Properly reset BinaryWriter after finish (#986)

Author: bhollis

packages/bundle-size/README.md

@@ -16,11 +16,11 @@ usually do. We repeat this for an increasing number of files.
 
 | code generator      | files | bundle size |  minified | compressed |
 | ------------------- | ----: | ----------: | --------: | ---------: |
-| Protobuf-ES         |     1 |   126,123 b |  65,653 b |   15,258 b |
-| Protobuf-ES         |     4 |   128,312 b |  67,161 b |   15,970 b |
-| Protobuf-ES         |     8 |   131,074 b |  68,932 b |   16,481 b |
-| Protobuf-ES         |    16 |   141,524 b |  76,913 b |   18,797 b |
-| Protobuf-ES         |    32 |   169,315 b |  98,931 b |   24,268 b |
+| Protobuf-ES         |     1 |   126,179 b |  65,684 b |   15,268 b |
+| Protobuf-ES         |     4 |   128,368 b |  67,192 b |   15,925 b |
+| Protobuf-ES         |     8 |   131,130 b |  68,963 b |   16,458 b |
+| Protobuf-ES         |    16 |   141,580 b |  76,944 b |   18,756 b |
+| Protobuf-ES         |    32 |   169,371 b |  98,962 b |   24,290 b |
 | protobuf-javascript |     1 |   334,193 b | 255,820 b |   42,481 b |
 | protobuf-javascript |     4 |   360,861 b | 271,092 b |   43,912 b |
 | protobuf-javascript |     8 |   382,904 b | 283,409 b |   45,038 b |

packages/bundle-size/chart.svg

@@ -134,6 +134,16 @@ describe("BinaryWriter", () => {
       },
     );
   });
+  it("should be completely reset after finish", () => {
+    const writer = new BinaryWriter();
+    // Make sure we have both a chunk and a buffer
+    writer.raw(new Uint8Array([1, 2, 3])).int32(1);
+    const bytes = writer.finish();
+    // Reuse the same writer to write the same data
+    writer.raw(new Uint8Array([1, 2, 3])).int32(1);
+    const bytes2 = writer.finish();
+    expect(bytes2).toStrictEqual(bytes);
+  });
 });
 
 describe("BinaryReader", () => {

packages/protobuf-test/src/wire/binary-encoding.test.ts

@@ -133,7 +133,10 @@ export class BinaryWriter {
    * Return all bytes written and reset this writer.
    */
   finish(): Uint8Array {
-    this.chunks.push(new Uint8Array(this.buf)); // flush the buffer
+    if (this.buf.length) {
+      this.chunks.push(new Uint8Array(this.buf)); // flush the buffer
+      this.buf = [];
+    }
     let len = 0;
     for (let i = 0; i < this.chunks.length; i++) len += this.chunks[i].length;
     let bytes = new Uint8Array(len);