Fix notebook error formatting

extensions/positron-python/python_files/.vscode/settings.json

@@ -9,7 +9,8 @@
         "editor.rulers": [100],
     },
     "python.testing.pytestArgs": [
-        "tests"
+        "tests",
+        "positron/positron_ipykernel/tests"
     ],
     "python.testing.unittestEnabled": false,
     "python.testing.pytestEnabled": true,

extensions/positron-python/python_files/positron/positron_ipykernel/positron_ipkernel.py

@@ -11,7 +11,7 @@
 import re
 import warnings
 from pathlib import Path
-from typing import Any, Callable, Container, Dict, List, Optional, Type
+from typing import Any, Callable, Container, Dict, List, Optional, Type, cast
 
 import traitlets
 from ipykernel.comm.manager import CommManager
@@ -45,6 +45,26 @@ class _CommTarget(str, enum.Enum):
     Connections = "positron.connection"
 
 
+class SessionMode(str, enum.Enum):
+    """
+    The mode that the kernel application was started in.
+    """
+
+    Console = "console"
+    Notebook = "notebook"
+    Background = "background"
+
+    Default = Console
+
+    def __str__(self) -> str:
+        # Override for better display in argparse help.
+        return self.value
+
+    @classmethod
+    def trait(cls) -> traitlets.Enum:
+        return traitlets.Enum(sorted(cls), help=cls.__doc__)
+
+
 logger = logging.getLogger(__name__)
 
 
@@ -138,6 +158,18 @@ class PositronShell(ZMQInteractiveShell):
         help="Class to use to instantiate the shell inspector",
     ).tag(config=True)
 
+    # Positron-specific attributes:
+    session_mode: SessionMode = SessionMode.trait()  # type: ignore
+
+    def __init__(self, *args, **kwargs):
+        # Set custom attributes from the parent object.
+        # It would be better to pass these as explicit arguments, but there's no easy way
+        # to override the parent to do that.
+        parent = cast(PositronIPyKernel, kwargs["parent"])
+        self.session_mode = parent.session_mode
+
+        super().__init__(*args, **kwargs)
+
     def init_events(self) -> None:
         super().init_events()
 
@@ -250,6 +282,11 @@ def _showtraceback(self, etype, evalue: Exception, stb: List[str]):  # type: ign
         """
         Enhance tracebacks for the Positron frontend.
         """
+        if self.session_mode == SessionMode.Notebook:
+            # Don't modify the traceback in a notebook. The frontend assumes that it's unformatted
+            # and applies its own formatting.
+            return super()._showtraceback(etype, evalue, stb)  # type: ignore IPython type annotation is wrong
+
         # Remove the first two lines of the traceback, which are the "---" header and the repeated
         # exception name and "Traceback (most recent call last)".
         # Also remove the last line of the traceback, which repeats f"{etype}: {evalue}".
@@ -305,7 +342,16 @@ class PositronIPyKernel(IPythonKernel):
         klass=InteractiveShell,
     )
 
+    # Positron-specific attributes:
+    session_mode: SessionMode = SessionMode.trait()  # type: ignore
+
     def __init__(self, **kwargs) -> None:
+        # Set custom attributes from the parent object.
+        # It would be better to pass these as explicit arguments, but there's no easy way
+        # to override the parent to do that.
+        parent = cast(PositronIPKernelApp, kwargs["parent"])
+        self.session_mode = parent.session_mode
+
         super().__init__(**kwargs)
 
         # Create Positron services
@@ -383,6 +429,9 @@ class PositronIPKernelApp(IPKernelApp):
     # Use the PositronIPyKernel class.
     kernel_class: Type[PositronIPyKernel] = traitlets.Type(PositronIPyKernel)  # type: ignore
 
+    # Positron-specific attributes:
+    session_mode: SessionMode = SessionMode.trait()  # type: ignore
+
 
 #
 # OSC8 functionality

extensions/positron-python/python_files/positron/positron_ipykernel/tests/conftest.py

@@ -3,13 +3,19 @@
 #
 
 from typing import Iterable
-from unittest.mock import Mock
+from unittest.mock import MagicMock, Mock
 
 import comm
 import pytest
+from traitlets.config import Config
 from positron_ipykernel.connections import ConnectionsService
 from positron_ipykernel.data_explorer import DataExplorerService
-from positron_ipykernel.positron_ipkernel import PositronIPyKernel, PositronShell
+from positron_ipykernel.positron_ipkernel import (
+    PositronIPKernelApp,
+    PositronIPyKernel,
+    PositronShell,
+    SessionMode,
+)
 from positron_ipykernel.variables import VariablesService
 
 
@@ -43,10 +49,15 @@ def kernel() -> PositronIPyKernel:
     """
     The Positron kernel, configured for testing purposes.
     """
-    # Create a Positron kernel. The kernel calls shell_class.instance() to get the globally
-    # registered shell instance, and IPython registers a TerminalInteractiveShell instead of a
-    # PositronShell. This causes a traitlets validation error unless we pass the shell_class explicitly.
-    kernel = PositronIPyKernel.instance(shell_class=PositronShell)
+    # Mock the application object. We haven't needed to use it in tests yet, but we do need it to
+    # pass our custom attributes down to the shell.
+    app = MagicMock(PositronIPKernelApp)
+    app.config = Config()  # Needed to avoid traitlets errors
+
+    # Positron-specific attributes:
+    app.session_mode = SessionMode.Console
+
+    kernel = PositronIPyKernel.instance(parent=app)
 
     return kernel
 

extensions/positron-python/python_files/positron/positron_ipykernel/tests/test_positron_ipkernel.py

