refactor(dbapi): add type annotations to pass mypy (part of #692)

[rikettsie]

Summary

Annotate the dbapi layer (initialization, connection, cursor) so it passes mypy cleanly and can be removed from the ignore_errors baseline in pyproject.toml. This is part of issue #692.

Some non-obvious choices I made:

• On Cursor, I declared self.names and self.types as Sequence (not list) since they can be both tuple (from query_result.column_names) and list (from the comprehensions a couple of lines below).

• I kept check_valid() the void guard it was, but enforced the use of cast(Sequence, self.data) in callers (e.g. fetchall, ...) to inform mypy the value is never None after that point. That's a zero-cost type hint, another option could be using an assert.

• I annotaed username and password in connect(), with str (not str | None) since their defaults were "". By contrast, None carries no distinct meaning here, unlike host, database, and interface which can legitimately be absent.

• In connection.py, I annotated the return type of command() as Any because its type is unknown until we annotate the driver layer in a follow-up PRs.
  In all the other points where I used Any, the data type is genuinely polymorphic (in my understanding of the possibilities).

Checklist

• A human-readable description of the changes was provided to include in CHANGELOG

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All committers have signed the CLA.

[Copilot]

Pull request overview

This PR continues the effort in #692 by adding/adjusting type annotations in the clickhouse_connect.dbapi layer so it passes mypy cleanly, and then removing the DB-API modules from the mypy ignore_errors baseline in pyproject.toml.

Changes:

• Remove clickhouse_connect.dbapi* modules from the mypy ignore baseline.
• Add/adjust type annotations for DB-API connect(), Connection, and Cursor methods/properties.
• Minor refactors in Cursor around bulk insert handling (e.g., op_columns normalization) to satisfy typing.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 5 comments.

File	Description
pyproject.toml	Removes DB-API modules from the mypy ignore baseline so they must type-check cleanly.
clickhouse_connect/dbapi/cursor.py	Adds method/property annotations and refines some insert-path typing logic.
clickhouse_connect/dbapi/connection.py	Annotates DB-API connection wrapper and normalizes args passed to create_client.
clickhouse_connect/dbapi/init.py	Annotates the DB-API connect() entrypoint and kwargs typing.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

[rikettsie]

@mshustov, I addressed all Copilot feedback. A couple of comments were genuine fixes. The others were false alarms as I explained in the resolution threads, specifically around "__default__" and port=0. These are documented sentinels in create_client and _parse_connection_params, not values introduced by this PR.

[rikettsie]

@joe-clickhouse, @peter-leonov-ch, @mshustov: the CI failure is a network timeout pulling the ClickHouse Docker image from Docker Hub, not related to the changes. Could you re-run it?

[joe-clickhouse]

@rikettsie awesome work so far! The annotations look good and I agree with your reasoning on the port and database sentinels. I took a look and also confirmed both Copilot's objections there are false alarms.

Two requests before merge though. The bulk-insert path now updates rowcount, _ix, and summary, and adds a Sequence guard. Those are good behavior improvements but they go beyond annotations. So please add unit tests for them. E.g. rowcount equals written_rows after a bulk executemany, the summary is appended, and a generator passed as parameters falls through to the row path without raising. It looks like the existing bulk-insert tests use a bare Mock client so none of this is covered yet. Second, I'd prefer the changelog entry highlight the the rowcount fix rather than the annotations right now. I think a note about the annotations work should get a changelog when py.typed is restored at the end of the series. Thanks agai!