Merge pull request #13 from nakanoasaservice/feature/cause-check

Fix: preserve falsy cause values in TaggedError

Author: nakanoasaservice

deno.json

@@ -1,5 +1,5 @@
 {
-  "version": "1.0.1",
+  "version": "1.0.2",
   "name": "@nakanoaas/tagged-error",
   "license": "MIT",
   "exports": "./index.ts",

index.test.ts

@@ -33,6 +33,29 @@ Deno.test("TaggedError - with cause data", () => {
   assertEquals(error.cause, causeData);
 });
 
+Deno.test("TaggedError - should set falsy cause values (0/empty string/false/null)", () => {
+  const errorWithZero = new TaggedError("CAUSE_ZERO", { cause: 0 });
+  assertEquals(errorWithZero.cause, 0);
+
+  const errorWithEmptyString = new TaggedError("CAUSE_EMPTY_STRING", {
+    cause: "",
+  });
+  assertEquals(errorWithEmptyString.cause, "");
+
+  const errorWithFalse = new TaggedError("CAUSE_FALSE", { cause: false });
+  assertEquals(errorWithFalse.cause, false);
+
+  const errorWithNull = new TaggedError<"CAUSE_NULL", null>("CAUSE_NULL", {
+    cause: null,
+  });
+  assertEquals(errorWithNull.cause, null);
+});
+
+Deno.test("TaggedError - should not set cause when cause is undefined", () => {
+  const error = new TaggedError("CAUSE_UNDEFINED", { cause: undefined });
+  assertEquals(error.cause, undefined);
+});
+
 describe("TaggedError in practice", () => {
   function divideAndSquareRoot(num: number, divisor: number) {
     if (divisor === 0) {

index.ts

@@ -64,7 +64,7 @@ export class TaggedError<Tag extends string, Cause = undefined> extends Error {
     this.tag = tag;
     this.name = `TaggedError('${tag}')`;
 
-    if (options?.cause) {
+    if (options?.cause !== undefined) {
       this.cause = options.cause;
     }
   }