arcanist: add postponed linter support

Summary:
This uses a similiar approach as with postponed unittests, allowing
the lint workflow/engine to report postponed linter names.  After
the lint engine is run, a separate method is used to collect any
postponed linters and these are reposted to the diff via the
"arc:lint-postponed" property.

Also, a ##diff.wasCreated## was added allowing hooks to be called
immediately after the call ##differential.creatediff## with the
returned diff ID.

Test Plan:
Created diffs with a dummy lint engine which always reports a
postponed linter.

Reviewers: epriestley, vrana

Reviewed By: epriestley

CC: aran, Korvin

Maniphest Tasks: T1332

Differential Revision: https://secure.phabricator.com/D2933

src/events/constant/ArcanistEventType.php

@@ -20,5 +20,6 @@ final class ArcanistEventType extends PhutilEventType {
 
   const TYPE_COMMIT_WILLCOMMITSVN   = 'commit.willCommitSVN';
   const TYPE_DIFF_WILLBUILDMESSAGE  = 'diff.willBuildMessage';
+  const TYPE_DIFF_WASCREATED        = 'diff.wasCreated';
 
 }

src/lint/engine/ArcanistLintEngine.php

@@ -72,6 +72,9 @@ abstract class ArcanistLintEngine {
   private $commitHookMode = false;
   private $hookAPI;
 
+  private $enableAsyncLint = false;
+  private $postponedLinters = array();
+
   public function __construct() {
 
   }
@@ -126,6 +129,15 @@ abstract class ArcanistLintEngine {
     return $this->hookAPI;
   }
 
+  public function setEnableAsyncLint($enable_async_lint) {
+    $this->enableAsyncLint = $enable_async_lint;
+    return $this;
+  }
+
+  public function getEnableAsyncLint() {
+    return $this->enableAsyncLint;
+  }
+
   public function loadData($path) {
     if (!isset($this->fileData[$path])) {
       if ($this->getCommitHookMode()) {
@@ -295,5 +307,13 @@ abstract class ArcanistLintEngine {
     return array($line, $char);
   }
 
+  public function getPostponedLinters() {
+    return $this->postponedLinters;
+  }
+
+  public function setPostponedLinters(array $linters) {
+    $this->postponedLinters = $linters;
+    return $this;
+  }
 
 }

src/workflow/ArcanistDiffWorkflow.php

@@ -36,6 +36,8 @@ final class ArcanistDiffWorkflow extends ArcanistBaseWorkflow {
   private $diffID;
   private $revisionID;
   private $unitWorkflow;
+  private $lintWorkflow;
+  private $postponedLinters;
 
   public function getCommandSynopses() {
     return phutil_console_format(<<<EOTEXT
@@ -387,6 +389,8 @@ EOTEXT
 
     $this->diffID = $diff_info['diffid'];
 
+    $this->dispatchDiffWasCreatedEvent($diff_info['diffid']);
+
     if ($this->unitWorkflow) {
       $this->unitWorkflow->setDifferentialDiffID($diff_info['diffid']);
     }
@@ -1093,6 +1097,7 @@ EOTEXT
         $argv[] = $repository_api->getRelativeCommit();
       }
       $lint_workflow = $this->buildChildWorkflow('lint', $argv);
+      $this->lintWorkflow = $lint_workflow;
 
       if ($this->shouldAmend()) {
         // TODO: We should offer to create a checkpoint commit.
@@ -1118,9 +1123,15 @@ EOTEXT
             "Lint issued unresolved errors!",
             'lint-excuses');
           break;
+        case ArcanistLintWorkflow::RESULT_POSTPONED:
+          echo phutil_console_format(
+            "<bg:yellow>** LINT POSTPONED **</bg> ".
+            "Lint results are postponed.\n");
+          break;
       }
 
