[JazibAli360]

Brief Information

This pull request is in the type of:

• bug fixing
• new feature
• others

What does this PR do?

LineView._newPolyline now detaches the end label from the polyline it replaces and resets _endLabel, so _initOrUpdateEndLabel creates a new label and attaches it to the new polyline. Added a Jest test that switches step back and forth with setOption.

Root cause: Changing series.step (or the coordinate system type) makes LineView build a new polyline, but this._endLabel still pointed to the label on the old polyline, which had been removed. _initOrUpdateEndLabel saw that the label already existed and skipped setTextContent, so the new polyline had no end label.

Fixes #21833

Fixed issues

• [Bug] Line endLabel lost when setOption changes series.step (6.1.0) #21833

Details

Before: What was the problem?

After setOption changes series.step on a line series with endLabel.show: true, the end label is no longer shown.

After: How does it behave after the fixing?

The end label is recreated on the new polyline and stays visible when step changes, in either direction.

Document Info

One of the following should be checked.

• This PR doesn't relate to document changes
• The document should be updated later
• The document changes have been made in apache/echarts-doc#xxx

Misc

Security Checking

• This PR uses security-sensitive Web APIs.

ZRender Changes

• This PR depends on ZRender changes (ecomfe/zrender#xxx).

Related test cases or examples to use the new APIs

N.A.

Merging options

• Please squash the commits into a single one when merging.

Other information

How it was verified

• npm test --silent passes
• npx jest --config test/ut/jest.config.cjs passes
• npm run lint passes
• npm run checktype passes
• npm run lint --silent passes
• added/updated test: test/ut/spec/series/line.test.ts::line should keep endLabel when step is changed by setOption

Notes for reviewers

The new test fails before the fix and passes after it, and it checks that the label is attached to the current polyline and has the right text. All 195 unit tests pass, and lint and checktype pass. This is the same cleanup that remove() and the no-endLabel branch already do. I did not check it visually in a browser, including the labelLayout moveOverlap case or the animated update path.

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