Update BSP connection build server config lookup path

Resolves #1695

Adopt `<workspace_root>/.bsp` search locations in addition to
`<workspace_root>/`.

Author: Rajveer100

Sources/BuildSystemIntegration/ExternalBuildSystemAdapter.swift

@@ -52,6 +52,10 @@ struct ExecutableNotFoundError: Error {
   let executableName: String
 }
 
+enum BuildServerNotFoundError: Error {
+  case fileNotFound
+}
+
 private struct BuildServerConfig: Codable {
   /// The name of the build tool.
   let name: String
@@ -142,7 +146,10 @@ actor ExternalBuildSystemAdapter {
 
   /// Create a new JSONRPCConnection to the build server.
   private func createConnectionToBspServer() async throws -> JSONRPCConnection {
-    let configPath = projectRoot.appending(component: "buildServer.json")
+    guard let configPath = getConfigPath() else {
+      throw BuildServerNotFoundError.fileNotFound
+    }
+
     let serverConfig = try BuildServerConfig.load(from: configPath)
     var serverPath = try AbsolutePath(validating: serverConfig.argv[0], relativeTo: projectRoot)
     var serverArgs = Array(serverConfig.argv[1...])
@@ -178,6 +185,48 @@ actor ExternalBuildSystemAdapter {
     ).connection
   }
 
+  private func getConfigPath() -> AbsolutePath? {
+    var buildServerConfigLocations: [AbsolutePath?] = []
+
+    let workspacePath = projectRoot.appending(component: ".bsp")
+    buildServerConfigLocations.append(workspacePath)
+
+    #if os(Windows)
+    let localAppDataPath = AbsolutePath(validatingOrNil: ProcessInfo.processInfo.environment["LOCALAPPDATA"])
+    let programDataPath = AbsolutePath(validatingOrNil: ProcessInfo.processInfo.environment["PROGRAMDATA"])
+
+    buildServerConfigLocations.append(contentsOf: [localAppDataPath, programDataPath])
+    #else
+    let xdgDataHomePath = AbsolutePath(validatingOrNil: ProcessInfo.processInfo.environment["XDG_DATA_HOME"])
+    let xdgDataDirsPath = AbsolutePath(validatingOrNil: ProcessInfo.processInfo.environment["XDG_DATA_DIRS"])
+
+    buildServerConfigLocations.append(contentsOf: [xdgDataHomePath, xdgDataDirsPath])
+
+    if let libraryUrl = FileManager.default.urls(for: .applicationSupportDirectory, in: .userDomainMask).first {
+      let libraryPath = AbsolutePath(validatingOrNil: libraryUrl.absoluteString)
+      buildServerConfigLocations.append(libraryPath)
+    }
+    #endif
+
+    for buildServerConfigLocation in buildServerConfigLocations {
+      guard let buildServerConfigLocation else {
+        continue
+      }
+      let fileManager = FileManager.default
+      do {
+        let items = try fileManager.contentsOfDirectory(atPath: buildServerConfigLocation.pathString)
+        let jsonFiles = items.filter { $0.hasSuffix(".json") }
+
+        if let configFilePath = jsonFiles.sorted().first {
+          return buildServerConfigLocation.appending(component: configFilePath)
+        }
+      } catch {
+        logger.error("Failed to read build server config file at \(buildServerConfigLocation): \(error)")
+      }
+    }
+    return nil
+  }
+
   /// Restart the BSP server after it has crashed.
   private func handleBspServerCrash() async throws {
     // Set `connectionToBuildServer` to `nil` to indicate that there is currently no BSP server running.

Tests/BuildSystemIntegrationTests/BuildServerBuildSystemTests.swift

@@ -303,4 +303,27 @@ final class BuildServerBuildSystemTests: XCTestCase {
     }
 
   }
+
+  func testBuildServerConfigPath() async throws {
+    let fileManager = FileManager.default
+    let jsonConfig = """
+      {
+        "name": "My Build Tool",
+        "version": "21.3",
+        "bspVersion": "2.0.0",
+        "languages": ["scala", "javascript", "rust"],
+        "argv": ["my-build-tool", "bsp"]
+      }
+    """
+
+    do {
+      let directoryPath = FileManager.default.currentDirectoryPath.appending(".bsp")
+      let filePath = directoryPath.appending("build_config.json")
+
+      try fileManager.createDirectory(atPath: directoryPath, withIntermediateDirectories: true)
+      fileManager.createFile(atPath: filePath, contents: jsonConfig.data(using: .utf8))
+    } catch {
+      print("Error creating directory: \(error.localizedDescription)")
+    }
+  }
 }