How to use the @jupyterlab/buildutils.readJSONFile function in @jupyterlab/buildutils

fs.writeFileSync(filePath, src, 'utf8');
});

// Create jest.config.js.
const jestConfig = `
const func = require('@jupyterlab/testutils/lib/jest-config');
module.exports = func('${name}', __dirname);
`;
fs.writeFileSync(path.join(testSrc, 'jest.config.js'), jestConfig, 'utf8');

// Open coreutils package.json
const coreUtils = path.resolve(__dirname, 'test-coreutils');
const coreUtilsData = require('./test-coreutils/package.json');

// Open target package.json
const targetData = utils.readJSONFile(path.join(testSrc, 'package.json'));

// Assign scripts from coreutils
targetData.scripts = coreUtilsData.scripts;

// Assign dependencies from coreutils
['jest', 'ts-jest', '@jupyterlab/testutils'].forEach(name => {
  targetData.dependencies[name] = coreUtilsData.dependencies[name];
});

// Assign devDependencies from coreutils
targetData.devDependencies = coreUtilsData.devDependencies;

// Write out the package.json file.
utils.writeJSONFile(path.join(testSrc, 'package.json'), targetData);

// Update tsconfig to use jest types.

fs.writeFileSync(filePath, src, 'utf8');
});

// Create jest.config.js.
const jestConfig = `
const func = require('@jupyterlab/testutils/lib/jest-config');
module.exports = func('${name}', __dirname);
`;
fs.writeFileSync(path.join(testSrc, 'jest.config.js'), jestConfig, 'utf8');

// Open coreutils package.json
const coreUtils = path.resolve(__dirname, 'test-coreutils');
const coreUtilsData = require('./test-coreutils/package.json');

// Open target package.json
const targetData = utils.readJSONFile(path.join(testSrc, 'package.json'));

// Assign scripts from coreutils
targetData.scripts = coreUtilsData.scripts;

// Assign dependencies from coreutils
['jest', 'ts-jest', '@jupyterlab/testutils'].forEach(name => {
  targetData.dependencies[name] = coreUtilsData.dependencies[name];
});

// Assign devDependencies from coreutils
targetData.devDependencies = coreUtilsData.devDependencies;

// Write out the package.json file.
utils.writeJSONFile(path.join(testSrc, 'package.json'), targetData);

// Update tsconfig to use jest types.

// Assign scripts from coreutils
targetData.scripts = coreUtilsData.scripts;

// Assign dependencies from coreutils
['jest', 'ts-jest', '@jupyterlab/testutils'].forEach(name => {
  targetData.dependencies[name] = coreUtilsData.dependencies[name];
});

// Assign devDependencies from coreutils
targetData.devDependencies = coreUtilsData.devDependencies;

// Write out the package.json file.
utils.writeJSONFile(path.join(testSrc, 'package.json'), targetData);

// Update tsconfig to use jest types.
const tsData = utils.readJSONFile(path.join(testSrc, 'tsconfig.json'));
const index = tsData.compilerOptions.types.indexOf('mocha');
tsData.compilerOptions.types[index] = 'jest';
utils.writeJSONFile(path.join(testSrc, 'tsconfig.json'), tsData);

// Git remove old tests infra
['karma-cov.conf.js', 'karma.conf.js', 'run-test.py'].forEach(fname => {
  utils.run(`git rm -f ./test-${name}/${fname} || true`);
});

// Copy common files from coreutils
['run.py', 'babel.config.js'].forEach(fname => {
  fs.copySync(path.join(coreUtils, fname), path.join(testSrc, fname));
});

// Add new files to git
utils.run(`git add ./test-${name}/run.py ./test-${name}/jest.config.js`);

// Assign scripts from coreutils
targetData.scripts = coreUtilsData.scripts;

// Assign dependencies from coreutils
['jest', 'ts-jest', '@jupyterlab/testutils'].forEach(name => {
  targetData.dependencies[name] = coreUtilsData.dependencies[name];
});

// Assign devDependencies from coreutils
targetData.devDependencies = coreUtilsData.devDependencies;

// Write out the package.json file.
utils.writeJSONFile(path.join(testSrc, 'package.json'), targetData);

// Update tsconfig to use jest types.
const tsData = utils.readJSONFile(path.join(testSrc, 'tsconfig.json'));
const index = tsData.compilerOptions.types.indexOf('mocha');
tsData.compilerOptions.types[index] = 'jest';
utils.writeJSONFile(path.join(testSrc, 'tsconfig.json'), tsData);

// Git remove old tests infra
['karma-cov.conf.js', 'karma.conf.js', 'run-test.py'].forEach(fname => {
  utils.run(`git rm -f ./test-${name}/${fname}`);
});

// Copy run.py from coreutils
fs.copySync(path.join(coreUtils, 'run.py'), path.join(testSrc, 'run.py'));

// Add new files to git
utils.run(`git add ./test-${name}/run.py ./test-${name}/jest.config.js`);

// Update deps and build test