Add rule duplicate_id, which detect xml element duplicate id

Rules.md

@@ -95,3 +95,11 @@ Display error when views are ambiguous.
 |   Default Rule  |  `false` |
 
 Check View as: set as a device specified by view_as_device_rule config.
+
+## DuplicateIDRule
+
+|    identifier   | `duplicate_id` |
+|:---------------:|:---------------:|
+|   Default Rule  |  `true` |
+
+Display warning when two element use the same id.

Sources/IBLinterKit/Rule.swift

@@ -29,6 +29,7 @@ public struct Rules {
             MisplacedViewRule.self,
             ForceToEnableAutoLayoutRule.self,
             DuplicateConstraintRule.self,
+            DuplicateIDRule.self,
             StoryboardViewControllerId.self,
             ImageResourcesRule.self,
             CustomModuleRule.self,

Sources/IBLinterKit/Rules/DuplicateIDRule.swift

@@ -0,0 +1,57 @@
+//
+//  DuplicateIDRule.swift
+//  IBLinterKit
+//
+//  Created by Eric Marchand on 2019/10/29.
+//
+
+import Foundation
+import IBDecodable
+
+extension Rules {
+
+    struct DuplicateIDRule: Rule {
+
+        static let identifier = "duplicate_id"
+        static let description = "Display warning when elements use same id."
+        static let isDefault = true
+
+        init(context: Context) {}
+
+        func validate(storyboard: StoryboardFile) -> [Violation] {
+            return validate(file: storyboard, in: storyboard.document)
+        }
+
+        func validate(xib: XibFile) -> [Violation] {
+            return validate(file: xib, in: xib.document)
+        }
+
+        private func validate<T: InterfaceBuilderFile>(file: T, in document: IBElement) -> [Violation] {
+            return duplicateIDs(in: document).map {
+                let message = "duplicate element id \($0.0)"
+                return Violation(
+                    pathString: file.pathString,
+                    message: message,
+                    level: .warning)
+            }
+        }
+
+        private func duplicateIDs(in document: IBElement) -> [(String, [IBIdentifiable])] {
+            var byId: [String: [IBIdentifiable]] = [:]
+            var duplicateId: [String] = []
+            _ = document.browse { element in
+                if let identifiable = element as? IBIdentifiable {
+                    if var arrayForId = byId[identifiable.id] {
+                        duplicateId.append(identifiable.id)
+                        arrayForId.append(identifiable)
+                        byId[identifiable.id] = arrayForId
+                    } else {
+                        byId[identifiable.id] = [identifiable]
+                    }
+                }
+                return true
+            }
+            return duplicateId.map { ($0, byId[$0] ?? []) }
+        }
+    }
+}

