Add combine_flatmap lint rule

Source/SwiftLintBuiltInRules/Models/BuiltInRules.swift

@@ -21,6 +21,7 @@ public let builtInRules: [any Rule.Type] = [
     ClosureSpacingRule.self,
     CollectionAlignmentRule.self,
     ColonRule.self,
+    CombineFlatMapRule.self,
     CommaInheritanceRule.self,
     CommaRule.self,
     CommentSpacingRule.self,

Source/SwiftLintBuiltInRules/Rules/Lint/CombineFlatMapRule.swift

@@ -0,0 +1,58 @@
+import SwiftSyntax
+
+@SwiftSyntaxRule
+struct CombineFlatMapRule: Rule {
+    var configuration = SeverityConfiguration<Self>(.warning)
+
+    static let description = RuleDescription(
+        identifier: "combine_flatmap",
+        name: "Combine FlatMap",
+        description: "Avoid using Combine's flatMap operator.",
+        kind: .lint,
+        nonTriggeringExamples: [
+            Example("[1, 2, 3].flatMap { $0 }"),
+            Example("array.flatMap { $0 }"),
+            Example("Combine.map { $0 }")
+        ],
+        triggeringExamples: [
+            Example("Combine.flatMap { $0 }"),
+            Example("let transform = Combine.flatMap")
+        ]
+    )
+}
+
+private extension CombineFlatMapRule {
+    final class Visitor: ViolationsSyntaxVisitor<ConfigurationType> {
+        override func visitPost(_ node: FunctionCallExprSyntax) {
+            guard let memberAccess = node.calledExpression.as(MemberAccessExprSyntax.self),
+                  memberAccess.isCombineFlatMap else {
+                return
+            }
+
+            violations.append(node.positionAfterSkippingLeadingTrivia)
+        }
+
+        override func visitPost(_ node: MemberAccessExprSyntax) {
+            guard node.isCombineFlatMap else {
+                return
+            }
+
+            if let parent = node.parent?.as(FunctionCallExprSyntax.self),
+               parent.calledExpression.id == node.id {
+                return
+            }
+
+            violations.append(node.positionAfterSkippingLeadingTrivia)
+        }
+    }
+}
+
+private extension MemberAccessExprSyntax {
+    var isCombineFlatMap: Bool {
+        guard declName.baseName.text == "flatMap" else {
+            return false
+        }
+
+        return base?.as(DeclReferenceExprSyntax.self)?.baseName.text == "Combine"
+    }
+}

Tests/GeneratedTests/GeneratedTests_01.swift

@@ -121,6 +121,12 @@ final class ColonRuleGeneratedTests: SwiftLintTestCase {
     }
 }
 
+final class CombineFlatMapRuleGeneratedTests: SwiftLintTestCase {
+    func testWithDefaultConfiguration() {
+        verifyRule(CombineFlatMapRule.description)
+    }
+}
+
 final class CommaInheritanceRuleGeneratedTests: SwiftLintTestCase {
     func testWithDefaultConfiguration() {
         verifyRule(CommaInheritanceRule.description)
@@ -150,9 +156,3 @@ final class ComputedAccessorsOrderRuleGeneratedTests: SwiftLintTestCase {
         verifyRule(ComputedAccessorsOrderRule.description)
     }
 }
-
-final class ConditionalReturnsOnNewlineRuleGeneratedTests: SwiftLintTestCase {
-    func testWithDefaultConfiguration() {
-        verifyRule(ConditionalReturnsOnNewlineRule.description)
-    }
-}

