1 files changed, 135 insertions, 0 deletions
diff --git a/lib/spack/spack/tag.py b/lib/spack/spack/tag.py
new file mode 100644
index 0000000000..6e2eea6864
--- /dev/null
+++ b/lib/spack/spack/tag.py
@@ -0,0 +1,135 @@
+# Copyright 2013-2021 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+"""Classes and functions to manage package tags"""
+import collections
+import copy
+import sys
+
+if sys.version_info >= (3, 5):
+    from collections.abc import Mapping  # novm
+else:
+    from collections import Mapping
+
+import spack.error
+import spack.util.spack_json as sjson
+
+
+def _get_installed_package_names():
+    """Returns names of packages installed in the active environment."""
+    specs = spack.environment.installed_specs()
+    return [spec.name for spec in specs]
+
+
+def packages_with_tags(tags, installed, skip_empty):
+    """
+    Returns a dict, indexed by tag, containing lists of names of packages
+    containing the tag or, if no tags, for all available tags.
+
+    Arguments:
+        tags (list or None): list of tags of interest or None for all
+        installed (bool): True if want names of packages that are installed;
+            otherwise, False if want all packages with the tag
+        skip_empty (bool): True if exclude tags with no associated packages;
+            otherwise, False if want entries for all tags even when no such
+            tagged packages
+    """
+    tag_pkgs = collections.defaultdict(lambda: list)
+    spec_names = _get_installed_package_names() if installed else []
+    keys = spack.repo.path.tag_index if tags is None else tags
+    for tag in keys:
+        packages = [name for name in spack.repo.path.tag_index[tag] if
+                    not installed or name in spec_names]
+        if packages or not skip_empty:
+            tag_pkgs[tag] = packages
+    return tag_pkgs
+
+
+class TagIndex(Mapping):
+    """Maps tags to list of packages."""
+
+    def __init__(self):
+        self._tag_dict = collections.defaultdict(list)
+
+    @property
+    def tags(self):
+        return self._tag_dict
+
+    def to_json(self, stream):
+        sjson.dump({'tags': self._tag_dict}, stream)
+
+    @staticmethod
+    def from_json(stream):
+        d = sjson.load(stream)
+
+        if not isinstance(d, dict):
+            raise TagIndexError("TagIndex data was not a dict.")
+
+        if 'tags' not in d:
+            raise TagIndexError("TagIndex data does not start with 'tags'")
+
+        r = TagIndex()
+
+        for tag, packages in d['tags'].items():
+            r[tag].extend(packages)
+
+        return r
+
+    def __getitem__(self, item):
+        return self._tag_dict[item]
+
+    def __iter__(self):
+        return iter(self._tag_dict)
+
+    def __len__(self):
+        return len(self._tag_dict)
+
+    def copy(self):
+        """Return a deep copy of this index."""
+        clone = TagIndex()
+        clone._tag_dict = copy.deepcopy(self._tag_dict)
+        return clone
+
+    def get_packages(self, tag):
+        """Returns all packages associated with the tag."""
+        return self.tags[tag] if tag in self.tags else []
+
+    def merge(self, other):
+        """Merge another tag index into this one.
+
+        Args:
+            other (TagIndex): tag index to be merged
+        """
+        other = other.copy()   # defensive copy.
+
+        for tag in other.tags:
+            if tag not in self.tags:
+                self.tags[tag] = other.tags[tag]
+                continue
+
+            spkgs, opkgs = self.tags[tag], other.tags[tag]
+            self.tags[tag] = sorted(list(set(spkgs + opkgs)))
+
+    def update_package(self, pkg_name):
+        """Updates a package in the tag index.
+
+        Args:
+            pkg_name (str): name of the package to be removed from the index
+
+        """
+        package = spack.repo.path.get(pkg_name)
+
+        # Remove the package from the list of packages, if present
+        for pkg_list in self._tag_dict.values():
+            if pkg_name in pkg_list:
+                pkg_list.remove(pkg_name)
+
+        # Add it again under the appropriate tags
+        for tag in getattr(package, 'tags', []):
+            tag = tag.lower()
+            self._tag_dict[tag].append(package.name)
+
+
+class TagIndexError(spack.error.SpackError):
+    """Raised when there is a problem with a TagIndex."""