Merge pull request swiftlang#106 from allevato/no-break-empty-parens

Don't break inside empty parens of a no-argument func/init decl.

Author: allevato

Sources/SwiftFormatPrettyPrint/TokenStreamCreator.swift

@@ -246,18 +246,29 @@ private final class TokenStreamCreator: SyntaxVisitor {
   // MARK: - Function and function-like declaration nodes (initializers, deinitializers, subscripts)
 
   func visit(_ node: FunctionDeclSyntax) -> SyntaxVisitorContinueKind {
-    // Prioritize keeping "<modifiers> func <name>" together.
-    let firstTokenAfterAttributes = node.modifiers?.firstToken ?? node.funcKeyword
-    before(firstTokenAfterAttributes, tokens: .open)
-    after(node.funcKeyword, tokens: .break)
-    after(node.identifier, tokens: .close)
+    let hasArguments = !node.signature.input.parameterList.isEmpty
 
-    // Prioritize keeping ") throws -> <return_type>" together.
-    if config.prioritizeKeepingFunctionOutputTogether {
+    // Prioritize keeping ") throws -> <return_type>" together. We can only do this if the function
+    // has arguments.
+    if hasArguments && config.prioritizeKeepingFunctionOutputTogether {
       // Due to visitation order, the matching .open break is added in ParameterClauseSyntax.
       after(node.signature.lastToken, tokens: .close)
     }
 
+    let mustBreak = node.body != nil || node.signature.output != nil
+    arrangeParameterClause(node.signature.input, forcesBreakBeforeRightParen: mustBreak)
+
+    // Prioritize keeping "<modifiers> func <name>(" together. Also include the ")" if the parameter
+    // list is empty.
+    let firstTokenAfterAttributes = node.modifiers?.firstToken ?? node.funcKeyword
+    before(firstTokenAfterAttributes, tokens: .open)
+    after(node.funcKeyword, tokens: .break)
+    if hasArguments || node.genericParameterClause != nil {
+      after(node.signature.input.leftParen, tokens: .close)
+    } else {
+      after(node.signature.input.rightParen, tokens: .close)
+    }
+
     // Add a non-breaking space after the identifier if it's an operator, to separate it visually
     // from the following parenthesis or generic argument list. Note that even if the function is
     // defining a prefix or postfix operator, or even if the operator isn't originally followed by a
@@ -266,9 +277,6 @@ private final class TokenStreamCreator: SyntaxVisitor {
       after(node.identifier.lastToken, tokens: .space)
     }
 
-    let mustBreak = node.body != nil || node.signature.output != nil
-    arrangeParameterClause(node.signature.input, forcesBreakBeforeRightParen: mustBreak)
-
     arrangeFunctionLikeDecl(
       node,
       attributes: node.attributes,
@@ -280,18 +288,22 @@ private final class TokenStreamCreator: SyntaxVisitor {
   }
 
   func visit(_ node: InitializerDeclSyntax) -> SyntaxVisitorContinueKind {
+    let hasArguments = !node.parameters.parameterList.isEmpty
+
+    arrangeParameterClause(node.parameters, forcesBreakBeforeRightParen: node.body != nil)
+
     // Prioritize keeping "<modifiers> init<punctuation>" together.
     let firstTokenAfterAttributes = node.modifiers?.firstToken ?? node.initKeyword
-    let lastTokenOfName = node.optionalMark ?? node.initKeyword
-    if firstTokenAfterAttributes != lastTokenOfName {
-      before(firstTokenAfterAttributes, tokens: .open)
-      after(lastTokenOfName, tokens: .close)
+    before(firstTokenAfterAttributes, tokens: .open)
+
+    if hasArguments || node.genericParameterClause != nil {
+      after(node.parameters.leftParen, tokens: .close)
+    } else {
+      after(node.parameters.rightParen, tokens: .close)
     }
 
     before(node.throwsOrRethrowsKeyword, tokens: .break)
 
-    arrangeParameterClause(node.parameters, forcesBreakBeforeRightParen: node.body != nil)
-
     arrangeFunctionLikeDecl(
       node,
       attributes: node.attributes,
@@ -313,16 +325,24 @@ private final class TokenStreamCreator: SyntaxVisitor {
   }
 
   func visit(_ node: SubscriptDeclSyntax) -> SyntaxVisitorContinueKind {
+    let hasArguments = !node.indices.parameterList.isEmpty
+
     before(node.firstToken, tokens: .open)
 
