Incorrect rendered template truncation for small `max_templated_fields_length` config

[amoghrajesh]

Apache Airflow version

main (development)

If "Other Airflow 3 version" selected, which one?

No response

What happened?

When AIRFLOW__CORE__MAX_TEMPLATED_FIELD_LENGTH is set to very small values (e.g., 1, 5, 10), the Rendered Templates view in the Airflow UI shows inconsistent and broken truncation behavior.

Let's take 1 as an example.

If we set AIRFLOW__CORE__MAX_TEMPLATED_FIELD_LENGTH=1 and run a task, it causes the Rendered Templates view to display truncated content inconsistently:

• Some fields show only the truncation suffix without any actual content
• Some fields are completely empty
• The truncation suffix itself exceeds the configured max length

What you think should happen instead?

With AIRFLOW__CORE__MAX_TEMPLATED_FIELD_LENGTH=1, each templated field should:

• Show at least 1 character of the actual value
• Behave consistently across all field types

How to reproduce

1. Set export AIRFLOW__CORE__MAX_TEMPLATED_FIELD_LENGTH=1 and run airflow
2. Create a dag like this one:

from datetime import datetime
from airflow.sdk import DAG
from airflow.providers.standard.operators.bash import BashOperator

with DAG(
    dag_id="test_max_length_1_bug",
    start_date=datetime(2024, 1, 1),
    schedule=None,
    catchup=False,
) as dag:
    task = BashOperator(
        task_id="test_truncation",
        bash_command="echo 'Field 1: {{ params.field1 }}' && echo 'Field 2: {{ params.field2 }}' && echo 'Field 3: {{ params.field3 }}'",
        params={
            "field1": "This is a long string that should be truncated",
            "field2": "Another long string for testing truncation behavior",
            "field3": "Short",
            "nested_dict": {
                "key1": "Long value that needs truncation",
                "key2": "Another long value",
                "key3": "X"
            },
            "list_field": ["Item 1", "Item 2", "Item 3", "Item 4"],
        },
        env={
            "ENV_VAR_1": "Long environment variable value",
            "ENV_VAR_2": "Another long environment variable",
            "ENV_VAR_3": "Short"
        }
    )

3. Observe rendered templates:

Operating System

MacOS

Versions of Apache Airflow Providers

No response

Deployment

Docker-Compose

Deployment details

No response

Anything else?

No response

Are you willing to submit PR?

• Yes I am willing to submit a PR!

Code of Conduct

• I agree to follow this project's Code of Conduct

[Ajay9704]

Hi @amoghrajesh , I’m a new contributor and would like to work on this issue if it’s still available. I’ll follow up with a PR soon.

[henry3260]

Hi @amoghrajesh , I’m a new contributor and would like to work on this issue if it’s still available. I’ll follow up with a PR soon.

Hi, thanks for your interest! There is actually an open PR for this already #59882.

Since you are interested, you are very welcome to help review or test that PR! That would be a great contribution as well.

[henry3260]

Hi @potiuk, I think you might have assigned me by mistake? It looks like @Jeevankumar-s already has a fix for this.

[potiuk]

Yeah. Mistake - BTW. I can't assign anyone who did not comment on the issue (this is how GH works) - so I can't assign @Jeevankumar-s before they comment here :)

[Ajay9704]

Hi @potiuk, @amoghrajesh, and other maintainers,

Thank you for assigning me to work on issue #59877. I appreciate the opportunity to contribute to Apache Airflow as a new contributor.

I've carefully reviewed the issue, the conversation in the thread, and the previous PR #59882 by @Jeevankumar-s. I've implemented a solution that addresses the edge cases with small max_templated_field_length values, particularly focusing on the !r formatting issue that could cause output to exceed the configured maximum length.

This is my first contribution to the Apache Airflow project, and I've tried to follow the community's best practices and coding standards. I'd appreciate your review and feedback to ensure this solution meets the project's requirements.

Thank you for your time and for maintaining this wonderful project!