Recover from PyLint raising messages at character "-1"

Summary: Fixes T9257. For some messages, PyLint can raise at "character -1", which we don't allow since we don't consider it to make sense.

Test Plan:
  - Added failing unit test from T9257.
  - Applied patch.
  - Test now passes.

Reviewers: joshuaspence, chad

Reviewed By: joshuaspence, chad

Maniphest Tasks: T9257

Differential Revision: https://secure.phabricator.com/D13991

src/lint/linter/ArcanistPyLintLinter.php

@@ -130,10 +130,15 @@ final class ArcanistPyLintLinter extends ArcanistExternalLinter {
         continue;
       }
 
+      // NOTE: PyLint sometimes returns -1 as the character offset for a
+      // message. If it does, treat it as 0. See T9257.
+      $char = (int)$matches[1];
+      $char = max(0, $char);
+
       $message = id(new ArcanistLintMessage())
         ->setPath($path)
         ->setLine($matches[0])
-        ->setChar($matches[1])
+        ->setChar($char)
         ->setCode($matches[2])
         ->setSeverity($this->getLintMessageSeverity($matches[2]))
         ->setName(ucwords(str_replace('-', ' ', $matches[3])))

src/lint/linter/__tests__/pylint/negativechar.lint-test

@@ -0,0 +1,6 @@
+"""Docstring"""
+
+"""
+Useless string """
+~~~~~~~~~~
+warning:4:0 See T9257.

src/lint/linter/__tests__/xml/languages-7.lint-test

@@ -1,7 +0,0 @@
-<?xml version="1.0" encoding="utf-8"?>
-<languages>
-    <lang>
-</languages>
-~~~~~~~~~~
-error:4:7
-error:5:1