fix: Raise error when aexpect_helper doesn't work properly

[PaulYuuu]

When aexpect_helper does not work properly, the process will hang without any log information. This fix checks the process status and raises an error if the process terminates prematurely.

[PaulYuuu]

Hello @ldoktor, would you please help to review this one, thanks.

[PaulYuuu]

All updated.

[ldoktor]

Thanks, looks almost good only pylint complains about too many branches (hard to read code). Could you please extract the helper init into a function? Something like:

diff --git a/aexpect/client.py b/aexpect/client.py
index 8e790c8..0946a32 100644
--- a/aexpect/client.py
+++ b/aexpect/client.py
@@ -178,34 +178,10 @@ class Spawn:
         # Start the server (which runs the command)
         if command:
             helper_cmd = utils_path.find_command('aexpect_helper')
-            self._aexpect_helper = subprocess.Popen([helper_cmd],  # pylint: disable=R1732
-                                                    shell=True,
-                                                    stdin=subprocess.PIPE,
-                                                    stdout=subprocess.PIPE,
-                                                    stderr=subprocess.STDOUT,
-                                                    pass_fds=pass_fds)
-            sub = self._aexpect_helper
-            # Send parameters to the server
-            sub.stdin.write(f"{self.a_id}\n".encode(self.encoding))
-            sub.stdin.write(f"{echo}\n".encode(self.encoding))
-            readers = ",".join(self.readers)
-            sub.stdin.write(f"{readers}\n".encode(self.encoding))
-            sub.stdin.write(f"{command}\n".encode(self.encoding))
-            sub.stdin.flush()
-            # Wait for the server to complete its initialization
-            full_output = ""
-            pattern = f"Server {self.a_id} ready"
-            end_time = time.time() + 60
-            while time.time() < end_time:
-                output = sub.stdout.readline().decode(self.encoding, "ignore")
-                if pattern in output:
-                    break
-                full_output += output
-                sub_status = sub.poll()
-                if sub_status is not None:
-                    raise ExpectProcessTerminatedError(pattern, sub_status, full_output)
-            else:
-                raise ExpectTimeoutError(pattern, full_output)
+            self._aexpect_helper = self._get_aexpect_helper(helper_cmd,
+                                                            pass_fds,
+                                                            echo,
+                                                            command)
 
         # Open the reading pipes
         if is_file_locked(self.lock_server_running_filename):
@@ -242,6 +218,36 @@ class Spawn:
         if self.auto_close:
             self.close()
 
+    def _get_aexpect_helper(self, helper_cmd, pass_fds, echo, command):
+        sub = subprocess.Popen([helper_cmd],  # pylint: disable=R1732
+                               shell=True,
+                               stdin=subprocess.PIPE,
+                               stdout=subprocess.PIPE,
+                               stderr=subprocess.STDOUT,
+                               pass_fds=pass_fds)
+        # Send parameters to the server
+        sub.stdin.write(f"{self.a_id}\n".encode(self.encoding))
+        sub.stdin.write(f"{echo}\n".encode(self.encoding))
+        readers = ",".join(self.readers)
+        sub.stdin.write(f"{readers}\n".encode(self.encoding))
+        sub.stdin.write(f"{command}\n".encode(self.encoding))
+        sub.stdin.flush()
+        # Wait for the server to complete its initialization
+        full_output = ""
+        pattern = f"Server {self.a_id} ready"
+        end_time = time.time() + 60
+        while time.time() < end_time:
+            output = sub.stdout.readline().decode(self.encoding, "ignore")
+            if pattern in output:
+                break
+            full_output += output
+            sub_status = sub.poll()
+            if sub_status is not None:
+                raise ExpectProcessTerminatedError(pattern, sub_status, full_output)
+        else:
+            raise ExpectTimeoutError(pattern, full_output)
+        return sub
+
     def _add_reader(self, reader):
         """
         Add a reader whose file descriptor can be obtained with _get_fd().

but with proper docstrings and better variable/function names

[PaulYuuu]

@ldoktor thank you for the reminder, I was forgot to check the CI, now updated.

[ldoktor]

Thank you, @PaulYuuu, you made my day. It's nice to be looking at well structured and documented python code :-). Let's hope the 1m deadline will be enough...