fix: resolve findings from the new SonarQube 26.9 rules

scripts/calibrate-capacity.ts

@@ -709,7 +709,7 @@ function isClassroomComplete(classroom: ClassroomMeasurement | null, expectedUse
 }
 
 function buildQueueRecommendation(classroom: ClassroomMeasurement | null, complete: boolean, config: CalibrationCliConfig): Recommendation<number> {
-  if (complete && classroom && classroom.queueWaitMs.length === config.expectedUsers) {
+  if (complete && classroom?.queueWaitMs.length === config.expectedUsers) {
     return recommendQueueTimeout(classroom.queueP95Ms, classroom.queueP99Ms, classroom.queueMaxMs, config.maxUserWaitSec);
   }
   return {

scripts/capacity-calibration-policy.ts

@@ -171,7 +171,7 @@ export function selectActiveRecommendation(
   const stable = measurements.filter((measurement) => activeIsStable(measurement, options));
   const target = stable.filter((measurement) => (measurement.cpuP95Percent ?? Infinity) <= options.targetCpuPercent);
   if (target.length > 0) {
-    const selected = target.reduce((best, current) => current.requested > best.requested ? current : best);
+    const selected = target.reduce((best, current) => current.requested > best.requested ? current : best, target[0]);
     return {
       value: selected.requested,
       status: "recommended",
@@ -181,7 +181,7 @@ export function selectActiveRecommendation(
     };
   }
   if (stable.length > 0) {
-    const selected = stable.reduce((best, current) => current.requested > best.requested ? current : best);
+    const selected = stable.reduce((best, current) => current.requested > best.requested ? current : best, stable[0]);
     return {
       value: selected.requested,
       status: "recommended",

scripts/check-bundle-budget.mjs

@@ -16,7 +16,7 @@ const largest = Math.max(...sizes.map((file) => file.bytes), 0);
 // 700 kB limit reflected Vite 5 chunk placement. Recalibrated together with the initial-path check below.
 const limits = { total: 6_000_000, largest: 4_500_000, initial: 710_000 };
 const initial = sizes
-  .filter((file) => /^index-/.test(file.name))
+  .filter((file) => file.name.startsWith("index-"))
   .reduce((sum, file) => sum + file.bytes, 0);
 
 // Initial load path: static import closure of the HTML entry, from the Vite build manifest.

scripts/check-node-version.mjs

@@ -1,7 +1,7 @@
 import { readFile } from "node:fs/promises";
 const expected = (await readFile(".nvmrc", "utf8")).trim();
 const declared = JSON.parse(await readFile("package.json", "utf8")).engines?.node;
-if (!declared || !declared.includes(expected)) {
+if (!declared?.includes(expected)) {
   console.error(`Node mismatch: expected ${expected}, engines=${declared}, runtime=${process.version}`);
   process.exit(1);
 }

scripts/deployment/deployment-support.ts

@@ -139,6 +139,10 @@ export async function httpsRequest(
   });
 }
 
+function describeError(error: unknown): string {
+  return error instanceof Error ? String(error) : JSON.stringify(error);
+}
+
 export async function waitFor(
   description: string,
   probe: () => Promise<boolean>,
@@ -154,7 +158,7 @@ export async function waitFor(
     }
     await sleep(500);
   }
-  const suffix = lastError ? `: ${String(lastError)}` : "";
+  const suffix = lastError ? `: ${describeError(lastError)}` : "";
   throw new Error(`Timed out waiting for ${description}${suffix}`);
 }
 
@@ -236,6 +240,12 @@ export function openWebSocket(
   });
 }
 
+/** `ws` delivers text frames as Buffer, ArrayBuffer or fragment list depending on its options. */
+function rawDataToString(raw: WebSocket.RawData): string {
+  if (Array.isArray(raw)) return Buffer.concat(raw).toString("utf8");
+  return Buffer.from(raw).toString("utf8");
+}
+
 export function nextWebSocketMessage(
   socket: WebSocket,
   predicate: (message: Record<string, any>) => boolean,
@@ -248,7 +258,7 @@ export function nextWebSocketMessage(
     }, timeoutMs);
     const onMessage = (raw: WebSocket.RawData) => {
       try {
-        const message = JSON.parse(raw.toString()) as Record<string, any>;
+        const message = JSON.parse(rawDataToString(raw)) as Record<string, any>;
         if (!predicate(message)) return;
         clearTimeout(timer);
         socket.removeListener("message", onMessage);

