Investigate why didSave notification is not sent if view closed immediately after saving

[jwortmann]

When a file is saved, a textDocument/didSave notifications should be sent to the server if it opts-in via TextDocumentSyncOptions.

But if the file gets closed immediately after saving, the notification is not sent (at least here on Windows, and apparently also on CI on all OS, but according to #2438 (comment) it seems to work in practice on Linux).

Key binding example:

    {
        "keys": ["f1"],
        "command": "chain",
        "args": {
            "commands": [
                ["save", {"async": false}],
                ["close", {}]
            ]
        }
    },

I expect to see textDocument/didSave in the LSP server log panel before textDocument/didClose, but it's missing.

If this gets fixed, this line in the tests could be uncommented:

LSP/tests/test_single_document.py

Line 394 in 4c8da78

# yield from self.await_message('textDocument/didSave') # TODO why is this not sent?