Add possibility to pass engine on table reflection

[ArtsiomAntropau]

No description provided.

[codecov-commenter]

Codecov Report

Merging #875 (f611221) into master (83ea663) will increase coverage by 0.00%.
The diff coverage is 100.00%.

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@@           Coverage Diff           @@
##           master     #875   +/-   ##
=======================================
  Coverage   92.11%   92.11%           
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  Files         107      107           
  Lines        8105     8106    +1     
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+ Hits         7466     7467    +1     
  Misses        639      639           

Files Changed	Coverage Δ
piccolo/table_reflection.py	89.65% <100.00%> (+0.12%)	⬆️

[sinisaos]

@ArtsiomAntropau Thanks for the PR. I don't know if this was intended, but I can see the value of this feature if you don't use piccolo_conf in your application like here. The same can be done without these PR changes by adding piccolo_conf.py to src like this

# piccolo_conf.py in src folder
from piccolo.engine import PostgresEngine
from config import CONFIG

DB = PostgresEngine(config={"dsn": CONFIG.dsn_by_name["local"]})


# app.py in src folder
__all__ = ("build_app",)

import asyncio

from blacksheep import Application
from blacksheep.plugins import json
from orjson import loads, dumps
from piccolo.engine import PostgresEngine
from piccolo_api.crud.endpoints import PiccoloCRUD
from piccolo_api.rate_limiting.middleware import (
    RateLimitingMiddleware,
    InMemoryLimitProvider,
)

from config import CONFIG
from piccolo.table_reflection import TableStorage
from piccolo_conf import DB


json.use(
    loads=loads,
    dumps=lambda *args, **kwargs: dumps(*args, **kwargs).decode("utf-8"),
    pretty_dumps=lambda *args, **kwargs: dumps(*args, **kwargs).decode(
        "utf-8"
    ),
)


def _add_db_pool(app: Application, engine: PostgresEngine) -> None:
    app.on_start(
        lambda *_, **__: engine.start_connection_pool(
            min_size=CONFIG.db_pool_min_size, max_size=CONFIG.db_pool_max_size
        )
    )
    app.on_stop(lambda *_, **__: engine.close_connection_pool())


def _wrap_rate_limit(app: Application) -> RateLimitingMiddleware:
    return RateLimitingMiddleware(
        app,
        provider=InMemoryLimitProvider(
            limit=CONFIG.rate_limiting_limit,
            timespan=CONFIG.rate_limiting_timespan,
            block_duration=CONFIG.rate_limiting_block_duration,
        ),
    )


def build_app() -> Application:
    app = Application()

    for dsn_name, dsn in CONFIG.dsn_by_name.items():
        dsn_app = Application()

        _add_db_pool(dsn_app, DB)

        dsn_tables_store = TableStorage()
        asyncio.run(dsn_tables_store.reflect())

        for dsn_table_name, dsn_table in dsn_tables_store.tables.items():
            dsn_table._meta.db = DB
            app.mount(
                f"/{dsn_table_name}",
                PiccoloCRUD(
                    table=dsn_table, read_only=False, allow_bulk_delete=True
                ),
            )

        app.mount(f"/{dsn_name}", _wrap_rate_limit(dsn_app))

    return app

Sorry if I missed your point.

[ArtsiomAntropau]

@sinisaos so, I see several reasons

1. anyway, I'd like to have possibility to not use things that I don't need.
2. potentially, these engines might be created on-fly – while app is working, not only from config.

I hope we're not a django to force folks to do that.