Fix mapped tasks does not validate task_id

[Andrushika]

Validate task_id for mapped tasks

Why

A regular task validates its task_id in BaseOperator.__init__. A mapped task is built on a path that skips __init__, so its id was never validated. A regular task and a mapped task then accept different sets of ids, breaking the invariant that every task_id is validated:

MyOperator(task_id="bad*id")                      # raises
MyOperator.partial(task_id="bad*id").expand(...)  # passed silently

The taskflow @task mapped form had the same gap.

What

Validate the id in both mapped paths, at the point where the final id is known (after the task-group prefix and unique-suffix), matching BaseOperator.__init__. Valid ids are unaffected. Tests lock that the final id is validated, not the raw one.

related: #69965, #69937

Was generative AI tooling used to co-author this PR?

• Yes (please specify the tool below)

Generated-by: Claude Code Opus 4.8 following the guidelines

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[Andrushika]

Hi @kaxil, could you please take a look if you have time? Thanks a lot!

[Andrushika]

Hi @ashb, if it's possible, could you please take a look on this PR? Thanks!

[potiuk]

Hello @Andrushika - thank you for your contributions to Apache Airflow!

The Airflow community has introduced a limit of 5 open pull requests at a time for contributors without write access to the repository. You currently have 7 open pull requests, so - as a one-time step of introducing the limit - we closed the ones where maintainers have not engaged yet:

• Preserve AirflowTaskTimeout when timeout logging fails #69713 - Preserve AirflowTaskTimeout when timeout logging fails
• Fix mapped tasks does not validate task_id #70135 - Fix mapped tasks does not validate task_id
• Reject consecutive dots in Dag and task IDs in the Task SDK #70630 - Reject consecutive dots in Dag and task IDs in the Task SDK
• Enforce execution_timeout from the task supervisor #72493 - Enforce execution_timeout from the task supervisor
• Add breeze verify to list local checks for changed files #73241 - Add breeze verify to list local checks for changed files
• Add task state store API to the Java SDK #73464 - Add task state store API to the Java SDK

These pull requests stay open because maintainers are already engaged in them - they count towards your limit:

• Warn on suspicious Dag and task IDs at Java SDK build time #69937 - Warn on suspicious Dag and task IDs at Java SDK build time

This is not a judgement of you or of your changes. We never told contributors before that opening many pull requests at once was a problem, so there is nothing to feel bad about - and nothing is lost: your branches, commits and the review history stay where they are.

What we ask you to do is to make your first prioritization decision: choose which of the pull requests above matter most to you, and reopen them (up to 5 open at a time, including the ones still open) with the "Reopen pull request" button or gh pr reopen <PR_NUMBER> --repo apache/airflow. Reopen the ones you are ready to follow through - keep them rebased, respond to review comments and fix failing checks.

While your pull requests are waiting for review, the most valuable thing you can do is help in other ways - reviewing other contributors' pull requests, helping with issues, and taking part in the discussions on the devlist and Slack.

Why we introduced the limit, what it means for you and how to reopen or restore a pull request is explained in https://github.com/apache/airflow/blob/main/contributing-docs/32_open_pull_request_limit.rst.

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Drafted-by: Claude Code (Opus 5); reviewed by @potiuk before posting