scripts/tutor-quality-real-provider-eval.ts

@@ -251,10 +251,10 @@ export function isTutorQualityRelevantUntrackedPath(relativePath: string, output
 export function readTutorQualityGitState(cwd: string, outputDir: string): TutorQualityGitState {
   const sha = execFileSync(resolveGitExecutable(), ["rev-parse", "HEAD"], { cwd, encoding: "utf8" }).trim();
   const lines = statusLines(cwd);
-  const trackedClean = lines.every((line) => line.slice(0, 2) === "??");
+  const trackedClean = lines.every((line) => line.startsWith("??"));
   const outputRelative = path.relative(cwd, path.resolve(cwd, outputDir));
   const relevantUntrackedClean = lines.every((line) => {
-    if (line.slice(0, 2) !== "??") return true;
+    if (!line.startsWith("??")) return true;
     return !isTutorQualityRelevantUntrackedPath(line.slice(3).trim(), outputRelative);
   });
   return { sha, trackedClean, relevantUntrackedClean };

scripts/validate-tutor-course-content.mjs

@@ -2,7 +2,7 @@ import path from "node:path";
 import { validateTutorCourseContentDirectory } from "../server/services/course-content/tutor-quality-directory-validator.ts";
 
 const directory = process.argv[2];
-if (directory === undefined || directory.length === 0) {
+if (!directory) {
   console.error("Usage: npm run validate:tutor-course-content -- <course-content-directory>");
   process.exitCode = 2;
 } else {

server/services/tutor/curriculum/sketch-facts.ts

@@ -25,7 +25,7 @@ const TYPE_ALIASES: Readonly<Record<string, SketchType>> = {
 };
 
 const TYPE_PATTERN = /\b(?:(?:unsigned|signed)\s+)?(?:char|byte|uint8_t|int|long|float)\b/g;
-const ARRAY_PATTERN = /\b(char|byte|uint8_t|int|long|float)\s+([A-Za-z_]\w*)\s*\[\s*([^\]]*)\s*\]/g;
+const ARRAY_PATTERN = /\b(char|byte|uint8_t|int|long|float)\s+([A-Za-z_]\w*)\s*\[([^\]]*)\]/g;
 const INITIALIZER_PATTERN = /^\s*=\s*\{([^}]*)\}/;
 const SERIAL_PATTERN = /\bSerial\s*\.\s*(print|println|write)\s*\(/gi;
 

tests/client/examples-menu.behavior.test.tsx

@@ -98,7 +98,7 @@ describe("ExamplesMenu behavior", () => {
     expect(screen.getByText("Load Example")).toHaveClass("ui-type-menu-title");
     fireEvent.click(screen.getByRole("button", { name: "Built-in" }));
     expect(
-      screen.queryByRole("button", { name: "Built-in", exact: true }),
+      screen.getByRole("button", { name: "Built-in", exact: true }),
     ).toBeInTheDocument();
     expect(
       screen.queryByRole("button", { name: "Other" }),

tests/client/experimental-workspace-layout.test.tsx

@@ -398,6 +398,6 @@ describe("experimental workspace layout", () => {
       { credential: "volatile-key" },
       { credential: "volatile-key" },
     ]);
-    expect(localStorage.length).toBe(0);
+    expect(localStorage).toHaveLength(0);
   });
 });

tests/client/tutor.test.tsx

@@ -158,7 +158,7 @@ describe("useTutor", () => {
       difficulty: 30,
     });
     expect(result.current.question?.question).toBe("Welche Ausgabe erwartest du?");
-    expect(localStorage.length).toBe(0);
+    expect(localStorage).toHaveLength(0);
   });
 
   it("resets a pinned dialog when the active Course Content revision changes", async () => {

tests/integration/concurrent-50-clients.test.ts

@@ -421,10 +421,10 @@ void loop() { digitalWrite(13, HIGH); Serial.println("LED ON"); delay(500); digi
     const errored = results.filter((r) => r.errors.length > 0);
 
