[SwiftWarningControl] Add ability to query warning group behavior including client-specified enclosing control rules

Adds an optional parameter `with enclosingControls: [DiagnosticGroupIdentifier: WarningGroupBehavior] = [:]` to both:
- `SyntaxProtocol.warningGroupControlRegionTree`
- `SyntaxProtocol.warningGroupBehavior`
to specify enclosing global warning group behavior controls which span the entire syntax node.

This mechanism will be used by the compiler to specify global controls over certain diagnostic groups from the compilation configuration. For example, a command-line-specified `-Werror Group` will become an input to this mechanism to be used as *the* behavior control at source positions where no syntactic control (`@warn`) is specified.

With this in place, the `SwiftWarningControl` API can be used as a single query which captures both syntactic and command-line configuration of warning diagnostic group behavior.

Author: artemcm

Sources/SwiftWarningControl/SyntaxProtocol+WarningControl.swift

@@ -18,9 +18,13 @@ extension SyntaxProtocol {
   /// by determining its containing `WarningControlRegion`, if one is present.
   @_spi(ExperimentalLanguageFeatures)
   public func warningGroupBehavior(
-    for diagnosticGroupIdentifier: DiagnosticGroupIdentifier
+    for diagnosticGroupIdentifier: DiagnosticGroupIdentifier,
+    with enclosingControls: [DiagnosticGroupIdentifier: WarningGroupBehavior] = [:]
   ) -> WarningGroupBehavior? {
-    let warningControlRegions = root.warningGroupControlRegionTreeImpl(containing: self.position)
+    let warningControlRegions = root.warningGroupControlRegionTreeImpl(
+      with: enclosingControls,
+      containing: self.position
+    )
     return warningControlRegions.warningGroupBehavior(at: self.position, for: diagnosticGroupIdentifier)
   }
 }

Sources/SwiftWarningControl/WarningControlRegionBuilder.swift

@@ -15,16 +15,22 @@ import SwiftSyntax
 /// Compute the full set of warning control regions in this syntax node
 extension SyntaxProtocol {
   @_spi(ExperimentalLanguageFeatures)
-  public func warningGroupControlRegionTree() -> WarningControlRegionTree {
-    return warningGroupControlRegionTreeImpl()
+  public func warningGroupControlRegionTree(
+    with enclosingControls: [DiagnosticGroupIdentifier: WarningGroupBehavior] = [:]
+  ) -> WarningControlRegionTree {
+    return warningGroupControlRegionTreeImpl(with: enclosingControls)
   }
 
   /// Implementation of constructing a region tree with an optional parameter
   /// to specify that the constructed tree must only contain nodes which contain
   /// a specific absolute position - meant to speed up tree generation for individual
   /// queries.
-  func warningGroupControlRegionTreeImpl(containing position: AbsolutePosition? = nil) -> WarningControlRegionTree {
+  func warningGroupControlRegionTreeImpl(
+    with enclosingControls: [DiagnosticGroupIdentifier: WarningGroupBehavior],
+    containing position: AbsolutePosition? = nil
+  ) -> WarningControlRegionTree {
     let visitor = WarningControlRegionVisitor(self.range, containing: position)
+    visitor.tree.addWarningGroupControls(range: self.range, controls: enclosingControls)
     visitor.walk(self)
     return visitor.tree
   }

Sources/SwiftWarningControl/WarningControlRegions.swift

@@ -104,7 +104,7 @@ public struct DiagnosticGroupIdentifier: Hashable, Sendable, ExpressibleByString
 @_spi(ExperimentalLanguageFeatures)
 public struct WarningControlRegionTree {
   /// Root region representing top-level (file) scope
-  private var rootRegionNode: WarningControlRegionNode
+  var rootRegionNode: WarningControlRegionNode
 