Tests/IBLinterKitTest/Resources/Rules/DuplicateIdRule/DuplicateID.xib

@@ -0,0 +1,46 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<document type="com.apple.InterfaceBuilder3.CocoaTouch.XIB" version="3.0" toolsVersion="14113" targetRuntime="iOS.CocoaTouch" propertyAccessControl="none" useAutolayout="YES" useTraitCollections="YES" useSafeAreas="YES" colorMatched="YES">
+    <device id="retina4_7" orientation="portrait">
+        <adaptation id="fullscreen"/>
+    </device>
+    <dependencies>
+        <plugIn identifier="com.apple.InterfaceBuilder.IBCocoaTouchPlugin" version="14088"/>
+        <capability name="Safe area layout guides" minToolsVersion="9.0"/>
+        <capability name="documents saved in the Xcode 8 format" minToolsVersion="8.0"/>
+    </dependencies>
+    <objects>
+        <placeholder placeholderIdentifier="IBFilesOwner" id="-1" userLabel="File's Owner"/>
+        <placeholder placeholderIdentifier="IBFirstResponder" id="-2" customClass="UIResponder"/>
+        <view contentMode="scaleToFill" id="iN0-l3-epB">
+            <rect key="frame" x="0.0" y="0.0" width="375" height="667"/>
+            <autoresizingMask key="autoresizingMask" widthSizable="YES" heightSizable="YES"/>
+            <subviews>
+                <label opaque="NO" userInteractionEnabled="NO" contentMode="left" horizontalHuggingPriority="251" verticalHuggingPriority="251" text="Label" textAlignment="natural" lineBreakMode="tailTruncation" baselineAdjustment="alignBaselines" adjustsFontSizeToFit="NO" translatesAutoresizingMaskIntoConstraints="NO" id="ItZ-vi-bgh">
+                    <rect key="frame" x="166" y="323" width="42" height="21"/>
+                    <fontDescription key="fontDescription" type="system" pointSize="17"/>
+                    <nil key="textColor"/>
+                    <nil key="highlightedColor"/>
+                </label>
+                <button opaque="NO" contentMode="scaleToFill" contentHorizontalAlignment="center" contentVerticalAlignment="center" buttonType="roundedRect" lineBreakMode="middleTruncation" translatesAutoresizingMaskIntoConstraints="NO" id="aEU-56-OK8">
+                    <rect key="frame" x="164" y="457" width="46" height="30"/>
+                    <constraints>
+                        <constraint firstAttribute="height" relation="greaterThanOrEqual" constant="30" id="hhg-lH-Emq"/>
+                        <constraint firstAttribute="height" priority="750" constant="30" id="s6a-gw-F2T"/>
+                    </constraints>
+                    <state key="normal" title="Button"/>
+                </button>
+            </subviews>
+            <color key="backgroundColor" red="1" green="1" blue="1" alpha="1" colorSpace="custom" customColorSpace="sRGB"/>
+            <constraints>
+                <constraint firstItem="vUN-kp-3ea" firstAttribute="top" secondItem="ItZ-vi-bgh" secondAttribute="top" constant="-303" id="8Jq-td-PfE"/>
+                <constraint firstItem="ItZ-vi-bgh" firstAttribute="top" secondItem="vUN-kp-3ea" secondAttribute="top" constant="303" id="Prh-uf-M6D"/>
+                <constraint firstItem="vUN-kp-3ea" firstAttribute="bottom" secondItem="Pfc-VO-bsH" secondAttribute="bottom" constant="180" id="RXI-db-JkZ"/>
+                <constraint firstItem="ItZ-vi-bgh" firstAttribute="centerX" secondItem="iN0-l3-epB" secondAttribute="centerX" id="iN0-l3-epB"/>
+                <constraint firstItem="ItZ-vi-bgh" firstAttribute="centerX" secondItem="iN0-l3-epB" secondAttribute="centerX" id="aEU-56-OK8"/>
+                <constraint firstItem="Pfc-VO-bsH" firstAttribute="centerX" secondItem="iN0-l3-epB" secondAttribute="centerX" id="m0f-LQ-wgj"/>
+                <constraint firstItem="ItZ-vi-bgh" firstAttribute="centerY" secondItem="iN0-l3-epB" secondAttribute="centerY" id="zWU-iS-F0Z"/>
+            </constraints>
+            <viewLayoutGuide key="safeArea" id="vUN-kp-3ea"/>
+        </view>
+    </objects>
+</document>

Tests/IBLinterKitTest/Rules/DuplicateIDRuleTests.swift

@@ -0,0 +1,24 @@
+//
+//  DuplicateConstraintRuleTests.swift
+//  IBLinterKitTest
+//
+//  Created by Eric Marchand on 2019/10/29.
+//
+
+@testable import IBLinterKit
+import XCTest
+import IBDecodable
+
+class DuplicateIDRuleTests: XCTestCase {
+
+    let fixture = Fixture()
+
+    func testDuplicateId() {
+        let url = fixture.path("Resources/Rules/DuplicateIDRule/DuplicateID.xib")
+        let rule = Rules.DuplicateIDRule(context: .mock(from: .default))
+        let violations = try! rule.validate(xib: XibFile(url: url))
+        XCTAssertEqual(violations.count, 2)
+        let expectedMessages = ["iN0-l3-epB", "aEU-56-OK8"].map { "duplicate element id \($0)"}
+        XCTAssertEqual(violations.map { $0.message }, expectedMessages)
+    }
+}