Add legacy_uigraphics_functions rule

CHANGELOG.md

@@ -28,7 +28,11 @@
 
 ### Enhancements
 
-* None.
+* Add `legacy_uigraphics_functions` rule to encourage the use of modern
+  UIGraphicsImageRenderer instead of legacy UIGraphics{Begin|End}ImageContext.
+  The modern replacement is safer, cleaner, Retina-aware and more performant.  
+  [Dimitri Dupuis-Latour](https://github.com/DimDL)
+  [#6268](https://github.com/realm/SwiftLint/issues/6268)
 
 ### Bug Fixes
 

Source/SwiftLintBuiltInRules/Models/BuiltInRules.swift

@@ -107,6 +107,7 @@ public let builtInRules: [any Rule.Type] = [
     LegacyNSGeometryFunctionsRule.self,
     LegacyObjcTypeRule.self,
     LegacyRandomRule.self,
+    LegacyUIGraphicsFunctionsRule.self,
     LetVarWhitespaceRule.self,
     LineLengthRule.self,
     LiteralExpressionEndIndentationRule.self,

Source/SwiftLintBuiltInRules/Rules/Lint/LegacyUIGraphicsFunctionsRule.swift

@@ -0,0 +1,82 @@
+import SwiftSyntax
+
+@SwiftSyntaxRule
+struct LegacyUIGraphicsFunctionsRule: Rule {
+    var configuration = SeverityConfiguration<Self>(.warning)
+
+    static let description = RuleDescription(
+        identifier: "legacy_uigraphics_functions",
+        name: "Legacy UIGraphics Functions",
+        description: "Prefer using `UIGraphicsImageRenderer` over legacy functions",
+        rationale: "The modern replacement is safer, cleaner, Retina-aware and more performant",
+        kind: .idiomatic,
+        nonTriggeringExamples: [
+            Example("""
+            let renderer = UIGraphicsImageRenderer(size: bounds.size)
+            let screenshot = renderer.image { _ in
+                myUIView.drawHierarchy(in: bounds, afterScreenUpdates: true)
+            }
+            """),
+
+            Example("""
+            let renderer = UIGraphicsImageRenderer(size: newSize)
+            let combined = renderer.image { _ in
+                background.draw(in: CGRect(origin: .zero, size: newSize))
+                watermark.draw(in: CGRect(origin: .zero, size: watermarkSize))
+            }
+            """),
+
+            Example("""
+            let format = UIGraphicsImageRendererFormat()
+            format.scale = 1.0
+            format.opaque = true
+
+            let renderer = UIGraphicsImageRenderer(size: newSize, format: format)
+            return renderer.image { _ in
+                image.draw(in: CGRect(origin: .zero, size: newSize))
+            }
+            """),
+        ],
+        triggeringExamples: [
+            Example("""
+            ↓UIGraphicsBeginImageContext(newSize)
+            myUIView.drawHierarchy(in: bounds, afterScreenUpdates: false)
+            let optionalScreenshot = ↓UIGraphicsGetImageFromCurrentImageContext()
+            ↓UIGraphicsEndImageContext()
+            """),
+
+            Example("""
+            ↓UIGraphicsBeginImageContext(newSize)
+            background.draw(in: CGRect(origin: .zero, size: newSize))
+            watermark.draw(in: CGRect(origin: .zero, size: watermarkSize))
+            let optionalOutput = ↓UIGraphicsGetImageFromCurrentImageContext()
+            ↓UIGraphicsEndImageContext()
+            """),
+
+            Example("""
+            ↓UIGraphicsBeginImageContextWithOptions(newSize, true, 1.0)
+            image.draw(in: CGRect(origin: .zero, size: newSize))
+            let optionalOutput = ↓UIGraphicsGetImageFromCurrentImageContext()
+            ↓UIGraphicsEndImageContext()
+            """),
+        ]
+    )
+}
+
+private extension LegacyUIGraphicsFunctionsRule {
+    final class Visitor: ViolationsSyntaxVisitor<ConfigurationType> {
+        private static let legacyUIGraphicsFunctions: Set<String> = [
+            "UIGraphicsBeginImageContext",
+            "UIGraphicsBeginImageContextWithOptions",
+            "UIGraphicsGetImageFromCurrentImageContext",
+            "UIGraphicsEndImageContext",
+        ]
+
+        override func visitPost(_ node: FunctionCallExprSyntax) {
+            if let function = node.calledExpression.as(DeclReferenceExprSyntax.self)?.baseName.text,
+               Self.legacyUIGraphicsFunctions.contains(function) {
+                violations.append(node.positionAfterSkippingLeadingTrivia)
+            }
+        }
+    }
+}

Tests/GeneratedTests/GeneratedTests_05.swift

@@ -37,6 +37,12 @@ final class LegacyRandomRuleGeneratedTests: SwiftLintTestCase {
     }
 }
 
