feat: add autofixer to tell the LLM to check if some function called in effect is assigning state

apps/mcp-remote/.env.example

@@ -1,4 +1,3 @@
 DATABASE_URL=file:test.db
 DATABASE_TOKEN=needs_to_be_set_but_it_can_be_anything
-VOYAGE_API_KEY=your_actual_api_key_here
-GITHUB_WEBHOOK_SECRET=some_secret
+VOYAGE_API_KEY=your_actual_api_key_here

apps/mcp-remote/package.json

@@ -65,7 +65,6 @@
 		"@sveltejs/mcp-schema": "workspace:^",
 		"@sveltejs/mcp-server": "workspace:^",
 		"@tmcp/transport-http": "^0.6.3",
-		"tmcp": "^1.14.0",
-		"valibot": "^1.1.0"
+		"tmcp": "^1.14.0"
 	}
 }

apps/mcp-remote/src/lib/schemas/index.ts

@@ -1,32 +0,0 @@
-import * as v from 'valibot';
-
-// not the full schema but it contains the information we need
-export const github_webhook_schema = v.object({
-	action: v.union([v.literal('closed')]),
-	pull_request: v.object({
-		patch_url: v.string(),
-		merged: v.boolean(),
-		user: v.object({
-			login: v.string(),
-		}),
-	}),
-});
-
-export const github_content_schema = v.object({
-	name: v.string(),
-	path: v.string(),
-	sha: v.string(),
-	size: v.number(),
-	url: v.string(),
-	html_url: v.string(),
-	git_url: v.string(),
-	download_url: v.nullable(v.string()),
-	type: v.literal('file'),
-	content: v.string(),
-	encoding: v.literal('base64'),
-	_links: v.object({
-		self: v.string(),
-		git: v.string(),
-		html: v.string(),
-	}),
-});

apps/mcp-remote/src/routes/webhooks/docs/+server.ts

@@ -1,54 +0,0 @@
-import { github_content_schema, github_webhook_schema } from '$lib/schemas/index.js';
-import * as v from 'valibot';
-
-export async function POST({ request, fetch }) {
-	const body = await request.json();
-	// TODO add secret validation
-	const validated_pull_request = v.safeParse(github_webhook_schema, body);
-	if (!validated_pull_request.success) {
-		return new Response('Invalid payload', { status: 400 });
-	}
-
-	const { pull_request } = validated_pull_request.output;
-
-	if (!pull_request.merged) {
-		return new Response(null, { status: 204 });
-	}
-
-	const patch = await fetch(pull_request.patch_url);
-	if (!patch.ok) {
-		return new Response('Failed to fetch patch', { status: 500 });
-	}
-
-	const patch_text = await patch.text();
-	const files = [
-		...patch_text.matchAll(
-			/^diff --git\sa\/(?<file>.+?)\sb\/\1\n(?:(?<action>deleted|new)\sfile mode)?/gm,
-		),
-	].map((res) => ({ file: res.groups!.file, action: res.groups?.action ?? 'modified' }));
-
-	for (const file of files) {
-		if (file.action === 'deleted') {
-			// delete path from db
-			continue;
-		}
-		const new_file_content = await fetch(
-			`https://api.github.com/repos/sveltejs/svelte.dev/contents/${file.file}`,
-		);
-		if (!new_file_content.ok) {
-			// push file in queue and try again later?
-			continue;
-		}
-		const new_file_json = await new_file_content.json();
-		const validated_content = v.safeParse(github_content_schema, new_file_json);
-		if (!validated_content.success) {
-			// push file in queue and try again later?
-			continue;
-		}
-		const content = Buffer.from(validated_content.output.content, 'base64').toString('utf-8');
-		// save content and distilled content in the db
-		console.log({ content, file: file.file });
-	}
-
-	return new Response(null, { status: 204 });
-}

