feat(v4): expose stringbool truthy/falsy/case via _zod.bag (#6357)

`z.stringbool()` builds a `$ZodCodec` whose transform closes over the
resolved `truthy`/`falsy` values, so nothing could read them back off the
schema. Introspection tools were regexing `transform.toString()` just to
detect a stringbool, and the values stayed out of reach either way.

The resolved config now lands on `._zod.bag` after construction, the same
way `z.instanceof` exposes `bag.Class`. The stored arrays are the
normalized ones — lowercased unless `case: "sensitive"` — so they match
what the codec actually accepts, and `truthy[0]`/`falsy[0]` are what it
encodes back to.

Requested in #5011.

Author: hamed-bavar

packages/zod/src/v4/classic/tests/stringbool.test.ts

@@ -104,3 +104,21 @@ test("z.stringbool codec round trip", () => {
   const encodedFalse = z.encode(schema, decodedFalse);
   expect(encodedFalse).toEqual("disabled"); // First element of falsy array
 });
+
+test("z.stringbool exposes truthy/falsy/case via _zod.bag", () => {
+  const a = z.stringbool();
+  expect(a._zod.bag.truthy).toEqual(["true", "1", "yes", "on", "y", "enabled"]);
+  expect(a._zod.bag.falsy).toEqual(["false", "0", "no", "off", "n", "disabled"]);
+  expect(a._zod.bag.case).toEqual("insensitive");
+
+  // values are normalized when case-insensitive
+  const b = z.stringbool({ truthy: ["Y", "yes"], falsy: ["N"] });
+  expect(b._zod.bag.truthy).toEqual(["y", "yes"]);
+  expect(b._zod.bag.falsy).toEqual(["n"]);
+  expect(b._zod.bag.case).toEqual("insensitive");
+
+  const c = z.stringbool({ truthy: ["Y"], falsy: ["N"], case: "sensitive" });
+  expect(c._zod.bag.truthy).toEqual(["Y"]);
+  expect(c._zod.bag.falsy).toEqual(["N"]);
+  expect(c._zod.bag.case).toEqual("sensitive");
+});

packages/zod/src/v4/core/api.ts

@@ -1828,6 +1828,10 @@ export function _stringbool(
     error: params.error,
   }) as any;
 
+  codec._zod.bag.truthy = truthyArray;
+  codec._zod.bag.falsy = falsyArray;
+  codec._zod.bag.case = params.case ?? "insensitive";
+
   return codec;
 }
 

packages/zod/src/v4/mini/tests/index.test.ts

@@ -912,12 +912,15 @@ test("z.stringbool", () => {
   expect(z.parse(b, "n")).toEqual(false);
   expect(z.safeParse(b, "true")).toMatchObject({ success: false });
   expect(z.safeParse(b, "false")).toMatchObject({ success: false });
+  expect(b._zod.bag.truthy).toEqual(["y"]);
+  expect(b._zod.bag.falsy).toEqual(["n"]);
 
   const c = z.stringbool({
     case: "sensitive",
   });
   expect(z.parse(c, "true")).toEqual(true);
   expect(z.safeParse(c, "TRUE")).toMatchObject({ success: false });
+  expect(c._zod.bag.case).toEqual("sensitive");
 });
 
 // promise