module file : added filtering based on environment variable name

etc/spack/modules.yaml

@@ -6,3 +6,7 @@
 # -------------------------------------------------------------------------
 modules:
   enable: ['tcl', 'dotkit']
+
+  dotkit:
+    filter:
+      environment_modifications: ['CPATH', 'LIBRARY_PATH']  # Exclude changes to any of these variables

lib/spack/spack/config.py

@@ -146,7 +146,7 @@
         'type': 'object',
         'additionalProperties': False,
         'patternProperties': {
-            'compilers:?': { # optional colon for overriding site config.
+            'compilers:?': {  # optional colon for overriding site config.
                 'type': 'object',
                 'default': {},
                 'additionalProperties': False,
@@ -195,6 +195,7 @@
                 'default': [],
                 'items': {
                     'type': 'string'},},},},
+
     'packages': {
         '$schema': 'http://json-schema.org/schema#',
         'title': 'Spack package configuration file schema',
@@ -238,11 +239,35 @@
                                 'default' : {},
                             }
                         },},},},},},
+
     'modules': {
         '$schema': 'http://json-schema.org/schema#',
         'title': 'Spack module file configuration file schema',
         'type': 'object',
         'additionalProperties': False,
+        'definitions': {
+            'module_type_configuration': {
+                'type': 'object',
+                'default': {},
+                'additionalProperties': False,
+                'properties': {
+                    'filter': {
+                        'type': 'object',
+                        'default': {},
+                        'additionalProperties': False,
+                        'properties': {
+                            'environment_modifications': {
+                                'type': 'array',
+                                'default': [],
+                                'items': {
+                                    'type': 'string'
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        },
         'patternProperties': {
             r'modules:?': {
                 'type': 'object',
@@ -253,9 +278,22 @@
                         'type': 'array',
                         'default': [],
                         'items': {
-                            'type': 'string'
+                            'type': 'string',
+                            'enum': ['tcl', 'dotkit']
                         }
-                    }
+                    },
+                    'tcl': {
+                        'allOf': [
+                            {'$ref': '#/definitions/module_type_configuration'},  # Base configuration
+                            {}  # Specific tcl extensions
+                        ]
+                    },
+                    'dotkit': {
+                        'allOf': [
+                            {'$ref': '#/definitions/module_type_configuration'},  # Base configuration
+                            {}  # Specific dotkit extensions
+                        ]
+                    },
                 }
             },
         },

lib/spack/spack/environment.py

@@ -250,3 +250,19 @@ def validate(env, errstream):
     modifications = env.group_by_name()
     for variable, list_of_changes in sorted(modifications.items()):
         set_or_unset_not_first(variable, list_of_changes, errstream)
+
+
+def filter_environment_modifications(env, variables):
+    """
+    Generator that filters out any change to environment variables present in the input list
+
+    Args:
+        env: list of environment modifications
+        variables: list of variable names to be filtered
+
+    Yields:
+        items in env if they are not in variables
+    """
+    for item in env:
+        if item.name not in variables:
+            yield item

lib/spack/spack/modules.py

@@ -179,9 +179,17 @@ def write(self):
         if not env:
             return
 
+        # Filter modifications to the environment according to configuration files
+        try:
+            filter_list = CONFIGURATION[self.name]['filter']['environment_modifications']
+        except KeyError:
+            filter_list = []
+
         with open(self.file_name, 'w') as f:
             self.write_header(f)
-            for line in self.process_environment_command(env):
+            for line in self.process_environment_command(
+                    filter_environment_modifications(env, filter_list)
+            ):
                 f.write(line)
 
     def write_header(self, stream):