Teach ActiveSyntax(Any)Visitor to use configured regions or a build configuration

Rework the implementations of ActiveSyntax(Any)Visitor to allow configured
regions, so that clients can re-use the work of evaluating the build
configuration for later traversals.

As a side effect of this, ActiveSyntax(Any)Visitor are no longer generic
over the type of build configuration, which should make them easier to
use.

Author: DougGregor

Sources/SwiftIfConfig/ActiveSyntaxVisitor.swift

@@ -39,23 +39,30 @@ import SwiftSyntax
 /// All notes visited by this visitor will have the "active" state, i.e.,
 /// `node.isActive(in: configuration)` will have evaluated to `.active`.
 /// When errors occur, they will be recorded in the array of diagnostics.
-open class ActiveSyntaxVisitor<Configuration: BuildConfiguration>: SyntaxVisitor {
-  /// The build configuration, which will be queried for each relevant `#if`.
-  public let configuration: Configuration
+open class ActiveSyntaxVisitor: SyntaxVisitor {
+  /// The abstracted build configuration, which will be queried for each
+  /// relevant `#if`.
+  let activeClauses: ActiveClauseEvaluator
 
   /// The diagnostics accumulated during this walk of active syntax.
   public private(set) var diagnostics: [Diagnostic] = []
 
-  public init(viewMode: SyntaxTreeViewMode, configuration: Configuration) {
-    self.configuration = configuration
+  public init(viewMode: SyntaxTreeViewMode, configuration: some BuildConfiguration) {
+    self.activeClauses = .configuration(configuration)
+    self.diagnostics = activeClauses.priorDiagnostics
+    super.init(viewMode: viewMode)
+  }
+
+  public init(viewMode: SyntaxTreeViewMode, configuredRegions: ConfiguredRegions) {
+    self.activeClauses = .configuredRegions(configuredRegions)
+    self.diagnostics = activeClauses.priorDiagnostics
     super.init(viewMode: viewMode)
   }
 
   open override func visit(_ node: IfConfigDeclSyntax) -> SyntaxVisitorContinueKind {
     // Note: there is a clone of this code in ActiveSyntaxAnyVisitor. If you
     // change one, please also change the other.
-    let (activeClause, localDiagnostics) = node.activeClause(in: configuration)
-    diagnostics.append(contentsOf: localDiagnostics)
+    let activeClause = activeClauses.activeClause(for: node, diagnostics: &diagnostics)
 
     // If there is an active clause, visit it's children.
     if let activeClause, let elements = activeClause.elements {
@@ -93,15 +100,23 @@ open class ActiveSyntaxVisitor<Configuration: BuildConfiguration>: SyntaxVisitor
 /// All notes visited by this visitor will have the "active" state, i.e.,
 /// `node.isActive(in: configuration)` will have evaluated to `.active`.
 /// When errors occur, they will be recorded in the array of diagnostics.
-open class ActiveSyntaxAnyVisitor<Configuration: BuildConfiguration>: SyntaxAnyVisitor {
-  /// The build configuration, which will be queried for each relevant `#if`.
-  public let configuration: Configuration
+open class ActiveSyntaxAnyVisitor: SyntaxAnyVisitor {
+  /// The abstracted build configuration, which will be queried for each
+  /// relevant `#if`.
+  let activeClauses: ActiveClauseEvaluator
 
   /// The diagnostics accumulated during this walk of active syntax.
   public private(set) var diagnostics: [Diagnostic] = []
 
-  public init(viewMode: SyntaxTreeViewMode, configuration: Configuration) {
-    self.configuration = configuration
+  public init(viewMode: SyntaxTreeViewMode, configuration: some BuildConfiguration) {
+    self.activeClauses = .configuration(configuration)
+    self.diagnostics = activeClauses.priorDiagnostics
+    super.init(viewMode: viewMode)
+  }
+
+  public init(viewMode: SyntaxTreeViewMode, configuredRegions: ConfiguredRegions) {
+    self.activeClauses = .configuredRegions(configuredRegions)
+    self.diagnostics = activeClauses.priorDiagnostics
     super.init(viewMode: viewMode)
   }
 
@@ -110,8 +125,7 @@ open class ActiveSyntaxAnyVisitor<Configuration: BuildConfiguration>: SyntaxAnyV
     // change one, please also change the other.
 
