Add Externally Findable section to info command (#24503)

* Add Externally Findable section to info command

* Use comma delimited detection attributes in addition to boolean value

* Unit test externally detectable part of spack info

lib/spack/spack/cmd/info.py

@@ -155,6 +155,26 @@ def print_text_info(pkg):
         color.cprint('')
         color.cprint(section_title('Maintainers: ') + mnt)
 
+    color.cprint('')
+    color.cprint(section_title('Externally Detectable: '))
+
+    # If the package has an 'executables' field, it can detect an installation
+    if hasattr(pkg, 'executables'):
+        find_attributes = []
+        if hasattr(pkg, 'determine_version'):
+            find_attributes.append('version')
+
+        if hasattr(pkg, 'determine_variants'):
+            find_attributes.append('variants')
+
+        # If the package does not define 'determine_version' nor
+        # 'determine_variants', then it must use some custom detection
+        # mechanism. In this case, just inform the user it's detectable somehow.
+        color.cprint('    True{0}'.format(
+            ' (' + ', '.join(find_attributes) + ')' if find_attributes else ''))
+    else:
+        color.cprint('    False')
+
     color.cprint('')
     color.cprint(section_title("Tags: "))
     if hasattr(pkg, 'tags'):

lib/spack/spack/test/cmd/info.py

@@ -48,6 +48,22 @@ def test_it_just_runs(pkg):
     info(pkg)
 
 
+@pytest.mark.parametrize('pkg_query,expected', [
+    ('zlib', 'False'),
+    ('gcc', 'True (version, variants)'),
+])
+@pytest.mark.usefixtures('mock_print')
+def test_is_externally_detectable(pkg_query, expected, parser, info_lines):
+    args = parser.parse_args([pkg_query])
+    spack.cmd.info.info(parser, args)
+
+    line_iter = info_lines.__iter__()
+    for line in line_iter:
+        if 'Externally Detectable' in line:
+            is_externally_detectable = next(line_iter).strip()
+            assert is_externally_detectable == expected
+
+
 @pytest.mark.parametrize('pkg_query', [
     'hdf5',
     'cloverleaf3d',
@@ -59,6 +75,7 @@ def test_info_fields(pkg_query, parser, info_lines):
     expected_fields = (
         'Description:',
         'Homepage:',
+        'Externally Detectable:',
         'Safe versions:',
         'Variants:',
         'Installation Phases:',