[JExtract] Santize trivia for declartion signature string

Introduce `triviaSanitizedDescription` that prints tokens with
trivia condensed into a single whitespace, or removed after opening or
before closing parentheses.

Author: rintaro

Sources/JExtractSwift/Convenience/SwiftSyntax+Extensions.swift

@@ -177,17 +177,19 @@ extension DeclSyntaxProtocol {
   var signatureString: String {
     return switch DeclSyntax(self.detached).as(DeclSyntaxEnum.self) {
     case .functionDecl(let node):
-      node.with(\.body, nil).trimmedDescription
+      node.with(\.body, nil).triviaSanitizedDescription
     case .initializerDecl(let node):
-      node.with(\.body, nil).trimmedDescription
+      node.with(\.body, nil).triviaSanitizedDescription
     case .classDecl(let node):
-      node.with(\.memberBlock, "").trimmedDescription
+      node.with(\.memberBlock, "").triviaSanitizedDescription
     case .structDecl(let node):
-      node.with(\.memberBlock, "").trimmedDescription
+      node.with(\.memberBlock, "").triviaSanitizedDescription
     case .protocolDecl(let node):
-      node.with(\.memberBlock, "").trimmedDescription
+      node.with(\.memberBlock, "").triviaSanitizedDescription
     case .accessorDecl(let node):
-      node.with(\.body, nil).trimmedDescription
+      node.with(\.body, nil).triviaSanitizedDescription
+    case .subscriptDecl(let node):
+      node.with(\.accessorBlock, nil).triviaSanitizedDescription
     case .variableDecl(let node):
       node
         .with(\.bindings, PatternBindingListSyntax(
@@ -197,9 +199,47 @@ extension DeclSyntaxProtocol {
             .with(\.initializer, nil)
           }
         ))
-        .trimmedDescription
+        .triviaSanitizedDescription
     default:
       fatalError("unimplemented \(self.kind)")
     }
   }
+
+  /// Syntax text but without unnecessary trivia.
+  ///
+  /// Connective trivia are condensed into a single whitespace, but no space
+  /// after opening or before closing parentheses
+  var triviaSanitizedDescription: String {
+    let visitor = TriviaSanitizingDescriptionVisitor(viewMode: .sourceAccurate)
+    visitor.walk(self.trimmed)
+    return visitor.result
+  }
+}
+
+class TriviaSanitizingDescriptionVisitor: SyntaxVisitor {
+  var result: String = ""
+
+  var prevTokenKind: TokenKind = .endOfFile
+  var prevHadTrailingSpace: Bool = false
+
+  override func visit(_ node: TokenSyntax) -> SyntaxVisitorContinueKind {
+    let tokenKind = node.tokenKind
+    switch (prevTokenKind, tokenKind) {
+    case
+      // No whitespace after open parentheses.
+      (.leftAngle, _), (.leftParen, _), (.leftSquare, _), (.endOfFile, _),
+      // No whitespace before close parentheses.
+      (_, .rightAngle), (_, .rightParen), (_, .rightSquare):
+      break
+    default:
+      if prevHadTrailingSpace || !node.leadingTrivia.isEmpty {
+        result += " "
+      }
+    }
+    result += node.text
+    prevTokenKind = tokenKind
+    prevHadTrailingSpace = !node.trailingTrivia.isEmpty
+
+    return .skipChildren
+  }
 }

Sources/JExtractSwift/ImportedDecls.swift

@@ -50,7 +50,6 @@ public final class ImportedFunc: ImportedDecl, CustomStringConvertible {
   var translatedSignature: TranslatedFunctionSignature
 
   public var signatureString: String {
-    // FIXME: Remove comments and normalize trivia.
     self.swiftDecl.signatureString
   }
 

Tests/JExtractSwiftTests/MethodImportTests.swift

@@ -28,11 +28,16 @@ final class MethodImportTests {
     import _StringProcessing
     import _SwiftConcurrencyShims
 
-    public func helloWorld()
+    /// Hello World!
+    public func /*comment*/helloWorld()
 
     public func globalTakeInt(i: Int)
 
-    public func globalTakeIntLongString(i32: Int32, l: Int64, s: String)
+    public func globalTakeIntLongString(
+      i32: Int32,
+      l: Int64,
+      s: String
+    )
     
     public func globalReturnClass() -> MySwiftClass