add new emthod unique_ordered_append to easybuild.tools.utilities

Author: lexming

easybuild/tools/utilities.py

@@ -223,6 +223,25 @@ def nub(list_):
     return [x for x in list_ if x not in seen and not seen_add(x)]
 
 
+def unique_ordered_append(base, extra):
+    """Append elements of extra list to another base list keeping order and without duplicates"""
+    if extra and isinstance(extra, str):
+        extra = [extra]
+
+    try:
+        base.extend(extra)
+    except TypeError as err:
+        err_msg = f"_unique_ordered_list_append: given extra list is not iterable: {extra}"
+        raise EasyBuildError(err_msg) from err
+    except AttributeError as err:
+        err_msg = f"_unique_ordered_list_append: given base cannot be extended: {base}"
+        raise EasyBuildError(err_msg) from err
+    else:
+        base = nub(base)  # remove duplicates
+
+    return base
+
+
 def get_class_for(modulepath, class_name):
     """
     Get class for a given Python class name and Python module path.

test/framework/utilities_test.py

@@ -191,6 +191,23 @@ def test_LooseVersion(self):
         self.assertEqual(LooseVersion('2.a').version, [2, 'a'])
         self.assertEqual(LooseVersion('2.a5').version, [2, 'a', 5])
 
+    def test_unique_ordered_append(self):
+        """Test unique_ordered_list_append method"""
+        base = ["potato", "tomato", "orange"]
+
+        reference = ["potato", "tomato", "orange", "apple"]
+        self.assertEqual(tu.unique_ordered_append(base, ["apple"]), reference)
+        self.assertEqual(tu.unique_ordered_append(base, ["apple", "apple"]), reference)
+        self.assertEqual(tu.unique_ordered_append(base, "apple"), reference)
+        self.assertNotEqual(tu.unique_ordered_append(base, "apple"), sorted(reference))
+
+        error_pattern = "given extra list is not iterable"
+        self.assertErrorRegex(EasyBuildError, error_pattern, tu.unique_ordered_append, base, 0)
+
+        base = "potato"
+        error_pattern = "given base cannot be extended"
+        self.assertErrorRegex(EasyBuildError, error_pattern, tu.unique_ordered_append, base, reference)
+
 
 def suite():
     """ return all the tests in this file """