fix: calling destroy() should clear all internal state

If a client was in the process of receiving some binary attachments
when the connection was abruptly closed, then the manager would call
`decoder.destroy()` ([1]) but was then stuck in a "parse error" loop
upon reconnection (since it expected a binary attachment and not a
CONNECT packet).

[1]: https://github.com/socketio/socket.io-client/blob/a1c528b089773d7810a03befaeb982f7e01c3e11/lib/manager.ts#L520

lib/index.ts

@@ -288,6 +288,7 @@ export class Decoder extends Emitter<{}, {}, DecoderReservedEvents> {
   public destroy() {
     if (this.reconstructor) {
       this.reconstructor.finishedReconstruction();
+      this.reconstructor = null;
     }
   }
 }

test/arraybuffer.js

@@ -69,27 +69,6 @@ describe("ArrayBuffer", () => {
     return helpers.test_bin(packet);
   });
 
-  it("cleans itself up on close", () => {
-    const packet = {
-      type: PacketType.EVENT,
-      data: ["a", new ArrayBuffer(2), new ArrayBuffer(3)],
-      id: 0,
-      nsp: "/",
-    };
-
-    const encodedPackets = encoder.encode(packet);
-
-    const decoder = new Decoder();
-    decoder.on("decoded", (packet) => {
-      throw new Error("received a packet when not all binary data was sent.");
-    });
-
-    decoder.add(encodedPackets[0]); // add metadata
-    decoder.add(encodedPackets[1]); // add first attachment
-    decoder.destroy(); // destroy before all data added
-    expect(decoder.reconstructor.buffers.length).to.be(0); // expect that buffer is clean
-  });
-
   it("should not modify the input packet", () => {
     const packet = {
       type: PacketType.EVENT,

test/parser.js

@@ -127,4 +127,19 @@ describe("socket.io-parser", () => {
       /^Unknown type: 999$/
     );
   });
+
+  it("should resume decoding after calling destroy()", () => {
+    return new Promise((resolve) => {
+      const decoder = new Decoder();
+
+      decoder.on("decoded", (packet) => {
+        expect(packet.data).to.eql(["hello"]);
+        resolve();
+      });
+
+      decoder.add('51-["hello"]');
+      decoder.destroy();
+      decoder.add('2["hello"]');
+    });
+  });
 });