Expand trailing comma implementation

Author: mateusrodriguesxyz

Sources/SwiftParser/Attributes.swift

@@ -376,7 +376,10 @@ extension Parser {
       }
     case nil:
       return parseAttribute(argumentMode: .customAttribute) { parser in
-        let arguments = parser.parseArgumentListElements(pattern: .none, allowTrailingComma: false)
+        let arguments = parser.parseArgumentListElements(
+          pattern: .none,
+          allowTrailingComma: parser.experimentalFeatures.contains(.trailingComma)
+        )
         return .argumentList(RawLabeledExprListSyntax(elements: arguments, arena: parser.arena))
       }
     }

Sources/SwiftParser/Availability.swift

@@ -47,12 +47,17 @@ extension Parser {
             arena: self.arena
           )
         )
-      } while keepGoing != nil && self.hasProgressed(&availabilityArgumentProgress)
+      } while keepGoing != nil && !self.atAvailabilitySpecListTerminator()
+        && self.hasProgressed(&availabilityArgumentProgress)
     }
 
     return RawAvailabilityArgumentListSyntax(elements: elements, arena: self.arena)
   }
 
+  mutating func atAvailabilitySpecListTerminator() -> Bool {
+    return self.experimentalFeatures.contains(.trailingComma) && self.at(.rightParen)
+  }
+
   enum AvailabilityArgumentKind: TokenSpecSet {
     case message
     case renamed

Sources/SwiftParser/Declarations.swift

@@ -492,7 +492,7 @@ extension Parser {
             arena: self.arena
           )
         )
-      } while keepGoing != nil && self.hasProgressed(&loopProgress)
+      } while keepGoing != nil && !atGenericParametersListTerminator() && self.hasProgressed(&loopProgress)
     }
 
     let whereClause: RawGenericWhereClauseSyntax?
@@ -519,6 +519,10 @@ extension Parser {
     )
   }
 
+  mutating func atGenericParametersListTerminator() -> Bool {
+    return self.experimentalFeatures.contains(.trailingComma) && self.at(prefix: ">")
+  }
+
   mutating func parseGenericWhereClause() -> RawGenericWhereClauseSyntax {
     let (unexpectedBeforeWhereKeyword, whereKeyword) = self.expect(.keyword(.where))
 
@@ -700,7 +704,7 @@ extension Parser {
             arena: self.arena
           )
         )
-      } while keepGoing != nil && self.hasProgressed(&loopProgress)
+      } while keepGoing != nil && !self.atWhereClauseListTerminator() && self.hasProgressed(&loopProgress)
     }
 
     return RawGenericWhereClauseSyntax(
@@ -710,6 +714,10 @@ extension Parser {
       arena: self.arena
     )
   }
+
+  mutating func atWhereClauseListTerminator() -> Bool {
+    return self.at(.leftBrace)
+  }
 }
 
 extension Parser {
@@ -2029,7 +2037,10 @@ extension Parser {
     let unexpectedBeforeRightParen: RawUnexpectedNodesSyntax?
     let rightParen: RawTokenSyntax?
     if leftParen != nil {
-      args = parseArgumentListElements(pattern: .none, allowTrailingComma: false)
+      args = parseArgumentListElements(
+        pattern: .none,
+        allowTrailingComma: self.experimentalFeatures.contains(.trailingComma)
+      )
       (unexpectedBeforeRightParen, rightParen) = self.expect(.rightParen)
     } else {
       args = []

Sources/SwiftParser/Expressions.swift

@@ -786,7 +786,10 @@ extension Parser {
         if self.at(.rightSquare) {
           args = []
         } else {
-          args = self.parseArgumentListElements(pattern: pattern, allowTrailingComma: false)
+          args = self.parseArgumentListElements(
+            pattern: pattern,
+            allowTrailingComma: self.experimentalFeatures.contains(.trailingComma)
+          )
         }
         let (unexpectedBeforeRSquare, rsquare) = self.expect(.rightSquare)
 
