ec)[0]
+        eb = get_easyblock_instance(ec)
+
+        eb.prepare_for_extensions()
+        error_pattern = "ConfigureMake easyblock can not be used to install extensions"
+        self.assertErrorRegex(EasyBuildError, error_pattern, eb.init_ext_instances)
+
     def test_skip_extensions_step(self):
         """Test the skip_extensions_step"""