Refactor saveAssets code to allow out of tree overrides

.changeset/metal-ladybugs-wave.md

@@ -0,0 +1,5 @@
+---
+"@rnx-kit/metro-service": minor
+---
+
+Refactor saveAssets code to allow out of tree overrides

packages/metro-service/package.json

@@ -64,6 +64,7 @@
   },
   "depcheck": {
     "ignoreMatches": [
+      "@office-iss/react-native-win32",
       "metro-babel-transformer"
     ]
   },

packages/metro-service/src/asset/android.ts

@@ -2,7 +2,7 @@
 
 import * as path from "path";
 import { getResourceIdentifier } from "./assetPathUtils";
-import type { PackagerAsset } from "./types";
+import type { PackagerAsset, SaveAssetsPlugin } from "./types";
 
 export function getAndroidAssetSuffix(scale: number): string {
   const tolerance = 0.01;
@@ -52,3 +52,15 @@ export function getAssetDestPathAndroid(
   const fileName = getResourceIdentifier(asset);
   return path.join(androidFolder, `${fileName}.${asset.type}`);
 }
+
+export const saveAssetsAndroid: SaveAssetsPlugin = (
+  assets,
+  _platform,
+  _assetsDest,
+  _assetCatalogDest,
+  addAssetToCopy
+) => {
+  assets.forEach((asset) =>
+    addAssetToCopy(asset, undefined, getAssetDestPathAndroid)
+  );
+};

packages/metro-service/src/asset/default.ts

@@ -0,0 +1,32 @@
+/**
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ */
+
+import path from "path";
+import type { PackagerAsset, SaveAssetsPlugin } from "./types";
+
+export function getAssetDestPath(asset: PackagerAsset, scale: number): string {
+  const suffix = scale === 1 ? "" : `@${scale}x`;
+  const fileName = `${asset.name + suffix}.${asset.type}`;
+  return path.join(
+    // Assets can have relative paths outside of the project root.
+    // Replace `../` with `_` to make sure they don't end up outside of
+    // the expected assets directory.
+    asset.httpServerLocation.substr(1).replace(/\.\.\//g, "_"),
+    fileName
+  );
+}
+
+export const saveAssetsDefault: SaveAssetsPlugin = (
+  assets,
+  _platform,
+  _assetsDest,
+  _assetCatalogDest,
+  addAssetToCopy
+) => {
+  assets.forEach((asset) => addAssetToCopy(asset, undefined, getAssetDestPath));
+};

packages/metro-service/src/asset/filter.ts

@@ -1,14 +1,9 @@
 // https://github.com/react-native-community/cli/blob/716555851b442a83a1bf5e0db27b6226318c9a69/packages/cli-plugin-metro/src/commands/bundle/filterPlatformAssetScales.ts
 
-const ALLOWED_SCALES: { [key: string]: number[] } = {
-  ios: [1, 2, 3],
-};
-
 export function filterPlatformAssetScales(
-  platform: string,
+  allowlist: ReadonlyArray<number> | undefined,
   scales: readonly number[]
 ): readonly number[] {
-  const allowlist: number[] = ALLOWED_SCALES[platform];
   if (!allowlist) {
     return scales;
   }

packages/metro-service/src/asset/ios.ts

@@ -3,9 +3,12 @@
 
 import fs from "fs";
 import type { AssetData } from "metro";
+import { error, info } from "@rnx-kit/console";
 import path from "path";
 import { getResourceIdentifier } from "./assetPathUtils";
-import type { PackagerAsset } from "./types";
+import { filterPlatformAssetScales } from "./filter";
+import { getAssetDestPath } from "./default";
+import type { SaveAssetsPlugin } from "./types";
 
 type ImageSet = {
   basePath: string;
@@ -68,17 +71,44 @@ export function writeImageSet(imageSet: ImageSet): void {
   );
 }
 
