Fix: GCS To BigQuery source_object

[tegardp]

Fixes #16008 GCS To BigQuery Operator's parameter source_object to accept both str and list

---

^ Add meaningful description above

Read the Pull Request Guidelines for more information.
In case of fundamental code change, Airflow Improvement Proposal (AIP) is needed.
In case of a new dependency, check compliance with the ASF 3rd Party License Policy.
In case of backwards incompatible changes please leave a note in UPDATING.md.

[boring-cyborg]

Congratulations on your first Pull Request and welcome to the Apache Airflow community! If you have any issues or are unsure about any anything please check our Contribution Guide (https://github.com/apache/airflow/blob/master/CONTRIBUTING.rst)
Here are some useful points:

• Pay attention to the quality of your code (flake8, pylint and type annotations). Our pre-commits will help you with that.
• In case of a new feature add useful documentation (in docstrings or in docs/ directory). Adding a new operator? Check this short guide Consider adding an example DAG that shows how users should use it.
• Consider using Breeze environment for testing locally, it’s a heavy docker but it ships with a working Airflow and a lot of integrations.
• Be patient and persistent. It might take some time to get a review or get the final approval from Committers.
• Please follow ASF Code of Conduct for all communication including (but not limited to) comments on Pull Requests, Mailing list and Slack.
• Be sure to read the Airflow Coding style.
  Apache Airflow is a community-driven project and together we are making it better 🚀.
  In case of doubts contact the developers at:
  Mailing List: dev@airflow.apache.org
  Slack: https://s.apache.org/airflow-slack

[potiuk]

Could you please add a test for that @tegardp

[tegardp]

Could you please add a test for that @tegardp

ah, okay

EDIT: I already checked the test_gcs_to_bigquery.py, but I a little bit confused about how to write the test. Would you mind giving me a hint? @potiuk

[eladkal]

Wouldn't it be better to convert the string to list and then the code will work just fine without a special case for string?

[tegardp]

But if the input is a list, wouldn't it be converted to a 2-dimensional list?

self.source_objects = "file1.csv"
source_object = [self.source_objects]
output: ["file1.csv"]

self.source_objects = ["file1.csv", "file2.csv", "file3.csv"]
source_object = [self.source_objects]
output: [["file1.csv", "file2.csv", "file3.csv"]]

[eladkal]

No. I was thinking of converting the type to List (if needed) so the logic part of the code won't need any modification as it works fine with List type. something like:

if isinstance(obj, str):
   obj=[obj]

[tegardp]

ahh, I was thinking about that solution too. So, it doesn't have to be one line code?

[eladkal]

please remove this white space

[eladkal]

Also please add a test to https://github.com/apache/airflow/blob/master/tests/providers/google/cloud/transfers/test_gcs_to_bigquery.py I think just a test that verify once with list and once with string is enough

[potiuk]

EDIT: I already checked the test_gcs_to_bigquery.py, but I a little bit confused about how to write the test. Would you mind giving me a hint? @potiuk

@eladkal is correct - just add a test where the source_object is string /list of strings. In the current test TEST_SOURCE_OBJECTS is list of strings, but you can create another TEST_SOURCE_OBJECTS_AS_STRING (with string value) and copy one of the existing tests just using this new constant.

[tegardp]

Thanks, @potiuk @eladkal, I pushed my tests. Did I do it correctly?

[potiuk]

Looks good :). Running the workflow now !

[github-actions]

The PR is likely OK to be merged with just subset of tests for default Python and Database versions without running the full matrix of tests, because it does not modify the core of Airflow. If the committers decide that the full tests matrix is needed, they will add the label 'full tests needed'. Then you should rebase to the latest master or amend the last commit of the PR, and push it with --force-with-lease.

[boring-cyborg]

Awesome work, congrats on your first merged pull request!

[linchun3]

hey, @tegardp I noticed that this change could be missing an edge case when retrieving a list of files from x_com:

Example:

default_args = {
"render_template_as_native_obj": True
} 

...

# retrieval of files from x_com
files = ["file1.txt", "file2.txt", "file3.txt"]

since the rendering to native object only happens on execute, the value retrieve from x_comms would still be
"["file1.txt", "file2.txt", "file3.txt"]" on initialisation and self.source_objects of the operator would be ["["file1.txt", "file2.txt", "file3.txt"]"] which is not the intended behaviour.