fix(gatsby): close parcel cache db before clearing cache and retrying

packages/gatsby/package.json

@@ -30,6 +30,7 @@
     "@graphql-tools/load": "^7.5.10",
     "@jridgewell/trace-mapping": "^0.3.13",
     "@nodelib/fs.walk": "^1.2.8",
+    "@parcel/cache": "2.6.2",
     "@parcel/core": "2.6.2",
     "@pmmmwh/react-refresh-webpack-plugin": "^0.4.3",
     "@types/http-proxy": "^1.17.7",

packages/gatsby/src/utils/parcel/__tests__/__snapshots__/compile-gatsby-files.ts.snap

@@ -2,6 +2,7 @@
 
 exports[`gatsby file compilation constructBundler should construct Parcel relative to passed directory 1`] = `
 Object {
+  "cache": undefined,
   "cacheDir": "<PROJECT_ROOT>/packages/gatsby/src/utils/parcel/__tests__/fixtures/js/.cache/.parcel-cache",
   "defaultConfig": "<PROJECT_ROOT>/packages/gatsby-parcel-config/lib/index.json",
   "entries": Array [

packages/gatsby/src/utils/parcel/compile-gatsby-files.ts

@@ -1,4 +1,5 @@
 import { Parcel } from "@parcel/core"
+import { LMDBCache, Cache } from "@parcel/cache"
 import path from "path"
 import type { Diagnostic } from "@parcel/diagnostic"
 import reporter from "gatsby-cli/lib/reporter"
@@ -27,14 +28,15 @@ function exponentialBackoff(retry: number): Promise<void> {
  * Construct Parcel with config.
  * @see {@link https://parceljs.org/features/targets/}
  */
-export function constructParcel(siteRoot: string): Parcel {
+export function constructParcel(siteRoot: string, cache?: Cache): Parcel {
   return new Parcel({
     entries: [
       `${siteRoot}/${gatsbyFileRegex}`,
       `${siteRoot}/plugins/**/${gatsbyFileRegex}`,
     ],
     defaultConfig: require.resolve(`gatsby-parcel-config`),
     mode: `production`,
+    cache,
     targets: {
       root: {
         outputFormat: `commonjs`,
@@ -100,8 +102,22 @@ export async function compileGatsbyFiles(
 
     await exponentialBackoff(retry)
 
-    const parcel = constructParcel(siteRoot)
+    // for whatever reason TS thinks LMDBCache is some browser Cache and not actually Parcel's Cache
+    // so we force type it to Parcel's Cache
+    const cache = new LMDBCache(getCacheDir(siteRoot)) as any as Cache
+    const parcel = constructParcel(siteRoot, cache)
     const { bundleGraph } = await parcel.run()
+    let cacheClosePromise = Promise.resolve()
+    try {
+      // @ts-ignore store is public field on LMDBCache class, but public interface for Cache
+      // doesn't have it. There doesn't seem to be proper public API for this, so we have to
+      // resort to reaching into internals. Just in case this is wrapped in try/catch if
+      // parcel changes internals in future (closing cache is only needed when retrying
+      // so the if the change happens we shouldn't fail on happy builds)
+      cacheClosePromise = cache.store.close()
+    } catch (e) {
+      reporter.verbose(`Failed to close parcel cache\n${e.toString()}`)
+    }
 
     await exponentialBackoff(retry)
 
@@ -138,8 +154,15 @@ export async function compileGatsbyFiles(
           )
         }
 
-        // sometimes parcel cache gets in weird state
-        await remove(getCacheDir(siteRoot))
+        // sometimes parcel cache gets in weird state and we need to clear the cache
+        await cacheClosePromise
+
+        try {
+          await remove(getCacheDir(siteRoot))
+        } catch {
+          // in windows we might get "EBUSY" errors if LMDB failed to close, so this try/catch is
+          // to prevent EBUSY errors from potentially hiding real import errors
+        }
 
         await compileGatsbyFiles(siteRoot, retry + 1)
         return