Support obtaining captures by name on AnyRegexOutput (#300)

Resolves #266.

Author: rxwei

Sources/_StringProcessing/ByteCodeGen.swift

@@ -587,11 +587,11 @@ extension Compiler.ByteCodeGen {
         try emitConcatenationComponent(child)
       }
 
-    case let .capture(_, refId, child):
+    case let .capture(name, refId, child):
       options.beginScope()
       defer { options.endScope() }
 
-      let cap = builder.makeCapture(id: refId)
+      let cap = builder.makeCapture(id: refId, name: name)
       switch child {
       case let .matcher(_, m):
         emitMatcher(m, into: cap)

Sources/_StringProcessing/Engine/MEBuilder.swift

@@ -45,6 +45,7 @@ extension MEProgram where Input.Element: Hashable {
     // Symbolic reference resolution
     var unresolvedReferences: [ReferenceID: [InstructionAddress]] = [:]
     var referencedCaptureOffsets: [ReferenceID: Int] = [:]
+    var namedCaptureOffsets: [String: Int] = [:]
     var captureCount: Int {
       // We currently deduce the capture count from the capture register number.
       nextCaptureRegister.rawValue
@@ -353,7 +354,8 @@ extension MEProgram.Builder {
       staticMatcherFunctions: matcherFunctions,
       registerInfo: regInfo,
       captureStructure: captureStructure,
-      referencedCaptureOffsets: referencedCaptureOffsets)
+      referencedCaptureOffsets: referencedCaptureOffsets,
+      namedCaptureOffsets: namedCaptureOffsets)
   }
 
   mutating func reset() { self = Self() }
@@ -438,14 +440,20 @@ fileprivate extension MEProgram.Builder {
 
 // Register helpers
 extension MEProgram.Builder {
-  mutating func makeCapture(id: ReferenceID?) -> CaptureRegister {
+  mutating func makeCapture(
+    id: ReferenceID?, name: String?
+  ) -> CaptureRegister {
     defer { nextCaptureRegister.rawValue += 1 }
     // Register the capture for later lookup via symbolic references.
     if let id = id {
       let preexistingValue = referencedCaptureOffsets.updateValue(
         captureCount, forKey: id)
       assert(preexistingValue == nil)
     }
+    if let name = name {
+      // TODO: Reject duplicate capture names unless `(?J)`?
+      namedCaptureOffsets.updateValue(captureCount, forKey: name)
+    }
     return nextCaptureRegister
   }
 

Sources/_StringProcessing/Engine/MECapture.swift

@@ -145,6 +145,7 @@ extension Processor._StoredCapture: CustomStringConvertible {
 struct CaptureList {
   var values: Array<Processor<String>._StoredCapture>
   var referencedCaptureOffsets: [ReferenceID: Int]
+  var namedCaptureOffsets: [String: Int]
 
 //  func extract(from s: String) -> Array<Array<Substring>> {
 //    caps.map { $0.map { s[$0] }  }

Sources/_StringProcessing/Engine/MEProgram.swift

@@ -36,6 +36,7 @@ struct MEProgram<Input: Collection> where Input.Element: Equatable {
 
   let captureStructure: CaptureStructure
   let referencedCaptureOffsets: [ReferenceID: Int]
+  let namedCaptureOffsets: [String: Int]
 }
 
 extension MEProgram: CustomStringConvertible {

Sources/_StringProcessing/Executor.swift

@@ -37,7 +37,8 @@ struct Executor {
 
     let capList = CaptureList(
       values: cpu.storedCaptures,
-      referencedCaptureOffsets: engine.program.referencedCaptureOffsets)
+      referencedCaptureOffsets: engine.program.referencedCaptureOffsets,
+      namedCaptureOffsets: engine.program.namedCaptureOffsets)
 
     let capStruct = engine.program.captureStructure
     let range = inputRange.lowerBound..<endIdx
@@ -62,6 +63,7 @@ struct Executor {
       range: range,
       rawCaptures: caps,
       referencedCaptureOffsets: capList.referencedCaptureOffsets,
+      namedCaptureOffsets: capList.namedCaptureOffsets,
       value: value)
   }
 

