feat: strip empty import statements from Flow type imports (#1128)

* fix: add removeEmptyImports option to flow remove types APIs

* docs: update flow-remove-types related docs

* chore: bump flow-remove-types to 2.268.0

* chore: update lockfile

* chore: federation tester version warning

* chore: changeset

Author: jbroma

.changeset/lazy-eels-know.md

@@ -0,0 +1,5 @@
+---
+"@callstack/repack": minor
+---
+
+Strip empty import statements that are a leftover from stripping flow type imports

apps/tester-federation-v2/configs/rspack.host-app.mjs

@@ -49,7 +49,7 @@ export default (env) => {
           'react-native': {
             singleton: true,
             eager: true,
-            requiredVersion: '0.78.0',
+            requiredVersion: '0.79.1',
           },
           '@react-navigation/native': {
             singleton: true,

packages/repack/package.json

@@ -84,7 +84,7 @@
     "estree-util-is-identifier-name": "^1.1.0",
     "events": "^3.3.0",
     "execa": "^5.0.0",
-    "flow-remove-types": "^2.250.0",
+    "flow-remove-types": "^2.268.0",
     "gradient-string": "^2.0.2",
     "image-size": "^1.1.1",
     "jsonwebtoken": "^9.0.2",

packages/repack/src/loaders/flowLoader/options.ts

@@ -4,7 +4,8 @@ import { validate } from 'schema-utils';
 export interface FlowLoaderOptions {
   all?: boolean;
   ignoreUninitializedFields?: boolean;
-  pretty?: true;
+  pretty?: boolean;
+  removeEmptyImports?: boolean;
 }
 
 type Schema = Parameters<typeof validate>[0];
@@ -16,6 +17,7 @@ export const optionsSchema: Schema = {
     all: { type: 'boolean' },
     ignoreUninitializedFields: { type: 'boolean' },
     pretty: { type: 'boolean' },
+    removeEmptyImports: { type: 'boolean' },
   },
 };
 

packages/repack/src/types/flow-remove-types.d.ts

@@ -3,8 +3,9 @@ declare module 'flow-remove-types' {
     code: string,
     options: {
       all?: boolean;
-      pretty?: boolean;
       ignoreUninitializedFields?: boolean;
+      pretty?: boolean;
+      removeEmptyImports?: boolean;
     }
   ) => {
     toString(): string;

packages/repack/src/utils/getFlowTransformRules.ts

@@ -50,6 +50,12 @@ interface GetFlowTransformRulesOptions {
    * rather than only removing the type.
    */
   ignoreUninitializedFields?: boolean;
+
+  /**
+   * Whether to remove empty import statements which were
+   * only used for importing flow types.
+   */
+  removeEmptyImports?: boolean;
 }
 
 /**
@@ -61,6 +67,7 @@ interface GetFlowTransformRulesOptions {
  * @param options.exclude Array of module names to exclude from Flow transformation (defaults to empty array)
  * @param options.all If true, bypasses looking for @flow pragma comment before parsing (defaults to true)
  * @param options.ignoreUninitializedFields If true, removes uninitialized class fields completely rather than only removing the type (defaults to false)
+ * @param options.removeEmptyImports If true, removes empty import statements which were only used for importing flow types (defaults to true)
  *
  * @returns Array of rules for transforming Flow typed modules
  */
@@ -69,6 +76,7 @@ export function getFlowTransformRules({
   exclude = [],
   all = true,
   ignoreUninitializedFields = false,
+  removeEmptyImports = true,
 }: GetFlowTransformRulesOptions = {}) {
   return [
     {
@@ -78,7 +86,7 @@ export function getFlowTransformRules({
       exclude: getModulePaths(exclude),
       use: {
         loader: '@callstack/repack/flow-loader',
-        options: { all, ignoreUninitializedFields },
+        options: { all, ignoreUninitializedFields, removeEmptyImports },
       },
     },
   ];

packages/repack/src/utils/getJsTransformRules.ts

@@ -31,6 +31,8 @@ interface GetJsTransformRulesOptions {
     all?: boolean;
     /** If true, removes uninitialized class fields completely rather than only removing the type */
     ignoreUninitializedFields?: boolean;
+    /** If true, removes empty import statements which were only used for importing flow types */
+    removeEmptyImports?: boolean;
   };
   /** Configuration for enabling/disabling codegen transformations */
   codegen?: {

pnpm-lock.yaml

@@ -13,6 +13,7 @@ type FlowLoaderOptions = {
   all?: boolean;
   ignoreUninitializedFields?: boolean;
   pretty?: boolean;
+  removeEmptyImports?: boolean;
 };
 ```
 
@@ -37,6 +38,13 @@ If true, removes uninitialized class fields (`foo;`, `foo: string;`) completely
 
 If true, removes types completely rather than replacing with spaces. This may require using source maps.
 
+### removeEmptyImports
+
+- Type: `boolean`
+- Default: `true`
+
+If true, removes empty import statements (`import {} from 'flow-typed-module';`) which were only used for importing flow types.
+
 ## Example
 
 :::info

website/src/latest/api/loaders/flow-loader.md

@@ -18,6 +18,7 @@ interface GetFlowTransformRulesOptions {
   exclude?: string[];
   all?: boolean;
   ignoreUninitializedFields?: boolean;
+  removeEmptyImports?: boolean;
 }
 ```
 
@@ -85,6 +86,13 @@ Whether to bypass looking for `@flow` pragma comment before parsing
 
 Whether to remove uninitialized class fields completely rather than only removing the type (defaults to false)
 
+### options.removeEmptyImports
+
+- Type: `boolean`
+- Default: `true`
+
+Whether to remove empty import statements which were only used for importing flow types (defaults to true)
+
 ## Example
 
 ```js title=rspack.config.cjs
@@ -97,6 +105,7 @@ module.exports = {
         include: ["react-native", "@react-native"],
         all: true,
         ignoreUninitializedFields: false,
+        removeEmptyImports: true,
       }),
     ],
   },