add warnings for deprecated <svelte:options> attributes

Author: Rich-Harris

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

@@ -406,8 +406,20 @@ export function analyze_component(root, source, options) {
 		source
 	};
 
-	if (!options.customElement && root.options?.customElement) {
-		warn(analysis.warnings, root.options, [], 'missing-custom-element-compile-option');
+	if (root.options) {
+		for (const attribute of root.options.attributes) {
+			if (attribute.name === 'accessors') {
+				warn(analysis.warnings, attribute, [], 'deprecated-accessors');
+			}
+
+			if (attribute.name === 'customElement' && !options.customElement) {
+				warn(analysis.warnings, attribute, [], 'missing-custom-element-compile-option');
+			}
+
+			if (attribute.name === 'immutable') {
+				warn(analysis.warnings, attribute, [], 'deprecated-immutable');
+			}
+		}
 	}
 
 	if (analysis.runes) {

packages/svelte/src/compiler/warnings.js

@@ -238,7 +238,11 @@ const legacy = {
 		`Using <slot> to render parent content is deprecated. Use {@render ...} tags instead.`,
 	/** @param {string} name */
 	'deprecated-event-handler': (name) =>
-		`Using on:${name} to listen to the ${name} event is is deprecated. Use the event attribute on${name} instead.`
+		`Using on:${name} to listen to the ${name} event is is deprecated. Use the event attribute on${name} instead.`,
+	'deprecated-accessors': () =>
+		`The accessors option has been deprecated. It will have no effect in runes mode.`,
+	'deprecated-immutable': () =>
+		`The immutable option has been deprecated. It will have no effect in runes mode.`
 };
 
 const block = {

packages/svelte/tests/validator/samples/tag-custom-element-options-missing/warnings.json

@@ -4,11 +4,11 @@
 		"message": "The 'customElement' option is used when generating a custom element. Did you forget the 'customElement: true' compile option?",
 		"start": {
 			"line": 1,
-			"column": 0
+			"column": 16
 		},
 		"end": {
 			"line": 1,
-			"column": 49
+			"column": 46
 		}
 	}
 ]