@@ -10,6 +10,7 @@
 import pandas as pd
 import pytest
 from IPython.utils.syspathcontext import prepended_to_syspath
+from positron_ipykernel.positron_ipkernel import SessionMode
 from positron_ipykernel.help import help
 from positron_ipykernel.utils import alias_home
 
@@ -81,7 +82,12 @@ def g():
 """
 
 
-def test_traceback(shell: PositronShell, tmp_path: Path, mock_displayhook: Mock) -> None:
+def test_console_traceback(
+    shell: PositronShell, tmp_path: Path, mock_displayhook: Mock, monkeypatch
+) -> None:
+    # Ensure that we're in console mode.
+    monkeypatch.setattr(shell, "session_mode", SessionMode.Console)
+
     # We follow the approach of IPython's test_ultratb.py, which is to create a temporary module,
     # prepend its parent directory to sys.path, import it, then run a cell that calls a function
     # from it.
@@ -167,6 +173,44 @@ def test_traceback(shell: PositronShell, tmp_path: Path, mock_displayhook: Mock)
     )
 
 
+def test_notebook_traceback(
+    shell: PositronShell, tmp_path: Path, mock_displayhook: Mock, monkeypatch
+) -> None:
+    # Ensure that we're in notebook mode.
+    monkeypatch.setattr(shell, "session_mode", SessionMode.Notebook)
+
+    # We follow the approach of IPython's test_ultratb.py, which is to create a temporary module,
+    # prepend its parent directory to sys.path, import it, then run a cell that calls a function
+    # from it.
+
+    # Create a temporary module.
+    file = tmp_path / "test_traceback.py"
+    file.write_text(code)
+
+    # Temporarily add the module to sys.path and call a function from it, which should error.
+    with prepended_to_syspath(str(tmp_path)):
+        shell.run_cell("import test_traceback; test_traceback.g()")
+
+    # Check that a single message was sent to the frontend.
+    call_args_list = mock_displayhook.session.send.call_args_list
+    assert len(call_args_list) == 1
+
+    call_args = call_args_list[0]
+
+    # Check that the message was sent over the "error" stream.
+    assert call_args.args[1] == "error"
+
+    exc_content = call_args.args[2]
+
+    # Check that we haven't removed any frames.
+    # We don't check the traceback contents in this case since that's tested in IPython.
+    assert len(exc_content["traceback"]) == 6
+
+    # Check that we haven't modified any other contents.
+    assert exc_content["ename"] == "Exception"
+    assert exc_content["evalue"] == "This is an error!"
+
+
 def assert_ansi_string_startswith(actual: str, expected: str) -> None:
     """
     Assert that an ansi-formatted string starts with an expected string, in a way that gets pytest

extensions/positron-python/python_files/positron/positron_language_server.py

@@ -9,9 +9,8 @@
 import os
 import sys
 
-from positron_ipykernel.positron_ipkernel import PositronIPKernelApp
+from positron_ipykernel.positron_ipkernel import PositronIPKernelApp, SessionMode
 from positron_ipykernel.positron_jedilsp import POSITRON
-from traitlets.config import Config
 
 logger = logging.getLogger(__name__)
 
@@ -57,9 +56,9 @@ def parse_args() -> argparse.Namespace:
     parser.add_argument(
         "--session-mode",
         help="session mode in which the kernel is to be started",
-        type=str,
-        default="console",
-        choices=["console", "notebook", "background"],
+        type=SessionMode,
+        default=SessionMode.Default,
+        choices=sorted(SessionMode),
     )
     args = parser.parse_args()
     args.loglevel = args.loglevel.upper()
@@ -108,20 +107,17 @@ def parse_args() -> argparse.Namespace:
             }
         }
 
-    # Start Positron's IPyKernel as the interpreter for our console.
     # IPKernelApp expects an empty string if no connection_file is provided.
     if args.connection_file is None:
         args.connection_file = ""
 
-    config = Config(
-        IPKernelApp={
-            "connection_file": args.connection_file,
-            "log_level": args.loglevel,
-            "logging_config": logging_config,
-        },
+    # Start Positron's IPyKernel as the interpreter for our console.
+    app: PositronIPKernelApp = PositronIPKernelApp.instance(
+        connection_file=args.connection_file,
+        log_level=args.loglevel,
+        logging_config=logging_config,
+        session_mode=args.session_mode,
     )
-
-    app: PositronIPKernelApp = PositronIPKernelApp.instance(config=config)
     # Initialize with empty argv, otherwise BaseIPythonApplication.initialize reuses our
     # command-line arguments in unexpected ways (e.g. logfile instructs it to log executed code).
     app.initialize(argv=[])

src/vs/workbench/contrib/positronNotebook/browser/getOutputContents.ts

@@ -122,7 +122,7 @@ export function parseOutputData(output: ICellOutput['outputs'][number]): ParsedO
 		}
 
 		if (mime === 'application/vnd.code.notebook.error') {
-			return { type: 'error', content: parsedMessage.message };
+			return { type: 'error', content: parsedMessage.stack };
 		}
 
 	} catch (e) {

src/vs/workbench/contrib/positronNotebook/browser/notebookCells/CellTextOutput.css

@@ -4,4 +4,6 @@
 
 .positron-notebook-text-output {
 	font-family: var(--monaco-monospace-font, monospace);
+	font-size:  var(--notebook-cell-output-font-size, 12px);
+	white-space: pre-wrap;
 }