+final class LegacyUIGraphicsFunctionsRuleGeneratedTests: SwiftLintTestCase {
+    func testWithDefaultConfiguration() {
+        verifyRule(LegacyUIGraphicsFunctionsRule.description)
+    }
+}
+
 final class LetVarWhitespaceRuleGeneratedTests: SwiftLintTestCase {
     func testWithDefaultConfiguration() {
         verifyRule(LetVarWhitespaceRule.description)
@@ -150,9 +156,3 @@ final class NSObjectPreferIsEqualRuleGeneratedTests: SwiftLintTestCase {
         verifyRule(NSObjectPreferIsEqualRule.description)
     }
 }
-
-final class NestingRuleGeneratedTests: SwiftLintTestCase {
-    func testWithDefaultConfiguration() {
-        verifyRule(NestingRule.description)
-    }
-}

Tests/GeneratedTests/GeneratedTests_06.swift

@@ -7,6 +7,12 @@
 @testable import SwiftLintCore
 import TestHelpers
 
+final class NestingRuleGeneratedTests: SwiftLintTestCase {
+    func testWithDefaultConfiguration() {
+        verifyRule(NestingRule.description)
+    }
+}
+
 final class NimbleOperatorRuleGeneratedTests: SwiftLintTestCase {
     func testWithDefaultConfiguration() {
         verifyRule(NimbleOperatorRule.description)
@@ -150,9 +156,3 @@ final class PreferKeyPathRuleGeneratedTests: SwiftLintTestCase {
         verifyRule(PreferKeyPathRule.description)
     }
 }
-
-final class PreferNimbleRuleGeneratedTests: SwiftLintTestCase {
-    func testWithDefaultConfiguration() {
-        verifyRule(PreferNimbleRule.description)
-    }
-}

Tests/GeneratedTests/GeneratedTests_07.swift

@@ -7,6 +7,12 @@
 @testable import SwiftLintCore
 import TestHelpers
 
+final class PreferNimbleRuleGeneratedTests: SwiftLintTestCase {
+    func testWithDefaultConfiguration() {
+        verifyRule(PreferNimbleRule.description)
+    }
+}
+
 final class PreferSelfInStaticReferencesRuleGeneratedTests: SwiftLintTestCase {
     func testWithDefaultConfiguration() {
         verifyRule(PreferSelfInStaticReferencesRule.description)
@@ -150,9 +156,3 @@ final class RedundantSelfInClosureRuleGeneratedTests: SwiftLintTestCase {
         verifyRule(RedundantSelfInClosureRule.description)
     }
 }
-
-final class RedundantSendableRuleGeneratedTests: SwiftLintTestCase {
-    func testWithDefaultConfiguration() {
-        verifyRule(RedundantSendableRule.description)
-    }
-}

Tests/GeneratedTests/GeneratedTests_08.swift

@@ -7,6 +7,12 @@
 @testable import SwiftLintCore
 import TestHelpers
 
+final class RedundantSendableRuleGeneratedTests: SwiftLintTestCase {
+    func testWithDefaultConfiguration() {
+        verifyRule(RedundantSendableRule.description)
+    }
+}
+
 final class RedundantSetAccessControlRuleGeneratedTests: SwiftLintTestCase {
     func testWithDefaultConfiguration() {
         verifyRule(RedundantSetAccessControlRule.description)
@@ -150,9 +156,3 @@ final class SwitchCaseAlignmentRuleGeneratedTests: SwiftLintTestCase {
         verifyRule(SwitchCaseAlignmentRule.description)
     }
 }
-
-final class SwitchCaseOnNewlineRuleGeneratedTests: SwiftLintTestCase {
-    func testWithDefaultConfiguration() {
-        verifyRule(SwitchCaseOnNewlineRule.description)
-    }
-}

Tests/GeneratedTests/GeneratedTests_09.swift

@@ -7,6 +7,12 @@
 @testable import SwiftLintCore
 import TestHelpers
 
+final class SwitchCaseOnNewlineRuleGeneratedTests: SwiftLintTestCase {
+    func testWithDefaultConfiguration() {
+        verifyRule(SwitchCaseOnNewlineRule.description)
+    }
+}
+
 final class SyntacticSugarRuleGeneratedTests: SwiftLintTestCase {
     func testWithDefaultConfiguration() {
         verifyRule(SyntacticSugarRule.description)
@@ -150,9 +156,3 @@ final class UnusedControlFlowLabelRuleGeneratedTests: SwiftLintTestCase {
         verifyRule(UnusedControlFlowLabelRule.description)
     }
 }
-
-final class UnusedDeclarationRuleGeneratedTests: SwiftLintTestCase {
-    func testWithDefaultConfiguration() {
-        verifyRule(UnusedDeclarationRule.description)
-    }
-}

Tests/GeneratedTests/GeneratedTests_10.swift

@@ -7,6 +7,12 @@
 @testable import SwiftLintCore
 import TestHelpers
 
+final class UnusedDeclarationRuleGeneratedTests: SwiftLintTestCase {
+    func testWithDefaultConfiguration() {
+        verifyRule(UnusedDeclarationRule.description)
+    }
+}
+
 final class UnusedEnumeratedRuleGeneratedTests: SwiftLintTestCase {
     func testWithDefaultConfiguration() {
         verifyRule(UnusedEnumeratedRule.description)

Tests/IntegrationTests/default_rule_configurations.yml

@@ -607,6 +607,11 @@ legacy_random:
   meta:
     opt-in: false
     correctable: false
+legacy_uigraphics_functions:
+  severity: warning
+  meta:
+    opt-in: false
+    correctable: false
 let_var_whitespace:
   severity: warning
   meta: