From be4412509e1fed62b39665bd340079848ecb6c41 Mon Sep 17 00:00:00 2001
From: Simon Holthausen <simon.holthausen@vercel.com>
Date: Fri, 22 Nov 2024 10:22:27 +0100
Subject: [PATCH] feat: support `bind:value={get, set}`

Companion to https://github.com/sveltejs/svelte/pull/14307
---
 packages/svelte2tsx/repl/index.svelte         | 13 +--
 .../src/htmlxtojsx_v2/nodes/Binding.ts        | 87 +++++++++++--------
 packages/svelte2tsx/svelte-shims-v4.d.ts      |  2 +
 .../samples/.binding-get-set.v5/expectedv2.js |  8 ++
 .../samples/.binding-get-set.v5/input.svelte  |  8 ++
 5 files changed, 77 insertions(+), 41 deletions(-)
 create mode 100644 packages/svelte2tsx/test/htmlx2jsx/samples/.binding-get-set.v5/expectedv2.js
 create mode 100644 packages/svelte2tsx/test/htmlx2jsx/samples/.binding-get-set.v5/input.svelte

diff --git a/packages/svelte2tsx/repl/index.svelte b/packages/svelte2tsx/repl/index.svelte
index 4b1efc883..9334f7ac0 100644
--- a/packages/svelte2tsx/repl/index.svelte
+++ b/packages/svelte2tsx/repl/index.svelte
@@ -1,7 +1,8 @@
-<svelte:options runes />
+<input bind:value={get, set} />
+<input bind:value={() => v, new_v => v = new_v} />
 
-<script>
-    let name = "world"
-    let name2 = "world"
-    export { name as name3, name2 as name4 };
-</script>
+<div bind:clientWidth={null, set} />
+<div bind:contentRect={null, set} />
+
+<Input bind:value={get, set} />
+<Input bind:value={() => v, new_v => v = new_v} />
diff --git a/packages/svelte2tsx/src/htmlxtojsx_v2/nodes/Binding.ts b/packages/svelte2tsx/src/htmlxtojsx_v2/nodes/Binding.ts
index 5bb17cca7..73baf0352 100644
--- a/packages/svelte2tsx/src/htmlxtojsx_v2/nodes/Binding.ts
+++ b/packages/svelte2tsx/src/htmlxtojsx_v2/nodes/Binding.ts
@@ -9,6 +9,7 @@ import { BaseDirective, BaseNode } from '../../interfaces';
 import { Element } from './Element';
 import { InlineComponent } from './InlineComponent';
 import { surroundWithIgnoreComments } from '../../utils/ignore';
+import { SequenceExpression } from 'estree';
 
 /**
  * List of binding names that are transformed to sth like `binding = variable`.
@@ -58,47 +59,54 @@ export function handleBinding(
     preserveBind: boolean,
     isSvelte5Plus: boolean
 ): void {
-    // bind group on input
-    if (element instanceof Element && attr.name == 'group' && parent.name == 'input') {
-        // add reassignment to force TS to widen the type of the declaration (in case it's never reassigned anywhere else)
-        appendOneWayBinding(attr, ' = __sveltets_2_any(null)', element);
-        return;
-    }
+    const isGetSetBinding = attr.expression.type === 'SequenceExpression';
 
-    // bind this
-    if (attr.name === 'this' && supportsBindThis.includes(parent.type)) {
-        // bind:this is effectively only works bottom up - the variable is updated by the element, not
-        // the other way round. So we check if the instance is assignable to the variable.
-        // Note: If the component unmounts (it's inside an if block, or svelte:component this={null},
-        // the value becomes null, but we don't add it to the clause because it would introduce
-        // worse DX for the 99% use case, and because null !== undefined which others might use to type the declaration.
-        appendOneWayBinding(attr, ` = ${element.name}`, element);
-        return;
-    }
+    if (!isGetSetBinding) {
+        // bind group on input
+        if (element instanceof Element && attr.name == 'group' && parent.name == 'input') {
+            // add reassignment to force TS to widen the type of the declaration (in case it's never reassigned anywhere else)
+            appendOneWayBinding(attr, ' = __sveltets_2_any(null)', element);
+            return;
+        }
 
-    // one way binding
-    if (oneWayBindingAttributes.has(attr.name) && element instanceof Element) {
-        appendOneWayBinding(attr, `= ${element.name}.${attr.name}`, element);
-        return;
-    }
+        // bind this
+        if (attr.name === 'this' && supportsBindThis.includes(parent.type)) {
+            // bind:this is effectively only works bottom up - the variable is updated by the element, not
+            // the other way round. So we check if the instance is assignable to the variable.
+            // Note: If the component unmounts (it's inside an if block, or svelte:component this={null},
+            // the value becomes null, but we don't add it to the clause because it would introduce
+            // worse DX for the 99% use case, and because null !== undefined which others might use to type the declaration.
+            appendOneWayBinding(attr, ` = ${element.name}`, element);
+            return;
+        }
 