-export function getAssetDestPathIOS(
-  asset: PackagerAsset,
-  scale: number
-): string {
-  const suffix = scale === 1 ? "" : `@${scale}x`;
-  const fileName = `${asset.name + suffix}.${asset.type}`;
-  return path.join(
-    // Assets can have relative paths outside of the project root.
-    // Replace `../` with `_` to make sure they don't end up outside of
-    // the expected assets directory.
-    asset.httpServerLocation.substring(1).replace(/\.\.\//g, "_"),
-    fileName
-  );
-}
+const ALLOWED_SCALES = [1, 2, 3];
+
+export const saveAssetsIOS: SaveAssetsPlugin = (
+  assets,
+  _platform,
+  _assetsDest,
+  assetCatalogDest,
+  addAssetToCopy
+) => {
+  if (assetCatalogDest != null) {
+    // Use iOS Asset Catalog for images. This will allow Apple app thinning to
+    // remove unused scales from the optimized bundle.
+    const catalogDir = path.join(assetCatalogDest, "RNAssets.xcassets");
+    if (!fs.existsSync(catalogDir)) {
+      error(
+        `Could not find asset catalog 'RNAssets.xcassets' in ${assetCatalogDest}. Make sure to create it if it does not exist.`
+      );
+      return;
+    }
+
+    info("Adding images to asset catalog", catalogDir);
+    cleanAssetCatalog(catalogDir);
+    for (const asset of assets) {
+      if (isCatalogAsset(asset)) {
+        const imageSet = getImageSet(
+          catalogDir,
+          asset,
+          filterPlatformAssetScales(ALLOWED_SCALES, asset.scales)
+        );
+        writeImageSet(imageSet);
+      } else {
+        addAssetToCopy(asset, ALLOWED_SCALES, getAssetDestPath);
+      }
+    }
+    info("Done adding images to asset catalog");
+  } else {
+    assets.forEach((asset) =>
+      addAssetToCopy(asset, ALLOWED_SCALES, getAssetDestPath)
+    );
+  }
+};

packages/metro-service/src/asset/types.ts

@@ -1,5 +1,19 @@
+import type { AssetData } from "metro";
+
 export type PackagerAsset = {
   httpServerLocation: string;
   name: string;
   type: string;
 };
+
+export type SaveAssetsPlugin = (
+  assets: ReadonlyArray<AssetData>,
+  platform: string,
+  assetsDest: string | undefined,
+  assetCatalogDest: string | undefined,
+  addAssetToCopy: (
+    asset: AssetData,
+    allowedScales: number[] | undefined,
+    getAssetDestPath: (asset: AssetData, scale: number) => string
+  ) => void
+) => void;

packages/metro-service/src/asset/write.ts

@@ -1,18 +1,11 @@
 // https://github.com/react-native-community/cli/blob/716555851b442a83a1bf5e0db27b6226318c9a69/packages/cli-plugin-metro/src/commands/bundle/saveAssets.ts
 
-import { error, info, warn } from "@rnx-kit/console";
+import { info, warn } from "@rnx-kit/console";
 import * as fs from "fs";
 import type { AssetData } from "metro";
 import * as path from "path";
-import { getAssetDestPathAndroid } from "./android";
 import { filterPlatformAssetScales } from "./filter";
-import {
-  cleanAssetCatalog,
-  getAssetDestPathIOS,
-  getImageSet,
-  isCatalogAsset,
-  writeImageSet,
-} from "./ios";
+import type { SaveAssetsPlugin } from "./types";
 
 function copy(
   src: string,
@@ -62,7 +55,8 @@ export function saveAssets(
   assets: ReadonlyArray<AssetData>,
   platform: string,
   assetsDest: string | undefined,
-  assetCatalogDest: string | undefined
+  assetCatalogDest: string | undefined,
+  saveAssetsPlugin: SaveAssetsPlugin
 ): Promise<void> {
   if (!assetsDest) {
     warn("Assets destination folder is not set, skipping...");
@@ -71,53 +65,40 @@ export function saveAssets(
 
   const filesToCopy: Record<string, string> = Object.create(null); // Map src -> dest
 
-  const getAssetDestPath =
-    platform === "android" ? getAssetDestPathAndroid : getAssetDestPathIOS;
-
-  const addAssetToCopy = (asset: AssetData) => {
+  const addAssetToCopy = (
+    asset: AssetData,
+    allowedScales: number[] | undefined,
+    getAssetDestPath: (asset: AssetData, scale: number) => string
+  ) => {
     const validScales = new Set(
-      filterPlatformAssetScales(platform, asset.scales)
+      filterPlatformAssetScales(allowedScales, asset.scales)
     );
 
-    asset.scales.forEach((scale, idx) => {
+    asset.scales.forEach((scale: number, idx: number) => {
       if (!validScales.has(scale)) {
         return;
       }
       const src = asset.files[idx];
       const dest = path.join(assetsDest, getAssetDestPath(asset, scale));
       filesToCopy[src] = dest;
     });
-  };
-
-  if (platform === "ios" && assetCatalogDest != null) {
-    // Use iOS Asset Catalog for images. This will allow Apple app thinning to
-    // remove unused scales from the optimized bundle.
-    const catalogDir = path.join(assetCatalogDest, "RNAssets.xcassets");
-    if (!fs.existsSync(catalogDir)) {
-      error(
-        `Could not find asset catalog 'RNAssets.xcassets' in ${assetCatalogDest}. Make sure to create it if it does not exist.`
-      );
-      return Promise.reject();
-    }
 
