Get rid of "throwResult()" for control flow in MFA factors

Summary: Depends on D20034. Ref T13222. This is just cleanup -- I thought we'd have like two of these, but we ended up having a whole lot in Duo and a decent number in SMS. Just let factors return a result explicitly if they can make a decision early. I think using `instanceof` for control flow is a lesser evil than using `catch`, on the balance.

Test Plan: `grep`, went through enroll/gate flows on SMS and Duo.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13222

Differential Revision: https://secure.phabricator.com/D20035

src/__phutil_library_map__.php

@@ -2241,7 +2241,6 @@ phutil_register_library_map(array(
     'PhabricatorAuthFactorProviderTransactionType' => 'applications/auth/xaction/PhabricatorAuthFactorProviderTransactionType.php',
     'PhabricatorAuthFactorProviderViewController' => 'applications/auth/controller/mfa/PhabricatorAuthFactorProviderViewController.php',
     'PhabricatorAuthFactorResult' => 'applications/auth/factor/PhabricatorAuthFactorResult.php',
-    'PhabricatorAuthFactorResultException' => 'applications/auth/exception/PhabricatorAuthFactorResultException.php',
     'PhabricatorAuthFactorTestCase' => 'applications/auth/factor/__tests__/PhabricatorAuthFactorTestCase.php',
     'PhabricatorAuthFinishController' => 'applications/auth/controller/PhabricatorAuthFinishController.php',
     'PhabricatorAuthHMACKey' => 'applications/auth/storage/PhabricatorAuthHMACKey.php',
@@ -7970,7 +7969,6 @@ phutil_register_library_map(array(
     'PhabricatorAuthFactorProviderTransactionType' => 'PhabricatorModularTransactionType',
     'PhabricatorAuthFactorProviderViewController' => 'PhabricatorAuthFactorProviderController',
     'PhabricatorAuthFactorResult' => 'Phobject',
-    'PhabricatorAuthFactorResultException' => 'Exception',
     'PhabricatorAuthFactorTestCase' => 'PhabricatorTestCase',
     'PhabricatorAuthFinishController' => 'PhabricatorAuthController',
     'PhabricatorAuthHMACKey' => 'PhabricatorAuthDAO',

src/applications/auth/engine/PhabricatorAuthSessionEngine.php

@@ -540,14 +540,22 @@ final class PhabricatorAuthSessionEngine extends Phobject {
       $provider = $factor->getFactorProvider();
       $impl = $provider->getFactor();
 
-      try {
       $new_challenges = $impl->getNewIssuedChallenges(
         $factor,
         $viewer,
         $issued_challenges);
-      } catch (PhabricatorAuthFactorResultException $ex) {
+
+      // NOTE: We may get a list of challenges back, or may just get an early
+      // result. For example, this can happen on an SMS factor if all SMS
+      // mailers have been disabled.
+      if ($new_challenges instanceof PhabricatorAuthFactorResult) {
+        $result = $new_challenges;
+
+        if (!$result->getIsValid()) {
           $ok = false;
-        $validation_results[$factor_phid] = $ex->getResult();
+        }
+
+        $validation_results[$factor_phid] = $result;
         $challenge_map[$factor_phid] = $issued_challenges;
         continue;
       }

src/applications/auth/exception/PhabricatorAuthFactorResultException.php

@@ -1,17 +0,0 @@
-<?php
-
-final class PhabricatorAuthFactorResultException
-  extends Exception {
-
-  private $result;
-
-  public function __construct(PhabricatorAuthFactorResult $result) {
-    $this->result = $result;
-    parent::__construct();
-  }
-
-  public function getResult() {
-    return $this->result;
-  }
-
-}

src/applications/auth/factor/PhabricatorAuthFactor.php

@@ -141,6 +141,11 @@ abstract class PhabricatorAuthFactor extends Phobject {
       $viewer,
       $challenges);
 
+    if ($new_challenges instanceof PhabricatorAuthFactorResult) {
+      unset($unguarded);
+      return $new_challenges;
+    }
+
     assert_instances_of($new_challenges, 'PhabricatorAuthChallenge');
 
     foreach ($new_challenges as $new_challenge) {
@@ -493,10 +498,6 @@ abstract class PhabricatorAuthFactor extends Phobject {
       $rows);
   }
 
-  final protected function throwResult(PhabricatorAuthFactorResult $result) {
-    throw new PhabricatorAuthFactorResultException($result);
-  }
-
   final protected function getInstallDisplayName() {
     $uri = PhabricatorEnv::getURI('/');
     $uri = new PhutilURI($uri);

src/applications/auth/factor/PhabricatorSMSAuthFactor.php

@@ -195,35 +195,29 @@ final class PhabricatorSMSAuthFactor
     }
 
     if (!$this->loadUserContactNumber($viewer)) {
-      $result = $this->newResult()
+      return $this->newResult()
         ->setIsError(true)
         ->setErrorMessage(
           pht(
             'Your account has no primary contact number.'));
-
-      $this->throwResult($result);
     }
 
     if (!$this->isSMSMailerConfigured()) {
-      $result = $this->newResult()
+      return $this->newResult()
         ->setIsError(true)
         ->setErrorMessage(
           pht(
             'No outbound mailer which can deliver SMS messages is '.
             'configured.'));
-
-      $this->throwResult($result);
     }
 
     if (!$this->hasCSRF($config)) {
-      $result = $this->newResult()
+      return $this->newResult()
         ->setIsContinue(true)
         ->setErrorMessage(
           pht(
             'A text message with an authorization code will be sent to your '.
             'primary contact number.'));
-
-      $this->throwResult($result);
     }
 
     // Otherwise, issue a new challenge.