Reject config with unknown directives before committing to it

Ideally, we want to reject configurations with unknown directives before
applying any configuration changes that correspond to known directives,
but current apply-as-you-parse architecture makes that impractical.
Pending smooth reconfiguration refactoring will make that possible, but
we can make a step towards that ideal future now.

Rejecting bad configurations before calling configDoConfigure() reduces
the set of configuration errors that Squid can detect in one execution
(because configDoConfigure() error-checking code is not reached), but
that small reduction is a lesser evil compared to running
configDoConfigure() with a clearly broken config, especially when we are
going to kill Squid anyway. While many legacy parse_foo() functions do
apply significant changes before configDoConfigure(), we cannot easily
prevent that (for now). We can easily prevent configDoConfigure().

src/cache_cf.cc

@@ -625,22 +625,16 @@ Configuration::Parse()
 
     defaults_postscriptum();
 
+    if (unrecognizedDirectives)
+        throw TextException(ToSBuf("Found ", unrecognizedDirectives, " unrecognized directive(s)"), Here());
+
     /*
      * We must call configDoConfigure() before leave_suid() because
      * configDoConfigure() is where we turn username strings into
      * uid values.
      */
     configDoConfigure();
 
-    // TODO: Throw before configDoConfigure(). Doing that would reduce the set
-    // of configuration errors Squid can detect in one execution, but we should
-    // not apply a clearly broken configuration, especially when we are going to
-    // quit anyway. While some legacy parse_foo() functions apply significant
-    // changes before configDoConfigure(), we cannot easily stop them. We can
-    // easily stop configDoConfigure().
-    if (unrecognizedDirectives)
-        throw TextException(ToSBuf("Found ", unrecognizedDirectives, " unrecognized directive(s)"), Here());
-
     if (opt_send_signal == -1) {
         Mgr::RegisterAction("config",
                             "Current Squid Configuration",