     // All must compile
-    expect(compiled.length).toBe(N);
+    expect(compiled).toHaveLength(N);
 
     // All must connect via WS
-    expect(connected.length).toBe(N);
+    expect(connected).toHaveLength(N);
 
     // All must receive serial output (the key user-visible requirement)
     if (gotOutput.length < N) {
@@ -439,10 +439,10 @@ void loop() { digitalWrite(13, HIGH); Serial.println("LED ON"); delay(500); digi
     }
 
     // All must see simulation end
-    expect(gotStopped.length).toBe(N);
+    expect(gotStopped).toHaveLength(N);
 
     // No errors
-    expect(errored.length).toBe(0);
+    expect(errored).toHaveLength(0);
   }, 30_000);
 
   // ─── Per-client isolation: different code per client ───────────────────
@@ -464,7 +464,7 @@ void loop() { digitalWrite(13, HIGH); Serial.println("LED ON"); delay(500); digi
     const gotOutput = results.filter(
       (r) => r.compiled && r.receivedSerialOutput,
     );
-    expect(gotOutput.length).toBe(N);
+    expect(gotOutput).toHaveLength(N);
 
     // Each client MUST see its own marker in the serial output.
     // This fails if the server uses a global shared lastCompiledCode

tests/integration/runtime-output-storm.test.ts

@@ -74,7 +74,7 @@ maybeDescribe("runtime output storm", () => {
     expect(floodLines).toBeLessThan(1_000);
     expect(errors.filter((line) => line.includes("Runtime output rate limit"))).toHaveLength(1);
     // Without aggregation every line produced its own diagnostic log entry.
-    expect(logCalls.filter((message) => message.includes("STDERR")).length).toBe(0);
+    expect(logCalls.filter((message) => message.includes("STDERR"))).toHaveLength(0);
     expect(logCalls.length).toBeLessThan(200);
   }, 90_000);
 });

tests/server/services/compiler-diagnostics-limit.test.ts

@@ -27,7 +27,7 @@ describe("compiler diagnostics limits", () => {
     const chunk = "x".repeat(100_000);
     for (let index = 0; index < 10; index += 1) appendCompilerDiagnostics(buffer, chunk);
 
-    expect(buffer.value.length).toBe(MAX_COMPILER_DIAGNOSTIC_CHARS);
+    expect(buffer.value).toHaveLength(MAX_COMPILER_DIAGNOSTIC_CHARS);
     expect(buffer.omittedChars).toBe(1_000_000 - MAX_COMPILER_DIAGNOSTIC_CHARS);
     expect(limitCompilerDiagnostics(buffer.value, buffer.omittedChars)).toMatch(/\.\.\. 737856 more characters/);
   });

tests/server/services/tutor/evaluation/tutor-quality-real-provider-cli.test.ts

@@ -146,7 +146,7 @@ describe("Tutor Quality real-provider CLI contract", () => {
       expect(transcripts.find(({ scenario }) => scenario.id === "TQ-REG-001")?.stateAfter)
         .toEqual(transcripts.find(({ scenario }) => scenario.id === "TQ-REG-001")?.stateBefore);
       const strategyTranscripts = transcripts.filter(({ scenario }) => scenario.id.startsWith("strategy-"));
-      expect(strategyTranscripts.length).toBe(scenarios.filter(({ id }) => id.startsWith("strategy-")).length);
+      expect(strategyTranscripts).toHaveLength(scenarios.filter(({ id }) => id.startsWith("strategy-")).length);
       expect(strategyTranscripts.every(({ turns }) => turns.every(({ deterministicChecks }) => deterministicChecks.some(
         ({ name, passed }) => name === "expected-learning-phase" && passed,
       )))).toBe(true);

tests/shared/source-project.test.ts

@@ -54,7 +54,7 @@ describe("source project validation and include resolution", () => {
       ].join("\n"),
     }));
 
-    expect(result.lineOrigins.length).toBe(result.source.split("\n").length);
+    expect(result.lineOrigins).toHaveLength(result.source.split("\n").length);
     expect(result.lineOrigins).toEqual([
       { file: "a.h", line: 1 },
       { file: "sub/b.h", line: 1 },