Use exists_ok in error handling instead of pre-condition (#44)

Fixes exception raised in `CouchDB.create()` even with exists_ok
This can happen in a race condition case.

Author: bmario

aiocouch/couchdb.py

@@ -91,13 +91,13 @@ async def create(
 
         """
         db = Database(self, id)
-        if not await db._exists():
+        try:
             await db._put(**kwargs)
-            return db
-        elif exists_ok:
-            return db
-        else:
-            raise PreconditionFailedError(f"The database '{id}' does already exist.")
+        except PreconditionFailedError as e:
+            if not exists_ok:
+                raise e
+
+        return db
 
     async def __getitem__(self, id: str) -> "Database":
         """Returns a representation for the given database identifier

tests/conftest.py

@@ -79,8 +79,15 @@ async def couchdb_with_user_access(
 
 
 @pytest.fixture
-async def database(couchdb: CouchDB) -> AsyncGenerator[Database, None]:
-    database = await couchdb.create("aiocouch_test_fixture_database")
+def database_id() -> str:
+    return "aiocouch_test_fixture_database"
+
+
+@pytest.fixture
+async def database(
+    couchdb: CouchDB, database_id: str
+) -> AsyncGenerator[Database, None]:
+    database = await couchdb.create(database_id)
 
     yield database
 

tests/test_server.py

@@ -1,3 +1,5 @@
+import asyncio
+
 import pytest
 
 from aiocouch import CouchDB, Database
@@ -35,6 +37,29 @@ async def test_create_for_existing(couchdb: CouchDB, database: Database) -> None
         await couchdb.create(database.id)
 
 
+async def test_create_for_existing_but_mismatching_params(
+    couchdb: CouchDB, database: Database
+) -> None:
+    from aiocouch import PreconditionFailedError
+
+    with pytest.raises(PreconditionFailedError):
+        await couchdb.create(database.id, partitioned=True)
+
+
+async def test_create_for_existing_ok_with_race(
+    couchdb: CouchDB, database_id: str
+) -> None:
+    try:
+        # try to trigger a race-condition during the creation of the database
+        await asyncio.gather(
+            *[couchdb.create(database_id, exists_ok=True) for _ in range(5)]
+        )
+    finally:
+        # for this specific test, we need to do a manual cleanup
+        db = await couchdb.create(database_id, exists_ok=True)
+        await db.delete()
+
+
 async def test_create_for_existing_ok(couchdb: CouchDB, database: Database) -> None:
     await couchdb.create(database.id, exists_ok=True)