Publish python logging events to the Language Client (#27)

lib/esbonio/changes/26.fix.rst

@@ -1,2 +1,2 @@
-Fix discovery of roles so that roles in Sphinx domains are used and that unimplemented
-``docutils`` roles are not surfaced.
+**Language Server:** Fix discovery of roles so that roles in Sphinx domains are used and
+that unimplemented ``docutils`` roles are not surfaced.

lib/esbonio/changes/27.feature.rst

@@ -0,0 +1 @@
+**Language Server:** Python log events can now published to Language Clients

lib/esbonio/esbonio/__main__.py

@@ -1,36 +1,37 @@
 import argparse
 import logging
-import pathlib
 import sys
 
-import appdirs
 import esbonio.lsp as lsp
 
 from esbonio import __version__
+from esbonio.lsp.logger import LspHandler
 
 LOG_LEVELS = [logging.ERROR, logging.INFO, logging.DEBUG]
 
 
-def start_server(verbose):
-    """Start the language server."""
+def configure_logging(verbose, server):
 
     try:
-        level = LOG_LEVELS[verbose]
+        level = LOG_LEVELS[-1]
     except IndexError:
         level = LOG_LEVELS[-1]
 
-    logdir = pathlib.Path(appdirs.user_log_dir("esbonio", "swyddfa"))
-    if not logdir.exists():
-        logdir.mkdir(parents=True)
+    logger = logging.getLogger("esbonio")
+    logger.setLevel(level)
+
+    handler = LspHandler(server)
+    handler.setLevel(level)
 
-    logfile = logdir / "language_server.log"
-    logging.basicConfig(
-        level=level,
-        format="[%(levelname)s][%(name)s]: %(message)s",
-        filemode="w",
-        filename=str(logfile),
-    )
+    formatter = logging.Formatter("[%(name)s] %(message)s")
+    handler.setFormatter(formatter)
+    logger.addHandler(handler)
+
+
+def start_server(verbose):
+    """Start the language server."""
 
+    configure_logging(verbose, lsp.server)
     lsp.server.start_io()
 
 

lib/esbonio/esbonio/lsp/logger.py

@@ -0,0 +1,34 @@
+"""This module defines a custom logging handler that publishes log messages to an LSP
+client."""
+
+import logging
+
+from pygls.server import LanguageServer
+from pygls.types import MessageType
+
+_LOG_LEVELS = {
+    logging.DEBUG: MessageType.Info,
+    logging.INFO: MessageType.Info,
+    logging.WARNING: MessageType.Warning,
+    logging.ERROR: MessageType.Error,
+    logging.CRITICAL: MessageType.Error,
+}
+
+
+class LspHandler(logging.Handler):
+    """A logging handler that will send log records to an LSP client."""
+
+    def __init__(self, server: LanguageServer):
+        super().__init__()
+        self.server = server
+
+    def emit(self, record: logging.LogRecord) -> None:
+        """Sends the record to the client."""
+
+        # To avoid infinite recursions, it's simpler to just ignore all log records
+        # coming from pygls...
+        if "pygls" in record.name:
+            return
+
+        log = self.format(record)
+        self.server.show_message_log(log, msg_type=_LOG_LEVELS[record.levelno])