From 746921b86d7bcf4cd3e4c652111f818a7ebd0b09 Mon Sep 17 00:00:00 2001
From: Navid EMAD <navid.emad@yespark.fr>
Date: Mon, 27 Apr 2026 03:44:33 +0200
Subject: [PATCH] Fix SubmitEvent.submitter for requestSubmit() with no
 argument

When Form.requestSubmit() is called without a submitter argument, the
HTML spec defaults the internal submitter variable to the form element
itself (step 2). The subsequent "submit a form element" algorithm then
collapses submitter === form back to submitterButton = null before
constructing the SubmitEvent. We were skipping that collapse and using
the form as the SubmitEvent's submitter, which diverges from Chrome /
Firefox / WPT.

Frame.submitForm now coerces submitter_ to null when it equals the
form element, mirroring the spec algorithm. The form.html fixture
that previously asserted the wrong behavior is updated to assert
.submitter === null per spec.

https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#concept-form-submit

Closes #2252
---
 src/browser/Frame.zig                    | 10 +++++++++-
 src/browser/tests/element/html/form.html |  7 ++++---
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/src/browser/Frame.zig b/src/browser/Frame.zig
index 17c49d0e..9b28c25a 100644
--- a/src/browser/Frame.zig
+++ b/src/browser/Frame.zig
@@ -3701,7 +3701,15 @@ pub fn submitForm(self: *Frame, submitter_: ?*Element, form_: ?*Element.Html.For
     };
 
     if (submit_opts.fire_event) {
-        const submitter_html: ?*HtmlElement = if (submitter_) |s| s.is(HtmlElement) else null;
+        // Per HTML spec "submit a form element" algorithm: SubmitEvent.submitter
+        // must be null when the submitter is the form itself, which is what
+        // Form.requestSubmit() passes when called with no submitter argument.
+        // https://html.spec.whatwg.org/multipage/form-control-infrastructure.html#concept-form-submit
+        const submitter_html: ?*HtmlElement = blk: {
+            const s = submitter_ orelse break :blk null;
+            if (s == form_element) break :blk null;
+            break :blk s.is(HtmlElement);
+        };
         const submit_event = (try SubmitEvent.initTrusted(comptime .wrap("submit"), .{ .bubbles = true, .cancelable = true, .submitter = submitter_html }, self)).asEvent();
 
         // so submit_event is still valid when we check _prevent_default
diff --git a/src/browser/tests/element/html/form.html b/src/browser/tests/element/html/form.html
index 31f5d648..8a92cb10 100644
--- a/src/browser/tests/element/html/form.html
+++ b/src/browser/tests/element/html/form.html
@@ -485,12 +485,13 @@
 }
 </script>
 
-<!-- Test: requestSubmit() without submitter sets submitter to the form element -->
+<!-- Test: requestSubmit() without submitter sets SubmitEvent.submitter to null
+     per the HTML spec "submit a form element" algorithm step 4. -->
 <form id="test_form_submitter2" action="/should-not-navigate7" method="get">
   <input type="text" name="q" value="test">
 </form>
 
-<script id="requestSubmit_default_submitter_is_form">
+<script id="requestSubmit_default_submitter_is_null">
 {
   const form = $('#test_form_submitter2');
   let capturedSubmitter = undefined;
@@ -501,7 +502,7 @@
   });
 
   form.requestSubmit();
-  testing.expectEqual(form, capturedSubmitter);
+  testing.expectEqual(null, capturedSubmitter);
 }
 </script>