Add ROSLaunchController for controlling ROS launch processes (fixes #354

) (#359)

* added ROSLaunchController class

* added terminate method

* added filename to controller

* added command attribute

* added close method

* added pid property

* added ROSLaunchController to launch method

* added __enter__ and __exit__ methods

* added is_running method

* added missing import

* updated CHANGELOG

* Added missing `not`

Co-authored-by: afsafzal <afsoona@cs.cmu.edu>

* mark running as property

Co-authored-by: afsafzal <afsoona@cs.cmu.edu>

CHANGELOG.md

@@ -4,6 +4,8 @@
   systems
 * Allowed mypy to discover type hints via PEP 561
 * Added missing type annotations
+* Added ROSLaunchController for dynamically inspecting and controlling
+  roslaunch processes
 
 
 # 1.2.1 (2020-05-27)

src/roswire/proxy/roslaunch/controller.py

@@ -0,0 +1,54 @@
+# -*- coding: utf-8 -*-
+__all__ = ('ROSLaunchController',)
+
+from types import TracebackType
+from typing import Iterator, Optional, Type
+
+import attr
+import dockerblade
+
+
+@attr.s(frozen=True, slots=True, auto_attribs=True)
+class ROSLaunchController:
+    """Provides an interface to a roslaunch process.
+
+    Attributes
+    ----------
+    filename: str
+        The absolute path of the XML launch file used by this process.
+    command: str
+        The command string that was used by this process.
+    popen: dockerblade.popen.Popen
+        An interface to the underlying exec process for this roslaunch process.
+    pid: Optional[int]
+        The PID of the launch process inside the container, if known.
+    """
+    filename: str
+    popen: dockerblade.popen.Popen = attr.ib(repr=False)
+
+    def __enter__(self) -> 'ROSLaunchController':
+        return self
+
+    def __exit__(self,
+                 ex_type: Optional[Type[BaseException]],
+                 ex_val: Optional[BaseException],
+                 ex_tb: Optional[TracebackType]
+                 ) -> None:
+        self.close()
+
+    @property
+    def stream(self) -> Iterator[str]:
+        yield from self.popen.stream()  # type: ignore
+
+    @property
+    def running(self) -> bool:
+        """Checks whether or not this roslaunch process is still running."""
+        return not self.popen.finished
+
+    def terminate(self) -> None:
+        """Terminates this roslaunch process."""
+        self.popen.terminate()
+
+    def close(self) -> None:
+        """Terminates this roslaunch process."""
+        self.terminate()

src/roswire/proxy/roslaunch/roslaunch.py

@@ -11,6 +11,7 @@
 import dockerblade
 
 from .config import LaunchConfig
+from .controller import ROSLaunchController
 from .reader import LaunchFileReader
 from ... import exceptions as exc
 
@@ -130,7 +131,7 @@ def launch(self,
                args: Optional[Mapping[str, Union[int, str]]] = None,
                prefix: Optional[str] = None,
                launch_prefixes: Optional[Mapping[str, str]] = None
-               ) -> None:
+               ) -> ROSLaunchController:
         """Provides an interface to the roslaunch command.
 
         Parameters
@@ -148,6 +149,11 @@ def launch(self,
             An optional mapping from nodes, given by their names, to their
             individual launch prefix.
 
+        Returns
+        -------
+        ROSLaunchController
+            An interface for inspecting and managing the launch process.
+
         Raises
         ------
         PackageNotFound
@@ -172,6 +178,9 @@ def launch(self,
         if prefix:
             cmd = [prefix] + cmd
         cmd_str = ' '.join(cmd)
-        shell.popen(cmd_str, stdout=False, stderr=False)
+        popen = shell.popen(cmd_str, stdout=False, stderr=False)
+
+        return ROSLaunchController(filename=filename,
+                                   popen=popen)
 
     __call__ = launch