packages/mcp-server/src/mcp/autofixers/add-autofixers-issues.test.ts

@@ -117,6 +117,36 @@ describe('add_autofixers_issues', () => {
 				);
 			});
 		});
+
+		it('should add a suggestion when calling a function inside an effect', () => {
+			const content = run_autofixers_on_code(`
+			<script>
+				import { fetch_data } from './data.js';
+				$effect(() => {
+					fetch_data();
+				});
+			</script>`);
+
+			expect(content.suggestions.length).toBeGreaterThanOrEqual(1);
+			expect(content.suggestions).toContain(
+				`You are calling the function \`fetch_data\` inside an $effect. Please check if the function is reassigning a stateful variable because that's considered malpractice and check if it could use  \`$derived\` instead. Ignore this suggestion if you are sure this function is not assigning any stateful variable or if you can't check if it does.`,
+			);
+		});
+
+		it('should add a suggestion when calling a function inside an effect (with non identifier callee)', () => {
+			const content = run_autofixers_on_code(`
+			<script>
+				import { fetch_data } from './data.js';
+				$effect(() => {
+					fetch_data.fetch();
+				});
+			</script>`);
+
+			expect(content.suggestions.length).toBeGreaterThanOrEqual(1);
+			expect(content.suggestions).toContain(
+				`You are calling a function inside an $effect. Please check if the function is reassigning a stateful variable because that's considered malpractice and check if it could use  \`$derived\` instead. Ignore this suggestion if you are sure this function is not assigning any stateful variable or if you can't check if it does.`,
+			);
+		});
 	});
 
 	with_possible_inits('($init)', ({ init }) => {

packages/mcp-server/src/mcp/autofixers/visitors/assign-in-effect.ts

@@ -1,4 +1,10 @@
-import type { AssignmentExpression, Identifier, Node, UpdateExpression } from 'estree';
+import type {
+	AssignmentExpression,
+	CallExpression,
+	Identifier,
+	Node,
+	UpdateExpression,
+} from 'estree';
 import type { Autofixer, AutofixerState } from './index.js';
 import { left_most_id } from '../ast/utils.js';
 import type { AST } from 'svelte-eslint-parser';
@@ -27,9 +33,9 @@ function run_if_in_effect(
 	}
 }
 
-function visitor(
+function assign_or_update_visitor(
 	node: UpdateExpression | AssignmentExpression,
-	{ state, path }: Context<Node | AST.SvelteNode, AutofixerState>,
+	{ state, path, next }: Context<Node | AST.SvelteNode, AutofixerState>,
 ) {
 	run_if_in_effect(path, state, () => {
 		function check_if_stateful_id(id: Identifier) {
@@ -58,9 +64,25 @@ function visitor(
 			}
 		}
 	});
+	next();
+}
+
+function call_expression_visitor(
+	node: CallExpression,
+	{ state, path, next }: Context<Node | AST.SvelteNode, AutofixerState>,
+) {
+	run_if_in_effect(path, state, () => {
+		const function_name =
+			node.callee.type === 'Identifier' ? `the function \`${node.callee.name}\`` : 'a function';
+		state.output.suggestions.push(
+			`You are calling ${function_name} inside an $effect. Please check if the function is reassigning a stateful variable because that's considered malpractice and check if it could use  \`$derived\` instead. Ignore this suggestion if you are sure this function is not assigning any stateful variable or if you can't check if it does.`,
+		);
+	});
+	next();
 }
 
 export const assign_in_effect: Autofixer = {
-	UpdateExpression: visitor,
-	AssignmentExpression: visitor,
+	UpdateExpression: assign_or_update_visitor,
+	AssignmentExpression: assign_or_update_visitor,
+	CallExpression: call_expression_visitor,
 };

pnpm-lock.yaml

@@ -62,9 +62,6 @@ importers:
       tmcp:
         specifier: ^1.14.0
         version: 1.14.0(typescript@5.9.2)
-      valibot:
-        specifier: ^1.1.0
-        version: 1.1.0(typescript@5.9.2)
     devDependencies:
       '@eslint/compat':
         specifier: ^1.3.2