feat(js): m01 util and m02 model with tests, fixtures, purity audit

Co-Authored-By: Claude Sonnet 5.5 <[email protected]>
2026-10-28 23:38:29 +01:00
parent 5be3cebe71
commit 22c221a042
14 changed files with 508 additions and 4 deletions
@@ -0,0 +1,75 @@
+import test from 'node:test'
+import assert from 'node:assert/strict'
+import { readdirSync, readFileSync } from 'node:fs'
+import { fileURLToPath } from 'node:url'
+import { dirname, join, basename } from 'node:path'
+
+const srcDir = join(dirname(fileURLToPath(import.meta.url)), '..', 'src')
+
+// Files that are allowed to touch the outside world.
+const excluded = (file) => ['runtime.js', 'browser.js', 'main.js'].includes(basename(file))
+
+const banned = [
+  ['let', /\blet\b/],
+  ['var', /\bvar\b/],
+  ['++', /\+\+/],
+  ['--', /--/],
+  ['.push(', /\.push\(/],
+  ['.pop(', /\.pop\(/],
+  ['.shift(', /\.shift\(/],
+  ['.unshift(', /\.unshift\(/],
+  ['.splice(', /\.splice\(/],
+  ['.sort(', /\.sort\(/],
+  ['.reverse(', /\.reverse\(/],
+  ['Math.random', /\bMath\.random\b/],
+  ['Date.now', /\bDate\.now\b/],
+  ['performance.now', /\bperformance\.now\b/],
+  ['document', /\bdocument\b/],
+  ['window', /\bwindow\b/],
+  ['addEventListener', /\baddEventListener\b/],
+]
+
+const stripComments = (code) => code.replace(/\/\*[\s\S]*?\*\//g, '').replace(/\/\/.*$/gm, '')
+const violations = (code) => banned.filter(([, re]) => re.test(stripComments(code))).map(([name]) => name)
+
+const jsFiles = (dir) =>
+  readdirSync(dir, { withFileTypes: true }).flatMap((e) =>
+    e.isDirectory() ? jsFiles(join(dir, e.name)) : e.name.endsWith('.js') ? [join(dir, e.name)] : [])
+
+banned.forEach(([name]) =>
+  test(`purity scanner flags a known-bad sample using ${name}`, () => {
+    const samples = {
+      let: 'let n = 0',
+      var: 'var n = 0',
+      '++': 'n++',
+      '--': 'n--',
+      '.push(': 'xs.push(1)',
+      '.pop(': 'xs.pop()',
+      '.shift(': 'xs.shift()',
+      '.unshift(': 'xs.unshift(1)',
+      '.splice(': 'xs.splice(0, 1)',
+      '.sort(': 'xs.sort()',
+      '.reverse(': 'xs.reverse()',
+      'Math.random': 'const r = Math.random()',
+      'Date.now': 'const t = Date.now()',
+      'performance.now': 'const t = performance.now()',
+      document: 'document.title',
+      window: 'window.alert(1)',
+      addEventListener: 'x.addEventListener("click", f)',
+    }
+    assert.ok(violations(samples[name]).includes(name))
+  }))
+
+test('purity scanner ignores banned words inside comments', () => {
+  const code = '// let var Math.random()\n/* xs.push(1); document; n++ */\nconst a = 1 // window\n'
+  assert.deepEqual(violations(code), [])
+})
+
+test('purity scanner accepts ordinary pure code', () =>
+  assert.deepEqual(violations('export const f = (xs) => xs.map((x) => x + 1)'), []))
+
+jsFiles(srcDir)
+  .filter((f) => !excluded(f))
+  .forEach((f) =>
+    test(`purity: ${f.slice(srcDir.length + 1)} has no banned constructs`, () =>
+      assert.deepEqual(violations(readFileSync(f, 'utf8')), [])))