From a0adeffe227158f7d953bcba989e2e090c582b34 Mon Sep 17 00:00:00 2001
From: aymandakir-gh <aymandakir-gh@users.noreply.github.com>
Date: Thu, 18 Jun 2026 10:46:30 +0200
Subject: [PATCH] fix(types): make `tsc --noEmit` clean and add a typecheck
 script
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`npx tsc --noEmit` failed with 3× TS2802 in lib/pdf-report.test.ts:
`String.fromCharCode(...bytes.slice(0, 5))` spreads a Uint8Array, which
under TypeScript 5.7+ (Uint8Array became generic) "can only be iterated
through with --downlevelIteration / target es2015+". Neither tsconfig knob
clears it — the spread itself is the issue. CI runs lint/test/build but not
tsc, so this stayed invisible.

Read the leading bytes via `Array.from(bytes.slice(0, len), (b) =>
String.fromCharCode(b)).join("")` (small `magic()` helper, used at all three
sites) and add a `"typecheck": "tsc --noEmit"` script so the project has a
first-class way to catch this and it can be wired into CI.

Verified: `tsc --noEmit` now exits 0, the 6 pdf-report tests still pass, and
the full unit suite (228) and lint stay green.

Co-authored-by: mattia-mamini-gh <281593356+mattia-mamini-gh@users.noreply.github.com>
---
 lib/pdf-report.test.ts | 14 +++++++++++---
 package.json           |  1 +
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/lib/pdf-report.test.ts b/lib/pdf-report.test.ts
index abc85e3..2cdcf35 100644
--- a/lib/pdf-report.test.ts
+++ b/lib/pdf-report.test.ts
@@ -11,11 +11,19 @@ function allAnswers(d: Diagnostic, value: AnswerValue) {
 
 const PDF_MAGIC = "%PDF-";
 
+// Read the leading bytes as a string without spreading the typed array.
+// `String.fromCharCode(...bytes.slice(0, 5))` trips TS2802 under TypeScript
+// 5.7+ (Uint8Array became generic); Array.from with a map callback avoids the
+// iteration requirement.
+function magic(bytes: Uint8Array, len = 5): string {
+  return Array.from(bytes.slice(0, len), (b) => String.fromCharCode(b)).join("");
+}
+
 describe.each(listDiagnostics())("buildReportPdf — $id", (diagnostic) => {
   it("produces a valid, non-trivial PDF for a weak result", () => {
     const result = scoreDiagnostic(diagnostic, allAnswers(diagnostic, 0));
     const bytes = new Uint8Array(buildReportPdf(diagnostic, result));
-    const head = String.fromCharCode(...bytes.slice(0, 5));
+    const head = magic(bytes);
     expect(head).toBe(PDF_MAGIC);
     expect(bytes.byteLength).toBeGreaterThan(2000);
   });
@@ -23,7 +31,7 @@ describe.each(listDiagnostics())("buildReportPdf — $id", (diagnostic) => {
   it("produces a valid PDF for a strong result (no bottleneck playbook edge)", () => {
     const result = scoreDiagnostic(diagnostic, allAnswers(diagnostic, 4));
     const bytes = new Uint8Array(buildReportPdf(diagnostic, result));
-    expect(String.fromCharCode(...bytes.slice(0, 5))).toBe(PDF_MAGIC);
+    expect(magic(bytes)).toBe(PDF_MAGIC);
     expect(bytes.byteLength).toBeGreaterThan(2000);
   });
 
@@ -34,6 +42,6 @@ describe.each(listDiagnostics())("buildReportPdf — $id", (diagnostic) => {
     });
     const result = scoreDiagnostic(diagnostic, answers);
     const bytes = new Uint8Array(buildReportPdf(diagnostic, result));
-    expect(String.fromCharCode(...bytes.slice(0, 5))).toBe(PDF_MAGIC);
+    expect(magic(bytes)).toBe(PDF_MAGIC);
   });
 });
diff --git a/package.json b/package.json
index 4ed089a..9df31c1 100644
--- a/package.json
+++ b/package.json
@@ -7,6 +7,7 @@
     "build": "next build",
     "start": "next start",
     "lint": "next lint",
+    "typecheck": "tsc --noEmit",
     "test": "vitest run",
     "e2e": "playwright test",
     "screenshot": "node scripts/screenshot.mjs"