Improve arcanist + prototool integration

Summary:
Running prototool once per proto file causes a variety of problems,
a common one of which is the fact that it will warn on new proto files.

This causes us to lose information about what file the breaking change comes
from but should ease some of the other painpoints from this linter.

Test Plan: Ran `arc lint` after making some breaking proto changes.

Reviewers: michelle, zasgar

Reviewed By: michelle

Differential Revision: https://phab.corp.pixielabs.ai/D9042

GitOrigin-RevId: 72a08085270b7dff3da4dc96384d389be747c82e

tools/arc_addons/pixielabs/lint/ArcanistProtoBreakCheckLinter.php

@@ -19,6 +19,8 @@
  */
 
 final class ArcanistProtoBreakCheckLinter extends ArcanistExternalLinter {
+  private $future;
+
   public function getInfoName() {
     return 'proto-break-check';
   }
@@ -49,35 +51,46 @@ final class ArcanistProtoBreakCheckLinter extends ArcanistExternalLinter {
   }
 
   protected function getMandatoryFlags() {
-    return array('--git-branch=main');
+    return array('--git-branch=main', '--json');
   }
 
-  protected function buildFutures(array $paths) {
+  // Running prototool once per file causes spurious errors around new proto files
+  // or moving protos between files while maintaining the package name etc.
+  // Instead we want to run prototool once over the entire repo.
+  // So we override the arcanist default behavior of running a linter once per file
+  // to trigger a repo wide prototool lint only once if any proto files change.
+  public function willLintPaths(array $paths) {
+    if ($this->future) {
+      return;
+    }
     $executable = $this->getExecutableCommand();
     $flags = $this->getCommandFlags();
+    $this->future = new ExecFuture('%C break check %Ls', $executable, $flags);
+  }
 
-    $futures = array();
-    foreach ($paths as $path) {
-      $future = new ExecFuture('%C break check %Ls %s', $executable, $flags, $path);
-      $futures[$path] = $future;
-      $future->setCWD($this->getProjectRoot());
+  public function didLintPaths(array $paths) {
+    if (!$this->future) {
+      return;
     }
-    return $futures;
-  }
 
-  protected function parseLinterOutput($path, $err, $stdout, $stderr) {
-    $messages = array();
+    list($err, $stdout, $stderr) = $this->future->resolve();
     if ($err !== 0) {
-      $message = id(new ArcanistLintMessage())
-        ->setPath($path)
-        ->setCode('breaking-change')
-        ->setName('prototool')
-        ->setDescription($stdout)
-        ->setSeverity(ArcanistLintSeverity::SEVERITY_WARNING);
-
-      $messages[] = $message;
+      $lines = phutil_split_lines($stdout, false);
+      foreach ($lines as $line) {
+        $json = phutil_json_decode($line);
+        $this->addLintMessage(id(new ArcanistLintMessage())
+          ->setPath(isset($json['filename']) ? $json['filename'] : '')
+          ->setCode(isset($json['lint_id']) ? $json['lint_id'] : '')
+          ->setName('prototool')
+          ->setDescription(isset($json['message']) ? $json['message'] : $line)
+          ->setSeverity(ArcanistLintSeverity::SEVERITY_WARNING));
+      }
     }
-    return $messages;
+
+    $this->future = null;
   }
 
+  public function parseLinterOutput($path, $err, $stdout, $stderr) {
+    return;
+  }
 }