     // If there is an active clause, visit it's children.
-    let (activeClause, localDiagnostics) = node.activeClause(in: configuration)
-    diagnostics.append(contentsOf: localDiagnostics)
+    let activeClause = activeClauses.activeClause(for: node, diagnostics: &diagnostics)
 
     if let activeClause, let elements = activeClause.elements {
       walk(elements)

Sources/SwiftIfConfig/SwiftIfConfig.docc/SwiftIfConfig.md

@@ -29,4 +29,5 @@ The `SwiftIfConfig` library provides utilities to determine which syntax nodes a
 * <doc:ActiveSyntaxVisitor> and <doc:ActiveSyntaxAnyVisitor> are visitor types that only visit the syntax nodes that are included ("active") for a given build configuration, implicitly skipping any nodes within inactive `#if` clauses.
 * `SyntaxProtocol.removingInactive(in:)` produces a syntax node that removes all inactive regions (and their corresponding `IfConfigDeclSyntax` nodes) from the given syntax tree, returning a new tree that is free of `#if` conditions.
 * `IfConfigDeclSyntax.activeClause(in:)` determines which of the clauses of an `#if` is active for the given build configuration, returning the active clause.
-* `SyntaxProtocol.configuredRegions(in:)` produces a `ConfiguredRegions` value that can be used to efficiently test whether a given syntax node is in an active, inactive, or unparsed region (via `isActive`).
+* `SyntaxProtocol.configuredRegions(in:)` produces a `ConfiguredRegions` value that can be used to efficiently test whether a given syntax node is in an active, inactive, or unparsed region, remove inactive syntax, or determine the
+    active clause for a given `#if`. Use `ConfiguredRegions` for repeated queries.

Tests/SwiftIfConfigTest/VisitorTests.swift

@@ -23,26 +23,49 @@ import _SwiftSyntaxTestSupport
 ///
 /// This cross-checks the visitor itself with the `SyntaxProtocol.isActive(in:)`
 /// API.
-class AllActiveVisitor: ActiveSyntaxAnyVisitor<TestingBuildConfiguration> {
-  init(configuration: TestingBuildConfiguration) {
-    super.init(viewMode: .sourceAccurate, configuration: configuration)
+class AllActiveVisitor: ActiveSyntaxAnyVisitor {
+  let configuration: TestingBuildConfiguration
+
+  init(
+    configuration: TestingBuildConfiguration,
+    configuredRegions: ConfiguredRegions? = nil
+  ) {
+    self.configuration = configuration
+
+    if let configuredRegions {
+      super.init(viewMode: .sourceAccurate, configuredRegions: configuredRegions)
+    } else {
+      super.init(viewMode: .sourceAccurate, configuration: configuration)
+    }
   }
+
   open override func visitAny(_ node: Syntax) -> SyntaxVisitorContinueKind {
     XCTAssertEqual(node.isActive(in: configuration).state, .active)
     return .visitChildren
   }
 }
 
-class NameCheckingVisitor: ActiveSyntaxAnyVisitor<TestingBuildConfiguration> {
+class NameCheckingVisitor: ActiveSyntaxAnyVisitor {
+  let configuration: TestingBuildConfiguration
+
   /// The set of names we are expected to visit. Any syntax nodes with
   /// names that aren't here will be rejected, and each of the names listed
   /// here must occur exactly once.
   var expectedNames: Set<String>
 
-  init(configuration: TestingBuildConfiguration, expectedNames: Set<String>) {
+  init(
+    configuration: TestingBuildConfiguration,
+    expectedNames: Set<String>,
+    configuredRegions: ConfiguredRegions? = nil
+  ) {
+    self.configuration = configuration
     self.expectedNames = expectedNames
 
