pfexec become plugin: fix broken defaults for illumos/SmartOS

The pfexec become plugin has had incorrect defaults since it was
migrated from Ansible core, making it unusable on illumos without
manual workarounds:

1. become_flags defaulted to '-H -S -n' which are sudo flags.
   pfexec does not accept any of these options, causing:
   'exec: illegal option -- H'

2. wrap_exe defaulted to false. Unlike sudo, pfexec does not
   interpret shell constructs internally. Since Ansible generates
   compound commands (echo BECOME-SUCCESS-xxx ; python3), these
   must be wrapped in /bin/sh -c for pfexec to execute them.

These issues were originally reported in 2016 (ansible/ansible#15642),
migrated to community.general as #3671, and partially fixed by PR #3889
in 2022 (which corrected quoting but not the defaults). Users have had
to work around this with explicit inventory settings ever since.

Changes:
- become_flags default: '-H -S -n' -> '' (empty)
- wrap_exe default: false -> true
- build_become_command: handle empty flags cleanly
- Updated tests to match corrected defaults
- Added test for custom flags
- Improved wrap_exe description to explain why it should be enabled

tests/unit/plugins/become/test_pfexec.py

@@ -15,13 +15,13 @@ from .helper import call_become_plugin
 
 
 def test_pfexec_basic(mocker, parser, reset_cli_args):
+    """Test pfexec with default settings (no flags, wrap_exe enabled)."""
     options = parser.parse_args([])
     context._init_global_context(options)
 
     default_cmd = "/bin/foo"
     default_exe = "/bin/bash"
     pfexec_exe = "pfexec"
-    pfexec_flags = "-H -S -n"
 
     success = "BECOME-SUCCESS-.+?"
 
@@ -31,39 +31,63 @@ def test_pfexec_basic(mocker, parser, reset_cli_args):
     var_options = {}
     cmd = call_become_plugin(task, var_options, cmd=default_cmd, executable=default_exe)
     print(cmd)
-    assert re.match(f"""{pfexec_exe} {pfexec_flags} 'echo {success}; {default_cmd}'""", cmd) is not None
+    # With wrap_exe=true (default), command is wrapped in shell -c
+    assert re.match(f"""{pfexec_exe} {default_exe} -c 'echo {success}; {default_cmd}'""", cmd) is not None
 
 
-def test_pfexec(mocker, parser, reset_cli_args):
+def test_pfexec_no_wrap(mocker, parser, reset_cli_args):
+    """Test pfexec with wrap_exe disabled (legacy behaviour)."""
     options = parser.parse_args([])
     context._init_global_context(options)
 
     default_cmd = "/bin/foo"
     default_exe = "/bin/bash"
     pfexec_exe = "pfexec"
-    pfexec_flags = ""
 
     success = "BECOME-SUCCESS-.+?"
 
     task = {
-        "become_user": "foo",
+        "become_method": "community.general.pfexec",
+        "become_flags": "",
+    }
+    var_options = {
+        "ansible_pfexec_wrap_execution": "false",
+    }
+    cmd = call_become_plugin(task, var_options, cmd=default_cmd, executable=default_exe)
+    print(cmd)
+    assert re.match(f"""{pfexec_exe} 'echo {success}; {default_cmd}'""", cmd) is not None
+
+
+def test_pfexec_custom_flags(mocker, parser, reset_cli_args):
+    """Test pfexec with custom flags."""
+    options = parser.parse_args([])
+    context._init_global_context(options)
+
+    default_cmd = "/bin/foo"
+    default_exe = "/bin/bash"
+    pfexec_exe = "pfexec"
+    pfexec_flags = "-P basic"
+
+    success = "BECOME-SUCCESS-.+?"
+
+    task = {
         "become_method": "community.general.pfexec",
         "become_flags": pfexec_flags,
     }
     var_options = {}
     cmd = call_become_plugin(task, var_options, cmd=default_cmd, executable=default_exe)
     print(cmd)
-    assert re.match(f"""{pfexec_exe} {pfexec_flags} 'echo {success}; {default_cmd}'""", cmd) is not None
+    assert re.match(f"""{pfexec_exe} {pfexec_flags} {default_exe} -c 'echo {success}; {default_cmd}'""", cmd) is not None
 
 
 def test_pfexec_varoptions(mocker, parser, reset_cli_args):
+    """Test that var_options override task options."""
     options = parser.parse_args([])
     context._init_global_context(options)
 
     default_cmd = "/bin/foo"
     default_exe = "/bin/bash"
     pfexec_exe = "pfexec"
-    pfexec_flags = ""
 
     success = "BECOME-SUCCESS-.+?"
 
@@ -74,8 +98,9 @@ def test_pfexec_varoptions(mocker, parser, reset_cli_args):
     }
     var_options = {
         "ansible_become_user": "bar",
-        "ansible_become_flags": pfexec_flags,
+        "ansible_become_flags": "",
     }
     cmd = call_become_plugin(task, var_options, cmd=default_cmd, executable=default_exe)
     print(cmd)
-    assert re.match(f"""{pfexec_exe} {pfexec_flags} 'echo {success}; {default_cmd}'""", cmd) is not None
+    # var_options override task flags, so flags should be empty
+    assert re.match(f"""{pfexec_exe} {default_exe} -c 'echo {success}; {default_cmd}'""", cmd) is not None