[Lint] Add a rule to detect that type declarations are not capitalized

Author: xedin

Sources/SwiftFormat/Pipelines+Generated.swift

@@ -51,6 +51,7 @@ class LintPipeline: SyntaxVisitor {
     visitIfEnabled(BeginDocumentationCommentWithOneLineSummary.visit, for: node)
     visitIfEnabled(DontRepeatTypeInStaticProperties.visit, for: node)
     visitIfEnabled(NoLeadingUnderscores.visit, for: node)
+    visitIfEnabled(TypeNamesShouldBeCapitalized.visit, for: node)
     visitIfEnabled(UseTripleSlashForDocumentationComments.visit, for: node)
     return .visitChildren
   }
@@ -108,6 +109,7 @@ class LintPipeline: SyntaxVisitor {
     visitIfEnabled(FullyIndirectEnum.visit, for: node)
     visitIfEnabled(NoLeadingUnderscores.visit, for: node)
     visitIfEnabled(OneCasePerLine.visit, for: node)
+    visitIfEnabled(TypeNamesShouldBeCapitalized.visit, for: node)
     visitIfEnabled(UseTripleSlashForDocumentationComments.visit, for: node)
     return .visitChildren
   }
@@ -165,12 +167,22 @@ class LintPipeline: SyntaxVisitor {
     return .visitChildren
   }
 
+  override func visit(_ node: GenericSpecializationExprSyntax) -> SyntaxVisitorContinueKind {
+    visitIfEnabled(UseShorthandTypeNames.visit, for: node)
+    return .visitChildren
+  }
+
   override func visit(_ node: IdentifierPatternSyntax) -> SyntaxVisitorContinueKind {
     visitIfEnabled(IdentifiersMustBeASCII.visit, for: node)
     visitIfEnabled(NoLeadingUnderscores.visit, for: node)
     return .visitChildren
   }
 
+  override func visit(_ node: IdentifierTypeSyntax) -> SyntaxVisitorContinueKind {
+    visitIfEnabled(UseShorthandTypeNames.visit, for: node)
+    return .visitChildren
+  }
+
   override func visit(_ node: IfExprSyntax) -> SyntaxVisitorContinueKind {
     visitIfEnabled(NoParensAroundConditions.visit, for: node)
     return .visitChildren
@@ -194,13 +206,13 @@ class LintPipeline: SyntaxVisitor {
     return .visitChildren
   }
 
-  override func visit(_ node: MemberBlockSyntax) -> SyntaxVisitorContinueKind {
-    visitIfEnabled(AmbiguousTrailingClosureOverload.visit, for: node)
+  override func visit(_ node: MemberBlockItemListSyntax) -> SyntaxVisitorContinueKind {
+    visitIfEnabled(DoNotUseSemicolons.visit, for: node)
     return .visitChildren
   }
 
-  override func visit(_ node: MemberBlockItemListSyntax) -> SyntaxVisitorContinueKind {
-    visitIfEnabled(DoNotUseSemicolons.visit, for: node)
+  override func visit(_ node: MemberBlockSyntax) -> SyntaxVisitorContinueKind {
+    visitIfEnabled(AmbiguousTrailingClosureOverload.visit, for: node)
     return .visitChildren
   }
 
@@ -224,6 +236,7 @@ class LintPipeline: SyntaxVisitor {
     visitIfEnabled(BeginDocumentationCommentWithOneLineSummary.visit, for: node)
     visitIfEnabled(DontRepeatTypeInStaticProperties.visit, for: node)
     visitIfEnabled(NoLeadingUnderscores.visit, for: node)
+    visitIfEnabled(TypeNamesShouldBeCapitalized.visit, for: node)
     visitIfEnabled(UseTripleSlashForDocumentationComments.visit, for: node)
     return .visitChildren
   }
@@ -233,11 +246,6 @@ class LintPipeline: SyntaxVisitor {
     return .visitChildren
   }
 
-  override func visit(_ node: IdentifierTypeSyntax) -> SyntaxVisitorContinueKind {
-    visitIfEnabled(UseShorthandTypeNames.visit, for: node)
-    return .visitChildren
-  }
-
   override func visit(_ node: SourceFileSyntax) -> SyntaxVisitorContinueKind {
     visitIfEnabled(AlwaysUseLowerCamelCase.visit, for: node)
     visitIfEnabled(AmbiguousTrailingClosureOverload.visit, for: node)
@@ -249,16 +257,12 @@ class LintPipeline: SyntaxVisitor {
     return .visitChildren
   }
 