-    info("Adding images to asset catalog", catalogDir);
-    cleanAssetCatalog(catalogDir);
-    for (const asset of assets) {
-      if (isCatalogAsset(asset)) {
-        const imageSet = getImageSet(
-          catalogDir,
-          asset,
-          filterPlatformAssetScales(platform, asset.scales)
-        );
-        writeImageSet(imageSet);
-      } else {
-        addAssetToCopy(asset);
+    asset.scales.forEach((scale, idx) => {
+      if (!validScales.has(scale)) {
+        return;
       }
-    }
-    info("Done adding images to asset catalog");
-  } else {
-    assets.forEach(addAssetToCopy);
-  }
+      const src = asset.files[idx];
+      const dest = path.join(assetsDest, getAssetDestPath(asset, scale));
+      filesToCopy[src] = dest;
+    });
+  };
 
+  saveAssetsPlugin(
+    assets,
+    platform,
+    assetsDest,
+    assetCatalogDest,
+    addAssetToCopy
+  );
   return copyAll(filesToCopy);
 }

packages/metro-service/src/bundle.ts

@@ -9,6 +9,10 @@ import Server from "metro/src/Server";
 import Bundle from "metro/src/shared/output/bundle";
 import path from "path";
 import { saveAssets } from "./asset";
+import type { SaveAssetsPlugin } from "./asset/types";
+import { saveAssetsAndroid } from "./asset/android";
+import { saveAssetsDefault } from "./asset/default";
+import { saveAssetsIOS } from "./asset/ios";
 import { ensureBabelConfig } from "./babel";
 
 export type BundleArgs = {
@@ -41,6 +45,34 @@ type RequestOptions = {
   unstable_transformProfile?: BundleOptions["unstable_transformProfile"];
 };
 
+// Eventually this will be part of the rn config, but we require it on older rn versions for win32 and the cli doesn't allow extra config properties.
+// See https://github.com/react-native-community/cli/pull/2002
+function getSaveAssetsPlugin(
+  platform: string,
+  projectRoot: string
+): SaveAssetsPlugin {
+  if (platform === "win32") {
+    try {
+      const saveAssetsPlugin = require.resolve(
+        "@office-iss/react-native-win32/saveAssetPlugin",
+        { paths: [projectRoot] }
+      );
+      return require(saveAssetsPlugin);
+    } catch (_) {
+      /* empty */
+    }
+  }
+
+  switch (platform) {
+    case "ios":
+      return saveAssetsIOS;
+    case "android":
+      return saveAssetsAndroid;
+    default:
+      return saveAssetsDefault;
+  }
+}
+
 export async function bundle(
   args: BundleArgs,
   config: ConfigT,
@@ -49,6 +81,11 @@ export async function bundle(
   // ensure Metro can find Babel config
   ensureBabelConfig(config);
 
+  const saveAssetsPlugin = getSaveAssetsPlugin(
+    args.platform,
+    config.projectRoot
+  );
+
   if (config.resolver.platforms.indexOf(args.platform) === -1) {
     error(
       `Invalid platform ${
@@ -107,7 +144,8 @@ export async function bundle(
       outputAssets,
       args.platform,
       args.assetsDest,
-      args.assetCatalogDest
+      args.assetCatalogDest,
+      saveAssetsPlugin
     );
   } finally {
     server.end();

packages/metro-service/test/asset/ios.test.ts → packages/metro-service/test/asset/default.test.ts

@@ -1,15 +1,15 @@
 import * as path from "path";
-import { getAssetDestPathIOS } from "../../src/asset/ios";
+import { getAssetDestPath } from "../../src/asset/default";
 
-describe("getAssetDestPathIOS", () => {
+describe("getAssetDestPath", () => {
   test("should build correct path", () => {
     const asset = {
       name: "icon",
       type: "png",
       httpServerLocation: "/assets/test",
     };
 
-    expect(getAssetDestPathIOS(asset, 1)).toBe(
+    expect(getAssetDestPath(asset, 1)).toBe(
       path.normalize("assets/test/icon.png")
     );
   });
@@ -21,10 +21,10 @@ describe("getAssetDestPathIOS", () => {
       httpServerLocation: "/assets/test",
     };
 
-    expect(getAssetDestPathIOS(asset, 2)).toBe(
+    expect(getAssetDestPath(asset, 2)).toBe(
       path.normalize("assets/test/icon@2x.png")
     );
-    expect(getAssetDestPathIOS(asset, 3)).toBe(
+    expect(getAssetDestPath(asset, 3)).toBe(
       path.normalize("assets/test/icon@3x.png")
     );
   });
@@ -36,7 +36,7 @@ describe("getAssetDestPathIOS", () => {
       httpServerLocation: "/assets/../../test",
     };
 
-    expect(getAssetDestPathIOS(asset, 1)).toBe(
+    expect(getAssetDestPath(asset, 1)).toBe(
       path.normalize("assets/__test/icon.png")
     );
   });