Detect and raise setup warnings from within Phabricator

Summary:
This is basicaly a light version of D4286. The major problem with D4286 is that it's a huge leap and completely replaces the setup process in one step.

Instead, I want to do this:

  - Add the post-setup warnings (yellow bar with "6 unresolved warnings...").
  - Copy all setup checks into post-setup warnings (so every check has an old-style check and a new-style check).
  - Run that for a little bit and make sure it's stable.
  - Implement fatal post-setup checks (the red screen, vs the yellow bar).
  - Run that for a little bit.
  - Nuke setup mode and delete all the old checks.

This should give us a bunch of very gradual steps toward the brave new world of simpler setup.

Test Plan:
 - Faked APC setup failures, saw warnings raise.
 - Verified that this runs after restart (get + set).
 - Verified that this costs us only one cache hit after first-run (get only).

Reviewers: btrahan, codeblock, vrana, chad

Reviewed By: codeblock

CC: aran

Maniphest Tasks: T2228

Differential Revision: https://secure.phabricator.com/D4295

src/applications/config/check/PhabricatorSetupCheck.php

@@ -0,0 +1,79 @@
+<?php
+
+abstract class PhabricatorSetupCheck {
+
+  private $issues;
+
+  abstract protected function executeChecks();
+
+  final protected function newIssue($key) {
+    $issue = id(new PhabricatorSetupIssue())
+      ->setIssueKey($key);
+
+    $this->issues[$key] = $issue;
+
+    return $issue;
+  }
+
+  final public function getIssues() {
+    return $this->issues;
+  }
+
+  final public function runSetupChecks() {
+    $this->issues = array();
+    $this->executeChecks();
+  }
+
+  final public static function getOpenSetupIssueCount() {
+    $cache = PhabricatorCaches::getSetupCache();
+    return $cache->getKey('phabricator.setup.issues');
+  }
+
+  final public static function setOpenSetupIssueCount($count) {
+    $cache = PhabricatorCaches::getSetupCache();
+    $cache->setKey('phabricator.setup.issues', $count);
+  }
+
+  final public static function willProcessRequest() {
+    $issue_count = self::getOpenSetupIssueCount();
+    if ($issue_count !== null) {
+      // We've already run setup checks, didn't hit any fatals, and then set
+      // an issue count. This means we're good and don't need to do any extra
+      // work.
+      return null;
+    }
+
+    $issues = self::runAllChecks();
+
+    self::setOpenSetupIssueCount(count($issues));
+
+    return null;
+  }
+
+  final public static function runAllChecks() {
+    $symbols = id(new PhutilSymbolLoader())
+      ->setAncestorClass('PhabricatorSetupCheck')
+      ->setConcreteOnly(true)
+      ->selectAndLoadSymbols();
+
+    $checks = array();
+    foreach ($symbols as $symbol) {
+      $checks[] = newv($symbol['name'], array());
+    }
+
+    $issues = array();
+    foreach ($checks as $check) {
+      $check->runSetupChecks();
+      foreach ($check->getIssues() as $key => $issue) {
+        if (isset($issues[$key])) {
+          throw new Exception(
+            "Two setup checks raised an issue with key '{$key}'!");
+        }
+        $issues[$key] = $issue;
+      }
+    }
+
+    return $issues;
+  }
+
+}