Codecov Report

Merging #936 into main will increase coverage by 0.02%. The diff coverage is n/a.

```diff @@ Coverage Diff @@

main #936 +/-

========================================== + Coverage 84.02% 84.04% +0.02%
========================================== Files 28 28
Lines 3774 3774
========================================== + Hits 3171 3172 +1
+ Misses 603 602 -1
```

| Impacted Files | Coverage Δ | | |---|---|---| | datasette/app.py | 96.18% <0.00%> (+0.18%) | :arrow_up: |

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Test failure: ``` tests/test_canned_queries.py F

captured stdout >>> enter traceback >>>

canned_write_client = <datasette.utils.testing.TestClient object at 0x108ec5040>

def test_insert(canned_write_client):
    response = canned_write_client.post(
        "/data/add_name",
        {"name": "Hello"},
        allow_redirects=False,
        csrftoken_from=True,
        cookies={"foo": "bar"},
    )
    assert 302 == response.status

  assert "/data/add_name?success" == response.headers["Location"]

E AssertionError: assert '/data/add_name?success' == '/data/add_name' E - /data/add_name E + /data/add_name?success E ? ++++++++

/Users/simon/Dropbox/Development/datasette/tests/test_canned_queries.py:66: AssertionError ``` No idea why this change would affect that test.

This implementation seems to fix it, need to work out how to test though. ```diff diff --git a/datasette/database.py b/datasette/database.py index ffa7a79..7ba1456 100644 --- a/datasette/database.py +++ b/datasette/database.py @@ -89,14 +89,22 @@ class Database: def _execute_writes(self): # Infinite looping thread that protects the single write connection # to this database - conn = self.connect(write=True) + conn_exception = None + conn = None + try: + conn = self.connect(write=True) + except Exception as e: + conn_exception = e while True: task = self._write_queue.get() - try: - result = task.fn(conn) - except Exception as e: - print(e) - result = e + if conn_exception is not None: + result = conn_exception + else: + try: + result = task.fn(conn) + except Exception as e: + print(e) + result = e task.reply_queue.sync_q.put(result)

 async def execute_fn(self, fn):

```

The easiest way to recreate this is to attempt a write against an immutable database, which triggers this assertion error:

https://github.com/simonw/datasette/blob/13b3b51087964d5e1a8c1cdd2495e07bdbe176b8/datasette/database.py#L47-L55

The bug is here:

https://github.com/simonw/datasette/blob/13b3b51087964d5e1a8c1cdd2495e07bdbe176b8/datasette/database.py#L89-L100

If conn = self.connect(write=True) raises an exception the entire server hangs, like this: ``` % datasette -i fixtures.db --get /
Exception in thread Thread-1: Traceback (most recent call last): File "/usr/local/opt/python@3.8/Frameworks/Python.framework/Versions/3.8/lib/python3.8/threading.py", line 932, in _bootstrap_inner self.run() File "/usr/local/opt/python@3.8/Frameworks/Python.framework/Versions/3.8/lib/python3.8/threading.py", line 870, in run self._target(self._args, *self._kwargs) File "/Users/simon/.local/share/virtualenvs/latest-datasette-with-all-plugins-PJL_Xy9e/lib/python3.8/site-packages/datasette/database.py", line 92, in _execute_writes conn = self.connect(write=True) File "/Users/simon/.local/share/virtualenvs/latest-datasette-with-all-plugins-PJL_Xy9e/lib/python3.8/site-packages/datasette/database.py", line 55, in connect assert not (write and not self.is_mutable) AssertionError

... server hangs here ... ```