fix: Sass partials imports from node_modules

Sass supports importing partials with or without the leading underscore:
https://sass-lang.com/documentation/at-rules/import#partials

Because `applyModuleNameMapper()` uses `require.resolve()` to employ
node module resolution on a bare import, it throws an exception if the
import elides the leading `_` from the basename.

e2e/__projects__/style/components/Scss.vue

@@ -4,6 +4,7 @@
 
 <style lang="scss" module>
 @import '~__styles/scss-a';
+@import '~vue-jest-test/partial.scss';
 
 .c {
   background-color: $primary-color;

e2e/__projects__/style/package.json

@@ -5,7 +5,7 @@
   "license": "MIT",
   "private": true,
   "scripts": {
-    "test": "jest --no-cache test.js"
+    "test": "node setup.js && jest --no-cache test.js"
   },
   "dependencies": {
     "vue": "^2.5.21",
@@ -17,8 +17,7 @@
     "@vue/test-utils": "^1.0.0-beta.28",
     "jest": "^24.0.0",
     "postcss": "^7.0.13",
-    "sass": "^1.23.7",
-    "vue-jest": "file:../../../"
+    "sass": "^1.23.7"
   },
   "jest": {
     "moduleFileExtensions": [

e2e/__projects__/style/setup.js

@@ -0,0 +1,9 @@
+const fs = require('fs')
+
+const testDir = 'node_modules/vue-jest-test'
+
+if (!fs.existsSync(testDir)) {
+  fs.mkdirSync(testDir)
+}
+
+fs.openSync(`${testDir}/_partial.scss`, 'w')

e2e/test-runner.js

@@ -4,6 +4,11 @@ const fs = require('fs-extra')
 const chalk = require('chalk')
 
 const IGNORE_FILES = ['.DS_Store']
+const cwd = process.cwd()
+
+// Can be run as `yarn test:e2e --cache` to forego reinstalling node_modules, or
+// `yarn test:e2e <projects dir>`, or `yarn test:e2e --cache <projects dir>`.
+const args = process.argv.slice(2)
 
 function success(msg) {
   console.info(chalk.green('\n[vue-jest]: ' + msg + '\n'))
@@ -31,29 +36,49 @@ function runTest(dir) {
 
   const log = msg => info(`(${dir}) ${msg}`)
 
-  log('Running tests')
+  if (!args.filter(arg => arg === '--cache').length) {
+    log('Removing node_modules')
+    fs.removeSync(`${resolvedPath}/node_modules`)
 
-  log('Removing node_modules')
-  fs.removeSync(`${resolvedPath}/node_modules`)
+    log('Removing package-lock.json')
+    fs.removeSync(`${resolvedPath}/package-lock.json`)
 
-  log('Removing package-lock.json')
-  fs.removeSync(`${resolvedPath}/package-lock.json`)
+    log('Installing node_modules')
+    run('npm install --silent')
+  }
 
-  log('Installing node_modules')
-  run('npm install --silent')
+  // For tests that need vue-jest to successfully `require.resolve()` a file in
+  // the project directory's node_modules, we can't symlink vue-jest from a
+  // parent directory (as node module resolution walks up the file tree,
+  // starting from the realpath of the caller), we must copy it.
+  if (
+    !fs.existsSync(`${resolvedPath}/node_modules/vue-jest`) ||
+    !fs.lstatSync(`${resolvedPath}/node_modules/vue-jest`).isSymbolicLink()
+  ) {
+    log('Copying vue-jest into node_modules')
+    fs.mkdirSync(`${resolvedPath}/node_modules/vue-jest`, { recursive: true })
+    run(`cp ${cwd}/package.json node_modules/vue-jest/`)
+    run(`cp -r ${cwd}/lib node_modules/vue-jest/`)
+  }
 
   log('Running tests')
   run('npm run test')
 
   success(`(${dir}) Complete`)
 }
 
-async function testRunner(dir) {
+async function testRunner() {
   const directories = fs
     .readdirSync(path.resolve(__dirname, '__projects__'))
     .filter(d => !IGNORE_FILES.includes(d))
 
-  directories.forEach(runTest)
+  const matches = args.filter(d => directories.includes(d))
+
+  if (matches.length) {
+    matches.forEach(runTest)
+  } else {
+    directories.forEach(runTest)
+  }
 }
 
 testRunner()

lib/module-name-mapper-helper.js

@@ -11,10 +11,18 @@ const matchModuleImport = /^[^?]*~/
 function resolve(to, importPath, fileType) {
   importPath =
     path.extname(importPath) === '' ? `${importPath}.${fileType}` : importPath
+
   if (path.isAbsolute(importPath)) {
     return importPath
   } else if (matchModuleImport.test(importPath)) {
-    return require.resolve(importPath.replace(matchModuleImport, ''))
+    const dirname = path.dirname(importPath).replace(matchModuleImport, '')
+    const basename = path.basename(importPath)
+
+    try {
+      return require.resolve(path.join(dirname, basename))
+    } catch (_) {
+      return require.resolve(path.join(dirname, `_${basename}`))
+    }
   }
   return path.join(path.dirname(to), importPath)
 }