-  override func visit(_ node: GenericSpecializationExprSyntax) -> SyntaxVisitorContinueKind {
-    visitIfEnabled(UseShorthandTypeNames.visit, for: node)
-    return .visitChildren
-  }
-
   override func visit(_ node: StructDeclSyntax) -> SyntaxVisitorContinueKind {
     visitIfEnabled(AllPublicDeclarationsHaveDocumentation.visit, for: node)
     visitIfEnabled(BeginDocumentationCommentWithOneLineSummary.visit, for: node)
     visitIfEnabled(DontRepeatTypeInStaticProperties.visit, for: node)
     visitIfEnabled(NoLeadingUnderscores.visit, for: node)
+    visitIfEnabled(TypeNamesShouldBeCapitalized.visit, for: node)
     visitIfEnabled(UseSynthesizedInitializer.visit, for: node)
     visitIfEnabled(UseTripleSlashForDocumentationComments.visit, for: node)
     return .visitChildren

Sources/SwiftFormatConfiguration/RuleRegistry+Generated.swift

@@ -41,6 +41,7 @@ enum RuleRegistry {
     "OnlyOneTrailingClosureArgument": true,
     "OrderedImports": true,
     "ReturnVoidInsteadOfEmptyTuple": true,
+    "TypeNamesShouldBeCapitalized": true,
     "UseEarlyExits": false,
     "UseLetInEveryBoundCaseVariable": true,
     "UseShorthandTypeNames": true,

Sources/SwiftFormatRules/RuleNameCache+Generated.swift

@@ -41,6 +41,7 @@ public let ruleNameCache: [ObjectIdentifier: String] = [
   ObjectIdentifier(OnlyOneTrailingClosureArgument.self): "OnlyOneTrailingClosureArgument",
   ObjectIdentifier(OrderedImports.self): "OrderedImports",
   ObjectIdentifier(ReturnVoidInsteadOfEmptyTuple.self): "ReturnVoidInsteadOfEmptyTuple",
+  ObjectIdentifier(TypeNamesShouldBeCapitalized.self): "TypeNamesShouldBeCapitalized",
   ObjectIdentifier(UseEarlyExits.self): "UseEarlyExits",
   ObjectIdentifier(UseLetInEveryBoundCaseVariable.self): "UseLetInEveryBoundCaseVariable",
   ObjectIdentifier(UseShorthandTypeNames.self): "UseShorthandTypeNames",

Sources/SwiftFormatRules/TypeNamesShouldBeCapitalized.swift

@@ -0,0 +1,52 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2023 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import SwiftFormatCore
+import SwiftSyntax
+
+/// `struct`, `class`, `enum` and `protocol` declarations should have a capitalized name.
+///
+/// Lint:  Types with un-capitalized names will yield a lint error.
+public final class TypeNamesShouldBeCapitalized : SyntaxLintRule {
+  public override func visit(_ node: StructDeclSyntax) -> SyntaxVisitorContinueKind {
+    diagnoseNameConventionMismatch(node, name: node.name)
+    return .visitChildren
+  }
+
+  public override func visit(_ node: ClassDeclSyntax) -> SyntaxVisitorContinueKind {
+    diagnoseNameConventionMismatch(node, name: node.name)
+    return .visitChildren
+  }
+
+  public override func visit(_ node: EnumDeclSyntax) -> SyntaxVisitorContinueKind {
+    diagnoseNameConventionMismatch(node, name: node.name)
+    return .visitChildren
+  }
+
+  public override func visit(_ node: ProtocolDeclSyntax) -> SyntaxVisitorContinueKind {
+    diagnoseNameConventionMismatch(node, name: node.name)
+    return .visitChildren
+  }
+
+  private func diagnoseNameConventionMismatch<T: DeclSyntaxProtocol>(_ type: T, name: TokenSyntax) {
+    if let firstChar = name.text.first, !firstChar.isUppercase {
+      diagnose(.capitalizeTypeName(name: name.text), on: type, severity: .convention)
+    }
+  }
+}
+
+extension Finding.Message {
+  public static func capitalizeTypeName(name: String) -> Finding.Message {
+    let capitalized = name.prefix(1).uppercased() + name.dropFirst()
+    return "type names should be capitalized: \(name) -> \(capitalized)"
+  }
+}

Tests/SwiftFormatRulesTests/TypeNamesShouldBeCapitalizedTests.swift

@@ -0,0 +1,27 @@
+import SwiftFormatRules
+
+final class TypeNamesShouldBeCapitalizedTests: LintOrFormatRuleTestCase {
+  func testConstruction() {
+    let input =
+      """
+      struct a {}
+      class klassName {
+        struct subType {}
+      }
+      protocol myProtocol {}
+
+      extension myType {
+        struct innerType {}
+      }
+      """
+
+    performLint(TypeNamesShouldBeCapitalized.self, input: input)
+
+    XCTAssertDiagnosed(.capitalizeTypeName(name: "a"))
+    XCTAssertDiagnosed(.capitalizeTypeName(name: "klassName"))
+    XCTAssertDiagnosed(.capitalizeTypeName(name: "subType"))
+    XCTAssertDiagnosed(.capitalizeTypeName(name: "myProtocol"))
+    XCTAssertNotDiagnosed(.capitalizeTypeName(name: "myType"))
+    XCTAssertDiagnosed(.capitalizeTypeName(name: "innerType"))
+  }
+}