From 417978e1315cc792cd4b64339d393da1ba9c6e9f Mon Sep 17 00:00:00 2001
From: Jackson Mills <jmills@ripple.com>
Date: Thu, 21 Apr 2022 14:36:10 -0700
Subject: [PATCH] Fix deriveXAddress null behavior (#1964)

* Fix deriveXAddress null behavior

* Also check for undefined

* Simplify theTag

* Add test case for undefined
---
 packages/ripple-address-codec/HISTORY.md   |  3 +++
 packages/ripple-address-codec/src/index.ts |  5 +++--
 packages/xrpl/test/utils/deriveXAddress.ts | 26 ++++++++++++++++++++++
 3 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/packages/ripple-address-codec/HISTORY.md b/packages/ripple-address-codec/HISTORY.md
index 80e59f29..13e5af0f 100644
--- a/packages/ripple-address-codec/HISTORY.md
+++ b/packages/ripple-address-codec/HISTORY.md
@@ -1,5 +1,8 @@
 # ripple-address-codec
 
+## Unreleased
+- Fixed `encodeXAddress` to handle `null` equivalently to `false`.
+
 ## 4.2.1 (2021-12-1)
 - Fix issue where npm < 7 could not install the library
 - Initial pass at linting this codebase with new rules
diff --git a/packages/ripple-address-codec/src/index.ts b/packages/ripple-address-codec/src/index.ts
index f94ea796..f380dce2 100644
--- a/packages/ripple-address-codec/src/index.ts
+++ b/packages/ripple-address-codec/src/index.ts
@@ -43,8 +43,9 @@ function encodeXAddress(
   if (tag > MAX_32_BIT_UNSIGNED_INT) {
     throw new Error('Invalid tag')
   }
-  const theTag = tag === false ? 0 : tag
-  const flag = tag === false ? 0 : 1
+  const theTag = tag || 0
+  // eslint-disable-next-line @typescript-eslint/no-unnecessary-condition -- Passing null is a common js mistake
+  const flag = tag === false || tag == null ? 0 : 1
   /* eslint-disable no-bitwise ---
    * need to use bitwise operations here */
   const bytes = Buffer.concat([
diff --git a/packages/xrpl/test/utils/deriveXAddress.ts b/packages/xrpl/test/utils/deriveXAddress.ts
index ebe38af8..fa19a8a9 100644
--- a/packages/xrpl/test/utils/deriveXAddress.ts
+++ b/packages/xrpl/test/utils/deriveXAddress.ts
@@ -22,4 +22,30 @@ describe('deriveXAddress', function () {
       'TVVrSWtmQQssgVcmoMBcFQZKKf56QscyWLKnUyiuZW8ALU4',
     )
   })
+
+  it('does not include tag when null', function () {
+    assert.equal(
+      deriveXAddress({
+        publicKey:
+          'ED02C98225BD1C79E9A4F95C6978026D300AFB7CA2A34358920BCFBCEBE6AFCD6A',
+        // @ts-expect-error -- Assessing null behavior (Common js mistake)
+        tag: null,
+        test: false,
+      }),
+      'X7FbrqVEqdTNoX5qq94rTdarGjeVYmkxi8A1TKAJUnyLL9g',
+    )
+  })
+
+  it('does not include tag when undefined', function () {
+    assert.equal(
+      deriveXAddress({
+        publicKey:
+          'ED02C98225BD1C79E9A4F95C6978026D300AFB7CA2A34358920BCFBCEBE6AFCD6A',
+        // @ts-expect-error -- Assessing undefined behavior
+        tag: undefined,
+        test: false,
+      }),
+      'X7FbrqVEqdTNoX5qq94rTdarGjeVYmkxi8A1TKAJUnyLL9g',
+    )
+  })
 })