Add options support to the compiler (#112)

MatchingOptions provides an interface for the compiler
to manage group-scoped matching options, to apply matching
option sequences from the AST, and to query when building
out matching behavior.

Includes support and tests for the `s` and `u` option flags.

Sources/_MatchingEngine/Regex/AST/MatchingOptions.swift

@@ -36,6 +36,11 @@ extension AST {
       // be unset, only flipped between)
       case textSegmentGraphemeMode  // y{g}
       case textSegmentWordMode      // y{w}
+
+      // Swift semantic matching level
+      case graphemeClusterSemantics // X
+      case unicodeScalarSemantics   // u
+      case byteSemantics            // b
     }
     public var kind: Kind
     public var location: SourceLocation
@@ -53,6 +58,15 @@ extension AST {
         return false
       }
     }
+
+    public var isSemanticMatchingLevel: Bool {
+      switch kind {
+      case .graphemeClusterSemantics, .unicodeScalarSemantics, .byteSemantics:
+        return true
+      default:
+        return false
+      }
+    }
   }
 
   /// A sequence of matching options written in source.

Sources/_MatchingEngine/Regex/Parse/Diagnostics.swift

@@ -65,6 +65,7 @@ enum ParseError: Error, Hashable {
   case identifierCannotStartWithNumber(IdentifierKind)
 
   case cannotRemoveTextSegmentOptions
+  case cannotRemoveSemanticsOptions
   case expectedCalloutArgument
 }
 
@@ -145,6 +146,8 @@ extension ParseError: CustomStringConvertible {
       return "\(i.diagDescription) must not start with number"
     case .cannotRemoveTextSegmentOptions:
       return "text segment mode cannot be unset, only changed"
+    case .cannotRemoveSemanticsOptions:
+      return "semantic level cannot be unset, only changed"
     case .expectedCalloutArgument:
       return "expected argument to callout"
     }

Sources/_MatchingEngine/Regex/Parse/LexicalAnalysis.swift

@@ -574,6 +574,11 @@ extension Source {
         try src.expect("}")
         return opt
 
+      // Swift semantic level options
+      case "X": return advanceAndReturn(.graphemeClusterSemantics)
+      case "u": return advanceAndReturn(.unicodeScalarSemantics)
+      case "b": return advanceAndReturn(.byteSemantics)
+
       default:
         return nil
       }
@@ -618,6 +623,10 @@ extension Source {
         if opt.isTextSegmentMode {
           throw ParseError.cannotRemoveTextSegmentOptions
         }
+        // Matching semantics options can only be added, not removed.
+        if opt.isSemanticMatchingLevel {
+          throw ParseError.cannotRemoveSemanticsOptions
+        }
         removing.append(opt)
       }
       return .init(caretLoc: nil, adding: adding, minusLoc: ateMinus.location,

Sources/_StringProcessing/CharacterClass.swift

@@ -338,12 +338,19 @@ extension AST.Atom {
     switch kind {
     case let .escaped(b): return b.characterClass
 
-    case .any: return .any
-
     case .property:
       // TODO: Would our model type for character classes include
       // this? Or does grapheme-semantic mode complicate that?
       return nil
+
+    case .any:
+      // `.any` is handled in the matching engine by Compiler.emitAny() and in
+      // the legacy compiler by the `.any` instruction, which can provide lower
+      // level instructions than the CharacterClass-generated consumer closure
+      //
+      // FIXME: We shouldn't be returning `nil` here, but instead fixing the call
+      // site to check for any before trying to construct a character class.
+      return nil
 
     default: return nil
 

Sources/_StringProcessing/Compiler.swift

@@ -18,18 +18,13 @@ struct RegexProgram {
 
 class Compiler {
   let ast: AST
-  let matchLevel: CharacterClass.MatchLevel
-  let options: REOptions
+  private var options = MatchingOptions()
   private var builder = RegexProgram.Program.Builder()
 
   init(
-    ast: AST,
-    matchLevel: CharacterClass.MatchLevel = .graphemeCluster,
-    options: REOptions = []
+    ast: AST
   ) {
     self.ast = ast
-    self.matchLevel = matchLevel
-    self.options = options
   }
 
