fix: serialize prettier formatting to prevent flaky tests

src/sql/recent-query.ts

@@ -11,6 +11,7 @@ import {
   type TableReference,
 } from "@query-doctor/core";
 import { parse } from "@libpg-query/parser";
+import { Sema } from "async-sema";
 import z from "zod";
 import type { LiveQueryOptimization } from "../remote/optimization.ts";
 
@@ -21,6 +22,7 @@ import type { LiveQueryOptimization } from "../remote/optimization.ts";
 export class RecentQuery {
   private static HARDCODED_LIMIT = 50;
   private static rewriter = new PssRewriter();
+  private static prettierMutex = new Sema(1);
 
   readonly formattedQuery: string;
   readonly username: string;
@@ -134,15 +136,19 @@ export class RecentQuery {
   }
 
   private static async formatQuery(query: string): Promise<string> {
+    await RecentQuery.prettierMutex.acquire();
     try {
       return await prettier.format(query, {
         parser: "sql",
         plugins: [prettierPluginSql],
         language: "postgresql",
         keywordCase: "upper",
       });
-    } catch {
+    } catch (error) {
+      console.error(`[prettier] Failed to format query: ${error}`);
       return query;
+    } finally {
+      RecentQuery.prettierMutex.release();
     }
   }