Make minor-freeze version bump idempotent for already-completed bumps

[edsavage]

Summary

When the Centralized Version Bump pipeline re-triggered the 9.5.0 minor bump (to unblock another service) ml-cpp's ml-cpp-version-bump build #59 failed because the bump had already completed. Release engineering asked that the version-bump logic be idempotent: it should not fail if the minor branch has already been cut and main has already been bumped to the next expected version.

Root cause (Leg A): validate_minor_freeze_params (used by create_minor_branch.sh) hard-required main == NEW_VERSION. After a completed freeze, main is at MAIN_NEW_VERSION (e.g. 9.6.0) while NEW_VERSION is still 9.5.0, so validation raised and the step failed. Leg B (validate_main_minor_bump) was already idempotent (no-ops when current == MAIN_NEW_VERSION).

Changes

• dev-tools/version_bump_validation.py: validate_minor_freeze_params now accepts main being at either:

  • NEW_VERSION — freeze not yet applied (normal pre-freeze), or
  • the derived MAIN_NEW_VERSION — freeze already completed, only when the release branch already exists (idempotent re-run).

  main advancing to MAIN_NEW_VERSION without the release branch being cut is still rejected as a genuinely inconsistent state. The validator also logs a clear "minor freeze already completed (idempotent no-op)" line for the Buildkite log.

• dev-tools/unittest/test_version_bump_validation.py: added regression tests for the completed-freeze re-run, the branch-cut-but-main-not-yet-bumped intermediate state, and the two states that must still be rejected.

Effect on the pipeline

With this fix, a re-run after a completed freeze no-ops cleanly:

• Leg A: create_minor_branch.sh validates OK, sees the branch already exists, sets ml_cpp_minor_branch_needed=false, and exits 0.
• Leg B: bump_main_minor_freeze.sh validates OK (no-op), finds no gradle.properties/.backportrc.json diff, prints "nothing to do", sets ml_cpp_main_bump_needed=false, and exits 0.

Test plan

• python3 -m pytest dev-tools/unittest/test_version_bump_validation.py -q passes (26 passed, 2 git-integration skipped)
• CLI check: validate-minor-freeze --main-version 9.6.0 --new 9.5.0 --branch 9.5 --release-branch-exists --release-branch-version 9.5.0 returns 0
• CLI check: validate-main-minor-bump --current 9.6.0 --main-new-version 9.6.0 --release-branch-version 9.5.0 returns 0
• Optional: dry-run re-trigger of ml-cpp-version-bump against the completed 9.5.0 freeze confirms both legs no-op

Related

• Follows the same minor-freeze automation touched by [ML] Automate minor version bump in CI pipeline #3064, [ML] Skip backport for minor-freeze version bump PRs #3070, Fix branchLabelMapping precedence for main override in .backportrc.json #3072.

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[elasticsearchmachine]

Pinging @elastic/ml-core (Team:ML)

[Copilot]

Pull request overview

This PR makes the minor-freeze (feature-freeze) version bump validation idempotent so that re-triggering the centralized version bump pipeline does not fail after a freeze has already completed (i.e., the release branch exists at NEW_VERSION and main has already advanced to the derived MAIN_NEW_VERSION).

Changes:

• Relax validate_minor_freeze_params to accept main being at MAIN_NEW_VERSION when (and only when) the release branch already exists, preserving detection of inconsistent states.
• Add CLI logging to clearly indicate the “already completed (idempotent no-op)” case.
• Add regression tests covering completed-freeze re-runs and key intermediate/invalid states.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
dev-tools/version_bump_validation.py	Updates minor-freeze validation to allow idempotent re-runs when the release branch already exists and main is already bumped.
dev-tools/unittest/test_version_bump_validation.py	Adds unit tests for the new idempotent and intermediate-state behaviors, plus preserved rejection cases.

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[ninalee12]

Looks good to me

Ran function locally and works as expected:

python3 dev-tools/version_bump_validation.py validate-minor-freeze \
  --main-version 9.6.0 \
  --new 9.5.0 \
  --branch 9.5 \
  --release-branch-exists \
  --release-branch-version 9.5.0
OK: minor freeze NEW_VERSION=9.5.0 on branch 9.5
OK: main already bumped to 9.6.0 and branch 9.5 exists — minor freeze already completed (idempotent no-op).
OK: main bump target MAIN_NEW_VERSION=9.6.0