Add a linter rule for unnecessary use of the final modifier

Summary: Ref T7409. This was based on rhttps://github.com/squizlabs/PHP_CodeSniffer/blob/master/CodeSniffer/Standards/Generic/Sniffs/CodeAnalysis/UnnecessaryFinalModifierSniff.php.

Test Plan: Added unit tests.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, epriestley

Maniphest Tasks: T7409

Differential Revision: https://secure.phabricator.com/D12135

src/lint/linter/ArcanistXHPASTLinter.php

@@ -54,6 +54,7 @@ final class ArcanistXHPASTLinter extends ArcanistBaseXHPASTLinter {
   const LINT_IMPLICIT_VISIBILITY        = 52;
   const LINT_CALL_TIME_PASS_BY_REF      = 53;
   const LINT_FORMATTED_STRING           = 54;
+  const LINT_UNNECESSARY_FINAL_MODIFIER = 55;
 
   private $blacklistedFunctions = array();
   private $naminghook;
@@ -121,6 +122,7 @@ final class ArcanistXHPASTLinter extends ArcanistBaseXHPASTLinter {
       self::LINT_IMPLICIT_VISIBILITY        => 'Implicit Method Visibility',
       self::LINT_CALL_TIME_PASS_BY_REF      => 'Call-Time Pass-By-Reference',
       self::LINT_FORMATTED_STRING           => 'Formatted String',
+      self::LINT_UNNECESSARY_FINAL_MODIFIER => 'Unnecessary Final Modifier',
     );
   }
 
@@ -163,6 +165,7 @@ final class ArcanistXHPASTLinter extends ArcanistBaseXHPASTLinter {
       self::LINT_ARRAY_SEPARATOR            => $advice,
       self::LINT_CONSTRUCTOR_PARENTHESES    => $advice,
       self::LINT_IMPLICIT_VISIBILITY        => $advice,
+      self::LINT_UNNECESSARY_FINAL_MODIFIER => $advice,
     );
   }
 
@@ -230,7 +233,7 @@ final class ArcanistXHPASTLinter extends ArcanistBaseXHPASTLinter {
 
   public function getVersion() {
     // The version number should be incremented whenever a new rule is added.
-    return '16';
+    return '17';
   }
 
   protected function resolveFuture($path, Future $future) {
@@ -308,6 +311,7 @@ final class ArcanistXHPASTLinter extends ArcanistBaseXHPASTLinter {
       'lintPropertyModifier' => self::LINT_IMPLICIT_VISIBILITY,
       'lintCallTimePassByReference' => self::LINT_CALL_TIME_PASS_BY_REF,
       'lintFormattedString' => self::LINT_FORMATTED_STRING,
+      'lintUnnecessaryFinalModifier' => self::LINT_UNNECESSARY_FINAL_MODIFIER,
     );
 
     foreach ($method_codes as $method => $codes) {
@@ -3188,6 +3192,43 @@ final class ArcanistXHPASTLinter extends ArcanistBaseXHPASTLinter {
     }
   }
 
+  private function lintUnnecessaryFinalModifier(XHPASTNode $root) {
+    $classes = $root->selectDescendantsOfType('n_CLASS_DECLARATION');
+
+    foreach ($classes as $class) {
+      $attributes = $class->getChildOfType(0, 'n_CLASS_ATTRIBUTES');
+      $is_final = false;
+
+      foreach ($attributes->getChildren() as $attribute) {
+        if ($attribute->getConcreteString() == 'final') {
+          $is_final = true;
+          break;
+        }
+      }
+
+      if (!$is_final) {
+        continue;
+      }
+
+      $methods = $class->selectDescendantsOfType('n_METHOD_DECLARATION');
+      foreach ($methods as $method) {
+        $attributes = $method->getChildOfType(0, 'n_METHOD_MODIFIER_LIST');
+
+        foreach ($attributes->getChildren() as $attribute) {
+          if ($attribute->getConcreteString() == 'final') {
+            $this->raiseLintAtNode(
+              $attribute,
+              self::LINT_UNNECESSARY_FINAL_MODIFIER,
+              pht(
+                'Unnecessary %s modifier in %s class.',
+                'final',
+                'final'));
+          }
+        }
+      }
+    }
+  }
+
   public function getSuperGlobalNames() {
     return array(
       '$GLOBALS',

src/lint/linter/__tests__/xhpast/decl-parens-hug-closing.lint-test

@@ -11,8 +11,8 @@ final class X {
   public function a($x) {}
   public function b($x ) {}
 
-  final public static function &c($x) {}
-  final public static function &d($x ) {}
+  public static function &c($x) {}
+  public static function &d($x ) {}
 
   abstract private function e($x);
   abstract private function f($x );
@@ -27,7 +27,7 @@ warning:4:14
 warning:7:15
 error:9:13
 warning:12:23
-warning:15:37
+warning:15:31
 warning:18:33
 warning:23:14
 warning:24:14
@@ -45,8 +45,8 @@ final class X {
   public function a($x) {}
   public function b($x) {}
 
-  final public static function &c($x) {}
-  final public static function &d($x) {}
+  public static function &c($x) {}
+  public static function &d($x) {}
 
   abstract private function e($x);
   abstract private function f($x);

src/lint/linter/__tests__/xhpast/unnecessary-final-modifier.lint-test

@@ -0,0 +1,8 @@
+<?php
+final class Foo {
+  public function bar() {}
+  public final function baz() {}
+}
+~~~~~~~~~~
+error:2:13 XHP19
+advice:4:10