feat: Skip type injection if template uses TypeScript (#440)

Author: baseballyama

.changeset/grumpy-dolphins-pay.md

@@ -0,0 +1,5 @@
+---
+"svelte-eslint-parser": minor
+---
+
+feat: skip type injection if template uses TypeScript

explorer-v2/package.json

@@ -18,7 +18,7 @@
 		"eslint-scope": "^7.2.2",
 		"esquery": "^1.5.0",
 		"pako": "^2.1.0",
-		"svelte": "^5.0.0-next.8",
+		"svelte": "^5.0.0-next.10",
 		"svelte-eslint-parser": "link:..",
 		"tslib": "^2.6.2"
 	},

package.json

@@ -46,7 +46,7 @@
     "version:ci": "env-cmd -e version-ci pnpm run build:meta && changeset version"
   },
   "peerDependencies": {
-    "svelte": "^3.37.0 || ^4.0.0 || ^5.0.0-next.8"
+    "svelte": "^3.37.0 || ^4.0.0 || ^5.0.0-next.10"
   },
   "peerDependenciesMeta": {
     "svelte": {
@@ -104,7 +104,7 @@
     "prettier-plugin-svelte": "^3.0.0",
     "rimraf": "^5.0.1",
     "semver": "^7.5.1",
-    "svelte": "^5.0.0-next.8",
+    "svelte": "^5.0.0-next.10",
     "svelte2tsx": "^0.6.25",
     "typescript": "~5.1.3",
     "typescript-eslint-parser-for-extra-files": "^0.5.0"

src/parser/converts/attr.ts

@@ -34,6 +34,7 @@ import { ParseError } from "../../errors";
 import type { ScriptLetCallback } from "../../context/script-let";
 import type { AttributeToken } from "../html";
 import { svelteVersion } from "../svelte-version";
+import { hasTypeInfo } from "../../utils";
 
 /** Convert for Attributes */
 export function* convertAttributes(
@@ -922,6 +923,9 @@ function buildProcessExpressionForExpression(
   typing: string | null,
 ): (expression: ESTree.Expression) => ScriptLetCallback<ESTree.Expression>[] {
   return (expression) => {
+    if (hasTypeInfo(expression)) {
+      return ctx.scriptLet.addExpression(expression, directive, null);
+    }
     return ctx.scriptLet.addExpression(expression, directive, typing);
   };
 }

src/parser/converts/mustache.ts

@@ -6,6 +6,8 @@ import type {
 } from "../../ast";
 import type { Context } from "../../context";
 import type * as SvAST from "../svelte-ast-types";
+import { hasTypeInfo } from "../../utils";
+
 /** Convert for MustacheTag */
 export function convertMustacheTag(
   node: SvAST.MustacheTag,
@@ -76,8 +78,14 @@ function convertMustacheTag0<T extends SvelteMustacheTag>(
     parent,
     ...ctx.getConvertLocation(node),
   } as T;
-  ctx.scriptLet.addExpression(node.expression, mustache, typing, (es) => {
-    mustache.expression = es;
-  });
+
+  ctx.scriptLet.addExpression(
+    node.expression,
+    mustache,
+    hasTypeInfo(node.expression) ? null : typing,
+    (es) => {
+      mustache.expression = es;
+    },
+  );
   return mustache;
 }

src/utils/index.ts

@@ -59,3 +59,22 @@ export function sortedLastIndex<T>(
 
   return upper;
 }
+
+export function hasTypeInfo(element: any): boolean {
+  if (element.type?.startsWith("TS")) {
+    return true;
+  }
+  for (const key of Object.keys(element)) {
+    if (key === "parent") continue;
+    const value = element[key];
+    if (value == null) continue;
+    if (typeof value === "object") {
+      if (hasTypeInfo(value)) return true;
+    } else if (Array.isArray(value)) {
+      for (const v of value) {
+        if (typeof v === "object" && hasTypeInfo(v)) return true;
+      }
+    }
+  }
+  return false;
+}

tests/fixtures/parser/ast/svelte5/ts-event07-input.svelte

@@ -0,0 +1,10 @@
+<script lang="ts">
+	let count = $state(0);
+</script>
+
+<button
+	on:click={(e: MouseEvent) => {
+		const next: number = count + 1;
+		count = next;
+	}}
+>clicks: {count}</button>

tests/fixtures/parser/ast/svelte5/ts-event07-no-unused-vars-result.json

@@ -0,0 +1,8 @@
+[
+  {
+    "ruleId": "no-unused-vars",
+    "code": "e: MouseEvent",
+    "line": 6,
+    "column": 13
+  }
+]