Withhold diagnostics when fallback arguments are being used (#281)

While fallback arguments are being used (either from the fallback build system or fallback settings from the primary build system), withhold semantic diagnostics from sourcekitd and all diagnostics from clangd. This helps prevent user confusion from spurious errors.

- Also remove the DocumentURI standardization in favor of proper equality + hash checks to work around the %40 --> @ encoding issue seen on CI.

Author: DavidGoldman

Sources/LanguageServerProtocol/SupportTypes/DocumentURI.swift

@@ -12,22 +12,6 @@
 
 import Foundation
 
-/// Standardize the URL.
-///
-/// This normalizes escape sequences in file URLs, like `%40` --> `@`.
-/// But for non-file URLs, has no effect.
-fileprivate func standardize(url: URL) -> URL {
-  guard url.isFileURL else { return url }
-
-  // This has the side-effect of removing trailing slashes from file URLs
-  // on Linux, so we may need to add it back.
-  let standardized = url.standardizedFileURL
-  if url.absoluteString.hasSuffix("/") && !standardized.absoluteString.hasSuffix("/") {
-    return URL(fileURLWithPath: standardized.path, isDirectory: true)
-  }
-  return standardized
-}
-
 public struct DocumentURI: Codable, Hashable {
   /// The URL that store the URIs value
   private let storage: URL
@@ -69,7 +53,7 @@ public struct DocumentURI: Codable, Hashable {
     guard let url = URL(string: string) else {
       fatalError("Failed to construct DocumentURI from '\(string)'")
     }
-    self.init(standardize(url: url))
+    self.init(url)
   }
 
   public init(_ url: URL) {
@@ -81,6 +65,16 @@ public struct DocumentURI: Codable, Hashable {
     self.init(string: try decoder.singleValueContainer().decode(String.self))
   }
 
+  /// Equality check to handle escape sequences in file URLs.
+  public static func == (lhs: DocumentURI, rhs: DocumentURI) -> Bool {
+    return lhs.storage.scheme == rhs.storage.scheme && lhs.pseudoPath == rhs.pseudoPath
+  }
+
+  public func hash(into hasher: inout Hasher) {
+    hasher.combine(self.storage.scheme)
+    hasher.combine(self.pseudoPath)
+  }
+
   public func encode(to encoder: Encoder) throws {
     try storage.absoluteString.encode(to: encoder)
   }

Sources/SKCore/BuildSystemManager.swift

@@ -21,10 +21,12 @@ enum MainFileStatus: Equatable {
   /// Waiting for the `BuildSystem` to return settings.
   case waiting
 
-  /// No response from `BuildSystem` yet, using fallback arguments.
+  /// No response from `BuildSystem` yet, using arguments from the fallback build system.
   case waitingUsingFallback(FileBuildSettings)
 
-  /// `BuildSystem` didn't handle the file, using fallback arguments.
+  /// Two cases here:
+  /// - Primary build system gave us fallback arguments to use.
+  /// - Primary build system didn't handle the file, using arguments from the fallback build system.
   /// No longer waiting.
   case fallback(FileBuildSettings)
 
@@ -64,8 +66,8 @@ extension MainFileStatus {
     switch self {
     case .waiting: return nil
     case .unsupported: return .removedOrUnavailable
-    case .waitingUsingFallback(let settings): return .modified(settings)
-    case .fallback(let settings): return .modified(settings)
+    case .waitingUsingFallback(let settings): return .fallback(settings)
+    case .fallback(let settings): return .fallback(settings)
     case .primary(let settings): return .modified(settings)
     }
   }
@@ -194,7 +196,7 @@ extension BuildSystemManager: BuildSystem {
       // Only have a fallback build system. We consider it be a primary build
       // system that functions synchronously.
       if let settings = fallback.settings(for: mainFile, language) {
-        newStatus = .fallback(settings)
+        newStatus = .primary(settings)
       } else {
         newStatus = .unsupported
       }
@@ -331,7 +333,7 @@ extension BuildSystemManager: BuildSystemDelegate {
         let newStatus: MainFileStatus
 
         if let newSettings = settingsChange.newSettings {
-          newStatus = .primary(newSettings)
+          newStatus = settingsChange.isFallback ? .fallback(newSettings) : .primary(newSettings)
         } else if let fallback = self.fallbackBuildSystem {
           // FIXME: we need to stop threading the language everywhere, or we need the build system
           // itself to pass it in here. Or alteratively cache the fallback settings/language earlier?

Sources/SKCore/FileBuildSettingsChange.swift

@@ -16,8 +16,11 @@ public enum FileBuildSettingsChange {
   /// The `BuildSystem` has no `FileBuildSettings` for the file.
   case removedOrUnavailable
 
-  /// The `FileBuildSettings` have been modified.
+  /// The `FileBuildSettings` have been modified or are newly available.
   case modified(FileBuildSettings)
+
+  /// The `BuildSystem` is providing fallback arguments which may not be correct.
+  case fallback(FileBuildSettings)
 }
 
 extension FileBuildSettingsChange {
@@ -27,12 +30,26 @@ extension FileBuildSettingsChange {
       return nil
     case .modified(let settings):
       return settings
+    case .fallback(let settings):
+      return settings
+    }
+  }
+
+  /// Whether the change represents fallback arguments.
+  public var isFallback: Bool {
+    switch self {
+    case .removedOrUnavailable:
+      return false
+    case .modified(_):
+      return false
+    case .fallback(_):
+      return true
     }
   }
 
-  public init(_ settings: FileBuildSettings?) {
+  public init(_ settings: FileBuildSettings?, fallback: Bool = false) {
     if let settings = settings {
-      self = .modified(settings)
+      self = fallback ? .fallback(settings) : .modified(settings)
     } else {
       self = .removedOrUnavailable
     }