@@ -1019,7 +1022,10 @@ extension Parser {
         if self.at(.rightSquare) {
           args = []
         } else {
-          args = self.parseArgumentListElements(pattern: pattern, allowTrailingComma: false)
+          args = self.parseArgumentListElements(
+            pattern: pattern,
+            allowTrailingComma: self.experimentalFeatures.contains(.trailingComma)
+          )
         }
         let (unexpectedBeforeRSquare, rsquare) = self.expect(.rightSquare)
 
@@ -1314,7 +1320,10 @@ extension Parser {
     let unexpectedBeforeRightParen: RawUnexpectedNodesSyntax?
     let rightParen: RawTokenSyntax?
     if leftParen != nil {
-      args = parseArgumentListElements(pattern: pattern, allowTrailingComma: false)
+      args = parseArgumentListElements(
+        pattern: pattern,
+        allowTrailingComma: self.experimentalFeatures.contains(.trailingComma)
+      )
       (unexpectedBeforeRightParen, rightParen) = self.expect(.rightParen)
     } else {
       args = []
@@ -1740,7 +1749,7 @@ extension Parser {
               arena: self.arena
             )
           )
-        } while keepGoing != nil && self.hasProgressed(&loopProgress)
+        } while keepGoing != nil && !self.atCaptureListTerminator() && self.hasProgressed(&loopProgress)
       }
       // We were promised a right square bracket, so we're going to get it.
       var unexpectedNodes = [RawSyntax]()
@@ -1827,6 +1836,10 @@ extension Parser {
     )
   }
 
+  mutating func atCaptureListTerminator() -> Bool {
+    return self.at(.rightSquare)
+  }
+
   mutating func parseClosureCaptureSpecifiers() -> RawClosureCaptureSpecifierSyntax? {
     // Check for the strength specifier: "weak", "unowned", or
     // "unowned(safe/unsafe)".
@@ -1938,7 +1951,7 @@ extension Parser {
   }
 
   mutating func atArgumentListTerminator(_ allowTrailingComma: Bool) -> Bool {
-    return allowTrailingComma && self.at(.rightParen)
+    return allowTrailingComma && (self.at(.rightParen) || self.at(.rightSquare))
   }
 }
 
@@ -2383,7 +2396,7 @@ extension Parser {
         } else {
           unexpectedPrePatternCase = nil
         }
-      } while keepGoing != nil && self.hasProgressed(&loopProgress)
+      } while keepGoing != nil && !self.atSwitchCaseListTerminator() && self.hasProgressed(&loopProgress)
     }
     let (unexpectedBeforeColon, colon) = self.expect(.colon)
     return RawSwitchCaseLabelSyntax(
@@ -2396,6 +2409,10 @@ extension Parser {
     )
   }
 
+  mutating func atSwitchCaseListTerminator() -> Bool {
+    return self.experimentalFeatures.contains(.trailingComma) && self.at(.colon)
+  }
+
   /// Parse a switch case with a 'default' label.
   mutating func parseSwitchDefaultLabel(
     _ handle: RecoveryConsumptionHandle

Sources/SwiftParser/Nominals.swift

@@ -315,7 +315,7 @@ extension Parser {
             arena: self.arena
           )
         )
-      } while keepGoing != nil && self.hasProgressed(&loopProgress)
+      } while keepGoing != nil && !self.atInheritanceListTerminator() && self.hasProgressed(&loopProgress)
     }
 
     let unexpectedAfterInheritedTypeCollection: RawUnexpectedNodesSyntax?
@@ -339,6 +339,10 @@ extension Parser {
     )
   }
 
