Use one argument 'module swap' statements in Tcl modulefiles (required by Modules 4.2.3+)

easybuild/tools/module_generator.py

@@ -962,7 +962,12 @@ def swap_module(self, mod_name_out, mod_name_in, guarded=True):
         :param mod_name_in: name of module to load (swap in)
         :param guarded: guard 'swap' statement, fall back to 'load' if module being swapped out is not loaded
         """
-        body = "module swap %s %s" % (mod_name_out, mod_name_in)
+        # In Modules 4.2.3+ a 2-argument swap 'module swap foo foo/X.Y.Z' will fail as the unloaded 'foo'
+        # means all 'foo' modules conflict and 'foo/X.Y.Z' will not load.  A 1-argument swap like
+        # 'module swap foo/X.Y.Z' will unload any currently loaded 'foo' without it becoming conflicting
+        # and successfully load the new module.
+        # See: https://modules.readthedocs.io/en/latest/NEWS.html#modules-4-2-3-2019-03-23
+        body = "module swap %s" % (mod_name_in)
         if guarded:
             alt_body = self.LOAD_TEMPLATE % {'mod_name': mod_name_in}
             swap_statement = [self.conditional_statement(self.is_loaded(mod_name_out), body, else_body=alt_body)]

test/framework/module_generator.py

@@ -44,7 +44,7 @@
 from easybuild.framework.easyblock import EasyBlock
 from easybuild.framework.easyconfig.easyconfig import EasyConfig, ActiveMNS
 from easybuild.tools.build_log import EasyBuildError
-from easybuild.tools.modules import EnvironmentModulesC, Lmod
+from easybuild.tools.modules import EnvironmentModulesC, EnvironmentModulesTcl, Lmod
 from easybuild.tools.utilities import quote_str
 from test.framework.utilities import EnhancedTestCase, TestLoaderFiltered, find_full_path, init_config
 
@@ -610,7 +610,7 @@ def test_swap(self):
         if self.MODULE_GENERATOR_CLASS == ModuleGeneratorTcl:
             expected = '\n'.join([
                 '',
-                "module swap foo bar",
+                "module swap bar",
                 '',
             ])
         else:
@@ -627,7 +627,7 @@ def test_swap(self):
             expected = '\n'.join([
                 '',
                 "if { [ is-loaded foo ] } {",
-                "    module swap foo bar",
+                "    module swap bar",
                 '} else {',
                 "    module load bar",
                 '}',
@@ -647,6 +647,24 @@ def test_swap(self):
         self.assertEqual(expected, self.modgen.swap_module('foo', 'bar', guarded=True))
         self.assertEqual(expected, self.modgen.swap_module('foo', 'bar'))
 
+        # create tiny test Tcl module to make sure that tested modules tools support single-argument swap
+        # see https://github.com/easybuilders/easybuild-framework/issues/3396;
+        # this is known to fail with the ancient Tcl-only implementation of environment modules,
+        # but that's considered to be a non-issue (since this is mostly relevant for Cray systems,
+        # which are either using EnvironmentModulesC (3.2.10), EnvironmentModules (4.x) or Lmod...
+        if self.MODULE_GENERATOR_CLASS == ModuleGeneratorTcl and self.modtool.__class__ != EnvironmentModulesTcl:
+            test_mod_txt = "#%Module\nmodule swap GCC/7.3.0-2.30"
+
+            test_mod_fn = 'test_single_arg_swap/1.2.3'
+            write_file(os.path.join(self.test_prefix, test_mod_fn), test_mod_txt)
+
+            self.modtool.load(['GCC/4.6.3'])
+            self.modtool.use(self.test_prefix)
+            self.modtool.load(['test_single_arg_swap/1.2.3'])
+
+            expected = ['GCC/7.3.0-2.30', 'test_single_arg_swap/1.2.3']
+            self.assertEqual(sorted([m['mod_name'] for m in self.modtool.list()]), expected)
+
     def test_append_paths(self):
         """Test generating append-paths statements."""
         # test append_paths