ansible: better emulate _low_level_execute_command()

Still needs a ton of work to emulate argument handling, shell selection,
and output emulation in every case. Unsurprisingly, Ansible documents
none of this.

ansible_mitogen/helpers.py

@@ -26,6 +26,8 @@
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 import json
+import os
+import pwd
 import subprocess
 import time
 
@@ -112,19 +114,41 @@ def run_module(module, raw_params=None, args=None):
         return json.dumps(e.dct)
 
 
-def exec_command(cmd, in_data=''):
+def get_user_shell():
     """
-    Run a command in subprocess, arranging for `in_data` to be supplied on its
-    standard input.
+    For commands executed directly via an SSH command-line, SSH looks up the
+    user's shell via getpwuid() and only defaults to /bin/sh if that field is
+    missing or empty.
+    """
+    try:
+        pw_shell = pwd.getpwuid(os.geteuid()).pw_shell
+    except KeyError:
+        pw_shell = None
+
+    return pw_shell or '/bin/sh'
+
 
+def exec_command(cmd, in_data='', chdir=None, shell=None):
+    """
+    Run a command in a subprocess, emulating the argument handling behaviour of
+    SSH.
+
+    :param bytes cmd:
+        String command line, passed to user's shell.
+    :param bytes in_data:
+        Optional standard input for the command.
     :return:
         (return code, stdout bytes, stderr bytes)
     """
-    proc = subprocess.Popen(cmd,
+    assert isinstance(cmd, basestring)
+
+    proc = subprocess.Popen(
+        args=[get_user_shell(), '-c', cmd],
         stdout=subprocess.PIPE,
         stderr=subprocess.PIPE,
         stdin=subprocess.PIPE,
-        shell=True)
+        cwd=chdir,
+    )
     stdout, stderr = proc.communicate(in_data)
     return proc.returncode, stdout, stderr
 

ansible_mitogen/mixins.py

@@ -26,6 +26,7 @@
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 from __future__ import absolute_import
+import commands
 import os
 import pwd
 import shutil
@@ -177,17 +178,24 @@ class ActionModuleMixin(ansible.plugins.action.ActionBase):
 
     def _low_level_execute_command(self, cmd, sudoable=True, in_data=None,
                                    executable=None,
-                                   encoding_errors='surrogate_then_replace'):
+                                   encoding_errors='surrogate_then_replace',
+                                   chdir=None):
+        if executable is None:  # executable defaults to False
+            executable = self._play_context.executable
+        if executable:
+            cmd = executable + ' -c ' + commands.mkarg(cmd)
+
         # replaces 57 lines
         # replaces 126 lines of make_become_cmd()
         rc, stdout, stderr = self.call(
             ansible_mitogen.helpers.exec_command,
-            cmd,
-            in_data,
+            cast(cmd),
+            cast(in_data),
+            chdir=cast(chdir),
         )
         return {
             'rc': rc,
-            'stdout': to_text(stdout, encoding_errors),
-            'stdout_lines': '\n'.split(to_text(stdout, encoding_errors)),
+            'stdout': to_text(stdout, errors=encoding_errors),
+            'stdout_lines': to_text(stdout, errors=encoding_errors).splitlines(),
             'stderr': stderr,
         }

examples/playbook/low_level_execute_command.yml

+---
+
+# Verify the behaviour of _low_level_execute_command().
+
+- hosts: all
+  gather_facts: false
+  tasks:
+
+    # "echo -en" to test we actually hit bash shell too.
+    - name: Run raw module without sudo
+      raw: 'echo -en $((1 + 1))'
+      register: raw
+
+    - name: Verify raw module output.
+      assert:
+        that:
+          - 'raw.rc == 0'
+          - 'raw.stdout_lines == ["2"]'
+          - 'raw.stdout == "2"'
+
+    - name: Run raw module with sudo
+      become: true
+      raw: 'whoami'
+      register: raw
+
+    # Can't test stdout because TTY inserts \r in Ansible version.
+    - debug: msg={{raw}}
+    - name: Verify raw module output.
+      assert:
+        that:
+          - 'raw.rc == 0'
+          - 'raw.stdout_lines == ["root"]'