vega-lite, a grammar whose package ships its own source and four CLI converters

The title line is an anchor tag closed by a stray img tag

The page opens with the project name as a heading linked to the project site, followed by five badges for the npm package, the GitHub actions run, codecov, prettier, and jsdelivr. The rest of the README is short by design: a paragraph on what the grammar does, five links to the documentation site, an invitation to try the online editor, and pointers to the contributing guide, the code of conduct, and the roadmap.

The exports map points into build/, and build/ is committed

The package is `"type": "module"` and its exports map sends the root import to `./build/index.d.ts` for types and `./build/index.js` for the default condition. There are two more entries. One exposes the JSON schema itself at `./vega-lite-schema.json`, which is what makes editor completion and spec validation possible from the installed package. The other is a subpath, `./types_unstable/*`, mapped to `./build/*`, whose name marks the types reached through it as unstable. Meanwhile `build/` appears in the repository's own top level listing, so the directory the exports point at is checked in rather than produced by your install, and the published `files` array carries `bin`, `build`, `src`, `vega-lite*`, and `tsconfig.json`. Shipping `src` next to `build` is the unusual part.

Four converter binaries come with the library

The manifest declares a `bin` block with four names:

  "bin": {
    "vl2pdf": "./bin/vl2pdf",
    "vl2png": "./bin/vl2png",
    "vl2svg": "./bin/vl2svg",
    "vl2vg": "./bin/vl2vg"
  },

Three of them are the obvious image formats, and the fourth, `vl2vg`, does not follow the same pattern, exporting to Vega's own JSON rather than to a picture. So installing the package as a library dependency also puts four executables on your path, which matters in a container image or anywhere the install is not a human at a terminal. The scripts behind them live in the `bin/` directory in the tree, separate from the `scripts/` directory that holds build tooling, and the two CDN entry points, `unpkg` and `jsdelivr`, both point at `build/vega-lite.min.js`.

Every example spec is checked against the schema the package ships

The examples directory is not a folder of loose snippets. It holds `specs/`, a `compiled/` directory for the output, and two test files, `examples.test.ts` and `schema.test.ts`. The second one, by its name, tests the examples against the schema. Building them is a separate script from building the library, though `prebuild:examples` runs the library build (`build:only`) first.

Example images are built with the timezone pinned to one city

Two scripts build the examples, and both set the timezone inline rather than relying on the machine:

    "build:examples": "npm run data && TZ=America/Los_Angeles scripts/build-examples.sh",
    "build:examples-full": "TZ=America/Los_Angeles scripts/build-examples.sh 1",

The single file variant does the same thing through `build:example` with `scripts/build-example.sh`. Pinning `TZ` to `America/Los_Angeles` is the kind of fix that only gets added after a diff shows a timestamp moving between machines, and it means the committed example images are only reproducible if you keep that environment variable. The full variant passes an argument of `1` to the shell script, and nothing in the README explains what that argument selects, so the difference between a quick examples build and a full one is only visible in the scripts directory. A separate target builds the documentation table of contents, which runs a Jekyll build and then a generator.

Angular commit conventions, prettier for formatting, release-it for tags

The tooling tells you how the project is run day to day. Formatting is prettier, with `prettier.config.js` at the root and a `.prettierignore`, and one of the five badges links to the prettier project. Linting is ESLint through the flat config file `eslint.config.js`. Git hooks live in `.husky/`, and releases are configured in `.release-it.json`, and the tag history and the manifest version agree: both currently read 6.5.0. Tests run on vitest, with a config file and a separate global setup file. Two TypeScript configs exist, one for the build and one for everything else.

Every named lead is listed with where they are now

The team section says development is led by alumni and members of the University of Washington Interactive Data Lab, then names four people with their current positions rather than their roles in the project. Kanit Wongsuphasawat is listed as now at Databricks, Dominik Moritz as now at CMU and Apple, Arvind Satyanarayan as now at MIT, and Jeffrey Heer as still at UW IDL. Three of the four links for those people point at Bluesky profiles rather than at a lab or company page, so the section reads as a record of where the maintainers ended up rather than as a statement of who owns what. The section closes by pointing at the contributors graph for the full list. The citation block below it names the same four authors in a different order, with Satyanarayan, Moritz, Wongsuphasawat and Heer, a 2017 journal article, and a DOI registered a year earlier.

Editorial conclusion

Vega-Lite fits anyone generating charts from data in JavaScript or Python who wants a spec an editor can validate and a compiler that emits Vega rather than drawing code. Check three things before you depend on it. The exports map exposes a `types_unstable` subpath, so anything you import through it carries no stability promise. The build output is committed, which means the tree you clone is not the same as a fresh build. And the example build pins the timezone to America/Los_Angeles, so example output is only reproducible with that setting.

Frequently asked questions

Official sources

1. License: BSD-3-Clause
2. Project website
3. README
4. Releases
5. vega/vega-lite on GitHub