Avoid use of priority in prepend_module_path

Author: Flamefire

easybuild/framework/easyblock.py

@@ -1555,7 +1555,7 @@ def load_fake_module(self, purge=False, extra_modules=None):
         fake_mod_path = self.make_module_step(fake=True)
 
         # load fake module
-        self.modules_tool.prepend_module_path(os.path.join(fake_mod_path, self.mod_subdir), priority=10000)
+        self.modules_tool.prepend_module_path(os.path.join(fake_mod_path, self.mod_subdir))
         self.load_module(purge=purge, extra_modules=extra_modules)
 
         return (fake_mod_path, env)

easybuild/tools/modules.py

@@ -153,6 +153,8 @@ class ModulesTool(object):
     VERSION_REGEXP = None
     # modules tool user cache directory
     USER_CACHE_DIR = None
+    # Priority used to put module paths at the front when priorities are otherwise used
+    HIGH_PRIORITY = 10000
 
     def __init__(self, mod_paths=None, testing=False):
         """
@@ -1473,7 +1475,17 @@ def prepend_module_path(self, path, set_mod_paths=True, priority=None):
         # Lmod pushes a path to the front on 'module use', no need for (costly) 'module unuse'
         modulepath = curr_module_paths()
         if not modulepath or os.path.realpath(modulepath[0]) != os.path.realpath(path):
+            # If no explicit priority is set, but priorities are already in use we need to use a high
+            # priority to make sure the path (very likely) ends up at the front
+            if priority is None and os.environ.get('__LMOD_Priority_MODULEPATH'):
+                priority = self.HIGH_PRIORITY
             self.use(path, priority=priority)
+            modulepath = curr_module_paths(clean=False)
+            path_idx = modulepath.index(path)
+            if path_idx != 0:
+                self.log.warn("Path '%s' could not be prepended to $MODULEPATH. The following paths have a higher "
+                              "priority: %s'",
+                              path, "; ".join(modulepath[:path_idx]))
             if set_mod_paths:
                 self.set_mod_paths()
 

test/framework/modules.py

@@ -620,8 +620,14 @@ def test_prepend_module_path(self):
         if isinstance(self.modtool, Lmod):
             self.modtool.prepend_module_path(test_path_1)
             modulepath = curr_module_paths()
-            self.assertEqual(test_path_0, modulepath[0])
+            self.assertEqual(test_path_1, modulepath[0])
+            self.assertEqual(test_path_0, modulepath[1])
+            test_path_2 = tempfile.mkdtemp(suffix='path_2')
+            self.modtool.prepend_module_path(test_path_2)
+            modulepath = curr_module_paths()
+            self.assertEqual(test_path_2, modulepath[0])
             self.assertEqual(test_path_1, modulepath[1])
+            self.assertEqual(test_path_0, modulepath[2])
 
     def test_ld_library_path(self):
         """Make sure LD_LIBRARY_PATH is what it should be when loaded multiple modules."""