Uniquify suffixes added to module names (#14920)

lib/spack/spack/modules/common.py

@@ -428,6 +428,7 @@ def suffixes(self):
         for constraint, suffix in self.conf.get('suffixes', {}).items():
             if constraint in self.spec:
                 suffixes.append(suffix)
+        suffixes = sorted(set(suffixes))
         if self.hash:
             suffixes.append(self.hash)
         return suffixes

lib/spack/spack/test/data/modules/tcl/suffix.yaml

@@ -5,3 +5,4 @@ tcl:
     suffixes:
       '+debug': foo
       '~debug': bar
+      '^mpich': foo

lib/spack/spack/test/modules/tcl.py

@@ -215,9 +215,10 @@ def test_suffixes(self, module_configuration, factory):
 
         writer, spec = factory('mpileaks+debug arch=x86-linux')
         assert 'foo' in writer.layout.use_name
+        assert 'foo-foo' not in writer.layout.use_name
 
         writer, spec = factory('mpileaks~debug arch=x86-linux')
-        assert 'bar' in writer.layout.use_name
+        assert 'bar-foo' in writer.layout.use_name
 
     def test_setup_environment(self, modulefile_content, module_configuration):
         """Tests the internal set-up of run-time environment."""