spack external find: allow to search by tags (#21407)

This commit adds an option to the `external find`
command that allows it to search by tags. In this
way group of executables with common purposes can
be grouped under a single name and a simple command
can be used to detect all of them.

As an example introduce the 'build-tools' tag to
search for common development tools on a system

5 files changed, 55 insertions, 9 deletions

diff --git a/lib/spack/spack/cmd/common/arguments.py b/lib/spack/spack/cmd/common/arguments.py
index c09f890114..f83708a7dd 100644
--- a/lib/spack/spack/cmd/common/arguments.py
+++ b/lib/spack/spack/cmd/common/arguments.py
@@ -250,8 +250,8 @@ def very_long():
 @arg
 def tags():
     return Args(
-        '-t', '--tags', action='append',
-        help='filter a package query by tags')
+        '-t', '--tag', action='append', dest='tags', metavar='TAG',
+        help='filter a package query by tag (multiple use allowed)')
 
 
 @arg
diff --git a/lib/spack/spack/cmd/external.py b/lib/spack/spack/cmd/external.py
index c4f3c0e854..c7d045e66d 100644
--- a/lib/spack/spack/cmd/external.py
+++ b/lib/spack/spack/cmd/external.py
@@ -16,6 +16,7 @@ import llnl.util.tty.colify as colify
 import six
 import spack
 import spack.cmd
+import spack.cmd.common.arguments
 import spack.error
 import spack.util.environment
 import spack.util.spack_yaml as syaml
@@ -42,6 +43,7 @@ def setup_parser(subparser):
         '--scope', choices=scopes, metavar=scopes_metavar,
         default=spack.config.default_modify_scope('packages'),
         help="configuration scope to modify")
+    spack.cmd.common.arguments.add_common_arguments(find_parser, ['tags'])
     find_parser.add_argument('packages', nargs=argparse.REMAINDER)
 
     sp.add_parser(
@@ -148,9 +150,28 @@ def _spec_is_valid(spec):
 
 
 def external_find(args):
+    # Construct the list of possible packages to be detected
+    packages_to_check = []
+
+    # Add the packages that have been required explicitly
     if args.packages:
         packages_to_check = list(spack.repo.get(pkg) for pkg in args.packages)
-    else:
+        if args.tags:
+            allowed = set(spack.repo.path.packages_with_tags(*args.tags))
+            packages_to_check = [x for x in packages_to_check if x in allowed]
+
+    if args.tags and not packages_to_check:
+        # If we arrived here we didn't have any explicit package passed
+        # as argument, which means to search all packages.
+        # Since tags are cached it's much faster to construct what we need
+        # to search directly, rather than filtering after the fact
+        packages_to_check = [
+            spack.repo.get(pkg) for pkg in
+            spack.repo.path.packages_with_tags(*args.tags)
+        ]
+
+    # If the list of packages is empty, search for every possible package
+    if not args.tags and not packages_to_check:
         packages_to_check = spack.repo.path.all_packages()
 
     pkg_to_entries = _get_external_packages(packages_to_check)
diff --git a/lib/spack/spack/test/cmd/external.py b/lib/spack/spack/test/cmd/external.py
index 5a94164e61..3249a92894 100644
--- a/lib/spack/spack/test/cmd/external.py
+++ b/lib/spack/spack/test/cmd/external.py
@@ -2,6 +2,8 @@
 # Spack Project Developers. See the top-level COPYRIGHT file for details.
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)
+import pytest
+
 import os
 import os.path
 
@@ -242,3 +244,26 @@ def test_new_entries_are_reported_correctly(
     # has been found
     output = external('find', 'gcc')
     assert 'No new external packages detected' in output
+
+
+@pytest.mark.parametrize('command_args', [
+    ('-t', 'build-tools'),
+    ('-t', 'build-tools', 'cmake'),
+])
+def test_use_tags_for_detection(
+        command_args, mock_executable, mutable_config, monkeypatch
+):
+    # Prepare an environment to detect a fake cmake
+    cmake_exe = mock_executable('cmake', output="echo cmake version 3.19.1")
+    prefix = os.path.dirname(cmake_exe)
+    monkeypatch.setenv('PATH', prefix)
+
+    openssl_exe = mock_executable('openssl', output="OpenSSL 2.8.3")
+    prefix = os.path.dirname(openssl_exe)
+    monkeypatch.setenv('PATH', prefix)
+
+    # Test that we detect specs
+    output = external('find', *command_args)
+    assert 'The following specs have been' in output
+    assert 'cmake' in output
+    assert 'openssl' not in output
diff --git a/lib/spack/spack/test/cmd/find.py b/lib/spack/spack/test/cmd/find.py
index ef73b629e0..762578a028 100644
--- a/lib/spack/spack/test/cmd/find.py
+++ b/lib/spack/spack/test/cmd/find.py
@@ -89,7 +89,7 @@ def test_query_arguments():
 @pytest.mark.usefixtures('database', 'mock_display')
 def test_tag1(parser, specs):
 
-    args = parser.parse_args(['--tags', 'tag1'])
+    args = parser.parse_args(['--tag', 'tag1'])
     spack.cmd.find.find(parser, args)
 
     assert len(specs) == 2
@@ -100,7 +100,7 @@ def test_tag1(parser, specs):
 @pytest.mark.db
 @pytest.mark.usefixtures('database', 'mock_display')
 def test_tag2(parser, specs):
-    args = parser.parse_args(['--tags', 'tag2'])
+    args = parser.parse_args(['--tag', 'tag2'])
     spack.cmd.find.find(parser, args)
 
     assert len(specs) == 1
@@ -110,7 +110,7 @@ def test_tag2(parser, specs):
 @pytest.mark.db
 @pytest.mark.usefixtures('database', 'mock_display')
 def test_tag2_tag3(parser, specs):
-    args = parser.parse_args(['--tags', 'tag2', '--tags', 'tag3'])
+    args = parser.parse_args(['--tag', 'tag2', '--tag', 'tag3'])
     spack.cmd.find.find(parser, args)
 
     assert len(specs) == 0
diff --git a/lib/spack/spack/test/cmd/list.py b/lib/spack/spack/test/cmd/list.py
index afa71de90e..f99b7420a4 100644
--- a/lib/spack/spack/test/cmd/list.py
+++ b/lib/spack/spack/test/cmd/list.py
@@ -33,15 +33,15 @@ def test_list_search_description():
 
 
 def test_list_tags():
-    output = list('--tags', 'proxy-app')
+    output = list('--tag', 'proxy-app')
     assert 'cloverleaf3d' in output
     assert 'hdf5' not in output
 
-    output = list('--tags', 'hpc')
+    output = list('--tag', 'hpc')
     assert 'nek5000' in output
     assert 'mfem' in output
 
-    output = list('--tags', 'HPC')
+    output = list('--tag', 'HPC')
     assert 'nek5000' in output
     assert 'mfem' in output