Fix missing isTypedArray when mixing versions of @tensorflow packages

A new function, `isTypedArray` was added to the `platform` interface by tensorflow#7181
and first published in tfjs-core 4.2.0. This made 4.2.0 incompatible with
earlier versions of backends that implemented `platform`, such as node and
react-native. This change adds a fallback to the use of `isTypedArray` so
earlier versions of platforms that don't implement `isTypedArray` will not throw
an error.

Note that the fallback behavior may not be perfect, such as when running Jest
tests in node. See tensorflow#7175 for more details and upgrade all @tensorflow scoped
packages to ^4.2.0 to avoid this.

Fixes tensorflow#7273

tfjs-core/src/platforms/platform_browser.ts

@@ -93,11 +93,16 @@ export class PlatformBrowser implements Platform {
 
   isTypedArray(a: unknown): a is Uint8Array | Float32Array | Int32Array
     | Uint8ClampedArray {
-    return a instanceof Float32Array || a instanceof Int32Array ||
-      a instanceof Uint8Array || a instanceof Uint8ClampedArray;
+    return isTypedArrayBrowser(a);
   }
 }
 
+export function isTypedArrayBrowser(a: unknown): a is Uint8Array
+  | Float32Array | Int32Array | Uint8ClampedArray {
+  return a instanceof Float32Array || a instanceof Int32Array ||
+    a instanceof Uint8Array || a instanceof Uint8ClampedArray;
+}
+
 if (env().get('IS_BROWSER')) {
   env().setPlatform('browser', new PlatformBrowser());
 

tfjs-core/src/util.ts

@@ -16,6 +16,7 @@
  */
 
 import {env} from './environment';
+import { isTypedArrayBrowser, PlatformBrowser } from './platforms/platform_browser';
 import {BackendValues, DataType, RecursiveArray, TensorLike, TypedArray} from './types';
 import * as base from './util_base';
 export * from './util_base';
@@ -134,7 +135,8 @@ export function decodeString(bytes: Uint8Array, encoding = 'utf-8'): string {
 
 export function isTypedArray(a: {}): a is Float32Array|Int32Array|Uint8Array|
     Uint8ClampedArray {
-  return env().platform.isTypedArray(a);
+  const isTypedArray = env().platform.isTypedArray || isTypedArrayBrowser;
+  return isTypedArray(a);
 }
 
 // NOTE: We explicitly type out what T extends instead of any so that