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@hypothesis/frontend-build

This package contains functions for building assets and running tests in Hypothesis frontend projects, typically as part of Gulp tasks.

It assumes that the project is using our standard frontend tech stack and follows certain conventions about the location and naming of files.

Prerequisites

This project assumes our standard tech stack for frontend projects:

  • Gulp for running tasks [1]
  • Rollup for building JavaScript bundles
  • Sass for authoring styles
  • Karma for running tests

[1] Gulp is not required as the task runner, but is how most of our projects are currently set up.

Usage

The typical structure of a Hypothesis frontend project looks like:

gulpfile.mjs  # Gulp tasks

src/  # Source files ("$PROJECT_NAME/static/scripts" in Python projects)
  karma.config.js  # Karma config file
  tests/
    bootstrap.js  # JS module that configures test environment

rollup.config.mjs  # Rollup config that builds application/library bundles
rollup-tests.config.mjs  # Rollup config that builds test bundle from `build/scripts/test-inputs.js`

build/  # Compiled frontend assets
  scripts/  # Generated JS bundles
    some-app.bundle.js
    some-app.bundle.js.map

  styles/  # Generated CSS bundles
    some-app.css
    some-app.css.map

Compiling frontend assets from source files is handled by tasks defined in gulpfile.mjs.

To use this package, first add it as a dependency to the project:

yarn add --dev @hypothesis/frontend-build

Then use the functions within Gulp tasks. For example:

import { buildCSS, buildJS, watchCSS, runTests } from '@hypothesis/frontend-build';

gulp.task('build-js', () => buildJS('rollup.config.mjs'));
gulp.task('watch-js', () => watchJS('rollup.config.mjs'));
gulp.task('build-css', () => buildCSS(
  ['src/my-app.scss', 'src/other-app.scss'],
  { tailwindConfig }
));
gulp.task('watch-css', () => gulp.watch('src/**/*.scss', 'build-css'));
gulp.task('watch', gulp.parallel('watch-js', 'watch-css'));
gulp.task('test', () => runTests({
  bootstrapFile: 'src/tests/bootstrap.js',
  karmaConfig: 'src/karma.config.js',
  rollupConfig: 'rollup-tests.config.mjs',
  testsPattern: '**/*-test.js',
});

// Project-specific tasks...

API reference

This section provides an overview of the functions in this package. See the JSDoc comments for individual functions for full details.

Building asset bundles

buildJS(rollupConfig) - Build one or more JavaScript bundles defined in a Rollup config file. The Rollup config file must be an ES module.

watchJS(rollupConfig) - Same as buildJS, but watches for updates to input files after building the bundle and rebuilds if they change.

buildCSS(inputs, options = {}) - Build one or more CSS bundles from CSS or SASS entry points, with optional support for Tailwind.

generateManifest(options) - Generate a JSON asset manifest suitable for use with the h-assets package used by Python apps to serve static assets.

Running tests

runTests(config) - Build a JavaScript bundle of tests from a set of input files and run them in Karma.

The test bundle is created by first finding all test files that match the testsPattern argument and generating an entry point, build/scripts/test-inputs.js, which imports all of the test files. The bundle is then built by passing the config specified by rollupConfig to Rollup. Once the bundle has been generated, Karma is started using the config file specified by karmaConfig, which should load the test bundle.

This command supports filtering which tests are run by using the --grep <file pattern> CLI argument. If the --live CLI flag is set, the test runner watches for changes and rebuild and re-runs the tests if the input files change.

Utilities

run(command, args) - Run a CLI command and forward the output to the terminal.

Additional documentation

Release guide. Note this is in the frontend-shared repository. The process is the same for this one.