Tests/GeneratedTests/GeneratedTests_02.swift

@@ -7,6 +7,12 @@
 @testable import SwiftLintCore
 import TestHelpers
 
+final class ConditionalReturnsOnNewlineRuleGeneratedTests: SwiftLintTestCase {
+    func testWithDefaultConfiguration() {
+        verifyRule(ConditionalReturnsOnNewlineRule.description)
+    }
+}
+
 final class ContainsOverFilterCountRuleGeneratedTests: SwiftLintTestCase {
     func testWithDefaultConfiguration() {
         verifyRule(ContainsOverFilterCountRule.description)
@@ -150,9 +156,3 @@ final class EmptyCountRuleGeneratedTests: SwiftLintTestCase {
         verifyRule(EmptyCountRule.description)
     }
 }
-
-final class EmptyEnumArgumentsRuleGeneratedTests: SwiftLintTestCase {
-    func testWithDefaultConfiguration() {
-        verifyRule(EmptyEnumArgumentsRule.description)
-    }
-}

Tests/GeneratedTests/GeneratedTests_03.swift

@@ -7,6 +7,12 @@
 @testable import SwiftLintCore
 import TestHelpers
 
+final class EmptyEnumArgumentsRuleGeneratedTests: SwiftLintTestCase {
+    func testWithDefaultConfiguration() {
+        verifyRule(EmptyEnumArgumentsRule.description)
+    }
+}
+
 final class EmptyParametersRuleGeneratedTests: SwiftLintTestCase {
     func testWithDefaultConfiguration() {
         verifyRule(EmptyParametersRule.description)
@@ -150,9 +156,3 @@ final class ForWhereRuleGeneratedTests: SwiftLintTestCase {
         verifyRule(ForWhereRule.description)
     }
 }
-
-final class ForceCastRuleGeneratedTests: SwiftLintTestCase {
-    func testWithDefaultConfiguration() {
-        verifyRule(ForceCastRule.description)
-    }
-}

Tests/GeneratedTests/GeneratedTests_04.swift

@@ -7,6 +7,12 @@
 @testable import SwiftLintCore
 import TestHelpers
 
+final class ForceCastRuleGeneratedTests: SwiftLintTestCase {
+    func testWithDefaultConfiguration() {
+        verifyRule(ForceCastRule.description)
+    }
+}
+
 final class ForceTryRuleGeneratedTests: SwiftLintTestCase {
     func testWithDefaultConfiguration() {
         verifyRule(ForceTryRule.description)
@@ -150,9 +156,3 @@ final class LegacyCGGeometryFunctionsRuleGeneratedTests: SwiftLintTestCase {
         verifyRule(LegacyCGGeometryFunctionsRule.description)
     }
 }
-
-final class LegacyConstantRuleGeneratedTests: SwiftLintTestCase {
-    func testWithDefaultConfiguration() {
-        verifyRule(LegacyConstantRule.description)
-    }
-}

Tests/GeneratedTests/GeneratedTests_05.swift

@@ -7,6 +7,12 @@
 @testable import SwiftLintCore
 import TestHelpers
 
+final class LegacyConstantRuleGeneratedTests: SwiftLintTestCase {
+    func testWithDefaultConfiguration() {
+        verifyRule(LegacyConstantRule.description)
+    }
+}
+
 final class LegacyConstructorRuleGeneratedTests: SwiftLintTestCase {
     func testWithDefaultConfiguration() {
         verifyRule(LegacyConstructorRule.description)
@@ -150,9 +156,3 @@ final class NSLocalizedStringRequireBundleRuleGeneratedTests: SwiftLintTestCase
         verifyRule(NSLocalizedStringRequireBundleRule.description)
     }
 }
-
-final class NSNumberInitAsFunctionReferenceRuleGeneratedTests: SwiftLintTestCase {
-    func testWithDefaultConfiguration() {
-        verifyRule(NSNumberInitAsFunctionReferenceRule.description)
-    }
-}

Tests/GeneratedTests/GeneratedTests_06.swift

@@ -7,6 +7,12 @@
 @testable import SwiftLintCore
 import TestHelpers
 
+final class NSNumberInitAsFunctionReferenceRuleGeneratedTests: SwiftLintTestCase {
+    func testWithDefaultConfiguration() {
+        verifyRule(NSNumberInitAsFunctionReferenceRule.description)
+    }
+}
+
 final class NSObjectPreferIsEqualRuleGeneratedTests: SwiftLintTestCase {
     func testWithDefaultConfiguration() {
         verifyRule(NSObjectPreferIsEqualRule.description)
@@ -150,9 +156,3 @@ final class PeriodSpacingRuleGeneratedTests: SwiftLintTestCase {
         verifyRule(PeriodSpacingRule.description)
     }
 }
-
-final class PreferAssetSymbolsRuleGeneratedTests: SwiftLintTestCase {
-    func testWithDefaultConfiguration() {
-        verifyRule(PreferAssetSymbolsRule.description)
-    }
-}

