use flags for prop_source, this will be useful later

Author: Rich-Harris

packages/svelte/src/compiler/phases/3-transform/client/utils.js

@@ -1,6 +1,7 @@
 import * as b from '../../../utils/builders.js';
 import { extract_paths, is_simple_expression } from '../../../utils/ast.js';
 import { error } from '../../../errors.js';
+import { PROPS_CALL_DEFAULT_VALUE, PROPS_IS_IMMUTABLE } from '../../../../constants.js';
 
 /**
  * @template {import('./types').ClientTransformState} State
@@ -359,29 +360,43 @@ export function get_props_method(binding, state, name, default_value) {
 		(state.analysis.immutable ? binding.reassigned : binding.mutated);
 
 	if (needs_source) {
-		args.push(b.literal(state.analysis.immutable));
-	}
+		let flags = 0;
 
-	if (default_value) {
-		// To avoid eagerly evaluating the right-hand-side, we wrap it in a thunk if necessary
-		if (is_simple_expression(default_value)) {
-			args.push(default_value);
-		} else {
-			if (
-				default_value.type === 'CallExpression' &&
-				default_value.callee.type === 'Identifier' &&
-				default_value.arguments.length === 0
-			) {
-				args.push(default_value.callee);
+		/** @type {import('estree').Expression | undefined} */
+		let arg;
+
+		if (state.analysis.immutable) {
+			flags |= PROPS_IS_IMMUTABLE;
+		}
+
+		if (default_value) {
+			// To avoid eagerly evaluating the right-hand-side, we wrap it in a thunk if necessary
+			if (is_simple_expression(default_value)) {
+				arg = default_value;
 			} else {
-				args.push(b.thunk(default_value));
+				if (
+					default_value.type === 'CallExpression' &&
+					default_value.callee.type === 'Identifier' &&
+					default_value.arguments.length === 0
+				) {
+					arg = default_value.callee;
+				} else {
+					arg = b.thunk(default_value);
+				}
+
+				flags |= PROPS_CALL_DEFAULT_VALUE;
 			}
+		}
 
-			args.push(b.true);
+		if (flags || arg) {
+			args.push(b.literal(flags));
+			if (arg) args.push(arg);
 		}
+
+		return b.call('$.prop_source', ...args);
 	}
 
-	return b.call(needs_source ? '$.prop_source' : '$.prop', ...args);
+	return b.call('$.prop', ...args);
 }
 
 /**

packages/svelte/src/constants.js

@@ -5,6 +5,9 @@ export const EACH_IS_CONTROLLED = 1 << 3;
 export const EACH_IS_ANIMATED = 1 << 4;
 export const EACH_IS_IMMUTABLE = 1 << 6;
 
+export const PROPS_IS_IMMUTABLE = 1;
+export const PROPS_CALL_DEFAULT_VALUE = 1 << 1;
+
 /** List of Element events that will be delegated */
 export const DelegatedEvents = [
 	'beforeinput',

packages/svelte/src/internal/client/runtime.js

@@ -2,6 +2,7 @@ import { DEV } from 'esm-env';
 import { subscribe_to_store } from '../../store/utils.js';
 import { EMPTY_FUNC, run_all } from '../common.js';
 import { get_descriptors, is_array } from './utils.js';
+import { PROPS_CALL_DEFAULT_VALUE, PROPS_IS_IMMUTABLE } from '../../constants.js';
 
 export const SOURCE = 1;
 export const DERIVED = 1 << 1;
@@ -1463,12 +1464,14 @@ export function is_store(val) {
  * @template V
  * @param {import('./types.js').MaybeSignal<Record<string, unknown>>} props_obj
  * @param {string} key
- * @param {boolean} immutable
+ * @param {number} flags
  * @param {V | (() => V)} [default_value]
- * @param {boolean} [call_default_value]
  * @returns {import('./types.js').Signal<V> | (() => V)}
  */
-export function prop_source(props_obj, key, immutable, default_value, call_default_value) {
+export function prop_source(props_obj, key, flags, default_value) {
+	const call_default_value = (flags & PROPS_CALL_DEFAULT_VALUE) !== 0;
+	const immutable = (flags & PROPS_IS_IMMUTABLE) !== 0;
+
 	const props = is_signal(props_obj) ? get(props_obj) : props_obj;
 	const possible_signal = /** @type {import('./types.js').MaybeSignal<V>} */ (
 		expose(() => props[key])

packages/svelte/tests/snapshot/samples/svelte-element/_expected/client/index.svelte.js

@@ -6,7 +6,7 @@ import * as $ from "svelte/internal";
 export default function Svelte_element($$anchor, $$props) {
 	$.push($$props, true);
 
-	let tag = $.prop_source($$props, "tag", true, 'hr');
+	let tag = $.prop_source($$props, "tag", 1, 'hr');
 	/* Init */
 	var fragment = $.comment($$anchor);
 	var node = $.child_frag(fragment);