-    // one way binding whose property is not on the element
-    if (oneWayBindingAttributesNotOnElement.has(attr.name) && element instanceof Element) {
+        // one way binding
+        if (oneWayBindingAttributes.has(attr.name) && element instanceof Element) {
+            appendOneWayBinding(attr, `= ${element.name}.${attr.name}`, element);
+            return;
+        }
+
+        // one way binding whose property is not on the element
+        if (oneWayBindingAttributesNotOnElement.has(attr.name) && element instanceof Element) {
+            element.appendToStartEnd([
+                [attr.expression.start, getEnd(attr.expression)],
+                `= ${surroundWithIgnoreComments(
+                    `null as ${oneWayBindingAttributesNotOnElement.get(attr.name)}`
+                )};`
+            ]);
+            return;
+        }
+
+        // add reassignment to force TS to widen the type of the declaration (in case it's never reassigned anywhere else)
+        const expressionStr = str.original.substring(
+            attr.expression.start,
+            getEnd(attr.expression)
+        );
         element.appendToStartEnd([
-            [attr.expression.start, getEnd(attr.expression)],
-            `= ${surroundWithIgnoreComments(
-                `null as ${oneWayBindingAttributesNotOnElement.get(attr.name)}`
-            )};`
+            surroundWithIgnoreComments(`() => ${expressionStr} = __sveltets_2_any(null);`)
         ]);
-        return;
     }
 
-    // add reassignment to force TS to widen the type of the declaration (in case it's never reassigned anywhere else)
-    const expressionStr = str.original.substring(attr.expression.start, getEnd(attr.expression));
-    element.appendToStartEnd([
-        surroundWithIgnoreComments(`() => ${expressionStr} = __sveltets_2_any(null);`)
-    ]);
-
     // other bindings which are transformed to normal attributes/props
     const isShorthand = attr.expression.start === attr.start + 'bind:'.length;
     const name: TransformationArray =
@@ -122,11 +130,20 @@ export function handleBinding(
                     ]
                 ];
 
+    const [get, set] = isGetSetBinding ? (attr.expression as SequenceExpression).expressions : [];
     const value: TransformationArray | undefined = isShorthand
         ? preserveBind && element instanceof Element
             ? [rangeWithTrailingPropertyAccess(str.original, attr.expression)]
             : undefined
-        : [rangeWithTrailingPropertyAccess(str.original, attr.expression)];
+        : isGetSetBinding
+          ? [
+                '__sveltets_2_get_set_binding(',
+                [get.start, get.end],
+                ',',
+                rangeWithTrailingPropertyAccess(str.original, set),
+                ')'
+            ]
+          : [rangeWithTrailingPropertyAccess(str.original, attr.expression)];
 
     if (isSvelte5Plus && element instanceof InlineComponent) {
         // To check if property is actually bindable
diff --git a/packages/svelte2tsx/svelte-shims-v4.d.ts b/packages/svelte2tsx/svelte-shims-v4.d.ts
index 2d36a539d..fcaf92f65 100644
--- a/packages/svelte2tsx/svelte-shims-v4.d.ts
+++ b/packages/svelte2tsx/svelte-shims-v4.d.ts
@@ -263,6 +263,8 @@ type __sveltets_2_PropsWithChildren<Props, Slots> = Props &
         : {});
 declare function __sveltets_2_runes_constructor<Props extends {}>(render: {props: Props }): import("svelte").ComponentConstructorOptions<Props>;
 
+declare function __sveltets_2_get_set_binding<T>(get: (() => T) | null | undefined, set: (t: T) => void): T;
+
 declare function __sveltets_$$bindings<Bindings extends string[]>(...bindings: Bindings): Bindings[number];
 
 declare function __sveltets_2_fn_component<
diff --git a/packages/svelte2tsx/test/htmlx2jsx/samples/.binding-get-set.v5/expectedv2.js b/packages/svelte2tsx/test/htmlx2jsx/samples/.binding-get-set.v5/expectedv2.js
new file mode 100644
index 000000000..370353fb4
--- /dev/null
+++ b/packages/svelte2tsx/test/htmlx2jsx/samples/.binding-get-set.v5/expectedv2.js
@@ -0,0 +1,8 @@
+ { svelteHTML.createElement("input", {   "bind:value":__sveltets_2_get_set_binding(get,set),});}
+ { svelteHTML.createElement("input", {   "bind:value":__sveltets_2_get_set_binding(() => v,new_v => v = new_v),});}
+
+ { svelteHTML.createElement("div", {   "bind:clientWidth":__sveltets_2_get_set_binding(null,set),});}
+ { svelteHTML.createElement("div", {   "bind:contentRect":__sveltets_2_get_set_binding(null,set),});}
+
+ { const $$_tupnI0C = __sveltets_2_ensureComponent(Input); const $$_tupnI0 = new $$_tupnI0C({ target: __sveltets_2_any(), props: {    value:__sveltets_2_get_set_binding(get,set),}});$$_tupnI0.$$bindings = 'value';}
+ { const $$_tupnI0C = __sveltets_2_ensureComponent(Input); const $$_tupnI0 = new $$_tupnI0C({ target: __sveltets_2_any(), props: {    value:__sveltets_2_get_set_binding(() => v,new_v => v = new_v),}});$$_tupnI0.$$bindings = 'value';}
\ No newline at end of file
diff --git a/packages/svelte2tsx/test/htmlx2jsx/samples/.binding-get-set.v5/input.svelte b/packages/svelte2tsx/test/htmlx2jsx/samples/.binding-get-set.v5/input.svelte
new file mode 100644
index 000000000..9334f7ac0
--- /dev/null
+++ b/packages/svelte2tsx/test/htmlx2jsx/samples/.binding-get-set.v5/input.svelte
@@ -0,0 +1,8 @@
+<input bind:value={get, set} />
+<input bind:value={() => v, new_v => v = new_v} />
+
+<div bind:clientWidth={null, set} />
+<div bind:contentRect={null, set} />
+
+<Input bind:value={get, set} />
+<Input bind:value={() => v, new_v => v = new_v} />