Adding plugin support to can.io Reader/Writer

can/io/logger.py

@@ -5,6 +5,7 @@
 import pathlib
 import typing
 
+from pkg_resources import iter_entry_points
 import can.typechecking
 
 from ..listener import Listener
@@ -38,6 +39,16 @@ class Logger(BaseIOHandler, Listener):  # pylint: disable=abstract-method
         arguments are passed on to the returned instance.
     """
 
+    fetched_plugins = False
+    message_writers = {
+        ".asc": ASCWriter,
+        ".blf": BLFWriter,
+        ".csv": CSVWriter,
+        ".db": SqliteWriter,
+        ".log": CanutilsLogWriter,
+        ".txt": Printer,
+    }
+
     @staticmethod
     def __new__(
         cls, filename: typing.Optional[can.typechecking.StringPathLike], *args, **kwargs
@@ -51,17 +62,18 @@ def __new__(
         if filename is None:
             return Printer(*args, **kwargs)
 
-        lookup = {
-            ".asc": ASCWriter,
-            ".blf": BLFWriter,
-            ".csv": CSVWriter,
-            ".db": SqliteWriter,
-            ".log": CanutilsLogWriter,
-            ".txt": Printer,
-        }
+        if not Logger.fetched_plugins:
+            Logger.message_writers.update(
+                {
+                    writer.name: writer.load()
+                    for writer in iter_entry_points("can.io.message_writer")
+                }
+            )
+            Logger.fetched_plugins = True
+
         suffix = pathlib.PurePath(filename).suffix
         try:
-            return lookup[suffix](filename, *args, **kwargs)
+            return Logger.message_writers[suffix](filename, *args, **kwargs)
         except KeyError:
             raise ValueError(
                 f'No write support for this unknown log format "{suffix}"'

can/io/player.py

@@ -8,6 +8,8 @@
 from time import time, sleep
 import typing
 
+from pkg_resources import iter_entry_points
+
 if typing.TYPE_CHECKING:
     import can
 
@@ -44,24 +46,33 @@ class LogReader(BaseIOHandler):
         arguments are passed on to the returned instance.
     """
 
+    fetched_plugins = False
+    message_readers = {
+        ".asc": ASCReader,
+        ".blf": BLFReader,
+        ".csv": CSVReader,
+        ".db": SqliteReader,
+        ".log": CanutilsLogReader,
+    }
+
     @staticmethod
     def __new__(cls, filename: "can.typechecking.StringPathLike", *args, **kwargs):
         """
         :param filename: the filename/path of the file to read from
         :raises ValueError: if the filename's suffix is of an unknown file type
         """
-        suffix = pathlib.PurePath(filename).suffix
+        if not LogReader.fetched_plugins:
+            LogReader.message_readers.update(
+                {
+                    reader.name: reader.load()
+                    for reader in iter_entry_points("can.io.message_reader")
+                }
+            )
+            LogReader.fetched_plugins = True
 
-        lookup = {
-            ".asc": ASCReader,
-            ".blf": BLFReader,
-            ".csv": CSVReader,
-            ".db": SqliteReader,
-            ".log": CanutilsLogReader,
-        }
         suffix = pathlib.PurePath(filename).suffix
         try:
-            return lookup[suffix](filename, *args, **kwargs)
+            return LogReader.message_readers[suffix](filename, *args, **kwargs)
         except KeyError:
             raise ValueError(
                 f'No read support for this unknown log format "{suffix}"'

doc/listeners.rst

@@ -30,6 +30,24 @@ readers are also documented here.
     completely unchanged message again, since some properties are not (yet)
     supported by some file formats.
 
+.. note ::
+
+    Additional file formats for both reading/writing log files can be added via
+    a plugin reader/writer. An external package can register a new reader
+    by using the ``can.io.message_reader`` entry point. Similarly, a writer can
+    be added using the ``can.io.message_writer`` entry point.
+
+    The format of the entry point is ``reader_name=module:classname`` where ``classname``
+    is a :class:`can.io.generic.BaseIOHandler` concrete implementation.
+
+    ::
+
+     entry_points={
+         'can.io.message_reader': [
+            '.asc = my_package.io.asc:ASCReader'
+        ]
+     },
+
 
 BufferedReader
 --------------