Small improvements for ConfiguredRegions

Add a debugDescription so it's easier to see what the regions are, and allow
us to test for exact results.

Tweak the set of configured regions more precisely so they match what the
compiler is expecting. The only difference here is that we create a separate
region for an active block within another active block.

Author: DougGregor

Sources/SwiftIfConfig/ConfiguredRegions.swift

@@ -51,9 +51,7 @@ public struct ConfiguredRegions {
         return currentState
       }
 
-      let ifRegionStart =
-        ifClause.condition?.endPosition ?? ifClause.elements?._syntaxNode.position ?? ifClause.poundKeyword.endPosition
-      if node.position >= ifRegionStart && node.position <= ifClause.endPosition {
+      if node.position >= ifClause.regionStart && node.position <= ifClause.endPosition {
         currentState = state
       }
     }
@@ -72,6 +70,33 @@ extension ConfiguredRegions: RandomAccessCollection {
   }
 }
 
+extension ConfiguredRegions: CustomDebugStringConvertible {
+  /// Provides source ranges for each of the configured regions.
+  public var debugDescription: String {
+    guard let firstRegion = first else {
+      return "[]"
+    }
+
+    let root = firstRegion.0.root
+    let converter = SourceLocationConverter(fileName: "", tree: root)
+    let regionDescriptions = regions.map { (ifClause, state) in
+      let startPosition = converter.location(for: ifClause.position)
+      let endPosition = converter.location(for: ifClause.endPosition)
+      return "[\(startPosition.line):\(startPosition.column) - \(endPosition.line):\(endPosition.column)] = \(state)"
+    }
+
+    return "[\(regionDescriptions.joined(separator: ", ")))]"
+  }
+}
+
+extension IfConfigClauseSyntax {
+  /// The effective start of the region after which code is subject to its
+  /// condition.
+  fileprivate var regionStart: AbsolutePosition {
+    condition?.endPosition ?? elements?._syntaxNode.position ?? poundKeyword.endPosition
+  }
+}
+
 extension SyntaxProtocol {
   /// Find all of the #if/#elseif/#else clauses within the given syntax node,
   /// indicating their active state. This operation will recurse into all
@@ -118,6 +143,9 @@ fileprivate class ConfiguredRegionVisitor<Configuration: BuildConfiguration>: Sy
   /// Whether we are currently within an active region.
   var inActiveRegion = true
 
+  /// Whether we are currently within an #if at all.
+  var inAnyIfConfig = false
+
   // All diagnostics encountered along the way.
   var diagnostics: [Diagnostic] = []
 
@@ -127,9 +155,17 @@ fileprivate class ConfiguredRegionVisitor<Configuration: BuildConfiguration>: Sy
   }
 
   override func visit(_ node: IfConfigDeclSyntax) -> SyntaxVisitorContinueKind {
+    // We are in an #if.
+    let priorInAnyIfConfig = inAnyIfConfig
+    inAnyIfConfig = true
+    defer {
+      inAnyIfConfig = priorInAnyIfConfig
+    }
+
     // Walk through the clauses to find the active one.
     var foundActive = false
     var syntaxErrorsAllowed = false
+    let outerState: IfConfigRegionState = inActiveRegion ? .active : .inactive
     for clause in node.clauses {
       let isActive: Bool
       if let condition = clause.condition {
@@ -192,7 +228,11 @@ fileprivate class ConfiguredRegionVisitor<Configuration: BuildConfiguration>: Sy
       case (false, false): currentState = .inactive
       case (false, true): currentState = .unparsed
       }
-      regions.append((clause, currentState))
+
+      // If there is a state change, record it.
+      if !priorInAnyIfConfig || currentState != .inactive || currentState != outerState {
+        regions.append((clause, currentState))
+      }
 
       // If this is a parsed region, recurse into it.
       if currentState != .unparsed, let elements = clause.elements {

Tests/SwiftIfConfigTest/ActiveRegionTests.swift

@@ -79,7 +79,9 @@ public class ActiveRegionTests: XCTestCase {
         "4️⃣": .unparsed,
         "5️⃣": .unparsed,
         "6️⃣": .active,
-      ]
+      ],
+      configuredRegionDescription:
+        "[[1:6 - 3:5] = active, [3:5 - 10:7] = inactive, [5:5 - 7:5] = unparsed, [7:5 - 9:5] = unparsed)]"
     )
   }
 
@@ -127,6 +129,7 @@ fileprivate func assertActiveCode(
   _ markedSource: String,
   configuration: some BuildConfiguration = TestingBuildConfiguration(),
   states: [String: IfConfigRegionState],
+  configuredRegionDescription: String? = nil,
   file: StaticString = #filePath,
   line: UInt = #line
 ) throws {
@@ -152,13 +155,23 @@ fileprivate func assertActiveCode(
     let (actualState, _) = token.isActive(in: configuration)
     XCTAssertEqual(actualState, expectedState, "isActive(in:) at marker \(marker)", file: file, line: line)
 
-    let actualViaRegions = token.isActive(inConfiguredRegions: configuredRegions)
+    let actualViaRegions = configuredRegions.isActive(token)
     XCTAssertEqual(
       actualViaRegions,
       expectedState,
       "isActive(inConfiguredRegions:) at marker \(marker)",
       file: file,
       line: line
     )
+
+    if let configuredRegionDescription {
+      XCTAssertEqual(
+        configuredRegions.debugDescription,
+        configuredRegionDescription,
+        "configured region descsription",
+        file: file,
+        line: line
+      )
+    }
   }
 }

Tests/SwiftIfConfigTest/TestingBuildConfiguration.swift

@@ -54,10 +54,10 @@ struct TestingBuildConfiguration: BuildConfiguration {
   }
 
   func canImport(
-    importPath: [String],
+    importPath: [(TokenSyntax, String)],
     version: CanImportVersion
   ) throws -> Bool {
-    guard let moduleName = importPath.first else {
+    guard let moduleName = importPath.first?.1 else {
       return false
     }