1 files changed, 60 insertions, 0 deletions
diff --git a/lib/spack/spack/modules/common.py b/lib/spack/spack/modules/common.py
index 5e34315c1c..748013ade4 100644
--- a/lib/spack/spack/modules/common.py
+++ b/lib/spack/spack/modules/common.py
@@ -33,6 +33,7 @@ import datetime
 import inspect
 import os.path
 import re
+import collections
 
 import six
 import llnl.util.filesystem
@@ -45,6 +46,7 @@ import spack.tengine as tengine
 import spack.util.path
 import spack.util.environment
 import spack.error
+import spack.util.spack_yaml as syaml
 
 #: config section for this file
 configuration = spack.config.get('modules')
@@ -215,6 +217,64 @@ def root_path(name):
     return spack.util.path.canonicalize_path(path)
 
 
+def generate_module_index(root, modules):
+    entries = syaml.syaml_dict()
+    for m in modules:
+        entry = {
+            'path': m.layout.filename,
+            'use_name': m.layout.use_name
+        }
+        entries[m.spec.dag_hash()] = entry
+    index = {'module_index': entries}
+    index_path = os.path.join(root, 'module-index.yaml')
+    llnl.util.filesystem.mkdirp(root)
+    with open(index_path, 'w') as index_file:
+        syaml.dump(index, index_file, default_flow_style=False)
+
+
+ModuleIndexEntry = collections.namedtuple(
+    'ModuleIndexEntry', ['path', 'use_name'])
+
+
+def read_module_index(root):
+    index_path = os.path.join(root, 'module-index.yaml')
+    if not os.path.exists(index_path):
+        return {}
+    with open(index_path, 'r') as index_file:
+        yaml_content = syaml.load(index_file)
+        index = {}
+        yaml_index = yaml_content['module_index']
+        for dag_hash, module_properties in yaml_index.items():
+            index[dag_hash] = ModuleIndexEntry(
+                module_properties['path'],
+                module_properties['use_name'])
+        return index
+
+
+def read_module_indices():
+    module_type_to_indices = {}
+    other_spack_instances = spack.config.get(
+        'upstreams') or {}
+
+    for install_properties in other_spack_instances.values():
+        module_type_to_root = install_properties.get('modules', {})
+        for module_type, root in module_type_to_root.items():
+            indices = module_type_to_indices.setdefault(module_type, [])
+            indices.append(read_module_index(root))
+
+    return module_type_to_indices
+
+
+module_type_to_indices = read_module_indices()
+
+
+def upstream_module(spec, module_type):
+    indices = module_type_to_indices[module_type]
+    for index in indices:
+        if spec.dag_hash() in index:
+            return index[spec.dag_hash()]
+
+
 class BaseConfiguration(object):
     """Manipulates the information needed to generate a module file to make
     querying easier. It needs to be sub-classed for specific module types.