fix: expose atlas file recreation logic to expo cli (#44)

* fix: reuse the Atlas file when exporting static web bundles

* refactor(cli): move atlas file recreation logic to cli

* docs: add docblock for `resetExpoAtlasFile` method

src/data/AtlasFileSource.ts

@@ -83,8 +83,9 @@ export async function readAtlasEntry(filePath: string, id: number): Promise<Atla
 let writeQueue: Promise<any> = Promise.resolve();
 
 /**
- * Add a new entry to the file.
- * This is appended on a new line, so we can load the selectively.
+ * Add a new entry to the Atlas file.
+ * This function also ensures the Atlas file is ready to be written to, due to complications with Expo CLI.
+ * Eventually, the entry is appended on a new line, so we can load them selectively.
  */
 export function writeAtlasEntry(filePath: string, entry: AtlasBundle) {
   const line = [
@@ -98,7 +99,9 @@ export function writeAtlasEntry(filePath: string, entry: AtlasBundle) {
     entry.serializeOptions,
   ];
 
-  return (writeQueue = writeQueue.then(() => appendJsonLine(filePath, line)));
+  writeQueue = writeQueue.then(() => appendJsonLine(filePath, line));
+
+  return writeQueue;
 }
 
 /** The default location of the metro file */
@@ -137,3 +140,21 @@ export async function createAtlasFile(filePath: string) {
   await fs.promises.rm(filePath, { force: true });
   await appendJsonLine(filePath, getAtlasMetdata());
 }
+
+/**
+ * Create the Atlas file if it doesn't exist, or recreate it if it's incompatible.
+ */
+export async function ensureAtlasFileExist(filePath: string) {
+  try {
+    await validateAtlasFile(filePath);
+  } catch (error: any) {
+    if (error.code === 'ATLAS_FILE_NOT_FOUND' || error.code === 'ATLAS_FILE_INCOMPATIBLE') {
+      await createAtlasFile(filePath);
+      return false;
+    }
+
+    throw error;
+  }
+
+  return true;
+}

src/index.ts

@@ -5,6 +5,7 @@ export { MetroGraphSource } from './data/MetroGraphSource';
 export {
   AtlasFileSource,
   createAtlasFile,
+  ensureAtlasFileExist,
   validateAtlasFile,
   getAtlasMetdata,
   getAtlasPath,

src/metro.ts

@@ -1,6 +1,11 @@
 import { type MetroConfig } from 'metro-config';
 
-import { createAtlasFile, getAtlasPath, writeAtlasEntry } from './data/AtlasFileSource';
+import {
+  createAtlasFile,
+  ensureAtlasFileExist,
+  getAtlasPath,
+  writeAtlasEntry,
+} from './data/AtlasFileSource';
 import { convertGraph, convertMetroConfig } from './data/MetroGraphSource';
 
 type ExpoAtlasOptions = Partial<{
@@ -36,7 +41,7 @@ export function withExpoAtlas(config: MetroConfig, options: ExpoAtlasOptions = {
   const metroConfig = convertMetroConfig(config);
 
   // Note(cedric): we don't have to await this, Metro would never bundle before this is finishes
-  createAtlasFile(atlasFile);
+  ensureAtlasFileExist(atlasFile);
 
   // @ts-expect-error
   config.serializer.customSerializer = (entryPoint, preModules, graph, serializeOptions) => {
@@ -51,3 +56,13 @@ export function withExpoAtlas(config: MetroConfig, options: ExpoAtlasOptions = {
 
   return config;
 }
+
+/**
+ * Fully reset, or recreate, the Expo Atlas file containing all Metro information.
+ * This method should only be called once per exporting session, to avoid overwriting data with mutliple Metro instances.
+ */
+export async function resetExpoAtlasFile(projectRoot: string) {
+  const filePath = getAtlasPath(projectRoot);
+  await createAtlasFile(filePath);
+  return filePath;
+}