       $this->unresolvedLint = $lint_workflow->getUnresolvedMessages();
+      $this->postponedLinters = $lint_workflow->getPostponedLinters();
 
       return $lint_result;
     } catch (ArcanistNoEngineException $ex) {
@@ -1945,6 +1956,7 @@ EOTEXT
       ArcanistLintWorkflow::RESULT_ERRORS     => 'fail',
       ArcanistLintWorkflow::RESULT_WARNINGS   => 'warn',
       ArcanistLintWorkflow::RESULT_SKIP       => 'skip',
+      ArcanistLintWorkflow::RESULT_POSTPONED  => 'postponed',
     );
     return idx($map, $lint_result, 'none');
   }
@@ -2052,10 +2064,8 @@ EOTEXT
    * @task diffprop
    */
   private function updateLintDiffProperty() {
-    if (!$this->unresolvedLint) {
-      return;
-    }
 
+    if ($this->unresolvedLint) {
       $data = array();
       foreach ($this->unresolvedLint as $message) {
         $data[] = array(
@@ -2076,6 +2086,13 @@ EOTEXT
       }
     }
 
+    $postponed = $this->postponedLinters;
+    if ($postponed) {
+      $this->updateDiffProperty('arc:lint-postponed', json_encode($postponed));
+    }
+
+  }
+
 
   /**
    * Update unit test information for the diff.
@@ -2157,4 +2174,13 @@ EOTEXT
     return $event->getValue('fields');
   }
 
+  private function dispatchDiffWasCreatedEvent($diff_id) {
+    $event = new PhutilEvent(
+      ArcanistEventType::TYPE_DIFF_WASCREATED,
+      array(
+        'diffID' => $diff_id,
+      ));
+
+    PhutilEventEngine::dispatchEvent($event);
+  }
 }

src/workflow/ArcanistLintWorkflow.php

@@ -27,11 +27,14 @@ class ArcanistLintWorkflow extends ArcanistBaseWorkflow {
   const RESULT_WARNINGS   = 1;
   const RESULT_ERRORS     = 2;
   const RESULT_SKIP       = 3;
+  const RESULT_POSTPONED  = 4;
 
   private $unresolvedMessages;
   private $shouldAmendChanges = false;
   private $shouldAmendWithoutPrompt = false;
   private $shouldAmendAutofixesWithoutPrompt = false;
+  private $engine;
+  private $postponedLinters;
 
   public function setShouldAmendChanges($should_amend) {
     $this->shouldAmendChanges = $should_amend;
@@ -173,6 +176,7 @@ EOTEXT
     }
 
     $engine = newv($engine, array());
+    $this->engine = $engine;
     $engine->setWorkingCopy($working_copy);
 
     if ($this->getArgument('advice')) {
@@ -195,8 +199,21 @@ EOTEXT
       }
     }
 
+    // Enable possible async linting only for 'arc diff' not 'arc unit'
+    if ($this->getParentWorkflow()) {
+      $engine->setEnableAsyncLint(true);
+    } else {
+      $engine->setEnableAsyncLint(false);
+    }
+
     $results = $engine->run();
 
+    // It'd be nice to just return a single result from the run method above
+    // which contains both the lint messages and the postponed linters.
+    // However, to maintain compatibility with existing lint subclasses, use
+    // a separate method call to grab the postponed linters.
+    $this->postponedLinters = $engine->getPostponedLinters();
+
     if ($this->getArgument('never-apply-patches')) {
       $apply_patches = false;
     } else {
@@ -342,6 +359,8 @@ EOTEXT
       $result_code = self::RESULT_ERRORS;
     } else if ($has_warnings) {
       $result_code = self::RESULT_WARNINGS;
+    } else if (!empty($this->postponedLinters)) {
+      $result_code = self::RESULT_POSTPONED;
     } else {
       $result_code = self::RESULT_OKAY;
     }
@@ -359,4 +378,8 @@ EOTEXT
     return $this->unresolvedMessages;
   }
 
+  public function getPostponedLinters() {
+    return $this->postponedLinters;
+  }
+
 }