     // Prioritize keeping "<modifiers> subscript" together.
     if let firstModifierToken = node.modifiers?.firstToken {
       before(firstModifierToken, tokens: .open)
-      after(node.subscriptKeyword, tokens: .close)
+
+      if hasArguments || node.genericParameterClause != nil {
+        after(node.indices.leftParen, tokens: .close)
+      } else {
+        after(node.indices.rightParen, tokens: .close)
+      }
     }
 
-    // Prioritize keeping ") -> <return_type>" together.
-    if config.prioritizeKeepingFunctionOutputTogether {
+    // Prioritize keeping ") -> <return_type>" together. We can only do this if the subscript has
+    // arguments.
+    if hasArguments && config.prioritizeKeepingFunctionOutputTogether {
       // Due to visitation order, the matching .open break is added in ParameterClauseSyntax.
       after(node.result.lastToken, tokens: .close)
     }
@@ -905,8 +925,9 @@ private final class TokenStreamCreator: SyntaxVisitor {
   }
 
   func visit(_ node: ParameterClauseSyntax) -> SyntaxVisitorContinueKind {
-    // Prioritize keeping ") throws -> <return_type>" together.
-    if config.prioritizeKeepingFunctionOutputTogether {
+    // Prioritize keeping ") throws -> <return_type>" together. We can only do this if the function
+    // has arguments.
+    if !node.parameterList.isEmpty && config.prioritizeKeepingFunctionOutputTogether {
       // Due to visitation order, this .open corresponds to a .close added in FunctionDeclSyntax
       // or SubscriptDeclSyntax.
       before(node.rightParen, tokens: .open)
@@ -2072,6 +2093,8 @@ private final class TokenStreamCreator: SyntaxVisitor {
   private func arrangeParameterClause(
     _ parameters: ParameterClauseSyntax, forcesBreakBeforeRightParen: Bool
   ) {
+    guard !parameters.parameterList.isEmpty else { return }
+
     after(parameters.leftParen, tokens: .break(.open, size: 0), .open(argumentListConsistency()))
     before(
       parameters.rightParen,

Tests/SwiftFormatPrettyPrintTests/FunctionDeclTests.swift

@@ -1019,4 +1019,24 @@ public class FunctionDeclTests: PrettyPrintTestCase {
 
     assertPrettyPrintEqual(input: input, expected: input, linelength: 80)
   }
+
+  func testDoesNotBreakInsideEmptyParens() {
+    // If the function name is so long that the parentheses of a no-argument parameter list would
+    // be pushed past the margin, don't break inside them.
+    let input =
+      """
+      func fooBarBaz() {}
+
+      """
+
+    let expected =
+      """
+      func
+        fooBarBaz()
+      {}
+
+      """
+
+    assertPrettyPrintEqual(input: input, expected: expected, linelength: 14)
+  }
 }

Tests/SwiftFormatPrettyPrintTests/InitializerDeclTests.swift

@@ -352,7 +352,8 @@ public class InitializerDeclTests: PrettyPrintTestCase {
     let expected =
       """
       struct Struct {
-        @objc @inlinable public init<
+        @objc @inlinable
+        public init<
           Elements: Collection, Element
         >(
           element: Element,
@@ -388,7 +389,8 @@ public class InitializerDeclTests: PrettyPrintTestCase {
     let expected =
     """
       struct Struct {
-        @objc @inlinable public init<
+        @objc @inlinable
+        public init<
           Elements: Collection, Element
         >(
           element: Element,

Tests/SwiftFormatPrettyPrintTests/XCTestManifests.swift

@@ -264,6 +264,7 @@ extension FunctionDeclTests {
         ("testBreaksBeforeOrInsideOutputWithAttributes_prioritizingKeepingOutputTogether", testBreaksBeforeOrInsideOutputWithAttributes_prioritizingKeepingOutputTogether),
         ("testBreaksBeforeOrInsideOutputWithWhereClause", testBreaksBeforeOrInsideOutputWithWhereClause),
         ("testBreaksBeforeOrInsideOutputWithWhereClause_prioritizingKeepingOutputTogether", testBreaksBeforeOrInsideOutputWithWhereClause_prioritizingKeepingOutputTogether),
+        ("testDoesNotBreakInsideEmptyParens", testDoesNotBreakInsideEmptyParens),
         ("testDoesNotCollapseFunctionParameterAttributes", testDoesNotCollapseFunctionParameterAttributes),
         ("testDoesNotCollapseStackedFunctionParameterAttributes", testDoesNotCollapseStackedFunctionParameterAttributes),
         ("testEmptyFunction", testEmptyFunction),