Keep existing package name when migrating

CHANGELOG.md

@@ -8,6 +8,7 @@
 - [#1804: Fix previewing templates with JavaScript in management pages](https://github.com/alphagov/govuk-prototype-kit/pull/1804)
 - [#1803: Stop installing dev dependencies when creating prototype](https://github.com/alphagov/govuk-prototype-kit/pull/1803)
 - [#1796: Fix link to docs in routes.js](https://github.com/alphagov/govuk-prototype-kit/pull/1796)
+- [#1791: Keep existing package name when migrating](https://github.com/alphagov/govuk-prototype-kit/pull/1791)
 
 ## 13.0.0
 

__tests__/spec/migrate.js

@@ -13,7 +13,7 @@ const fixtureProjectDirectory = path.join(__dirname, '..', 'fixtures', 'test-v11
 const cliPath = path.join(__dirname, '..', '..', 'bin', 'cli')
 
 const pkg = {
-  name: 'govuk-prototype-kit',
+  name: 'test-prototype',
   version: '11.0.0',
   dependencies: {
     'govuk-frontend': '^4.3.1',
@@ -44,6 +44,28 @@ describe('migrate test prototype', () => {
     })
   })
 
+  it('package.json', () => {
+    const pkgJson = fse.readJsonSync(path.join(projectDirectory, 'package.json'))
+
+    const { dependencies, name, scripts } = pkgJson
+
+    expect(Object.keys(dependencies)).toEqual([
+      '@govuk-prototype-kit/step-by-step',
+      'govuk-frontend',
+      'govuk-prototype-kit',
+      'jquery',
+      'notifications-node-client'
+    ])
+
+    expect(scripts).toEqual({
+      dev: 'govuk-prototype-kit dev',
+      serve: 'govuk-prototype-kit serve',
+      start: 'govuk-prototype-kit start'
+    })
+
+    expect(name).toEqual('test-prototype')
+  })
+
   it('routes.js', () => {
     const routesFileContents = fs.readFileSync(path.join(appDirectory, 'routes.js'), 'utf8')
 

lib/migrator/index.js

@@ -95,7 +95,11 @@ const patternsToDeleteIfUnchanged = [
 const prepareMigration = async (kitDependency, projectDirectory) => {
   await logger.setup()
 
-  await fs.writeJson(path.join(projectDirectory, 'package.json'), {}, packageJsonFormat)
+  // extract the name from the original package.json if it exists
+  const pkgJson = await fs.readJson(path.join(projectDirectory, 'package.json'))
+  const { name } = pkgJson
+  const pkgData = name ? { name } : {}
+  await fs.writeJson(path.join(projectDirectory, 'package.json'), pkgData, packageJsonFormat)
 
   console.log('Migrating your prototype to v13')