Add --debug option to flask run

[greyli]

The alternative of #4778, fixes #4777

Using flask run with --debug is common usage, and adding this option to flask run makes the command more intuitive:

flask run --debug

If this change is accepted, then I will update the docs and add tests.

Checklist:

• Add tests that demonstrate the correct behavior of the change. Tests should fail without the change.
• Add or update relevant docs, in the docs folder and in code.
• Add an entry in CHANGES.rst summarizing the change and linking to the issue.
• Add .. versionchanged:: entries in any relevant code docs.
• Run pre-commit hooks and fix any issues.
• Run pytest and tox, no tests failed.

[davidism]

It's a bit confusing to have both --debug and --debugger flags, but I'm guessing most people don't know about the second flag anyway. This mostly matches the signature for app.run, which calls them debug and use_debugger.

[greyli]

Rebased to 2.2.x and updated docs. I'm not sure if we need to add tests here, I was thinking something like this:

@pytest.mark.parametrize(
    "option,value",
    (
        (["--debug"], True),
        (["--no-debug"], False),
    )
)
def test_run_debug(option, value):
    ctx = run_command.make_context("run", option)
    assert ctx.params["debug"] == value

But it seems unnecessary.

[greyli]

It's a bit confusing to have both --debug and --debugger flags, but I'm guessing most people don't know about the second flag anyway. This mostly matches the signature for app.run, which calls them debug and use_debugger.

When this option was added, I think most people will use --debug over --reload and --debugger.

BTW, --reloader matches --debugger and use_reloader better. Do you think we need to rename --reload to --reloader?

[davidism]

I agree we should change reload to reloader as well, but I want to wait until Click can show a deprecation message for individual options.