chore(core): extract util for packager cache location

packages/core/src/index.ts

@@ -5,6 +5,7 @@ export {
   applyVariantToBabelConfig,
   applyVariantToTemplateCompiler,
   getAppMeta,
+  getPackagerCacheDir,
 } from './packager';
 export { HTMLEntrypoint } from './html-entrypoint';
 export { StatSummary } from './stat-summary';

packages/core/src/packager.ts

@@ -1,6 +1,7 @@
 import { AppMeta } from '@embroider/shared-internals';
 import { readFileSync } from 'fs-extra';
 import { join } from 'path';
+import { tmpdir } from 'os';
 
 // This is a collection of flags that convey what kind of build you want. They
 // are intended to be generic across Packagers, and it's up to Packager authors
@@ -98,3 +99,12 @@ export function applyVariantToTemplateCompiler(_variant: Variant, templateCompil
 export function getAppMeta(pathToVanillaApp: string): AppMeta {
   return JSON.parse(readFileSync(join(pathToVanillaApp, 'package.json'), 'utf8'))['ember-addon'] as AppMeta;
 }
+
+/**
+ * Get the path to a cache directory in the recommended location
+ *
+ * This ensures they have exactly the same lifetime as some of embroider's own caches.
+ */
+export function getPackagerCacheDir(name: string): string {
+  return join(tmpdir(), 'embroider', name);
+}

packages/core/tests/packager.test.ts

@@ -1,6 +1,7 @@
-import { AppMeta, getAppMeta } from '../src';
+import { AppMeta, getAppMeta, getPackagerCacheDir } from '../src';
 import { writeJSONSync } from 'fs-extra';
 import { join } from 'path';
+import { tmpdir } from 'os';
 import * as tmp from 'tmp';
 
 tmp.setGracefulCleanup();
@@ -33,3 +34,10 @@ describe('getAppMeta', () => {
     });
   });
 });
+
+describe('getPackagerCacheDir', () => {
+  test('getting the path to a cache directory', () => {
+    const cacheDir = getPackagerCacheDir('foo');
+    expect(cacheDir).toBe(join(tmpdir(), 'embroider', 'foo'));
+  });
+});

packages/webpack/src/ember-webpack.ts

@@ -18,6 +18,7 @@ import {
   Variant,
   applyVariantToBabelConfig,
   getAppMeta,
+  getPackagerCacheDir,
   getOrCreate,
 } from '@embroider/core';
 import webpack, { Configuration } from 'webpack';
@@ -550,11 +551,7 @@ function nonNullArray<T>(array: T[]): NonNullable<T>[] {
 function babelLoaderOptions(majorVersion: 6 | 7, variant: Variant, appBabelConfigPath: string) {
   // eslint-disable-next-line @typescript-eslint/no-require-imports
   let options = Object.assign({}, applyVariantToBabelConfig(variant, require(appBabelConfigPath)), {
-    // all stage3 packagers should keep persistent caches under
-    // `join(tmpdir(), 'embroider')`. An important reason is that
-    // they should have exactly the same lifetime as some of
-    // embroider's own caches.
-    cacheDirectory: join(tmpdir(), 'embroider', 'webpack-babel-loader'),
+    cacheDirectory: getPackagerCacheDir('webpack-babel-loader'),
   });
   if (majorVersion === 7) {
     if (options.plugins) {