From 868d5389585c41ff7ebe4ec18ba8b4a8489d2352 Mon Sep 17 00:00:00 2001
From: Harmen Stoppels <me@harmenstoppels.nl>
Date: Fri, 25 Apr 2025 11:48:36 +0200
Subject: [PATCH] simplify and speed up external list

---
 lib/spack/spack/cmd/external.py | 14 ++++++++------
 lib/spack/spack/package_base.py |  8 --------
 2 files changed, 8 insertions(+), 14 deletions(-)

diff --git a/lib/spack/spack/cmd/external.py b/lib/spack/spack/cmd/external.py
index 7650306bd19..510233b1460 100644
--- a/lib/spack/spack/cmd/external.py
+++ b/lib/spack/spack/cmd/external.py
@@ -5,7 +5,7 @@
 import errno
 import os
 import re
-import sys
+from collections import defaultdict
 from typing import List, Optional, Set
 
 import llnl.util.tty as tty
@@ -17,7 +17,6 @@
 import spack.cray_manifest as cray_manifest
 import spack.detection
 import spack.error
-import spack.package_base
 import spack.repo
 import spack.spec
 from spack.cmd.common import arguments
@@ -246,13 +245,16 @@ def _collect_and_consume_cray_manifest_files(
 
 
 def external_list(args):
-    # Trigger a read of all packages, might take a long time.
-    list(spack.repo.PATH.all_package_classes())
     # Print all the detectable packages
     tty.msg("Detectable packages per repository")
-    for namespace, pkgs in sorted(spack.package_base.detectable_packages.items()):
+    repo_to_packages = defaultdict(list)
+    for fullname in spack.repo.PATH.packages_with_tags("detectable", full=True):
+        repo, _, pkg = fullname.rpartition(".")
+        repo_to_packages[repo].append(pkg)
+
+    for namespace in sorted(repo_to_packages):
         print("Repository:", namespace)
-        colify.colify(pkgs, indent=4, output=sys.stdout)
+        colify.colify(repo_to_packages[namespace], indent=4)
 
 
 def external(parser, args):
diff --git a/lib/spack/spack/package_base.py b/lib/spack/spack/package_base.py
index cf2ca6c8de6..c33fe0baf0d 100644
--- a/lib/spack/spack/package_base.py
+++ b/lib/spack/spack/package_base.py
@@ -132,11 +132,6 @@ def windows_establish_runtime_linkage(self):
             win_rpath.establish_link()
 
 
-#: Registers which are the detectable packages, by repo and package name
-#: Need a pass of package repositories to be filled.
-detectable_packages = collections.defaultdict(list)
-
-
 class DetectablePackageMeta(type):
     """Check if a package is detectable and add default implementations
     for the detection function.
@@ -242,9 +237,6 @@ def determine_spec_details(cls, prefix, objs_in_prefix):
             def determine_variants(cls, objs, version_str):
                 return ""
 
-            # Register the class as a detectable package
-            detectable_packages[cls.namespace].append(cls.name)
-
             # Attach function implementations to the detectable class
             default = False
             if not hasattr(cls, "determine_spec_details"):