FindProxyForURL Beta

PAC-P007 · high-complexity

Many conditions and branches

info · Performance

A PAC with dozens of conditions is slow to read, slow to review and slow to run for default-route traffic. Complexity metrics are reported so the trend can be watched; grouping rules by domain and helper functions keep the file maintainable.

Why it matters

Each condition is evaluated for every connection that is not decided earlier. Beyond a few dozen rules, authors lose track of ordering effects (PAC-C014), duplicates (PAC-C013) and dead code (PAC-E016). The informational finding carries the metrics; the fix is structural: one rule per domain suffix instead of one per host, helper functions per rule group, and proxy-side policy for anything that is not routing.

How to fix

Collapse host lists into domain suffixes, group related rules in helper functions and move non-routing policy to the proxy.

Examples

Bad

function FindProxyForURL(url, host) {
  if (host == "a.corp.example") { return "DIRECT"; }
  if (host == "b.corp.example") { return "DIRECT"; }
  if (host == "c.corp.example") { return "DIRECT"; }
  if (host == "d.corp.example") { return "DIRECT"; }
  // ... dozens more
  return "PROXY proxy.corp.example:8080";
}
Open bad example in checker

Good

function isInternal(host) {
  return isPlainHostName(host) || dnsDomainIs(host, ".corp.example");
}
function FindProxyForURL(url, host) {
  if (isInternal(host)) {
    return "DIRECT";
  }
  return "PROXY proxy.corp.example:8080";
}
Open good example in checker

Related rules