Lazy-load fast-png to fix crash in React Native / Hermes

packages/roslib/src/core/transport/Transport.ts

@@ -187,12 +187,17 @@ export abstract class AbstractTransport
    * It is one technique for compressing JSON data.
    */
   private handleRosbridgePngMessage(message: RosbridgePngMessage) {
-    const decoded = decompressPng(message.data);
-    if (isRosbridgeMessage(decoded)) {
-      this.handleRosbridgeMessage(decoded);
-    } else {
-      throw new Error("Decompressed PNG data was invalid!");
-    }
+    decompressPng(message.data)
+      .then((decoded) => {
+        if (isRosbridgeMessage(decoded)) {
+          this.handleRosbridgeMessage(decoded);
+        } else {
+          this.emit("error", new Error("Decompressed PNG data was invalid!"));
+        }
+      })
+      .catch((error: unknown) => {
+        this.emit("error", error);
+      });
   }
 
   /**

packages/roslib/src/util/decompressPng.ts

@@ -4,7 +4,6 @@
  */
 
 import type { DecodedPng } from "fast-png";
-import { decode } from "fast-png";
 
 const textDecoder = new TextDecoder();
 
@@ -15,22 +14,27 @@ const textDecoder = new TextDecoder();
  *
  * @param data - An object containing the PNG data.
  */
-export default function decompressPng(data: string): unknown {
+export default async function decompressPng(data: string): Promise<unknown> {
+  // fast-png is imported dynamically (lazily) rather than statically to avoid
+  // a crash in environments such as React Native / Hermes. fast-png constructs
+  // a `new TextDecoder('latin1')` at module load time, and Hermes does not
+  // support the 'latin1' encoding, causing an immediate RangeError on import.
+  // By deferring the import until a PNG message is actually received, users
+  // who do not use PNG-compressed rosbridge messages are unaffected.
+  // See: https://github.com/image-js/fast-png/blob/77a4479d68d84246793f58f7bbf2a2ea3a80c0f5/src/helpers/text.ts#L11
+  const { decode } = await import("fast-png");
   const buffer = Uint8Array.from(atob(data), (char) => char.charCodeAt(0));
 
-  const decoded = tryDecodeBuffer(buffer);
-
+  let decoded: DecodedPng;
   try {
-    return JSON.parse(textDecoder.decode(decoded.data));
+    decoded = decode(buffer);
   } catch (error) {
-    throw new Error("Error parsing PNG JSON contents", { cause: error });
+    throw new Error("Error decoding PNG buffer", { cause: error });
   }
-}
 
-function tryDecodeBuffer(buffer: Uint8Array): DecodedPng {
   try {
-    return decode(buffer);
+    return JSON.parse(textDecoder.decode(decoded.data));
   } catch (error) {
-    throw new Error("Error decoding PNG buffer", { cause: error });
+    throw new Error("Error parsing PNG JSON contents", { cause: error });
   }
 }