More for formatting a selection <#297>

Do a better job of getting the whitespace right when entering/leaving a selection. For trivia, only enable/disable around comments.

Author: DaveEwing

Sources/SwiftFormat/API/Selection.swift

@@ -56,7 +56,7 @@ public struct Selection {
     return ranges.contains {
       let maxStart = max($0.offset, range.offset)
       let minEnd = (min($0.end, range.end))
-      return maxStart < minEnd
+      return maxStart <= minEnd
     }
   }
 }

Sources/SwiftFormat/PrettyPrint/PrettyPrint.swift

@@ -11,6 +11,7 @@
 //===----------------------------------------------------------------------===//
 
 import SwiftSyntax
+import Foundation
 
 /// PrettyPrinter takes a Syntax node and outputs a well-formatted, re-indented reproduction of the
 /// code as a String.
@@ -245,15 +246,18 @@ public class PrettyPrinter {
   /// Before printing the text, this function will print any line-leading indentation or interior
   /// leading spaces that are required before the text itself.
   private func write(_ text: String) {
-    guard writingIsEnabled else { return }
     if isAtStartOfLine {
-      writeRaw(currentIndentation.indentation())
+      if writingIsEnabled {
+        writeRaw(currentIndentation.indentation())
+      }
       spaceRemaining = maxLineLength - currentIndentation.length(in: configuration)
       isAtStartOfLine = false
-    } else if pendingSpaces > 0 {
+    } else if pendingSpaces > 0 && writingIsEnabled {
       writeRaw(String(repeating: " ", count: pendingSpaces))
     }
-    writeRaw(text)
+    if writingIsEnabled {
+      writeRaw(text)
+    }
     consecutiveNewlineCount = 0
     pendingSpaces = 0
   }
@@ -591,13 +595,21 @@ public class PrettyPrinter {
         } else {
           end = source.endIndex
         }
-        let text = String(source[start..<end])
+        var text = String(source[start..<end])
+        // strip trailing whitespace so that the next formatting can add the right amount
+        if let nonWhitespace = text.rangeOfCharacter(
+          from: CharacterSet.whitespaces.inverted, options: .backwards) {
+          text = String(text[..<nonWhitespace.upperBound])
+        }
+
         writeRaw(text)
         if text.hasSuffix("\n") {
           isAtStartOfLine = true
           consecutiveNewlineCount = 1
+        } else {
+          isAtStartOfLine = false
+          consecutiveNewlineCount = 0
         }
-        pendingSpaces = 0
         self.disabledPosition = nil
       }
 

Sources/SwiftFormat/PrettyPrint/TokenStreamCreator.swift

@@ -3263,20 +3263,23 @@ fileprivate final class TokenStreamCreator: SyntaxVisitor {
     var requiresNextNewline = false
 
     for (index, piece) in trivia.enumerated() {
-      generateEnable(Selection.Range(start: position, end: position + piece.sourceLength))
       if let cutoff = cutoffIndex, index == cutoff { break }
       switch piece {
       case .lineComment(let text):
         if index > 0 || isStartOfFile {
+          generateEnable(Selection.Range(start: position, end: position + piece.sourceLength))
           appendToken(.comment(Comment(kind: .line, text: text), wasEndOfLine: false))
+          generateDisable(position + piece.sourceLength)
           appendNewlines(.soft)
           isStartOfFile = false
         }
         requiresNextNewline = true
 
       case .blockComment(let text):
         if index > 0 || isStartOfFile {
+          generateEnable(Selection.Range(start: position, end: position + piece.sourceLength))
           appendToken(.comment(Comment(kind: .block, text: text), wasEndOfLine: false))
+          generateDisable(position + piece.sourceLength)
           // There is always a break after the comment to allow a discretionary newline after it.
           var breakSize = 0
           if index + 1 < trivia.endIndex {
@@ -3291,13 +3294,17 @@ fileprivate final class TokenStreamCreator: SyntaxVisitor {
         requiresNextNewline = false
 
       case .docLineComment(let text):
+        generateEnable(Selection.Range(start: position, end: position + piece.sourceLength))
         appendToken(.comment(Comment(kind: .docLine, text: text), wasEndOfLine: false))
+        generateDisable(position + piece.sourceLength)
         appendNewlines(.soft)
         isStartOfFile = false
         requiresNextNewline = true
 
       case .docBlockComment(let text):
+        generateEnable(Selection.Range(start: position, end: position + piece.sourceLength))
         appendToken(.comment(Comment(kind: .docBlock, text: text), wasEndOfLine: false))
+        generateDisable(position + piece.sourceLength)
         appendNewlines(.soft)
         isStartOfFile = false
         requiresNextNewline = false
@@ -3337,7 +3344,6 @@ fileprivate final class TokenStreamCreator: SyntaxVisitor {
         break
       }
       position += piece.sourceLength
-      generateDisable(position)
     }
   }