More robust fully qualified name resolution

Add a `components` property to MemberAccessExprSyntax that provides all
the base names and the member's name as an array. When resolving
swift-testing Tags check if they start with Tag or Testing.Tag and drop
that from the name.

Author: plemarquand

Sources/SourceKitLSP/Swift/SwiftTestingScanner.swift

@@ -97,10 +97,15 @@ struct TestingAttributeData {
       }.flatMap(\.arguments)
       .compactMap {
           if let stringLiteral = $0.expression.as(StringLiteralExprSyntax.self) {
-              return stringLiteral.representedLiteralValue
+            return stringLiteral.representedLiteralValue
           } else if let memberAccess = $0.expression.as(MemberAccessExprSyntax.self) {
-              let baseName = (memberAccess.baseName.map { "\($0)." } ?? "").replacing(#/Tag\./#, with: "")
-              return "\(baseName)\(memberAccess.declName.baseName.text)"
+            var components = memberAccess.components[...]
+            if components.starts(with: ["Testing", "Tag"]) {
+              components = components.dropFirst(2)
+            } else if components.starts(with: ["Tag"]) {
+              components = components.dropFirst(1)
+            }
+            return components.joined(separator: ".")
           }
           return nil
       }
@@ -336,36 +341,34 @@ fileprivate extension AttributeSyntax {
 }
 
 fileprivate extension MemberAccessExprSyntax {
-  /// The base name of this instance, i.e. the string value of `base` joined
-  /// with any preceding base names.
+  /// The fully-qualified name of this instance (subject to available
+  /// information.)
   ///
-  /// For example, if this instance represents the expression `x.y.z(123)`,
-  /// the value of this property is `"x.y"`. If the value of `base` is `nil`,
-  /// the value of this property is also `nil`.
-  var baseName: String? {
-    if let declReferenceExpr = base?.as(DeclReferenceExprSyntax.self) {
-      return declReferenceExpr.baseName.text
-    } else if let baseMemberAccessExpr = base?.as(MemberAccessExprSyntax.self) {
-      if let baseBaseName = baseMemberAccessExpr.baseName {
-        return "\(baseBaseName).\(baseMemberAccessExpr.declName.baseName.text)"
-      }
-      return baseMemberAccessExpr.declName.baseName.text
-    }
-
-    return nil
+  /// The value of this property are all the components of the based name
+  /// name joined together with `.`.
+  var fullyQualifiedName: String {
+    components.joined(separator: ".")
   }
 
-  /// The fully-qualified name of this instance (subject to available
+  /// The name components of this instance (subject to available
   /// information.)
   ///
-  /// The value of this property is this instance's `baseName` property joined
-  /// with its `name` property. For example, if this instance represents the
-  /// expression `x.y.z(123)`, the value of this property is `"x.y.z"`.
-  var fullyQualifiedName: String {
-    if let baseName {
-      return "\(baseName).\(declName.baseName.text)"
+  /// The value of this property is this base name of this instance,
+  /// i.e. the string value of `base` preceeded with any preceding base names
+  /// and followed by its `name` property.
+  ///
+  /// For example, if this instance represents
+  /// the expression `x.y.z(123)`, the value of this property is
+  /// `["x", "y", "z"]`.
+  var components: [String] {
+    if let declReferenceExpr = base?.as(DeclReferenceExprSyntax.self) {
+      return [declReferenceExpr.baseName.text, declName.baseName.text]
+    } else if let baseMemberAccessExpr = base?.as(MemberAccessExprSyntax.self) {
+      let baseBaseNames = baseMemberAccessExpr.components.dropLast()
+      return baseBaseNames + [baseMemberAccessExpr.declName.baseName.text, declName.baseName.text]
     }
-    return declName.baseName.text
+
+    return [declName.baseName.text]
   }
 }
 

Tests/SourceKitLSPTests/DocumentTestDiscoveryTests.swift

@@ -631,6 +631,61 @@ final class DocumentTestDiscoveryTests: XCTestCase {
     )
   }
 
+  func testSwiftTestingTestWithCustomTags() async throws {
+    let testClient = try await TestSourceKitLSPClient()
+    let uri = DocumentURI.for(.swift)
+
+    let positions = testClient.openDocument(
+      """
+      import Testing
+
+      extension Tag {
+        @Tag static var foo: Self
+        @Tag static var bar: Self
+
+        struct Nested {
+          @Tag static var foo: Tag
+        }
+      }
+
+      1️⃣@Suite(.tags("Suites"))
+      struct MyTests {
+        2️⃣@Test(.tags(.foo, Nested.foo, Testing.Tag.bar))
+        func oneIsTwo() {
+          #expect(1 == 2)
+        }3️⃣
+      }4️⃣
+      """,
+      uri: uri
+    )
+
+    let tests = try await testClient.send(DocumentTestsRequest(textDocument: TextDocumentIdentifier(uri)))
+    XCTAssertEqual(
+      tests,
+      [
+        TestItem(
+          id: "MyTests",
+          label: "MyTests",
+          disabled: false,
+          style: TestStyle.swiftTesting,
+          location: Location(uri: uri, range: positions["1️⃣"]..<positions["4️⃣"]),
+          children: [
+            TestItem(
+              id: "MyTests/oneIsTwo()",
+              label: "oneIsTwo()",
+              disabled: false,
+              style: TestStyle.swiftTesting,
+              location: Location(uri: uri, range: positions["2️⃣"]..<positions["3️⃣"]),
+              children: [],
+              tags: [TestTag(id: "foo"), TestTag(id: "Nested.foo"), TestTag(id: "bar")]
+            )
+          ],
+          tags: [TestTag(id: "Suites")]
+        )
+      ]
+    )
+  }
+
   func testSwiftTestingTestsWithExtension() async throws {
     let testClient = try await TestSourceKitLSPClient()
     let uri = DocumentURI.for(.swift)