   __consuming func emit() throws -> RegexProgram {
@@ -42,11 +37,9 @@ class Compiler {
   func emit(_ node: AST.Node) throws {
 
     switch node {
-    // Any: .
-    //     consume 1
-    case .atom(let a) where a.kind == .any && matchLevel == .graphemeCluster:
-      builder.buildAdvance(1)
-
+    case .atom(let a) where a.kind == .any:
+      try emitAny()
+
     // Single characters we just match
     case .atom(let a) where a.singleCharacter != nil :
       builder.buildMatch(a.singleCharacter!)
@@ -97,6 +90,9 @@ class Compiler {
       throw unsupported(node.renderAsCanonical())
 
     case .group(let g):
+      options.beginScope()
+      defer { options.endScope() }
+
       if let lookaround = g.lookaroundKind {
         try emitLookaround(lookaround, g.child)
         return
@@ -113,6 +109,10 @@ class Compiler {
         try emit(g.child)
         builder.buildEndCapture(cap)
 
+      case .changeMatchingOptions(let optionSequence, _):
+        options.apply(optionSequence)
+        try emit(g.child)
+
       default:
         // FIXME: Other kinds...
         try emit(g.child)
@@ -124,8 +124,8 @@ class Compiler {
     // For now, we model sets and atoms as consumers.
     // This lets us rapidly expand support, and we can better
     // design the actual instruction set with real examples
-    case _ where try node.generateConsumer(matchLevel) != nil:
-      try builder.buildConsume(by: node.generateConsumer(matchLevel)!)
+    case _ where try node.generateConsumer(options) != nil:
+      try builder.buildConsume(by: node.generateConsumer(options)!)
 
     case .quote(let q):
       // We stick quoted content into read-only constant strings
@@ -158,6 +158,31 @@ class Compiler {
       throw unsupported(node.renderAsCanonical())
     }
   }
+
+  func emitAny() throws {
+    switch (options.semanticLevel, options.dotMatchesNewline) {
+    case (.graphemeCluster, true):
+      builder.buildAdvance(1)
+    case (.graphemeCluster, false):
+      builder.buildConsume { input, bounds in
+        input[bounds.lowerBound].isNewline
+          ? nil
+          : input.index(after: bounds.lowerBound)
+      }
+
+    case (.unicodeScalar, true):
+      // TODO: builder.buildAdvanceUnicodeScalar(1)
+      builder.buildConsume { input, bounds in
+        input.unicodeScalars.index(after: bounds.lowerBound)
+      }
+    case (.unicodeScalar, false):
+      builder.buildConsume { input, bounds in
+        input[bounds.lowerBound].isNewline
+          ? nil
+          : input.unicodeScalars.index(after: bounds.lowerBound)
+      }
+    }
+  }
 
   func emitAssertion(_ kind: AST.Atom.AssertionKind) throws {
     // FIXME: Depends on API model we have... We may want to
@@ -458,7 +483,18 @@ class Compiler {
 
   func emitQuantification(_ quant: AST.Quantification) throws {
     let child = quant.child
-    let kind = quant.kind.value
+
+    // If in reluctant-by-default mode, eager and reluctant need to be switched.
+    let kind: AST.Quantification.Kind
+    if options.isReluctantByDefault
+        && quant.kind.value != .possessive
+    {
+      kind = quant.kind.value == .eager
+        ? .reluctant
+        : .eager
+    } else {
+      kind = quant.kind.value
+    }
 
     switch quant.amount.value.bounds {
     case (_, atMost: 0):

