From cd9662ab4cb29315a2c8667a0a879eb3c34a36ab Mon Sep 17 00:00:00 2001
From: Jaco <jacogr@gmail.com>
Date: Mon, 21 Feb 2022 19:07:11 +0100
Subject: [PATCH] Ensure `BTreeSet` has the correct decoded length (#4588)

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
---
 CHANGELOG.md                                    |  7 +++++++
 .../types-codec/src/extended/BTreeSet.spec.ts   | 17 +++++++++++++++++
 packages/types-codec/src/extended/BTreeSet.ts   |  2 +-
 3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index cdca14049f..2f1c59388b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,12 @@
 # CHANGELOG
 
+## master
+
+Changes:
+
+- Ensure `BTreeSet` has the correct decoded length
+
+
 ## 7.9.1 Feb 20, 2022
 
 Contributed:
diff --git a/packages/types-codec/src/extended/BTreeSet.spec.ts b/packages/types-codec/src/extended/BTreeSet.spec.ts
index b1ab001466..39437e6fbf 100644
--- a/packages/types-codec/src/extended/BTreeSet.spec.ts
+++ b/packages/types-codec/src/extended/BTreeSet.spec.ts
@@ -133,6 +133,23 @@ describe('BTreeSet', (): void => {
     ).toEqual(17);
   });
 
+  it('correctly encodes/decodes the length', (): void => {
+    const none = new (BTreeSet.with(U32))(registry, []).toHex();
+    const some = new (BTreeSet.with(U32))(registry, [1, 2]).toHex();
+
+    // only the length byte
+    expect(none).toEqual('0x00');
+    expect(
+      (new (BTreeSet.with(U32))(registry, none)).initialU8aLength
+    ).toEqual(1);
+
+    // length byte + 2 values, 2 << 2 with u32 values
+    expect(some).toEqual('0x080100000002000000');
+    expect(
+      (new (BTreeSet.with(U32))(registry, some)).initialU8aLength
+    ).toEqual(1 + (2 * 4));
+  });
+
   it('correctly sorts numeric values', (): void => {
     expect(
       Array.from(new (BTreeSet.with(I32))(registry, mockI32SetObj)).map((k) => k.toNumber())
diff --git a/packages/types-codec/src/extended/BTreeSet.ts b/packages/types-codec/src/extended/BTreeSet.ts
index 725ae83982..f3451ddc9c 100644
--- a/packages/types-codec/src/extended/BTreeSet.ts
+++ b/packages/types-codec/src/extended/BTreeSet.ts
@@ -20,7 +20,7 @@ function decodeSetFromU8a<V extends Codec> (registry: Registry, ValClass: CodecC
     output.add(values[i]);
   }
 
-  return [output, decodedLength + offset];
+  return [output, decodedLength];
 }
 
 /** @internal */