The pull request at #736

initially designated Pydantic as an optional dependency. However,
a subsequent pull request, #794,
introduced an implementation that requires Pydantic to be a mandatory
dependency for astronomer-cosmos. This pull request addresses the bug
encountered while running airflow db init, as described in issue
#936,
by enforcing Pydantic as a required dependency.

Furthermore, it's worth noting that Pydantic version 2 has known
issues with Airflow versions prior to 2.7.0. Given that the minimum
Airflow version supported by astronomer-cosmos is 2.3, we have
restricted the Pydantic version to be less than 2. Additionally,
a comment has been added indicating that we may remove this upper
bound once Airflow 2.7 becomes the minimum required version for
astronomer-cosmos.

closes: #936

pyproject.toml

@@ -32,6 +32,11 @@ dependencies = [
     "apache-airflow>=2.3.0",
     "importlib-metadata; python_version < '3.8'",
     "Jinja2>=3.0.0",
+    # The issue regarding Airflow and Pydantic, documented in https://github.com/apache/airflow/issues/32311, was
+    # resolved through the pull request https://github.com/apache/airflow/pull/32366. This PR was included in the
+    # release of Airflow 2.7.0. Therefore, once we set here the minimum version of Airflow to 2.7.0, we can eliminate
+    # the upper bound constraint on the version of Pydantic.
+    "pydantic>=1.10.0,<2.0.0",
     "typing-extensions; python_version < '3.8'",
     "virtualenv",
 ]