feat(invariants): require package-owned companions

scripts/gen-package-invariants.ts

@@ -0,0 +1,44 @@
+/** Generate or verify package-owned invariant companion baselines. */
+
+import { readFileSync, writeFileSync } from 'node:fs'
+import { resolve } from 'node:path'
+import {
+  GENERATED_INVARIANT_MARKER,
+  collectPackageInvariantViolations,
+  formatPackageInvariantViolation,
+  packageInvariantOwners,
+  renderBaselineInvariant,
+} from './package-invariants.ts'
+
+const root = resolve(import.meta.dirname, '..')
+const check = process.argv.includes('--check')
+
+if (!check) {
+  let generated = 0
+  for (const owner of packageInvariantOwners(root)) {
+    const path = resolve(root, owner.sourcePath)
+    let current: string | undefined
+    try {
+      current = readFileSync(path, 'utf8')
+    } catch (error) {
+      if ((error as NodeJS.ErrnoException).code !== 'ENOENT') throw error
+    }
+    if (current !== undefined && !current.includes(GENERATED_INVARIANT_MARKER)) continue
+    const expected = renderBaselineInvariant(owner)
+    if (current === expected) continue
+    writeFileSync(path, expected)
+    generated += 1
+  }
+  console.log(`gen-package-invariants: wrote ${generated} generated baseline companion(s).`)
+}
+
+const violations = collectPackageInvariantViolations(root)
+if (violations.length > 0) {
+  console.error('verify-package-invariants: violations found:')
+  for (const violation of violations) {
+    console.error(`  ${formatPackageInvariantViolation(root, violation)}`)
+  }
+  process.exit(1)
+}
+
+console.log(`verify-package-invariants: ${packageInvariantOwners(root).length} package companion(s) conform.`)