[flake8-return] Only add return None at end of function (RET503)

[JonathanPlasse]

Summary

• Fix Autofix for RET503 breaks RET505 (in one case) #5765

In RET503 documentation, it is said that it only adds return None at the end of functions.
The current behavior can add return None in multiple place in the function, but not at the end of the function.
This behavior does not match the documentation and goes against other flake8-return rules like RET505 and caused people to open #5765.
The new behavior only adds return None at the end of functions like in the documentation and results in more readable code.
The new behavior is only available in preview mode.
The range of RET503 is changed to be the entire function, as it will be more clear it concerns the entire function.

Before

def main(value: str) -> int | None:
    if value == "one":
        return 1

    if value.startswith("do_stuff"):
        print("doing stuff")

        if value.endswith("haha"):
            print("haha")
            return None
        else:
            print("Instruction unclear.")
            return None
    else:
        print("Doing nothing.")
        return None

After

def main(value: str) -> int | None:
    if value == "one":
        return 1

    if value.startswith("do_stuff"):
        print("doing stuff")

        if value.endswith("haha"):
            print("haha")
        else:
            print("Instruction unclear.")
    else:
        print("Doing nothing.")
    return None

Test Plan

I added a preview snapshot for RET503.
I compared the diff between the RET503 stable and preview snapshot.
I checked the ecosystem reports and fixed one regression.

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

ℹ️ ecosystem check detected linter changes. (+364 -400 violations, +0 -0 fixes in 6 projects; 38 projects unchanged)

apache/airflow (+68 -76 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --output-format concise --preview --select ALL

+ airflow/dag_processing/processor.py:654:9: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- airflow/dag_processing/processor.py:657:13: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ airflow/io/path.py:325:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- airflow/io/path.py:342:9: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ airflow/jobs/triggerer_job_runner.py:127:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- airflow/jobs/triggerer_job_runner.py:128:9: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ airflow/metrics/otel_logger.py:181:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- airflow/metrics/otel_logger.py:202:9: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ airflow/metrics/otel_logger.py:207:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- airflow/metrics/otel_logger.py:228:9: RET503 Missing explicit `return` at the end of function able to return non-`None` value
... 134 additional changes omitted for project

bokeh/bokeh (+43 -48 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --output-format concise --preview --select ALL

+ examples/server/app/clustering/main.py:82:1: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- examples/server/app/clustering/main.py:83:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ src/bokeh/core/has_props.py:314:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- src/bokeh/core/has_props.py:340:9: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ src/bokeh/core/has_props.py:342:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- src/bokeh/core/has_props.py:367:9: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ src/bokeh/core/serialization.py:386:9: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- src/bokeh/core/serialization.py:409:13: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ src/bokeh/core/serialization.py:438:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- src/bokeh/core/serialization.py:469:9: RET503 Missing explicit `return` at the end of function able to return non-`None` value
... 81 additional changes omitted for project

demisto/content (+245 -271 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --output-format concise --preview

