Make Blob/File/URL modules Flow strict-local (#57728)

Summary:
Pull Request resolved: #57728

Upgrade the Blob-related modules (`File`, `FileReader`, `URL`, `URLSearchParams`) from `flow` to `flow strict-local`. These expose spec-mandated getters/setters, so they opt out of the `unsafe-getters-setters` lint with a scoped `// flowlint unsafe-getters-setters:off` directive. `URL` also received small behavior-preserving refactors (local variables instead of parameter reassignment, explicit null/empty checks).

Changelog: [Internal]

Reviewed By: javache

Differential Revision: D113763778

fbshipit-source-id: 1e0ceb02270d458fae6b89886ae41d9893ae7329

Author: rubennorte

packages/react-native/Libraries/Blob/File.js

@@ -4,10 +4,12 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @flow
+ * @flow strict-local
  * @format
  */
 
+// flowlint unsafe-getters-setters:off
+
 'use strict';
 
 import type {BlobOptions} from './BlobTypes';

packages/react-native/Libraries/Blob/FileReader.js

@@ -4,10 +4,12 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @flow
+ * @flow strict-local
  * @format
  */
 
+// flowlint unsafe-getters-setters:off
+
 import type {EventCallback} from '../../src/private/webapis/dom/events/EventTarget';
 import type Blob from './Blob';
 

packages/react-native/Libraries/Blob/URL.js

@@ -4,10 +4,12 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @flow
+ * @flow strict-local
  * @format
  */
 
+// flowlint unsafe-getters-setters:off
+
 import type Blob from './Blob';
 
 import NativeBlobModule from './NativeBlobModule';
@@ -79,6 +81,7 @@ export class URL {
   // $FlowFixMe[missing-local-annot]
   constructor(url: string, base?: string | URL) {
     let baseUrl = null;
+    // $FlowFixMe[sketchy-null-string]
     if (!base || validateBaseUrl(url)) {
       this._url = url;
       if (this._url.includes('#')) {
@@ -112,13 +115,14 @@ export class URL {
       if (baseUrl.endsWith('/')) {
         baseUrl = baseUrl.slice(0, baseUrl.length - 1);
       }
-      if (!url.startsWith('/')) {
-        url = `/${url}`;
+      let path = url;
+      if (!path.startsWith('/')) {
+        path = `/${path}`;
       }
-      if (baseUrl.endsWith(url)) {
-        url = '';
+      if (baseUrl.endsWith(path)) {
+        path = '';
       }
-      this._url = `${baseUrl}${url}`;
+      this._url = `${baseUrl}${path}`;
     }
   }
 

packages/react-native/Libraries/Blob/URLSearchParams.js

@@ -4,10 +4,12 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @flow
+ * @flow strict-local
  * @format
  */
 
+// flowlint unsafe-getters-setters:off
+
 // Small subset from whatwg-url: https://github.com/jsdom/whatwg-url/tree/master/src
 // The reference code bloat comes from Unicode issues with URLs, so those won't work here.
 export class URLSearchParams {

packages/react-native/Libraries/Blob/URLSearchParams.js.flow

@@ -4,7 +4,7 @@
  * This source code is licensed under the MIT license found in the
  * LICENSE file in the root directory of this source tree.
  *
- * @flow
+ * @flow strict-local
  * @format
  */