[typescript-fetch] rebase on master: fold the #24509 null guards into the date helpers

Upstream #24509 null-guarded required date properties; keep that guard
but route the conversion through parseDate/serializeDate. Port the form
param date handling into the apisFormParams partial extracted by #23935,
and regenerate the affected samples.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: b2l

modules/openapi-generator/src/test/java/org/openapitools/codegen/typescript/fetch/TypeScriptFetchClientCodegenTest.java

@@ -1090,9 +1090,9 @@ public void testDateLibraryDateIsTheDefault() throws IOException {
         Path event = Paths.get(output + "/models/Event.ts");
         TestUtils.assertFileContains(event, "startsOn: Date;");
         TestUtils.assertFileContains(event, "createdAt?: Date;");
-        TestUtils.assertFileContains(event, "'startsOn': (parseDate(json['startsOn']))");
+        TestUtils.assertFileContains(event, "'startsOn': (json['startsOn'] == null ? json['startsOn'] : parseDate(json['startsOn']))");
         TestUtils.assertFileContains(event, "'createdAt': json['createdAt'] == null ? undefined : (parseDateTime(json['createdAt']))");
-        TestUtils.assertFileContains(event, "'startsOn': serializeDate(value['startsOn'])");
+        TestUtils.assertFileContains(event, "'startsOn': value['startsOn'] == null ? value['startsOn'] : serializeDate(value['startsOn'])");
 
         Path runtime = Paths.get(output + "/runtime.ts");
         TestUtils.assertFileContains(runtime, "export function parseDate(");

samples/client/petstore/typescript-fetch/builds/date-library-date/models/Event.ts

@@ -51,7 +51,7 @@ export function EventFromJSONTyped(json: any, ignoreDiscriminator: boolean): Eve
     }
     return {
 
-        'startsOn': (parseDate(json['startsOn'])),
+        'startsOn': (json['startsOn'] == null ? json['startsOn'] : parseDate(json['startsOn'])),
         'endsOn': json['endsOn'] === undefined ? undefined : json['endsOn'] === null ? null : (parseDate(json['endsOn'])),
         'createdAt': json['createdAt'] == null ? undefined : (parseDateTime(json['createdAt'])),
     };
@@ -68,7 +68,7 @@ export function EventToJSONTyped(value?: Event | null, ignoreDiscriminator: bool
 
     return {
 
-        'startsOn': serializeDate(value['startsOn']),
+        'startsOn': value['startsOn'] == null ? value['startsOn'] : serializeDate(value['startsOn']),
         'endsOn': value['endsOn'] == null ? value['endsOn'] : serializeDate(value['endsOn']),
         'createdAt': value['createdAt'] == null ? value['createdAt'] : serializeDateTime(value['createdAt']),
     };

samples/client/petstore/typescript-fetch/builds/default-v3.0/models/FormatTest.ts

@@ -116,7 +116,7 @@ export function FormatTestFromJSONTyped(json: any, ignoreDiscriminator: boolean)
         'string': json['string'] == null ? undefined : json['string'],
         '_byte': json['byte'],
         'binary': json['binary'] == null ? undefined : json['binary'],
-        'date': (parseDate(json['date'])),
+        'date': (json['date'] == null ? json['date'] : parseDate(json['date'])),
         'dateTime': json['dateTime'] == null ? undefined : (parseDateTime(json['dateTime'])),
         'uuid': json['uuid'] == null ? undefined : json['uuid'],
         'password': json['password'],
@@ -146,7 +146,7 @@ export function FormatTestToJSONTyped(value?: FormatTest | null, ignoreDiscrimin
         'string': value['string'],
         'byte': value['_byte'],
         'binary': value['binary'],
-        'date': serializeDate(value['date']),
+        'date': value['date'] == null ? value['date'] : serializeDate(value['date']),
         'dateTime': value['dateTime'] == null ? value['dateTime'] : serializeDateTime(value['dateTime']),
         'uuid': value['uuid'],
         'password': value['password'],

samples/client/petstore/typescript-fetch/builds/kebab-case/models/format-test.ts

@@ -116,7 +116,7 @@ export function FormatTestFromJSONTyped(json: any, ignoreDiscriminator: boolean)
         'string': json['string'] == null ? undefined : json['string'],
         '_byte': json['byte'],
         'binary': json['binary'] == null ? undefined : json['binary'],
-        'date': (parseDate(json['date'])),
+        'date': (json['date'] == null ? json['date'] : parseDate(json['date'])),
         'dateTime': json['dateTime'] == null ? undefined : (parseDateTime(json['dateTime'])),
         'uuid': json['uuid'] == null ? undefined : json['uuid'],
         'password': json['password'],
@@ -146,7 +146,7 @@ export function FormatTestToJSONTyped(value?: FormatTest | null, ignoreDiscrimin
         'string': value['string'],
         'byte': value['_byte'],
         'binary': value['binary'],
-        'date': serializeDate(value['date']),
+        'date': value['date'] == null ? value['date'] : serializeDate(value['date']),
         'dateTime': value['dateTime'] == null ? value['dateTime'] : serializeDateTime(value['dateTime']),
         'uuid': value['uuid'],
         'password': value['password'],

samples/client/petstore/typescript-fetch/builds/snakecase-discriminator/models/FormatTest.ts

