fix: don't issue a11y warning for video without captions if it has no src (#17311)

Author: Rich-Harris

.changeset/dark-buckets-hang.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: don't issue a11y warning for `<video>` without captions if it has no `src`

packages/svelte/src/compiler/phases/2-analyze/visitors/shared/a11y/index.js

@@ -486,9 +486,17 @@ export function check_element(node, context) {
 		case 'video': {
 			const aria_hidden_attribute = attribute_map.get('aria-hidden');
 			const aria_hidden_exist = aria_hidden_attribute && get_static_value(aria_hidden_attribute);
+
 			if (attribute_map.has('muted') || aria_hidden_exist === 'true' || has_spread) {
 				return;
 			}
+
+			if (!attribute_map.has('src')) {
+				// don't warn about missing captions if `<video>` has no `src` —
+				// could e.g. be playing a MediaStream
+				return;
+			}
+
 			let has_caption = false;
 			const track = /** @type {AST.RegularElement | undefined} */ (
 				node.fragment.nodes.find((i) => i.type === 'RegularElement' && i.name === 'track')

packages/svelte/tests/validator/samples/a11y-media-has-caption/input.svelte

@@ -1,6 +1,7 @@
-<video><track kind="captions"/></video>
-<video></video>
-<video><track /></video>
+<video src="x"><track kind="captions"/></video>
+<video src="x"></video>
+<video src="x"><track /></video>
 <audio></audio>
-<video aria-hidden="true"></video>
-<video aria-hidden="false"></video>
+<video src="x" aria-hidden="true"></video>
+<video src="x" aria-hidden="false"></video>
+<video></video> <!-- no src -->

packages/svelte/tests/validator/samples/a11y-media-has-caption/warnings.json

@@ -2,7 +2,7 @@
 	{
 		"code": "a11y_media_has_caption",
 		"end": {
-			"column": 15,
+			"column": 23,
 			"line": 2
 		},
 		"message": "`<video>` elements must have a `<track kind=\"captions\">`",
@@ -14,7 +14,7 @@
 	{
 		"code": "a11y_media_has_caption",
 		"end": {
-			"column": 24,
+			"column": 32,
 			"line": 3
 		},
 		"message": "`<video>` elements must have a `<track kind=\"captions\">`",
@@ -26,7 +26,7 @@
 	{
 		"code": "a11y_media_has_caption",
 		"end": {
-			"column": 35,
+			"column": 43,
 			"line": 6
 		},
 		"message": "`<video>` elements must have a `<track kind=\"captions\">`",