[GitHub] [airflow] ashb commented on a change in pull request #6601: [AIRFLOW-6010] Remove cyclic imports and pylint disables

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ashb commented on a change in pull request #6601: [AIRFLOW-6010] Remove cyclic imports and pylint disables
URL: https://github.com/apache/airflow/pull/6601#discussion_r348377993
 
 

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 File path: CONTRIBUTING.rst
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 @@ -509,6 +509,35 @@ You can always skip running the tests by providing ``--no-verify`` flag to the
 
 To check other usage types of the pre-commit framework, see `Pre-commit website <https://pre-commit.com/>`__.
 
+Importing Airflow core objects
+==============================
+
+When you implement core features or DAGs you might need to import some of the core objects or modules.
+Since airflow can be used both as application (by internal classes) and as library (by DAGs), there are
+different ways those core objects and packages are imported.
+
+Airflow imports some of the core objects directly to 'airflow' package so that they can be used from there.
+
+Those criteria were assumed for choosing what import path to use:
+
+* If you work on a core feature inside airflow, you should import the objects directly from the package where
+  the object is defined - this minimises the risk of cyclic imports.
+* If you import the objects from any of 'providers' classes, you should import the objects from
+  'airflow' or 'airflow.modules', It is very important for back-porting operators/hooks/sensors
 
 Review comment:
   ```suggestion
     'airflow' or 'airflow.models', It is very important for back-porting operators/hooks/sensors
   ```
   I think?

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