Resolve govuk-frontend at project level by default

Node.js `require.resolve()` paths are optionally provided, for example:

1. Review app uses local `node_modules` before project level
2. Package stats uses local `node_modules` before project level

This is necessary for workspace `govuk-frontend@4` installs to be found

shared/lib/names.js

@@ -1,5 +1,6 @@
 const { dirname, join, parse } = require('path')
 
+const { paths } = require('govuk-frontend-config')
 const { minimatch } = require('minimatch')
 
 /**
@@ -68,8 +69,12 @@ function componentPathToModuleName (componentPath) {
  * @param {PackageOptions} [options] - Package resolution options
  * @returns {string} Path to installed npm package entry
  */
-function packageEntryToPath (packageEntry, { modulePath } = {}) {
-  const packagePath = require.resolve(packageEntry)
+function packageEntryToPath (packageEntry, { modulePath, requirePaths } = {}) {
+  const packagePath = require.resolve(packageEntry, {
+    paths: requirePaths ?? [
+      join(paths.root, 'node_modules')
+    ]
+  })
 
   // Append optional module path
   return modulePath !== undefined ? join(dirname(packagePath), modulePath) : packagePath
@@ -82,16 +87,17 @@ function packageEntryToPath (packageEntry, { modulePath } = {}) {
  * @param {PackageOptions} [options] - Package resolution options
  * @returns {string} Path to installed npm package field
  */
-function packageFieldToPath (packageName, { modulePath, field = 'main' } = {}) {
+function packageFieldToPath (packageName, { modulePath, requirePaths, field = 'main' } = {}) {
   const packageEntry = `${packageName}/package.json`
 
   // Package field as child path
-  const entryPath = require(packageEntryToPath(packageEntry))[field]
+  const entryPath = require(packageEntryToPath(packageEntry, { requirePaths }))[field]
   const childPath = modulePath !== undefined ? join(dirname(entryPath), modulePath) : entryPath
 
   // Append optional module path
   return packageEntryToPath(packageEntry, {
-    modulePath: childPath
+    modulePath: childPath,
+    requirePaths
   })
 }
 
@@ -103,11 +109,13 @@ function packageFieldToPath (packageName, { modulePath, field = 'main' } = {}) {
  *
  * @param {string} packageName - Installed npm package name
  * @param {string} [childPath] - Child directory path (optional, relative to package.json), for example `src/govuk/all.mjs`
+ * @param {PackageOptions} [options] - Package resolution options
  * @returns {string} Path to installed npm package
  */
-function packageNameToPath (packageName, childPath = '') {
+function packageNameToPath (packageName, childPath = '', { requirePaths } = {}) {
   return packageEntryToPath(`${packageName}/package.json`, {
-    modulePath: childPath
+    modulePath: childPath,
+    requirePaths
   })
 }
 
@@ -124,4 +132,5 @@ module.exports = {
  * @typedef {object} PackageOptions
  * @property {string} [field] - Package field name from package.json, for example `module`
  * @property {string} [modulePath] - Module path (optional, relative to package entry), for example `all.mjs`
+ * @property {string[]} [requirePaths] - Node.js require 'node_modules` lookup paths
  */

shared/lib/names.unit.test.mjs

@@ -201,3 +201,35 @@ describe('packageNameToPath', () => {
       .toBe(resolvedPath)
   })
 })
+
+describe("packageNameToPath (with custom 'node_module' paths)", () => {
+  const packages = [
+    {
+      packageName: 'govuk-frontend',
+      childPath: 'src/govuk/all.mjs',
+      options: { requirePaths: [join(paths.root, 'node_modules')] },
+      resolvedPath: join(paths.package, 'src/govuk/all.mjs')
+    },
+    {
+      packageName: 'govuk-frontend-review',
+      childPath: 'src/app.mjs',
+      options: { requirePaths: [join(paths.root, 'node_modules')] },
+      resolvedPath: join(paths.app, 'src/app.mjs')
+    },
+    {
+      packageName: 'autoprefixer',
+      options: { requirePaths: [join(paths.package, 'node_modules')] },
+      resolvedPath: join(paths.root, 'node_modules/autoprefixer')
+    },
+    {
+      packageName: 'postcss',
+      options: { requirePaths: [join(paths.app, 'node_modules')] },
+      resolvedPath: join(paths.root, 'node_modules/postcss')
+    }
+  ]
+
+  it.each(packages)("locates path for npm package '$packageName'", ({ packageName, childPath, options = {}, resolvedPath }) => {
+    expect(packageNameToPath(packageName, childPath, options))
+      .toBe(resolvedPath)
+  })
+})

shared/stats/rollup.config.mjs

@@ -30,7 +30,7 @@ export default defineConfig(modulePaths
      * Input plugins
      */
     plugins: [
-      resolve({ modulePaths: [paths.root] }),
+      resolve({ modulePaths: packageOptions.requirePaths }),
 
       // Stats: File size
       visualizer({

shared/stats/src/index.mjs

@@ -16,7 +16,11 @@ const componentNamesWithJavaScript = await getComponentNames((componentName, com
  */
 export const packageOptions = {
   field: 'module',
-  modulePath: 'all.mjs'
+  modulePath: 'all.mjs',
+  requirePaths: [
+    join(paths.stats, 'node_modules'),
+    join(paths.root, 'node_modules')
+  ]
 }
 
 /**

shared/tasks/styles.mjs

@@ -39,10 +39,16 @@ export async function compile (pattern, options) {
  *
  * @param {AssetEntry} assetEntry - Asset entry
  */
-export async function compileStylesheet ([modulePath, { configPath, srcPath, destPath, filePath }]) {
+export async function compileStylesheet ([modulePath, { configPath, srcPath, destPath, filePath, workspace }]) {
   const moduleSrcPath = join(srcPath, modulePath)
   const moduleDestPath = join(destPath, filePath ? filePath(parse(modulePath)) : modulePath)
 
+  // Default paths to resolve @imports
+  const requirePaths = [
+    join(workspace, 'node_modules'),
+    join(paths.root, 'node_modules')
+  ]
+
   let css
   let map
 
@@ -81,8 +87,8 @@ export async function compileStylesheet ([modulePath, { configPath, srcPath, des
 
       // Resolve @imports via
       loadPaths: [
-        packageNameToPath('govuk-frontend', 'dist'),
-        join(paths.root, 'node_modules')
+        packageNameToPath('govuk-frontend', 'dist', { requirePaths }),
+        ...requirePaths
       ],
 
       // Sass custom logger