Reduce repeated compiler startup in monorepo QX formatting

src/capability-language/tool-cli.ts

@@ -595,6 +595,30 @@ const main = async () => {
     process.stdout.write(`${JSON.stringify(plan, null, 2)}\n`);
     return;
   }
+  if (command === "format" && (args[0] === "--check" || args[0] === "--write")) {
+    const check = args[0] === "--check",
+      files = args.slice(1);
+    if (!files.length || files.some((file) => file.startsWith("-")))
+      throw new Error("usage: quixos-qx format --check|--write FILE...");
+    for (const file of files) {
+      try {
+        const source = await readFile(file, "utf8"),
+          formatted = formatQx(source);
+        if (formatted === source) continue;
+        if (check) {
+          console.error(`Needs formatting: ${file}`);
+          process.exitCode = 1;
+        } else {
+          await writeFile(file, formatted);
+          console.log(`Formatted ${file}`);
+        }
+      } catch (error) {
+        console.error(`${file}: ${error instanceof Error ? error.message : error}`);
+        process.exitCode = 1;
+      }
+    }
+    return;
+  }
   const [file, flag, ...rest] = args;
   if (
     !file ||

test/qx-format-cli.test.ts

@@ -0,0 +1,55 @@
+import assert from "node:assert/strict";
+import { spawnSync } from "node:child_process";
+import { mkdtempSync, readFileSync, writeFileSync, rmSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join, resolve } from "node:path";
+import test from "node:test";
+import { formatQx } from "../src/capability-language/source.js";
+
+const cli = resolve(process.cwd(), "dist/src/capability-language/tool-cli.js");
+const run = (...args: string[]) => spawnSync(process.execPath, [cli, "format", ...args], { encoding: "utf8" });
+const source = `workspace Test id "w" revision "w@1" commit "${"1".repeat(40)}" {\n// 雪 🦊 comment preserved\n}\n`;
+
+test("QX batch checks are read-only; writes match single-file formatting and remain idempotent", (t) => {
+  const root = mkdtempSync(join(tmpdir(), "qx-format-"));
+  t.after(() => rmSync(root, { recursive: true, force: true }));
+  const files = [join(root, "one.qx"), join(root, "two 雪.qx")];
+  for (const file of files) writeFileSync(file, source);
+  const check = run("--check", ...files);
+  assert.notEqual(check.status, 0, check.stderr);
+  for (const file of files) {
+    assert(check.stderr.includes(file));
+    assert.equal(readFileSync(file, "utf8"), source);
+  }
+  const single = run(files[0]!);
+  assert.equal(single.status, 0, single.stderr);
+  assert.equal(single.stdout, formatQx(source));
+  const write = run("--write", ...files);
+  assert.equal(write.status, 0, write.stderr);
+  for (const file of files) assert.equal(readFileSync(file, "utf8"), single.stdout);
+  assert.equal(run("--check", ...files).status, 0);
+  assert.equal(run("--write", ...files).stdout, "");
+  writeFileSync(files[0]!, source);
+  assert.equal(run(files[0]!, "--write").status, 0);
+  assert.equal(readFileSync(files[0]!, "utf8"), single.stdout);
+});
+
+test("QX batch errors report every failure and do not truncate valid work", (t) => {
+  const root = mkdtempSync(join(tmpdir(), "qx-format-errors-"));
+  t.after(() => rmSync(root, { recursive: true, force: true }));
+  const broken = join(root, "broken.qx"),
+    missing = join(root, "missing.qx"),
+    valid = join(root, "valid.qx");
+  writeFileSync(broken, "workspace { invalid");
+  writeFileSync(valid, source);
+  const result = run("--write", broken, missing, valid);
+  assert.notEqual(result.status, 0);
+  assert(result.stderr.includes(broken));
+  assert(result.stderr.includes(missing));
+  assert.equal(readFileSync(broken, "utf8"), "workspace { invalid");
+  assert.equal(readFileSync(valid, "utf8"), formatQx(source));
+  writeFileSync(valid, source);
+  assert.notEqual(run("--write", valid, "--unknown").status, 0);
+  assert.equal(readFileSync(valid, "utf8"), source, "Validate arguments before writing any file");
+  assert.notEqual(run("--check").status, 0);
+});