Clean up pyproject.toml and build pipeline

[emilykl]

Link to issue

Closes #5537

Description of change

Configuration updates

• Switch build backend from setuptools to hatch
  • hatch is distributed by PyPA and has a number of advantages compared to setuptools, including being newer and more modern
• Update pyproject.toml config to work with hatch, and remove unused config sections
  • Remove MANIFEST.in file, since it's only required by setuptools, not needed for hatch
• Update js/package.json to reflect the correct version number matching plotly.py version, which we've forgotten to do for the last few releases
• Add js/webpack.config.js to make lab extension build output identical across platforms, which fixes the false failure of the "Check JS build" workflow when committing build artifacts built locally
• Remove keys from js/install.json file which I believe are not needed

Process updates

• Add CI step to check that version numbers in pyproject.toml and js/package.json match
• Add new command bumpversion to commands.py. Now, you can run python commands.py bumpversion X.Y.Z to update the version number to X.Y.Z everywhere across the package
• Update RELEASE.md instructions to use the bumpversion command

NOTE: The python package build command remains the same: python -m build .

Demo

python-m-build.mov

When running python -m build . locally, the output should look like the above.

Testing strategy

I've added a CI step in .github/workflows/check-js-build.yml to check that the version number in pyproject.toml matches the version number in js/project.json, which should prevent the two from getting out of sync again.

Show success case

Show failure case

No additional unit testing is needed: The CI already runs `python -m build .` , so if that step fails then we know something is wrong.

However, we should verify manually that the resulting build is the same before and after these changes.

This can be done by checking out this branch, running python -m build ., and comparing the .tar.gz and .whl files to the official 6.6.0 release artifacts.

Additional information (optional)

Because we manually pre-build the assets for the JupyterLab extension (by running npm run build from the js/ directory, as documented in the CONTRIBUTING.md), we do not use any of the hatch build hooks settings in the pyproject.toml, so this PR removes them.

The existing .github/check-js-build.yml step builds the lab extension in CI and ensures that the output matches the build artifacts in plotly/labextension/.

I don't like that this setup requires updating the version number in two places. But package.json doesn't support dynamic version numbers, so the only way to set up a single source of truth would be for the package.json to be the single source of truth, and pyproject.toml to load that version number dynamically, which is weird for a Python project

To make this less painful I've added python commands.py bumpversion X.Y.Z which automatically updates the version number everywhere.

Guidelines

• I have reviewed the pull request guidelines and the Code of Conduct and confirm that this PR follows them.
• I have added an entry to the changelog if needed (not required for documentation PRs).

[emilykl]

fyi @franred this is the PR I mentioned last week!

[Copilot]

Pull request overview

This PR modernizes plotly.py’s packaging/build configuration by switching the Python build backend to hatchling, cleaning up legacy pyproject.toml sections, and tightening the JupyterLab extension build/versioning workflow to reduce CI drift and cross-platform build artifact differences.

Changes:

• Switch Python build backend from setuptools to hatchling and remove legacy setuptools/jupyter-packaging config.
• Align JupyterLab extension versions and stabilize webpack output across platforms.
• Add CI checks to keep Python and JS version numbers in sync and improve the JS build artifact comparison workflow.

Reviewed changes

Copilot reviewed 10 out of 15 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
uv.lock	Updates dev/dev-build deps away from the jupyter meta-package toward explicit jupyterlab pins.
pyproject.toml	Switches to hatchling and replaces packaging data/sharing configuration for the labextension.
plotly/labextension/static/remoteEntry.*.js	Updates committed prebuilt labextension artifacts (hash/version changes).
plotly/labextension/static/*.LICENSE.txt	Adds/updates bundled license output from the JS build.
plotly/labextension/package.json	Updates extension version and build metadata (including webpack config and new remoteEntry filename).
js/webpack.config.js	Forces stable webpack IDs/content hashing for cross-platform deterministic outputs.
js/package.json	Updates JS package version and points JupyterLab builder at the custom webpack config.
js/package-lock.json	Updates lockfile; currently shows a version mismatch vs js/package.json.
js/install.json	Simplifies install metadata intended for JupyterLab extension installation UX.
RELEASE.md	Adds release step to update js/package.json version.
MANIFEST.in	Removed as part of moving away from setuptools.
.github/workflows/check-js-build.yml	Adds version-sync check and tweaks the artifact-compare workflow; still uses deprecated setup-node@v2.

Files not reviewed (1)

• js/package-lock.json: Language not supported

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