config: remove all module-scope calls to spack.config.get()

This avoids parsing modules.yaml on startup.

lib/spack/spack/modules/common.py

@@ -49,14 +49,11 @@
 import spack.util.spack_yaml as syaml
 import spack.util.file_permissions as fp
 
+
 #: config section for this file
-configuration = spack.config.get('modules')
+def configuration():
+    return spack.config.get('modules', {})
 
-#: Root folders where the various module files should be written
-roots = spack.config.get('config:module_roots', {})
-
-#: Inspections that needs to be done on spec prefixes
-prefix_inspections = spack.config.get('modules:prefix_inspections', {})
 
 #: Valid tokens for naming scheme and env variable names
 _valid_tokens = (
@@ -219,6 +216,8 @@ def root_path(name):
     Returns:
         root folder for module file installation
     """
+    # Root folders where the various module files should be written
+    roots = spack.config.get('config:module_roots', {})
     path = roots.get(name, os.path.join(spack.paths.share_path, name))
     return spack.util.path.canonicalize_path(path)
 
@@ -387,12 +386,12 @@ def __init__(self, spec):
         self.spec = spec
         # Dictionary of configuration options that should be applied
         # to the spec
-        self.conf = merge_config_rules(self.module.configuration, self.spec)
+        self.conf = merge_config_rules(self.module.configuration(), self.spec)
 
     @property
     def naming_scheme(self):
         """Naming scheme suitable for non-hierarchical layouts"""
-        scheme = self.module.configuration.get(
+        scheme = self.module.configuration().get(
             'naming_scheme',
             '{name}-{version}-{compiler.name}-{compiler.version}'
         )
@@ -461,7 +460,7 @@ def blacklisted(self):
         """
         # A few variables for convenience of writing the method
         spec = self.spec
-        conf = self.module.configuration
+        conf = self.module.configuration()
 
         # Compute the list of whitelist rules that match
         wlrules = conf.get('whitelist', [])
@@ -662,7 +661,7 @@ def environment_modifications(self):
         # Modifications guessed inspecting the spec prefix
         env = spack.util.environment.inspect_path(
             self.spec.prefix,
-            prefix_inspections,
+            spack.config.get('modules:prefix_inspections', {}),
             exclude=spack.util.environment.is_system_path
         )
 

lib/spack/spack/modules/lmod.py

@@ -18,8 +18,11 @@
 from .common import BaseConfiguration, BaseFileLayout
 from .common import BaseContext, BaseModuleFileWriter
 
+
 #: lmod specific part of the configuration
-configuration = spack.config.get('modules:lmod', {})
+def configuration():
+    return spack.config.get('modules:lmod', {})
+
 
 #: Caches the configuration {spec_hash: configuration}
 configuration_registry = {}
@@ -98,7 +101,7 @@ def core_compilers(self):
                 specified in the configuration file or the sequence
                 is empty
         """
-        value = configuration.get(
+        value = configuration().get(
             'core_compilers'
         ) or guess_core_compilers(store=True)
 
@@ -112,7 +115,7 @@ def hierarchy_tokens(self):
         """Returns the list of tokens that are part of the modulefile
         hierarchy. 'compiler' is always present.
         """
-        tokens = configuration.get('hierarchy', [])
+        tokens = configuration().get('hierarchy', [])
 
         # Check if all the tokens in the hierarchy are virtual specs.
         # If not warn the user and raise an error.

lib/spack/spack/modules/tcl.py

@@ -16,8 +16,11 @@
 from .common import BaseConfiguration, BaseFileLayout
 from .common import BaseContext, BaseModuleFileWriter
 
+
 #: TCL specific part of the configuration
-configuration = spack.config.get('modules:tcl', {})
+def configuration():
+    return spack.config.get('modules:tcl', {})
+
 
 #: Caches the configuration {spec_hash: configuration}
 configuration_registry = {}

lib/spack/spack/test/conftest.py

@@ -654,15 +654,21 @@ def _impl(filename):
         with open(file) as f:
             configuration = yaml.load(f)
 
+        def mock_config_function():
+            return configuration
+
+        def writer_key_function():
+            return mock_config_function()[writer_key]
+
         monkeypatch.setattr(
             spack.modules.common,
             'configuration',
-            configuration
+            mock_config_function
         )
         monkeypatch.setattr(
             writer_mod,
             'configuration',
-            configuration[writer_key]
+            writer_key_function
         )
         monkeypatch.setattr(
             writer_mod,