Sources/_StringProcessing/ConsumerInterface.swift

@@ -28,12 +28,8 @@ func unsupported(
   file: StaticString = #file,
   line: UInt = #line
 ) -> Unsupported {
-  // TODO: how do we not have a public init for this?
-  let fStr = file.withUTF8Buffer {
-    String(decoding: $0, as: UTF8.self)
-  }
   return Unsupported(
-    message: s, file: fStr, line: Int(line))
+    message: s, file: String(describing: file), line: Int(line))
 }
 
 extension AST.Node {
@@ -42,8 +38,7 @@ extension AST.Node {
   /// A consumer is a Swift closure that matches against
   /// the front of an input range
   func generateConsumer(
-    // TODO: Better option modeling
-    _ opts: CharacterClass.MatchLevel
+    _ opts: MatchingOptions
   ) throws -> Program<String>.ConsumeFunction? {
     switch self {
     case .atom(let a):
@@ -77,10 +72,10 @@ extension AST.Atom {
   }
 
   func generateConsumer(
-    _ opts: CharacterClass.MatchLevel
+    _ opts: MatchingOptions
   ) throws -> Program<String>.ConsumeFunction? {
     // TODO: Wean ourselves off of this type...
-    if let cc = self.characterClass?.withMatchLevel(opts) {
+    if let cc = self.characterClass?.withMatchLevel(opts.matchLevel) {
       return { input, bounds in
         // FIXME: should we worry about out of bounds?
         cc.matches(in: input, at: bounds.lowerBound)
@@ -109,10 +104,16 @@ extension AST.Atom {
         // TODO: alias? casing?
         $0.name == name || $0.nameAlias == name
       }
+
+    case .any:
+      fatalError(".atom(.any) is handled in emitAny")
 
+    case .startOfLine, .endOfLine:
+      // handled in emitAssertion
+      return nil
+
     case .escaped, .keyboardControl, .keyboardMeta, .keyboardMetaControl,
-        .any, .startOfLine, .endOfLine,
-        .backreference, .subpattern, .callout, .backtrackingDirective:
+      .backreference, .subpattern, .callout, .backtrackingDirective:
       // FIXME: implement
       return nil
     }
@@ -121,7 +122,7 @@ extension AST.Atom {
 
 extension AST.CustomCharacterClass.Member {
   func generateConsumer(
-    _ opts: CharacterClass.MatchLevel
+    _ opts: MatchingOptions
   ) throws -> Program<String>.ConsumeFunction {
     switch self {
     case .custom(let ccc):
@@ -212,7 +213,7 @@ extension AST.CustomCharacterClass.Member {
 
 extension AST.CustomCharacterClass {
   func generateConsumer(
-    _ opts: CharacterClass.MatchLevel
+    _ opts: MatchingOptions
   ) throws -> Program<String>.ConsumeFunction {
     // NOTE: Easy way to implement, obviously not performant
     let consumers = try members.map {
@@ -265,7 +266,7 @@ private func consumeScalar(
 
 extension AST.Atom.CharacterProperty {
   func generateConsumer(
-    _ opts: CharacterClass.MatchLevel
+    _ opts: MatchingOptions
   ) throws -> Program<String>.ConsumeFunction {
     // Handle inversion for us, albeit not efficiently
     func invert(
@@ -335,7 +336,7 @@ extension AST.Atom.CharacterProperty {
 extension Unicode.BinaryProperty {
   // FIXME: Semantic level, vet for precise defs
   func generateConsumer(
-    _ opts: CharacterClass.MatchLevel
+    _ opts: MatchingOptions
   ) throws -> Program<String>.ConsumeFunction {
     switch self {
 
@@ -499,7 +500,7 @@ extension Unicode.BinaryProperty {
 extension Unicode.POSIXProperty {
   // FIXME: Semantic level, vet for precise defs
   func generateConsumer(
-    _ opts: CharacterClass.MatchLevel
+    _ opts: MatchingOptions
   ) -> Program<String>.ConsumeFunction {
     // FIXME: semantic levels, modes, etc
     switch self {
@@ -545,7 +546,7 @@ extension Unicode.POSIXProperty {
 extension Unicode.ExtendedGeneralCategory {
   // FIXME: Semantic level
   func generateConsumer(
-    _ opts: CharacterClass.MatchLevel
+    _ opts: MatchingOptions
   ) throws -> Program<String>.ConsumeFunction {
     switch self {
     case .letter: