Reticulate: Recover tests (#11232)

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This PR overrides the default `post_handler_hook` and `pre_handler_hook`
in the IPyKernel instance, so that exceptions from executing it are not
raised with `exc_info=True`.
Those hooks were added in ipython/ipykernel#49
to allow customizing the signal behaviors.
Later, they started being executed in a try context and exceptions:
ipython/ipykernel#360
Their code hasn't changed in the last 10 years, so it seems safe to
override them like this.

Addresses #10953

The problem we are trying to solve described in #10953 is that in
Reticulate sessions on Linux, some execute requests hang, causing the
kernel to be completely unresponsive.

I'm not entirely sure why this fix works, but here's the hypothesis:

- The kernel receives an execute_request.
- The shell thread starts processing it and runs the `pre_handler_hook`
which fails in reticulate (because you can't signal from the main
thread)
- This causes a log message to be written with `self.log.debug("Unable
to signal in pre_handler_hook:", exc_info=True)`
- Log messages are written to an `OutStream`, which will eventually
[`flush`](https://github.com/ipython/ipykernel/blob/327589f5e0ed3759751daebb724b8f7d1a0e0c52/ipykernel/iostream.py#L587-L610).
- Flushing needs to re-schedule to the IO thread and is a locking
operation with a 10s timeout. This can cause hangs eg, we delay
responding to rpc status messages, etc.

The hypothesis is that larger tracebacks, makes the IO thread queue
larger, which makes more likely that flushing times out.

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#### New Features

- N/A

#### Bug Fixes

- N/A

### QA Notes

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@:reticulate @:web

Author: dfalbel

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

@@ -643,6 +643,24 @@ def _showwarning(self, message, category, filename, lineno, file=None, line=None
 
         return original_showwarning(message, category, filename, lineno, file, line)  # type: ignore reportAttributeAccessIssue
 
+    def pre_handler_hook(self):
+        # Override the default pre_handler_hook to add debug logging.
+        # The default logging in Ipykernel adds the exc_info=True which is causing
+        # huge tracebacks, specially in reticulate sessions - the pre_handler_hook and
+        # post_handler_hook always fail because they can't signal from a different thread.
+        # See: https://github.com/posit-dev/positron/issues/10953
+        try:
+            super().pre_handler_hook()
+        except Exception as e:
+            self.log.debug("Error in super().pre_handler_hook(): %s", e, exc_info=False)
+
+    def post_handler_hook(self):
+        # see the pre_handler_hook for details
+        try:
+            super().post_handler_hook()
+        except Exception as e:
+            self.log.debug("Error in super().post_handler_hook(): %s", e, exc_info=False)
+
 
 class PositronIPKernelApp(IPKernelApp):
     control_thread: ControlThread | None

test/e2e/tests/reticulate/reticulate-multiple.test.ts

@@ -14,7 +14,7 @@ test.use({
 // RETICULATE_PYTHON
 // to the installed python path
 
-test.describe.skip('Reticulate', {
+test.describe('Reticulate', {
 	tag: [tags.RETICULATE, tags.WEB, tags.ARK, tags.SOFT_FAIL],
 }, () => {
 	test.beforeAll(async function ({ app, settings }) {

test/e2e/tests/reticulate/reticulate-repl-python.test.ts

@@ -14,7 +14,7 @@ test.use({
 // RETICULATE_PYTHON
 // to the installed python path
 
-test.describe.skip('Reticulate', {
+test.describe('Reticulate', {
 	tag: [tags.RETICULATE, tags.WEB, tags.ARK, tags.SOFT_FAIL],
 }, () => {
 	test.beforeAll(async function ({ app, settings }) {

test/e2e/tests/reticulate/reticulate-restart.test.ts

@@ -14,7 +14,7 @@ test.use({
 // RETICULATE_PYTHON
 // to the installed python path
 
-test.describe.skip('Reticulate', {
+test.describe('Reticulate', {
 	tag: [tags.RETICULATE, tags.WEB, tags.SOFT_FAIL],
 }, () => {
 	test.beforeAll(async function ({ app, settings }) {

test/e2e/tests/reticulate/reticulate-stop-start.test.ts

@@ -14,7 +14,7 @@ test.use({
 // RETICULATE_PYTHON
 // to the installed python path
 
-test.describe.skip('Reticulate', {
+test.describe('Reticulate', {
 	tag: [tags.RETICULATE, tags.WEB, tags.SOFT_FAIL],
 }, () => {
 	test.beforeAll(async function ({ app, settings }) {

test/e2e/tests/reticulate/reticulate-variables.test.ts

@@ -12,7 +12,7 @@ test.use({
 // In order to run this test on Windows, I think we need to set the env var:
 // RETICULATE_PYTHON to the installed python path
 
-test.describe.skip('Reticulate - Variables pane support', {
+test.describe('Reticulate - Variables pane support', {
 	tag: [tags.RETICULATE, tags.WEB, tags.SOFT_FAIL],
 }, () => {
 	test('R - Verify Reticulate formats variables in the Variables pane', async function ({ app, sessions, logger }) {