fix: resolves viem#3278

Author: jxom

.changeset/yellow-numbers-hammer.md

@@ -0,0 +1,5 @@
+---
+"ox": patch
+---
+
+Fixed `AbiEvent.encode` for zeroish arguments.

src/core/AbiEvent.ts

@@ -530,7 +530,9 @@ export function encode<const abiEvent extends AbiEvent>(
             return args_[i].map((_: any, j: number) =>
               encode(param, args_[i][j]),
             )
-          return args_[i] ? encode(param, args_[i]) : null
+          return typeof args_[i] !== 'undefined' && args_[i] !== null
+            ? encode(param, args_[i])
+            : null
         }) ?? []
     }
   }

src/core/_test/AbiEvent.test.ts

@@ -863,6 +863,22 @@ describe('encode', () => {
     }
   `)
   })
+
+  test('https://github.com/wevm/viem/issues/3278', () => {
+    const event = AbiEvent.from('event test(uint32 indexed val)')
+    expect(
+      AbiEvent.encode(event, {
+        val: 0,
+      }),
+    ).toMatchInlineSnapshot(`
+      {
+        "topics": [
+          "0xe3cff634ef3ac1857ee74821b8b4103c803384af6152771eef3a2a92bdda6db6",
+          "0x0000000000000000000000000000000000000000000000000000000000000000",
+        ],
+      }
+    `)
+  })
 })
 
 describe('format', () => {