Sources/_StringProcessing/Regex/AnyRegexOutput.swift

@@ -38,12 +38,17 @@ extension Regex.Match where Output == AnyRegexOutput {
   ) -> Substring {
     input[range]
   }
+
+  public subscript(name: String) -> AnyRegexOutput.Element? {
+    namedCaptureOffsets[name].map { self[$0 + 1] }
+  }
 }
 
 /// A type-erased regex output
 @available(SwiftStdlib 5.7, *)
 public struct AnyRegexOutput {
   let input: String
+  let namedCaptureOffsets: [String: Int]
   fileprivate let _elements: [ElementRepresentation]
 
   /// The underlying representation of the element of a type-erased regex
@@ -94,9 +99,12 @@ extension AnyRegexOutput {
 @available(SwiftStdlib 5.7, *)
 extension AnyRegexOutput {
   internal init<C: Collection>(
-    input: String, elements: C
+    input: String, namedCaptureOffsets: [String: Int], elements: C
   ) where C.Element == StructuredCapture {
-    self.init(input: input, _elements: elements.map(ElementRepresentation.init))
+    self.init(
+      input: input,
+      namedCaptureOffsets: namedCaptureOffsets,
+      _elements: elements.map(ElementRepresentation.init))
   }
 }
 
@@ -170,6 +178,13 @@ extension AnyRegexOutput: RandomAccessCollection {
   }
 }
 
+@available(SwiftStdlib 5.7, *)
+extension AnyRegexOutput {
+  public subscript(name: String) -> Element? {
+    namedCaptureOffsets[name].map { self[$0 + 1] }
+  }
+}
+
 @available(SwiftStdlib 5.7, *)
 extension Regex.Match where Output == AnyRegexOutput {
   /// Creates a type-erased regex match from an existing match.

Sources/_StringProcessing/Regex/Match.swift

@@ -26,6 +26,8 @@ extension Regex {
 
     let referencedCaptureOffsets: [ReferenceID: Int]
 
+    let namedCaptureOffsets: [String: Int]
+
     let value: Any?
   }
 }
@@ -40,6 +42,7 @@ extension Regex.Match {
         storedCapture: StoredCapture(range: range, value: nil))
       let output = AnyRegexOutput(
         input: input,
+        namedCaptureOffsets: namedCaptureOffsets,
         elements: [wholeMatchAsCapture] + rawCaptures)
       return output as! Output
     } else if Output.self == Substring.self {

Tests/RegexBuilderTests/RegexDSLTests.swift

@@ -689,7 +689,9 @@ class RegexDSLTests: XCTestCase {
     }
     do {
       let regex = try Regex(
-        compiling: #"([0-9A-F]+)(?:\.\.([0-9A-F]+))?\s+;\s+(\w+).*"#)
+        compiling: #"""
+          (?<lower>[0-9A-F]+)(?:\.\.(?<upper>[0-9A-F]+))?\s+;\s+(?<desc>\w+).*
+          """#)
       let line = """
         A6F0..A6F1    ; Extend # Mn   [2] BAMUM COMBINING MARK KOQNDON..BAMUM \
         COMBINING MARK TUKWENTIS
@@ -699,13 +701,16 @@ class RegexDSLTests: XCTestCase {
       let output = match.output
       XCTAssertEqual(output[0].substring, line[...])
       XCTAssertTrue(output[1].substring == "A6F0")
+      XCTAssertTrue(output["lower"]?.substring == "A6F0")
       XCTAssertTrue(output[2].substring == "A6F1")
+      XCTAssertTrue(output["upper"]?.substring == "A6F1")
       XCTAssertTrue(output[3].substring == "Extend")
+      XCTAssertTrue(output["desc"]?.substring == "Extend")
       let typedOutput = try XCTUnwrap(output.as(
-        (Substring, Substring, Substring?, Substring).self))
+        (Substring, lower: Substring, upper: Substring?, Substring).self))
       XCTAssertEqual(typedOutput.0, line[...])
-      XCTAssertTrue(typedOutput.1 == "A6F0")
-      XCTAssertTrue(typedOutput.2 == "A6F1")
+      XCTAssertTrue(typedOutput.lower == "A6F0")
+      XCTAssertTrue(typedOutput.upper == "A6F1")
       XCTAssertTrue(typedOutput.3 == "Extend")
     }
   }