scriptc/packages/compiler/test/self-hosting-boundaries.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";

// These refusals protect native layouts: an asserted predicate cannot
// establish which union arm was found, and a second Error.cause slot would
// disagree with accesses through the Error base class.
test.each([
  ["annotated find predicate", `
    const rows: (number | string)[] = ["wrong"];
    console.log(rows.find((value): value is number => true));
  `, "inline callback with an inferred predicate"],
  ["annotated findLast predicate", `
    const rows: (number | string)[] = ["wrong"];
    console.log(rows.findLast((value): value is number => true));
  `, "inline callback with an inferred predicate"],
  ["named find predicate", `
    function isNumber(value: number | string): value is number { return true; }
    console.log((["wrong", 1] as (number | string)[]).find(isNumber));
  `, "inline callback with an inferred predicate"],
  ["cause field", `
    class Own extends Error { override cause = "own"; }
    const error: Error = new Own("message", { cause: "constructor" });
    console.log(error.cause);
  `, "redeclaring Error.cause"],
  ["cause parameter property", `
    class Own extends Error {
      constructor(public override cause: string) { super("message"); }
    }
    console.log(new Own("own").cause);
  `, "redeclaring Error.cause"],
  ["cause accessor", `
    class Options { get cause(): string { return "getter"; } }
    console.log(new Error("message", new Options()).cause);
  `, "Error options with a cause accessor"],
  ["forwarded cause accessor", `
    class Options { get cause(): string { return "getter"; } }
    const options: ErrorOptions = new Options();
    console.log(new Error("message", options).cause);
  `, "Error options with a cause accessor"],
] as const)("self-hosting boundary: %s", (_name, source, message) => {
  const dir = mkdtempSync(join(process.platform === "win32" ? tmpdir() : "/tmp", "scriptc-static-boundary-"));
  try {
    const entry = join(dir, "main.ts");
    writeFileSync(entry, `export {};\n${source}`);
    const { coverage } = analyze(entry, { dynamic: false });
    expect(coverage.preflightFailed).toBe(false);
    expect(coverage.diagnostics.some((d) => d.code === "SC1090" && d.message.includes(message)),
      JSON.stringify(coverage.diagnostics)).toBe(true);
  } finally {
    rmSync(dir, { recursive: true, force: true });
  }
});