@@ -116,7 +116,7 @@ export function FormatTestFromJSONTyped(json: any, ignoreDiscriminator: boolean)
         'string': json['string'] == null ? undefined : json['string'],
         '_byte': json['byte'],
         'binary': json['binary'] == null ? undefined : json['binary'],
-        'date': (parseDate(json['date'])),
+        'date': (json['date'] == null ? json['date'] : parseDate(json['date'])),
         'dateTime': json['dateTime'] == null ? undefined : (parseDateTime(json['dateTime'])),
         'uuid': json['uuid'] == null ? undefined : json['uuid'],
         'password': json['password'],
@@ -146,7 +146,7 @@ export function FormatTestToJSONTyped(value?: FormatTest | null, ignoreDiscrimin
         'string': value['string'],
         'byte': value['_byte'],
         'binary': value['binary'],
-        'date': serializeDate(value['date']),
+        'date': value['date'] == null ? value['date'] : serializeDate(value['date']),
         'dateTime': value['dateTime'] == null ? value['dateTime'] : serializeDateTime(value['dateTime']),
         'uuid': value['uuid'],
         'password': value['password'],

samples/client/petstore/typescript-fetch/builds/split-by-content-type/src/runtime.ts

@@ -359,7 +359,7 @@ function querystringSingleKey(key: string, value: string | number | null | undef
         return querystringSingleKey(key, valueAsArray, keyPrefix);
     }
     if (value instanceof Date) {
-        return `${encodeURIComponent(fullKey)}=${encodeURIComponent(value.toISOString())}`;
+        return `${encodeURIComponent(fullKey)}=${encodeURIComponent(serializeDateTime(value))}`;
     }
     if (value instanceof Object) {
         return querystring(value as HTTPQuery, fullKey);
@@ -372,6 +372,57 @@ export function exists(json: any, key: string) {
     return value !== null && value !== undefined;
 }
 
+/**
+ * Every generated date call site routes through these.
+ *
+ * `format: date` is a calendar date, with no time and no offset, so it is converted
+ * against the local calendar on both ends: they have to agree or the date shifts by
+ * a day. `format: date-time` is an instant and uses UTC.
+ */
+export function serializeDateTime(value: Date): string {
+    return value.toISOString();
+}
+
+export function serializeDate(value: Date): string {
+    if (isNaN(value.getTime())) {
+        throw new RangeError('Invalid time value');
+    }
+    const year = ('000' + value.getFullYear()).slice(-4);
+    const month = ('0' + (value.getMonth() + 1)).slice(-2);
+    const day = ('0' + value.getDate()).slice(-2);
+    return `${year}-${month}-${day}`;
+}
+
+
+export function parseDate(value: any): Date {
+    if (value instanceof Date) {
+        return value;
+    }
+    // `new Date("2026-08-05")` would parse as UTC midnight: a different day west of UTC.
+    // Local midnight is the stated day everywhere. setFullYear avoids the 1900 offset the
+    // multi-argument constructor applies to years 0-99.
+    const fullDate = /^(\d{4})-(\d{2})-(\d{2})$/.exec(String(value));
+    if (fullDate) {
+        const year = Number(fullDate[1]);
+        const month = Number(fullDate[2]) - 1;
+        const day = Number(fullDate[3]);
+        const date = new Date(0);
+        date.setFullYear(year, month, day);
+        date.setHours(0, 0, 0, 0);
+        // Out-of-range components (or a day the local zone skipped) silently roll over,
+        // which would hand back a date the server never sent.
+        if (date.getFullYear() !== year || date.getMonth() !== month || date.getDate() !== day) {
+            return new Date(NaN);
+        }
+        return date;
+    }
+    return new Date(value);
+}
+
+export function parseDateTime(value: any): Date {
+    return new Date(value);
+}
+
 export function mapValues(data: any, fn: (item: any) => any) {
     const result: { [key: string]: any } = {};
     for (const key of Object.keys(data)) {