scriptc/packages/compiler/test/class-field-updates.test.ts

import { mkdtempSync, rmSync, writeFileSync } from "node:fs";
import { tmpdir } from "node:os";
import { join } from "node:path";
import { expect, test } from "vitest";
import { analyze } from "../src/index.js";

test.each(["Child.count++", "++Child.count", "Child.count--", "--Child.count"])("refuses inherited static updates: %s", (update) => {
  const dir = mkdtempSync(join(tmpdir(), "scriptc-static-update-"));
  try {
    const entry = join(dir, "main.cjs");
    writeFileSync(entry, `class Base { static count = 1; } class Child extends Base {} console.log(${update}); ${update};`);
    const { coverage } = analyze(entry);
    const diagnostics = [...coverage.diagnostics, ...(coverage.runtimeFences ?? [])];
    expect(diagnostics.filter((d) => d.code === "SC1090" && d.message.includes("assigning the inherited static")).length).toBe(2);
    expect(coverage.stats.statementsIsland).toBe(0);
  } finally {
    rmSync(dir, { recursive: true, force: true });
  }
});

test("refuses updates to readonly static fields", () => {
  const dir = mkdtempSync(join(tmpdir(), "scriptc-static-readonly-"));
  try {
    const entry = join(dir, "main.ts");
    writeFileSync(entry, 'class C { static readonly count = 1; }\n// @ts-expect-error Exercise the compiler backstop too.\nconsole.log(C.count++);\n');
    const { coverage } = analyze(entry);
    expect([...coverage.diagnostics, ...(coverage.runtimeFences ?? [])].some((d) => d.code === "SC1090" && d.message.includes("readonly static"))).toBe(true);
  } finally {
    rmSync(dir, { recursive: true, force: true });
  }
});