- Packs/AWS-Enrichment-Remediation/Scripts/AWSAccountHierarchy/AWSAccountHierarchy_test.py:100:9: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ Packs/AWS-Enrichment-Remediation/Scripts/AWSAccountHierarchy/AWSAccountHierarchy_test.py:167:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- Packs/AWS-Enrichment-Remediation/Scripts/AWSAccountHierarchy/AWSAccountHierarchy_test.py:168:9: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ Packs/AWS-Enrichment-Remediation/Scripts/AWSAccountHierarchy/AWSAccountHierarchy_test.py:17:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- Packs/AWS-Enrichment-Remediation/Scripts/AWSAccountHierarchy/AWSAccountHierarchy_test.py:18:9: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ Packs/AWS-Enrichment-Remediation/Scripts/AWSAccountHierarchy/AWSAccountHierarchy_test.py:193:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- Packs/AWS-Enrichment-Remediation/Scripts/AWSAccountHierarchy/AWSAccountHierarchy_test.py:194:9: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ Packs/AWS-Enrichment-Remediation/Scripts/AWSAccountHierarchy/AWSAccountHierarchy_test.py:99:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ Packs/AgariPhishingDefense/Integrations/AgariPhishingDefense/AgariPhishingDefense.py:116:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- Packs/AgariPhishingDefense/Integrations/AgariPhishingDefense/AgariPhishingDefense.py:189:9: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ Packs/ApiModules/Scripts/DemistoClassApiModule/DemistoClassApiModule.py:214:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- Packs/ApiModules/Scripts/DemistoClassApiModule/DemistoClassApiModule.py:222:9: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ Packs/ApiModules/Scripts/DemistoClassApiModule/DemistoClassApiModule.py:246:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- Packs/ApiModules/Scripts/DemistoClassApiModule/DemistoClassApiModule.py:248:9: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ Packs/ApiModules/Scripts/DemistoClassApiModule/DemistoClassApiModule.py:251:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- Packs/ApiModules/Scripts/DemistoClassApiModule/DemistoClassApiModule.py:253:9: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ Packs/ApiModules/Scripts/DemistoClassApiModule/DemistoClassApiModule.py:85:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- Packs/ApiModules/Scripts/DemistoClassApiModule/DemistoClassApiModule.py:87:13: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ Packs/ApiModules/Scripts/MicrosoftAzureStorageApiModule/MicrosoftAzureStorageApiModule.py:106:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- Packs/ApiModules/Scripts/MicrosoftAzureStorageApiModule/MicrosoftAzureStorageApiModule.py:130:9: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ Packs/AppNovi/Integrations/appNovi/appNovi_test.py:17:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- Packs/AppNovi/Integrations/appNovi/appNovi_test.py:22:13: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ Packs/AzureStorageFileShare/Integrations/AzureStorageFileShare/AzureStorageFileShare.py:725:1: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- Packs/AzureStorageFileShare/Integrations/AzureStorageFileShare/AzureStorageFileShare.py:745:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ Packs/AzureStorageQueue/Integrations/AzureStorageQueue/AzureStorageQueue.py:792:1: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- Packs/AzureStorageQueue/Integrations/AzureStorageQueue/AzureStorageQueue.py:822:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ Packs/AzureStorageTable/Integrations/AzureStorageTable/AzureStorageTable.py:567:1: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- Packs/AzureStorageTable/Integrations/AzureStorageTable/AzureStorageTable.py:588:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ Packs/Base/Scripts/DBotPredictPhishingWords/DBotPredictPhishingWords.py:17:1: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- Packs/Base/Scripts/DBotPredictPhishingWords/DBotPredictPhishingWords.py:30:9: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- Packs/Base/Scripts/DBotPredictPhishingWords/DBotPredictPhishingWords.py:37:9: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ Packs/Base/Scripts/DBotPredictPhishingWords/DBotPredictPhishingWords.py:48:1: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- Packs/Base/Scripts/DBotPredictPhishingWords/DBotPredictPhishingWords.py:79:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
... 483 additional changes omitted for project

ibis-project/ibis (+4 -0 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --output-format concise --preview

+ ibis/backends/duckdb/__init__.py:518:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ ibis/backends/duckdb/__init__.py:572:39: RUF100 Unused `noqa` directive (unused: `RET503`)
+ ibis/backends/pyspark/__init__.py:698:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ ibis/backends/pyspark/__init__.py:740:39: RUF100 Unused `noqa` directive (unused: `RET503`)

milvus-io/pymilvus (+1 -1 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --output-format concise --preview

+ _version_helper.py:41:1: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- _version_helper.py:42:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value

zulip/zulip (+3 -4 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --output-format concise --preview --select ALL

- zerver/lib/addressee.py:136:13: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ zerver/lib/addressee.py:95:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ zerver/tests/test_import_export.py:1413:13: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- zerver/tests/test_import_export.py:1416:17: RET503 Missing explicit `return` at the end of function able to return non-`None` value
+ zerver/tests/test_openapi.py:483:5: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- zerver/tests/test_openapi.py:562:9: RET503 Missing explicit `return` at the end of function able to return non-`None` value
- zerver/tests/test_openapi.py:563:13: RET503 Missing explicit `return` at the end of function able to return non-`None` value

... Truncated remaining completed project reports due to GitHub comment length restrictions

Changes by rule (2 rules affected)

code	total	+ violation	- violation	+ fix	- fix
RET503	762	362	400	0	0
RUF100	2	2	0	0	0

[JonathanPlasse]

Early return if in preview mode because we only need to know if the function has at least one implicit return to add a single return None at the end of the function.
The stable version can add multiple return so it cannot return early.
The code should be simplified once the preview version become stable.

[JonathanPlasse]

A comment should be added that when the preview version becomes stable the code can be simplified with early return everywhere.