Prefer NODE_ENV to determine test or production builds

Fixes an issue where PostCSS automatically defaults `{ env: 'development' }`

We previously run `postcss.config.unit.test.mjs` in a JSDOM environment which removed `NODE_ENV`

package.json

@@ -23,9 +23,9 @@
     "predev": "npm run build",
     "dev": "concurrently \"npm run dev --workspace @govuk-frontend/review\" \"npm run dev --workspace govuk-frontend\" --kill-others --names \"app,pkg\" --prefix-colors \"red.dim,blue.dim\"",
     "build": "npm run build --workspace govuk-frontend --workspace @govuk-frontend/review",
-    "build:app": "npm run build --workspace @govuk-frontend/review",
-    "build:package": "npm run build:package --workspace govuk-frontend",
-    "build:release": "npm run build:release --workspace govuk-frontend",
+    "build:app": "cross-env-shell NODE_ENV=production npm run build --workspace @govuk-frontend/review",
+    "build:package": "cross-env-shell NODE_ENV=production npm run build:package --workspace govuk-frontend",
+    "build:release": "cross-env-shell NODE_ENV=production npm run build:release --workspace govuk-frontend",
     "build:types": "npm run build:types --workspaces --if-present",
     "postbuild:package": "jest --color --selectProjects \"Build tasks\" --testMatch \"**/build/package.unit.test.mjs\"",
     "postbuild:release": "jest --color --selectProjects \"Build tasks\" --testMatch \"**/build/release.unit.test.mjs\"",
@@ -55,6 +55,7 @@
     "@typescript-eslint/eslint-plugin": "^6.6.0",
     "@typescript-eslint/parser": "^6.6.0",
     "concurrently": "^8.2.1",
+    "cross-env": "^7.0.3",
     "editorconfig-checker": "^5.1.1",
     "eslint": "^8.49.0",
     "eslint-config-prettier": "^9.0.0",

packages/govuk-frontend/postcss.config.mjs

@@ -1,24 +1,25 @@
 import { pkg } from '@govuk-frontend/config'
-import { isDev } from '@govuk-frontend/tasks/helpers/task-arguments.mjs'
 import autoprefixer from 'autoprefixer'
 import cssnano from 'cssnano'
 import cssnanoPresetDefault from 'cssnano-preset-default'
 import postcss from 'postcss'
 import scss from 'postcss-scss'
 
+const { NODE_ENV } = process.env
+
 /**
  * PostCSS config
  *
  * @param {import('postcss-load-config').ConfigContext} [ctx] - Context options
  * @returns {import('postcss-load-config').Config} PostCSS Config
  */
-export default ({ to = '' } = {}) => ({
+export default ({ env = NODE_ENV, to = '' } = {}) => ({
   plugins: [
     // Add vendor prefixes
     autoprefixer({ env: 'stylesheets' }),
 
     // Add GOV.UK Frontend release version
-    !isDev && {
+    ['test', 'production'].includes(env) && {
       postcssPlugin: 'govuk-frontend-version',
       Declaration: {
         // Find CSS declaration for version, update value

packages/govuk-frontend/postcss.config.unit.test.mjs

@@ -41,6 +41,23 @@ describe('PostCSS config', () => {
   })
 
   describe('Plugins', () => {
+    describe('GOV.UK Frontend version', () => {
+      it('Skips version number for NODE_ENV=development', () => {
+        const config = configFn({ env: 'development' })
+        expect(getPluginNames(config)).not.toContain('govuk-frontend-version')
+      })
+
+      it('Adds version number for NODE_ENV=production', () => {
+        const config = configFn({ env: 'production' })
+        expect(getPluginNames(config)).toContain('govuk-frontend-version')
+      })
+
+      it('Adds version number for NODE_ENV=test', () => {
+        const config = configFn({ env: 'test' })
+        expect(getPluginNames(config)).toContain('govuk-frontend-version')
+      })
+    })
+
     describe('CSS syntax parser', () => {
       it.each([
         {

shared/tasks/npm.mjs

@@ -2,7 +2,6 @@ import { paths } from '@govuk-frontend/config'
 import runScript from '@npmcli/run-script'
 import PluginError from 'plugin-error'
 
-import { isDev } from './helpers/task-arguments.mjs'
 import { task } from './index.mjs'
 
 /**
@@ -31,7 +30,8 @@ export async function run(name, args = [], options) {
   } catch (cause) {
     const error = new Error(`Task for npm script '${name}' failed`, { cause })
 
-    if (!isDev) {
+    // Skip errors by default to allow Gulp to resume tasks
+    if (['test', 'production'].includes(process.env.NODE_ENV)) {
       throw new PluginError(`npm run ${name}`, error, {
         showProperties: false,
         showStack: false