fix: treat new expression references in template as possibly dynamic

Author: trueadm

.changeset/gorgeous-pugs-design.md

@@ -0,0 +1,5 @@
+---
+"svelte": patch
+---
+
+fix: treat new expression references in template as possibly dynamic

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

@@ -997,26 +997,37 @@ const common_visitors = {
 		const binding = context.state.scope.get(node.name);
 
 		// if no binding, means some global variable
-		if (binding && binding.kind !== 'normal') {
-			if (context.state.expression) {
-				context.state.expression.metadata.dynamic = true;
-			}
+		if (binding) {
+			if (binding.kind === 'normal') {
+				const initial = binding.initial;
+
+				if (initial?.type === 'NewExpression' && !binding.reassigned && context.state.expression) {
+					// If the identifier comes from a new expression, then the object might have a custom
+					// toString() and thus be reactive. So let's treat the expression as dynamic, unless the
+					// binding has been re-assigned.
+					context.state.expression.metadata.dynamic = true;
+				}
+			} else {
+				if (context.state.expression) {
+					context.state.expression.metadata.dynamic = true;
+				}
 
-			if (
-				node !== binding.node &&
-				// If we have $state that can be proxied or frozen and isn't re-assigned, then that means
-				// it's likely not using a primitive value and thus this warning isn't that helpful.
-				((binding.kind === 'state' &&
-					(binding.reassigned ||
-						(binding.initial?.type === 'CallExpression' &&
-							binding.initial.arguments.length === 1 &&
-							binding.initial.arguments[0].type !== 'SpreadElement' &&
-							!should_proxy_or_freeze(binding.initial.arguments[0], context.state.scope)))) ||
-					binding.kind === 'frozen_state' ||
-					binding.kind === 'derived') &&
-				context.state.function_depth === binding.scope.function_depth
-			) {
-				warn(context.state.analysis.warnings, node, context.path, 'static-state-reference');
+				if (
+					node !== binding.node &&
+					// If we have $state that can be proxied or frozen and isn't re-assigned, then that means
+					// it's likely not using a primitive value and thus this warning isn't that helpful.
+					((binding.kind === 'state' &&
+						(binding.reassigned ||
+							(binding.initial?.type === 'CallExpression' &&
+								binding.initial.arguments.length === 1 &&
+								binding.initial.arguments[0].type !== 'SpreadElement' &&
+								!should_proxy_or_freeze(binding.initial.arguments[0], context.state.scope)))) ||
+						binding.kind === 'frozen_state' ||
+						binding.kind === 'derived') &&
+					context.state.function_depth === binding.scope.function_depth
+				) {
+					warn(context.state.analysis.warnings, node, context.path, 'static-state-reference');
+				}
 			}
 		}
 	},

packages/svelte/tests/runtime-runes/samples/date/_config.js

@@ -1,8 +1,24 @@
 import { flushSync } from '../../../../src/main/main-client';
 import { test } from '../../test';
 
+const date_proto = Date.prototype;
+let date_proto_to_string = date_proto.toString;
+
 export default test({
-	html: `<div>getSeconds: 0</div><div>getMinutes: 0</div><div>getHours: 15</div><div>getTime: 1708700400000</div><div>toDateString: Fri Feb 23 2024</div><button>1 second</button><button>1 minute</button><button>1 hour</button>`,
+	html: `<div>getSeconds: 0</div><div>getMinutes: 0</div><div>getHours: 15</div><div>getTime: 1708700400000</div><div>toDateString: Fri Feb 23 2024</div><div>date: [date: 0, 0, 15]</div><button>1 second</button><button>1 minute</button><button>1 hour</button>`,
+
+	before_test() {
+		date_proto_to_string = date_proto.toString;
+
+		// This test will fail between different machines because of timezones, so we instead mock it to be a different toString().
+		date_proto.toString = function () {
+			return `[date: ${this.getSeconds()}, ${this.getMinutes()}, ${this.getHours()}]`;
+		};
+	},
+
+	after_test() {
+		date_proto.toString = date_proto_to_string;
+	},
 
 	test({ assert, target }) {
 		const [btn, btn2, btn3] = target.querySelectorAll('button');
@@ -13,7 +29,7 @@ export default test({
 
 		assert.htmlEqual(
 			target.innerHTML,
-			`<div>getSeconds: 1</div><div>getMinutes: 0</div><div>getHours: 15</div><div>getTime: 1708700401000</div><div>toDateString: Fri Feb 23 2024</div><button>1 second</button><button>1 minute</button><button>1 hour</button>`
+			`<div>getSeconds: 1</div><div>getMinutes: 0</div><div>getHours: 15</div><div>getTime: 1708700401000</div><div>toDateString: Fri Feb 23 2024</div><div>date: [date: 1, 0, 15]</div><button>1 second</button><button>1 minute</button><button>1 hour</button>`
 		);
 
 		flushSync(() => {
@@ -22,7 +38,7 @@ export default test({
 
 		assert.htmlEqual(
 			target.innerHTML,
-			`<div>getSeconds: 1</div><div>getMinutes: 1</div><div>getHours: 15</div><div>getTime: 1708700461000</div><div>toDateString: Fri Feb 23 2024</div><button>1 second</button><button>1 minute</button><button>1 hour</button>`
+			`<div>getSeconds: 1</div><div>getMinutes: 1</div><div>getHours: 15</div><div>getTime: 1708700461000</div><div>toDateString: Fri Feb 23 2024</div><div>date: [date: 1, 1, 15]</div><button>1 second</button><button>1 minute</button><button>1 hour</button>`
 		);
 
 		flushSync(() => {
@@ -31,7 +47,7 @@ export default test({
 
 		assert.htmlEqual(
 			target.innerHTML,
-			`<div>getSeconds: 1</div><div>getMinutes: 1</div><div>getHours: 16</div><div>getTime: 1708704061000</div><div>toDateString: Fri Feb 23 2024</div><button>1 second</button><button>1 minute</button><button>1 hour</button>`
+			`<div>getSeconds: 1</div><div>getMinutes: 1</div><div>getHours: 16</div><div>getTime: 1708704061000</div><div>toDateString: Fri Feb 23 2024</div><div>date: [date: 1, 1, 16]</div><button>1 second</button><button>1 minute</button><button>1 hour</button>`
 		);
 	}
 });

packages/svelte/tests/runtime-runes/samples/date/main.svelte

@@ -9,6 +9,7 @@
 <div>getHours: {date.getUTCHours()}</div>
 <div>getTime: {date.getTime()}</div>
 <div>toDateString: {date.toDateString()}</div>
+<div>date: {date}</div>
 
 <button onclick={() => {
 	date.setSeconds(date.getSeconds() + 1);