-    super.init(viewMode: .sourceAccurate, configuration: configuration)
+    if let configuredRegions {
+      super.init(viewMode: .sourceAccurate, configuredRegions: configuredRegions)
+    } else {
+      super.init(viewMode: .sourceAccurate, configuration: configuration)
+    }
   }
 
   deinit {
@@ -145,32 +168,31 @@ public class VisitorTests: XCTestCase {
 
   func testAnyVisitorVisitsOnlyActive() throws {
     // Make sure that all visited nodes are active nodes.
-    AllActiveVisitor(configuration: linuxBuildConfig).walk(inputSource)
-    AllActiveVisitor(configuration: iosBuildConfig).walk(inputSource)
+    assertVisitedAllActive(linuxBuildConfig)
+    assertVisitedAllActive(iosBuildConfig)
   }
 
   func testVisitsExpectedNodes() throws {
     // Check that the right set of names is visited.
-    NameCheckingVisitor(
-      configuration: linuxBuildConfig,
+    assertVisitedExpectedNames(
+      linuxBuildConfig,
       expectedNames: ["f", "h", "i", "S", "generationCount", "value", "withAvail"]
-    ).walk(inputSource)
+    )
 
-    NameCheckingVisitor(
-      configuration: iosBuildConfig,
+    assertVisitedExpectedNames(
+      iosBuildConfig,
       expectedNames: ["g", "h", "i", "a", "S", "generationCount", "value", "error", "withAvail"]
-    ).walk(inputSource)
+    )
   }
 
   func testVisitorWithErrors() throws {
     var configuration = linuxBuildConfig
     configuration.badAttributes.insert("available")
-    let visitor = NameCheckingVisitor(
-      configuration: configuration,
-      expectedNames: ["f", "h", "i", "S", "generationCount", "value", "notAvail"]
+    assertVisitedExpectedNames(
+      configuration,
+      expectedNames: ["f", "h", "i", "S", "generationCount", "value", "notAvail"],
+      diagnosticCount: 3
     )
-    visitor.walk(inputSource)
-    XCTAssertEqual(visitor.diagnostics.count, 3)
   }
 
   func testRemoveInactive() {
@@ -337,6 +359,44 @@ public class VisitorTests: XCTestCase {
   }
 }
 
+extension VisitorTests {
+  /// Ensure that all visited nodes are active nodes according to the given
+  /// build configuration.
+  fileprivate func assertVisitedAllActive(_ configuration: TestingBuildConfiguration) {
+    AllActiveVisitor(configuration: configuration).walk(inputSource)
+
+    let configuredRegions = inputSource.configuredRegions(in: configuration)
+    AllActiveVisitor(
+      configuration: configuration,
+      configuredRegions: configuredRegions
+    ).walk(inputSource)
+  }
+
+  /// Ensure that we visit nodes with the set of names we were expecting to
+  /// visit.
+  fileprivate func assertVisitedExpectedNames(
+    _ configuration: TestingBuildConfiguration,
+    expectedNames: Set<String>,
+    diagnosticCount: Int = 0
+  ) {
+    let firstVisitor = NameCheckingVisitor(
+      configuration: configuration,
+      expectedNames: expectedNames
+    )
+    firstVisitor.walk(inputSource)
+    XCTAssertEqual(firstVisitor.diagnostics.count, diagnosticCount)
+
+    let configuredRegions = inputSource.configuredRegions(in: configuration)
+    let secondVisitor = NameCheckingVisitor(
+      configuration: configuration,
+      expectedNames: expectedNames,
+      configuredRegions: configuredRegions
+    )
+    secondVisitor.walk(inputSource)
+    XCTAssertEqual(secondVisitor.diagnostics.count, diagnosticCount)
+  }
+}
+
 /// Assert that removing any inactive code according to the given build
 /// configuration returns the expected source and diagnostics.
 fileprivate func assertRemoveInactive(