Simplify imports of common classes

[simonw]

There are only a few classes that plugins need to import. It would be nice if these imports were as short and memorable as possible.

For example:

from datasette.app import Datasette
from datasette.utils.asgi import Response

Could both become:

from datasette import Datasette
from datasette import Response

[simonw]

Reviewing https://github.com/search?q=user%3Asimonw+%22from+datasette%22&type=Code I spotted these others:

# Various:
from datasette.utils import path_with_replaced_args
from datasette.plugins import pm
from datasette.utils import QueryInterrupted
from datasette.utils.asgi import Response, Forbidden, NotFound

# datasette-publish-vercel:
from datasette.publish.common import (
    add_common_publish_arguments_and_options,
    fail_if_publish_binary_not_installed
)
from datasette.utils import temporary_docker_directory

# datasette-insert
from datasette.utils import actor_matches_allow, sqlite3

# obsolete: russian-ira-facebook-ads-datasette 
from datasette.utils import TableFilter

# simonw/museums
from datasette.utils.asgi import asgi_send

# datasette-media
from datasette.utils.asgi import Response, asgi_send_file

# datasette/tests/plugins/my_plugin.py
from datasette.facets import Facet

# datasette-graphql
from datasette.views.table import TableView

[simonw]

Of these I think I'm going to promote the following to being importable directly from datasette:

• from datasette.app import Datasette
• from datasette.utils import QueryInterrupted
• from datasette.utils.asgi import Response, Forbidden, NotFound
• from datasette.utils import actor_matches_allow

All of the rest are infrequently used enough (or clearly named enough) that I'm happy to leave them as-is.

[simonw]

I tried doing this and got this error:

(datasette) datasette % pytest
==================================================================== test session starts =====================================================================
platform darwin -- Python 3.8.5, pytest-6.0.1, py-1.9.0, pluggy-0.13.1
rootdir: /Users/simon/Dropbox/Development/datasette, configfile: pytest.ini
plugins: asyncio-0.14.0, timeout-1.4.2
collected 1 item / 23 errors                                                                                                                                 

=========================================================================== ERRORS ===========================================================================
_____________________________________________________________ ERROR collecting tests/test_api.py _____________________________________________________________
ImportError while importing test module '/Users/simon/Dropbox/Development/datasette/tests/test_api.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
/usr/local/opt/python@3.8/Frameworks/Python.framework/Versions/3.8/lib/python3.8/importlib/__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
tests/test_api.py:1: in <module>
    from datasette.plugins import DEFAULT_PLUGINS
datasette/__init__.py:2: in <module>
    from .app import Datasette
datasette/app.py:30: in <module>
    from .views.base import DatasetteError, ureg
datasette/views/base.py:12: in <module>
    from datasette.plugins import pm
datasette/plugins.py:26: in <module>
    mod = importlib.import_module(plugin)
/usr/local/opt/python@3.8/Frameworks/Python.framework/Versions/3.8/lib/python3.8/importlib/__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
datasette/publish/heroku.py:2: in <module>
    from datasette import hookimpl
E   ImportError: cannot import name 'hookimpl' from partially initialized module 'datasette' (most likely due to a circular import) (/Users/simon/Dropbox/Development/datasette/datasette/__init__.py)

That's with datasette/__init__.py looking like this:

from datasette.version import __version_info__, __version__  # noqa
from .app import Datasette
from .utils.asgi import Forbidden, NotFound, Response
from .utils import actor_matches_allow, QueryInterrupted
from .hookspecs import hookimpl  # noqa
from .hookspecs import hookspec  # noqa


__all__ = [
    "actor_matches_allow",
    "hookimpl",
    "hookspec",
    "QueryInterrupted",
    "Forbidden",
    "NotFound",
    "Response",
    "Datasette",
]

[simonw]

Annoyingly this seems to be the line that causes the circular import:

from .utils.asgi import Forbidden, NotFound, Response

[simonw]

Weirdly even removing this single datasette import from utils/asgi.py didn't fix the circular import:

datasette/datasette/utils/asgi.py

Lines 1 to 3 in 44cf424

	import json
	from datasette.utils import MultiParams
	from mimetypes import guess_type

[simonw]

I'm just going with:

from datasette import Response
from datasette import Forbidden
from datasette import NotFound
from datasette import hookimpl
from datasette import actor_matches_allow

[simonw]

Documented here: https://docs.datasette.io/en/latest/internals.html#import-shortcuts