Update the command line to take an --offsets option of comma-separated "start:end" pairs (for <#297>).

Author: DaveEwing

Sources/SwiftFormat/API/Selection.swift

@@ -18,19 +18,13 @@ public enum Selection {
   case infinite
   case ranges([Range<AbsolutePosition>])
 
-  public init(json: String) {
-    if let data = json.data(using: .utf8),
-       let ranges = try? JSONDecoder().decode([Range<AbsolutePosition>].self, from: data) {
-      self = .ranges(ranges)
-    } else {
-      self = .infinite
-    }
-  }
-
-  public init(ranges: [Range<AbsolutePosition>]) {
-    if ranges.isEmpty {
+  public init(offsetPairs: [Range<Int>]) {
+    if offsetPairs.isEmpty {
       self = .infinite
     } else {
+      let ranges = offsetPairs.map {
+        AbsolutePosition(utf8Offset: $0.lowerBound) ..< AbsolutePosition(utf8Offset: $0.upperBound)
+      }
       self = .ranges(ranges)
     }
   }
@@ -66,11 +60,3 @@ public extension Syntax {
     }
   }
 }
-
-// FIXME: temporary until we convert argument parsing
-extension AbsolutePosition : Decodable {
-  public init(from decoder: any Decoder) throws {
-    var container = try decoder.unkeyedContainer()
-    self.init(utf8Offset: try container.decode(Int.self))
-  }
-}

Sources/_SwiftFormatTestSupport/MarkedText.swift

@@ -29,16 +29,16 @@ public struct MarkedText {
     var text = ""
     var markers = [String: Int]()
     var lastIndex = markedText.startIndex
-    var ranges = [Range<AbsolutePosition>]()
-    var lastRangeStart = AbsolutePosition(utf8Offset: 0)
+    var offsets = [Range<Int>]()
+    var lastRangeStart = 0
     for marker in findMarkedRanges(in: markedText) {
       text += markedText[lastIndex..<marker.range.lowerBound]
       lastIndex = marker.range.upperBound
 
       if marker.name == "⏩" {
-        lastRangeStart = AbsolutePosition(utf8Offset: text.utf8.count)
+        lastRangeStart = text.utf8.count
       } else if marker.name == "⏪" {
-        ranges.append(lastRangeStart ..< AbsolutePosition(utf8Offset: text.utf8.count))
+        offsets.append(lastRangeStart ..< text.utf8.count)
       } else {
         assert(markers[marker.name] == nil, "Marker names must be unique")
         markers[marker.name] = text.utf8.count
@@ -49,7 +49,7 @@ public struct MarkedText {
 
     self.markers = markers
     self.textWithoutMarkers = text
-    self.selection = Selection(ranges: ranges)
+    self.selection = Selection(offsetPairs: offsets)
   }
 }
 

Sources/swift-format/Frontend/Frontend.swift

@@ -126,11 +126,9 @@ class Frontend {
     }
 
     var selection: Selection = .infinite
-    if let selectionString = lintFormatOptions.selection {
-      // TODO: do this when parsing args to catch errors?
-      selection = Selection(json: selectionString)
+    if let offsets = lintFormatOptions.offsets {
+      selection = Selection(offsetPairs: offsets)
     }
-
     let fileToProcess = FileToProcess(
       fileHandle: FileHandle.standardInput,
       url: URL(fileURLWithPath: lintFormatOptions.assumeFilename ?? "<stdin>"),
@@ -179,9 +177,8 @@ class Frontend {
     }
 
     var selection: Selection = .infinite
-    if let selectionString = lintFormatOptions.selection {
-      // TODO: do this when parsing args to catch errors?
-      selection = Selection(json: selectionString)
+    if let offsets = lintFormatOptions.offsets {
+      selection = Selection(offsetPairs: offsets)
     }
     return FileToProcess(
       fileHandle: sourceFile,

Sources/swift-format/Subcommands/LintFormatOptions.swift

@@ -26,16 +26,15 @@ struct LintFormatOptions: ParsableArguments {
       """)
   var configuration: String?
 
-  /// A JSON string containing the selected ranges to process.
+  /// A list of comma-separated "start:end" pairs specifying UTF-8 offsets of the ranges to format.
   ///
   /// If not specified, the whole file will be formatted.
   @Option(
     name: .long,
     help: """
-      A JSON string containing an array of {"offset":<Int>, "length":<Int>} pairs specifying \
-      the source code ranges to format.
+      A list of comma-separated "start:end" pairs specifying UTF-8 offsets of the ranges to format.
       """)
-  var selection: String?
+  var offsets: [Range<Int>]?
 
 
   /// The filename for the source code when reading from standard input, to include in diagnostic
@@ -106,8 +105,8 @@ struct LintFormatOptions: ParsableArguments {
       throw ValidationError("'--assume-filename' is only valid when reading from stdin")
     }
 
-    if selection != nil && paths.count > 1 {
-      throw ValidationError("'--selection' is only valid when processing a single file")
+    if offsets?.isEmpty == false && paths.count > 1 {
+      throw ValidationError("'--offsets' is only valid when processing a single file")
     }
 
     if !paths.isEmpty && !recursive {
@@ -125,3 +124,18 @@ struct LintFormatOptions: ParsableArguments {
     }
   }
 }
+
+extension [Range<Int>] : @retroactive ExpressibleByArgument {
+  public init?(argument: String) {
+    let pairs = argument.components(separatedBy: ",")
+    let ranges: [Range<Int>] = pairs.compactMap {
+      let pair = $0.components(separatedBy: ":")
+      if pair.count == 2, let start = Int(pair[0]), let end = Int(pair[1]), start <= end {
+        return start ..< end
+      } else {
+        return nil
+      }
+    }
+    self = ranges
+  }
+}