add basic migration support

fetch_posts.py

@@ -9,10 +9,10 @@ import pendulum
 import operator
 import aiosqlite
 import contextlib
-from utils import shield
 from pleroma import Pleroma
 from bs4 import BeautifulSoup
 from functools import partial
+from utils import shield, suppress
 from typing import Iterable, NewType
 from third_party.utils import extract_post_content
 
@@ -26,6 +26,8 @@ UTC = pendulum.timezone('UTC')
 JSON_CONTENT_TYPE = 'application/json'
 ACTIVITYPUB_CONTENT_TYPE = 'application/activity+json'
 
+MIGRATION_VERSION = 1
+
 class PostFetcher:
 	def __init__(self, *, config):
 		self.config = config
@@ -47,10 +49,26 @@ class PostFetcher:
 			),
 		)
 		self._db = await stack.enter_async_context(aiosqlite.connect(self.config['db_path']))
+		await self._maybe_run_migrations()
 		self._db.row_factory = aiosqlite.Row
 		self._ctx_stack = stack
 		return self
 
+	async def _maybe_run_migrations(self):
+		async with self._db.cursor() as cur, suppress(aiosqlite.OperationalError):
+			if await (await cur.execute('SELECT migration_version FROM migrations')).fetchone(): return
+
+		await self._run_migrations()
+
+	async def _run_migrations(self):
+		# TODO proper migrations, not just "has the schema ever been run" migrations
+		async with await (anyio.Path(__file__).parent/'schema.sql').open() as f:
+			schema = await f.read()
+
+		async with self._db.cursor() as cur:
+			await cur.executescript(schema)
+			await cur.execute('INSERT INTO migrations (migration_version) VALUES (?)', (MIGRATION_VERSION,))
+
 	async def __aexit__(self, *excinfo):
 		return await self._ctx_stack.__aexit__(*excinfo)
 

schema.sql

@@ -6,3 +6,7 @@ CREATE TABLE posts (
 	-- UTC Unix timestamp in seconds
 	published_at REAL NOT NULL
 );
+
+CREATE TABLE migrations (
+	migration_version INTEGER NOT NULL
+);

utils.py

@@ -1,7 +1,25 @@
 # SPDX-License-Identifier: AGPL-3.0-only
 
 import anyio
+import contextlib
 from functools import wraps
+from datetime import datetime, timezone
+
+def as_corofunc(f):
+	@wraps(f)
+	async def wrapped(*args, **kwargs):
+		# can't decide if i want an `anyio.sleep(0)` here.
+		return f(*args, **kwargs)
+	return wrapped
+
+def as_async_cm(cls):
+	@wraps(cls, updated=())  # cls.__dict__ doesn't support .update()
+	class wrapped(cls, contextlib.AbstractAsyncContextManager):
+		__aenter__ = as_corofunc(cls.__enter__)
+		__aexit__ = as_corofunc(cls.__exit__)
+	return wrapped
+
+suppress = as_async_cm(contextlib.suppress)
 
 def shield(f):
 	@wraps(f)