feat: allow passing Temporal objects to islands (#3701)

## Summary

- Add serialization/deserialization for all 8 Temporal types in the
jsonify module (used for island props): Instant, ZonedDateTime,
PlainDate, PlainTime, PlainDateTime, PlainYearMonth, PlainMonthDay,
Duration
- Stringify side guards with `typeof Temporal !== "undefined"` to avoid
ReferenceError when Temporal is unavailable
- Uses `.toString()` for serialization and `Type.from()` for
deserialization

Co-authored-by: Nano Miratus <nanomiratus@gmail.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 3 people

packages/fresh/src/jsonify/__snapshots__/round_trip_test.ts.snap

@@ -54,6 +54,22 @@ snapshot[`round trip - [ 1, <1 empty item>, 3 ] 1`] = `"[[1,-7,2],1,3]"`;
 
 snapshot[`round trip - /foo["]/ 1`] = `'[["RegExp","foo[\\\\"]", ""]]'`;
 
+snapshot[`round trip - 2020-01-01T12:34:56.789101112Z 1`] = `'[["Temporal.Instant","2020-01-01T12:34:56.789101112Z"]]'`;
+
+snapshot[`round trip - 2020-01-01T12:34:56.789101112+00:00[UTC] 1`] = `'[["Temporal.ZonedDateTime","2020-01-01T12:34:56.789101112+00:00[UTC]"]]'`;
+
+snapshot[`round trip - 2020-01-01 1`] = `'[["Temporal.PlainDate","2020-01-01"]]'`;
+
+snapshot[`round trip - 12:34:56.789101112 1`] = `'[["Temporal.PlainTime","12:34:56.789101112"]]'`;
+
+snapshot[`round trip - 2020-01-01T12:34:56.789101112 1`] = `'[["Temporal.PlainDateTime","2020-01-01T12:34:56.789101112"]]'`;
+
+snapshot[`round trip - 2020-01 1`] = `'[["Temporal.PlainYearMonth","2020-01"]]'`;
+
+snapshot[`round trip - 01-01 1`] = `'[["Temporal.PlainMonthDay","01-01"]]'`;
+
+snapshot[`round trip - P1Y2M3W4DT5H6M7.00800901S 1`] = `'[["Temporal.Duration","P1Y2M3W4DT5H6M7.00800901S"]]'`;
+
 snapshot[`round trip - { a: { foo: 123 }, b: [ { foo: 123 }, { foo: 123 } ] } 1`] = `'[{"a":1,"b":3},{"foo":2},123,[1,1]]'`;
 
 snapshot[`round trip - <ref *1> { a: 1, b: [Circular *1] } 1`] = `'[{"a":1,"b":0},1]'`;

packages/fresh/src/jsonify/parse.ts

@@ -93,6 +93,22 @@ function unpack(
         }
         case "Uint8Array":
           return hydrated[idx] = b64decode(current[1]);
+        case "Temporal.Instant":
+          return hydrated[idx] = Temporal.Instant.from(current[1]);
+        case "Temporal.ZonedDateTime":
+          return hydrated[idx] = Temporal.ZonedDateTime.from(current[1]);
+        case "Temporal.PlainDate":
+          return hydrated[idx] = Temporal.PlainDate.from(current[1]);
+        case "Temporal.PlainTime":
+          return hydrated[idx] = Temporal.PlainTime.from(current[1]);
+        case "Temporal.PlainDateTime":
+          return hydrated[idx] = Temporal.PlainDateTime.from(current[1]);
+        case "Temporal.PlainYearMonth":
+          return hydrated[idx] = Temporal.PlainYearMonth.from(current[1]);
+        case "Temporal.PlainMonthDay":
+          return hydrated[idx] = Temporal.PlainMonthDay.from(current[1]);
+        case "Temporal.Duration":
+          return hydrated[idx] = Temporal.Duration.from(current[1]);
       }
     } else {
       const actual = new Array(current.length);

packages/fresh/src/jsonify/round_trip_test.ts

@@ -39,6 +39,14 @@ const TESTS = [
   new Set([1, 2, null, -2, NaN]),
   [1, , 3],
   /foo["]/,
+  Temporal.Instant.from("2020-01-01T12:34:56.789101112Z"),
+  Temporal.ZonedDateTime.from("2020-01-01T12:34:56.789101112Z[UTC]"),
+  Temporal.PlainDate.from("2020-01-01"),
+  Temporal.PlainTime.from("12:34:56.789101112"),
+  Temporal.PlainDateTime.from("2020-01-01T12:34:56.789101112"),
+  Temporal.PlainYearMonth.from("2020-01"),
+  Temporal.PlainMonthDay.from("2020-01-01"),
+  Temporal.Duration.from("P1Y2M3W4DT5H6M7.00800901S"),
   references,
   circular,
 ];

packages/fresh/src/jsonify/stringify.ts

@@ -31,6 +31,14 @@ export type Stringifiers = Record<
  * - `RegExp`
  * - `Set`
  * - `Map`
+ * - `Temporal.Instant`
+ * - `Temporal.ZonedDateTime`
+ * - `Temporal.PlainDate`
+ * - `Temporal.PlainTime`
+ * - `Temporal.PlainDateTime`
+ * - `Temporal.PlainYearMonth`
+ * - `Temporal.PlainMonthDay`
+ * - `Temporal.Duration`
  *
  * Circular references are supported and objects with the same reference are
  * serialized only once.
@@ -134,6 +142,42 @@ function serializeInner(
         items[i++] = serializeInner(out, indexes, v, custom);
       });
       str += `["Map",[${items.join(",")}]]`;
+    } else if (
+      typeof Temporal !== "undefined" && value instanceof Temporal.Instant
+    ) {
+      str += `["Temporal.Instant","${value.toString()}"]`;
+    } else if (
+      typeof Temporal !== "undefined" &&
+      value instanceof Temporal.ZonedDateTime
+    ) {
+      str += `["Temporal.ZonedDateTime","${value.toString()}"]`;
+    } else if (
+      typeof Temporal !== "undefined" && value instanceof Temporal.PlainDate
+    ) {
+      str += `["Temporal.PlainDate","${value.toString()}"]`;
+    } else if (
+      typeof Temporal !== "undefined" && value instanceof Temporal.PlainTime
+    ) {
+      str += `["Temporal.PlainTime","${value.toString()}"]`;
+    } else if (
+      typeof Temporal !== "undefined" &&
+      value instanceof Temporal.PlainDateTime
+    ) {
+      str += `["Temporal.PlainDateTime","${value.toString()}"]`;
+    } else if (
+      typeof Temporal !== "undefined" &&
+      value instanceof Temporal.PlainYearMonth
+    ) {
+      str += `["Temporal.PlainYearMonth","${value.toString()}"]`;
+    } else if (
+      typeof Temporal !== "undefined" &&
+      value instanceof Temporal.PlainMonthDay
+    ) {
+      str += `["Temporal.PlainMonthDay","${value.toString()}"]`;
+    } else if (
+      typeof Temporal !== "undefined" && value instanceof Temporal.Duration
+    ) {
+      str += `["Temporal.Duration","${value.toString()}"]`;
     } else {
       str += "{";
       const keys = Object.keys(value);