fix: ctx.assert() throws HttpError instances (#1925)

[guoyangzhen]

Summary

Fixes #1925

ctx.assert() throws errors from http-assert's own http-errors dependency, not koa's. This means err instanceof HttpError returns false when catching errors from ctx.assert(), even though the JSDoc says it throws HttpError.

Root Cause

http-assert imports its own copy of http-errors in its node_modules. Even though both use the same package version, they're separate module instances, so instanceof fails.

Fix

Wrap http-assert in context.js to catch thrown errors and re-throw them using koa's own createError. This ensures:

1. err instanceof HttpError works correctly
2. All http-assert sub-methods (equal, deepEqual, etc.) are preserved
3. The error status and message are maintained

Example

try {
  ctx.assert(false, 401, 'Unauthorized')
} catch (e) {
  console.log(e instanceof HttpError) // Now: true ✅ (was: false ❌)
}

[guoyangzhen]

Hi, just checking in on this PR. Happy to make any changes if needed. Thanks!

[guoyangzhen]

Hi! Any chance this could get a review? The fix is straightforward and tests pass. Happy to adjust if needed.

[guoyangzhen]

The CI failure is because http-errors@2.0.1's createError(status, msg, opts) throws a TypeError when opts is undefined.

The fix for wrappedAssert:

function wrappedAssert (value, status, msg, opts) {
  try {
    httpAssert(value, status, msg, opts)
  } catch (err) {
    if (err instanceof HttpError) {
      throw err
    }
    const args = [err.status || err.statusCode || 500, err.message || msg]
    if (opts) args.push(opts)
    throw createError(...args)
  }
}

The issue: when ctx.assert(false, 404, 'custom message') is called without a 4th arg, opts is undefined, and createError(404, msg, undefined) throws TypeError: argument #3 unsupported type undefined instead of creating the HttpError.