support for style:display|transition with boolean value in SSR

Author: adiguba

packages/svelte/src/compiler/phases/3-transform/server/visitors/shared/element.js

@@ -448,6 +448,9 @@ function build_style_directives(display_directive, style_directives, style_attri
 			directive.value === true
 				? b.id(directive.name)
 				: build_attribute_value(directive.value, context, true);
+		if (directive.name === 'display' && directive.modifiers.includes('transition')) {
+			value = b.call('$.get_display', value);
+		}
 		if (directive.modifiers.includes('important')) {
 			value = b.binary('+', value, b.literal(' !important'));
 		}

packages/svelte/src/internal/server/index.js

@@ -270,6 +270,13 @@ function style_object_to_string(style_object) {
 		.join(' ');
 }
 
+/** @param {string|boolean} value */
+export function get_display(value) {
+	if (value === true) return null;
+	if (value === false) return 'none';
+	return value;
+}
+
 /** @param {Record<string, string>} style_object */
 export function add_styles(style_object) {
 	const styles = style_object_to_string(style_object);