+  mutating func atInheritanceListTerminator() -> Bool {
+    return self.experimentalFeatures.contains(.trailingComma) && (self.at(.leftBrace) || self.at(.keyword(.where)))
+  }
+
   mutating func parsePrimaryAssociatedTypes() -> RawPrimaryAssociatedTypeClauseSyntax {
     let langle = self.consumePrefix("<", as: .leftAngle)
     var associatedTypes = [RawPrimaryAssociatedTypeSyntax]()

Sources/SwiftParser/StringLiterals.swift

@@ -551,7 +551,10 @@ extension Parser {
         )
         let leftParen = self.expectWithoutRecoveryOrLeadingTrivia(.leftParen)
         let expressions = RawLabeledExprListSyntax(
-          elements: self.parseArgumentListElements(pattern: .none, allowTrailingComma: false),
+          elements: self.parseArgumentListElements(
+            pattern: .none,
+            allowTrailingComma: self.experimentalFeatures.contains(.trailingComma)
+          ),
           arena: self.arena
         )
 

Sources/SwiftParser/Types.swift

@@ -1025,7 +1025,10 @@ extension Parser {
       }
     case nil:  // Custom attribute
       return parseAttribute(argumentMode: .customAttribute) { parser in
-        let arguments = parser.parseArgumentListElements(pattern: .none, allowTrailingComma: false)
+        let arguments = parser.parseArgumentListElements(
+          pattern: .none,
+          allowTrailingComma: parser.experimentalFeatures.contains(.trailingComma)
+        )
         return .argumentList(RawLabeledExprListSyntax(elements: arguments, arena: parser.arena))
       }
 

Tests/SwiftParserTest/TrailingCommaTests.swift

@@ -231,4 +231,113 @@ final class TrailingCommaTests: ParserTestCase {
   func testWhileConditions() {
     assertParse("while true, { print(0) }")
   }
+
+  func testSubscriptArguments() {
+    assertParse("d[1, 2,]")
+  }
+
+  func testStringLiteralInterpolation() {
+    assertParse(#""\(1, 2,)""#)
+  }
+
+  func testKeyPathExpressionArguments() {
+    assertParse(
+      """
+      \\Foo.bar[0,]
+      """
+    )
+  }
+
+  func testCustomAttributes() {
+    assertParse("@Foo(a, b, c,) struct S { }")
+    
+    assertParse("f(_: @foo(1, 2,) Int)")
+  }
+
+  func testTypeAttribute() {
+    assertParse("f(_: @foo(1, 2,) Int)")
+  }
+
+  func testMacroExpansionExpressionArguments() {
+    assertParse(
+      """
+      #foo(1, 2,)
+      """
+    )
+  }
+
+  func testMacroExpansionDeclarationArguments() {
+    assertParse(
+      """
+      struct S {
+      #foo(1, 2,)
+      }
+      """
+    )
+  }
+
+  func testGenericParameters() {
+    assertParse(
+      """
+      struct S<T1, T2,> { }
+      """
+    )
+  }
+
+  func testSwitchCaseLabel() {
+    assertParse(
+      """
+      switch number {
+      case 1, 2,:
+          break
+      default:
+          break
+      }
+      """
+    )
+  }
+
+  func testClosureCaptureList() {
+    assertParse(
+      """
+      { [obj1, obj2,] in }
+      """
+    )
+  }
+
+  func testInheritance() {
+    assertParse(
+      """
+      struct T: P1, P2, { }
+      """
+    )
+
+    assertParse(
+      """
+      struct T: P1, P2, where P1: Equatable, P2: Equatable { }
+      """
+    )
+  }
+
+  func testGenericWhereClause() {
+    assertParse(
+      """
+      struct T: P1, P2, where P1: Equatable, P2: Equatable, { }
+      """
+    )
+  }
+
+  func testAvailabilityArgumentSpecList() {
+    assertParse(
+      """
+      if #available(iOS 15, watchOS 9, *,) { }
+      """
+    )
+
+    assertParse(
+      """
+      if #unavailable(iOS 15, watchOS 9,) { }
+      """
+    )
+  }
 }