Tests/GeneratedTests/GeneratedTests_07.swift

@@ -7,6 +7,12 @@
 @testable import SwiftLintCore
 import TestHelpers
 
+final class PreferAssetSymbolsRuleGeneratedTests: SwiftLintTestCase {
+    func testWithDefaultConfiguration() {
+        verifyRule(PreferAssetSymbolsRule.description)
+    }
+}
+
 final class PreferConditionListRuleGeneratedTests: SwiftLintTestCase {
     func testWithDefaultConfiguration() {
         verifyRule(PreferConditionListRule.description)
@@ -150,9 +156,3 @@ final class RedundantDiscardableLetRuleGeneratedTests: SwiftLintTestCase {
         verifyRule(RedundantDiscardableLetRule.description)
     }
 }
-
-final class RedundantNilCoalescingRuleGeneratedTests: SwiftLintTestCase {
-    func testWithDefaultConfiguration() {
-        verifyRule(RedundantNilCoalescingRule.description)
-    }
-}

Tests/GeneratedTests/GeneratedTests_08.swift

@@ -7,6 +7,12 @@
 @testable import SwiftLintCore
 import TestHelpers
 
+final class RedundantNilCoalescingRuleGeneratedTests: SwiftLintTestCase {
+    func testWithDefaultConfiguration() {
+        verifyRule(RedundantNilCoalescingRule.description)
+    }
+}
+
 final class RedundantObjcAttributeRuleGeneratedTests: SwiftLintTestCase {
     func testWithDefaultConfiguration() {
         verifyRule(RedundantObjcAttributeRule.description)
@@ -150,9 +156,3 @@ final class StrictFilePrivateRuleGeneratedTests: SwiftLintTestCase {
         verifyRule(StrictFilePrivateRule.description)
     }
 }
-
-final class StrongIBOutletRuleGeneratedTests: SwiftLintTestCase {
-    func testWithDefaultConfiguration() {
-        verifyRule(StrongIBOutletRule.description)
-    }
-}

Tests/GeneratedTests/GeneratedTests_09.swift

@@ -7,6 +7,12 @@
 @testable import SwiftLintCore
 import TestHelpers
 
+final class StrongIBOutletRuleGeneratedTests: SwiftLintTestCase {
+    func testWithDefaultConfiguration() {
+        verifyRule(StrongIBOutletRule.description)
+    }
+}
+
 final class SuperfluousElseRuleGeneratedTests: SwiftLintTestCase {
     func testWithDefaultConfiguration() {
         verifyRule(SuperfluousElseRule.description)
@@ -150,9 +156,3 @@ final class UnneededSynthesizedInitializerRuleGeneratedTests: SwiftLintTestCase
         verifyRule(UnneededSynthesizedInitializerRule.description)
     }
 }
-
-final class UnneededThrowsRuleGeneratedTests: SwiftLintTestCase {
-    func testWithDefaultConfiguration() {
-        verifyRule(UnneededThrowsRule.description)
-    }
-}

Tests/GeneratedTests/GeneratedTests_10.swift

@@ -7,6 +7,12 @@
 @testable import SwiftLintCore
 import TestHelpers
 
+final class UnneededThrowsRuleGeneratedTests: SwiftLintTestCase {
+    func testWithDefaultConfiguration() {
+        verifyRule(UnneededThrowsRule.description)
+    }
+}
+
 final class UnownedVariableCaptureRuleGeneratedTests: SwiftLintTestCase {
     func testWithDefaultConfiguration() {
         verifyRule(UnownedVariableCaptureRule.description)