   init(range: Range<AbsolutePosition>) {
     rootRegionNode = WarningControlRegionNode(range: range)
@@ -115,6 +115,7 @@ public struct WarningControlRegionTree {
     range: Range<AbsolutePosition>,
     controls: [DiagnosticGroupIdentifier: WarningGroupBehavior]
   ) {
+    guard !controls.isEmpty else { return }
     let newNode = WarningControlRegionNode(range: range)
     for (diagnosticGroupIdentifier, behavior) in controls {
       newNode.addWarningGroupControl(for: diagnosticGroupIdentifier, behavior: behavior)
@@ -157,7 +158,8 @@ extension WarningControlRegionTree: CustomDebugStringConvertible {
       let spacing = String(repeating: "  ", count: indent)
       result += "\(spacing)[\(node.range.lowerBound), \(node.range.upperBound)]"
       if !node.warningGroupControls.isEmpty {
-        result += " id(s): \(node.warningGroupControls.keys.map { $0.identifier }.joined(separator: ", "))\n"
+        result +=
+          " control(s): \(node.warningGroupControls.map { $0.key.identifier + ":" + $0.value.rawValue }.joined(separator: ", "))\n"
       } else {
         result += "\n"
       }
@@ -185,7 +187,7 @@ extension WarningControlRegionTree {
 
 /// A node in the warning control region tree, representing a collection of warning
 /// group controls and references to its nested child regions.
-private class WarningControlRegionNode {
+class WarningControlRegionNode {
   let range: Range<AbsolutePosition>
   var warningGroupControls: [DiagnosticGroupIdentifier: WarningGroupBehavior] = [:]
   var children: [WarningControlRegionNode] = []

Tests/SwiftWarningControlTest/WarningControlTests.swift

@@ -228,6 +228,57 @@ public class WarningGroupControlTests: XCTestCase {
       ]
     )
   }
+
+  func testEnclosingGlobalControlOverride() throws {
+    // Global control does not override syntactic control
+    try assertWarningGroupControl(
+      """
+      @warn(GroupID, as: error)
+      func foo() {
+        1️⃣let x = 1
+      }
+      """,
+      diagnosticGroupID: "GroupID",
+      states: [
+        "1️⃣": .error
+      ],
+      enclosingControls: ["GroupID": .warning]
+    )
+
+    try assertWarningGroupControl(
+      """
+      func foo() {
+        1️⃣let x = 1
+        @warn(GroupID, as: ignored)
+        func bar() {
+          2️⃣let x = 1
+        }
+      }
+      """,
+      diagnosticGroupID: "GroupID",
+      states: [
+        "1️⃣": .error,
+        "2️⃣": .ignored,
+      ],
+      enclosingControls: ["GroupID": .error]
+    )
+  }
+
+  func testEnclosingGlobalControlOnly() throws {
+    // Global control used in absense of a syntactic control
+    try assertWarningGroupControl(
+      """
+      func foo() {
+        1️⃣let x = 1
+      }
+      """,
+      diagnosticGroupID: "GroupID",
+      states: [
+        "1️⃣": .warning
+      ],
+      enclosingControls: ["GroupID": .warning]
+    )
+  }
 }
 
 /// Assert that the various marked positions in the source code have the
@@ -236,6 +287,7 @@ private func assertWarningGroupControl(
   _ markedSource: String,
   diagnosticGroupID: DiagnosticGroupIdentifier,
   states: [String: WarningGroupBehavior?],
+  enclosingControls: [DiagnosticGroupIdentifier: WarningGroupBehavior] = [:],
   file: StaticString = #filePath,
   line: UInt = #line
 ) throws {
@@ -244,9 +296,6 @@ private func assertWarningGroupControl(
 
   var parser = Parser(source)
   let tree = SourceFileSyntax.parse(from: &parser)
-
-  let warningControlRegions = tree.warningGroupControlRegionTree()
-
   for (marker, location) in markerLocations {
     guard let expectedState = states[marker] else {
       XCTFail("Missing marker \(marker) in expected states", file: file, line: line)
@@ -259,7 +308,12 @@ private func assertWarningGroupControl(
       continue
     }
 
-    let groupBehavior = token.warningGroupBehavior(for: diagnosticGroupID)
+    let warningControlRegions = tree.warningGroupControlRegionTree(with: enclosingControls)
+    print(warningControlRegions)
+    let groupBehavior = token.warningGroupBehavior(
+      for: diagnosticGroupID,
+      with: enclosingControls
+    )
     XCTAssertEqual(groupBehavior, expectedState)
 
     let groupBehaviorViaRegions = warningControlRegions.warningGroupBehavior(