sqlalchemy optional in presto provider (#59944)

Author: steveahnahn

providers/presto/pyproject.toml

@@ -74,6 +74,9 @@ dependencies = [
 "google" = [
     "apache-airflow-providers-google"
 ]
+"sqlalchemy" = [
+    "sqlalchemy>=1.4.49",
+]
 
 [dependency-groups]
 dev = [
@@ -85,6 +88,7 @@ dev = [
     "apache-airflow-providers-google",
     # Additional devel dependencies (do not remove this line and add extra development dependencies)
     "apache-airflow-providers-common-sql[pandas,polars]",
+    "apache-airflow-providers-presto[sqlalchemy]",
 ]
 
 # To build docs:

providers/presto/src/airflow/providers/presto/hooks/presto.py

@@ -25,7 +25,6 @@
 from deprecated import deprecated
 from prestodb.exceptions import DatabaseError
 from prestodb.transaction import IsolationLevel
-from sqlalchemy.engine import URL
 
 from airflow.configuration import conf
 from airflow.exceptions import AirflowOptionalProviderFeatureException, AirflowProviderDeprecationWarning
@@ -42,6 +41,8 @@
     )
 
 if TYPE_CHECKING:
+    from sqlalchemy.engine import URL
+
     from airflow.models import Connection
 
 T = TypeVar("T")
@@ -150,6 +151,14 @@ def get_conn(self) -> Connection:
     @property
     def sqlalchemy_url(self) -> URL:
         """Return a `sqlalchemy.engine.URL` object constructed from the connection."""
+        try:
+            from sqlalchemy.engine import URL
+        except (ImportError, ModuleNotFoundError) as err:
+            raise AirflowOptionalProviderFeatureException(
+                "SQLAlchemy is not installed. Please install it with "
+                "`pip install 'apache-airflow-providers-presto[sqlalchemy]'`."
+            ) from err
+
         conn = self.get_connection(self.get_conn_id())
         extra = conn.extra_dejson or {}