From 72a18e4aec97fe879c1a9c5a72bcd670fa2eea2f Mon Sep 17 00:00:00 2001
From: Almaz Ibragimov <almazrafi@yandex-team.ru>
Date: Thu, 14 Feb 2019 03:05:46 +0300
Subject: [PATCH] Fix false positives on no_grouping_extension rule when using
 where clause

---
 CHANGELOG.md                                  |  3 ++
 Rules.md                                      |  6 +++
 .../Idiomatic/NoGroupingExtensionRule.swift   | 40 +++++++++++++++----
 3 files changed, 42 insertions(+), 7 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f9befa9f2..f2d84d547 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -48,6 +48,9 @@
 
 #### Bug Fixes
 
+* Fix false positives on `no_grouping_extension` rule when using `where` clause.
+  [Almaz Ibragimov](https://github.com/almazrafi)
+
 * Fix `explicit_type_interface` when used in statements.  
   [Daniel Metzing](https://github.com/dirtydanee)
   [#2154](https://github.com/realm/SwiftLint/issues/2154)
diff --git a/Rules.md b/Rules.md
index 072f34702..623b2d41e 100644
--- a/Rules.md
+++ b/Rules.md
@@ -13143,6 +13143,12 @@ extension Oranges {}
 
 ```
 
+```swift
+class Box<T> {}
+extension Box where T: Vegetable {}
+
+```
+
 </details>
 <details>
 <summary>Triggering Examples</summary>
diff --git a/Source/SwiftLintFramework/Rules/Idiomatic/NoGroupingExtensionRule.swift b/Source/SwiftLintFramework/Rules/Idiomatic/NoGroupingExtensionRule.swift
index ed0c6c1c5..c9c9090df 100644
--- a/Source/SwiftLintFramework/Rules/Idiomatic/NoGroupingExtensionRule.swift
+++ b/Source/SwiftLintFramework/Rules/Idiomatic/NoGroupingExtensionRule.swift
@@ -12,7 +12,8 @@ public struct NoGroupingExtensionRule: OptInRule, ConfigurationProviderRule, Aut
         kind: .idiomatic,
         nonTriggeringExamples: [
             "protocol Food {}\nextension Food {}\n",
-            "class Apples {}\nextension Oranges {}\n"
+            "class Apples {}\nextension Oranges {}\n",
+            "class Box<T> {}\nextension Box where T: Vegetable {}\n"
         ],
         triggeringExamples: [
             "enum Fruit {}\n↓extension Fruit {}\n",
@@ -28,12 +29,37 @@ public struct NoGroupingExtensionRule: OptInRule, ConfigurationProviderRule, Aut
 
         let susceptibleNames = Set(elements.compactMap { $0.kind != .extension ? $0.name : nil })
 
-        return elements
-            .filter { $0.kind == .extension && susceptibleNames.contains($0.name) }
-            .map {
-                StyleViolation(ruleDescription: type(of: self).description,
-                               severity: configuration.severity,
-                               location: Location(file: file, byteOffset: $0.offset))
+        return elements.compactMap { element in
+            guard element.kind == .extension, susceptibleNames.contains(element.name) else {
+                return nil
             }
+
+            guard !hasWhereClause(element: element, file: file) else {
+                return nil
+            }
+
+            return StyleViolation(ruleDescription: type(of: self).description,
+                                  severity: configuration.severity,
+                                  location: Location(file: file, byteOffset: element.offset))
+        }
+    }
+
+    private func hasWhereClause(element: NamespaceCollector.Element, file: File) -> Bool {
+        let contents = file.contents.bridge()
+
+        guard let nameOffset = element.dictionary.nameOffset,
+            let nameLength = element.dictionary.nameLength,
+            let bodyOffset = element.dictionary.bodyOffset else {
+            return false
+        }
+
+        let rangeStart = nameOffset + nameLength
+        let rangeLength = bodyOffset - rangeStart
+
+        guard let range = contents.byteRangeToNSRange(start: rangeStart, length: rangeLength) else {
+            return false
+        }
+
+        return (regex(" where ").firstMatch(in: file.contents, options: [], range: range) != nil)
     }
 }