Update index store to enum (#3469) (#3493)

motivation: The issue is caused by indexStoreMode: Bool? so it's set to nil when running --help on any subcommand. It can be solved by setting to either true or false, but by choosing either true or false we lose auto which is our default. Using an enum solves the issue of having a nil value by using the case autoIndexStoreand preserves the ability to use auto as our default.

changes: move indexStoreMode to an enum
(cherry picked from commit 09ec01b)

Author: miggs597

Sources/Commands/Options.swift

@@ -246,15 +246,30 @@ public struct SwiftToolOptions: ParsableArguments {
     @Flag(name: [.long, .customLong("disable-automatic-resolution")], help: "Disable automatic resolution if Package.resolved file is out-of-date")
     var forceResolvedVersions: Bool = false
 
-    @Flag(name: .customLong("index-store"), inversion: .prefixedEnableDisable, help: "Enable or disable  indexing-while-building feature")
-    var indexStoreEnable: Bool?
-    
-    /// The mode to use for indexing-while-building feature.
-    var indexStore: BuildParameters.IndexStoreMode {
-        guard let enable = indexStoreEnable else { return .auto }
-        return enable ? .on : .off
+    // @Flag works best when there is a default value present
+    // if true, false aren't enough and a third state is needed
+    // nil should not be the goto. Instead create an enum
+    enum StoreMode: EnumerableFlag {
+        case autoIndexStore
+        case enableIndexStore
+        case disableIndexStore
+        
+        /// The mode to use for indexing-while-building feature.
+        var indexStoreMode: BuildParameters.IndexStoreMode {
+            switch self {
+            case .autoIndexStore:
+                return .auto
+            case .enableIndexStore:
+                return .on
+            case .disableIndexStore:
+                return .off
+            }
+        }
     }
 
+    @Flag(help: "Enable or disable indexing-while-building feature")
+    var indexStoreMode: StoreMode = .autoIndexStore
+
     /// Whether to enable generation of `.swiftinterface`s alongside `.swiftmodule`s.
     @Flag(name: .customLong("enable-parseable-module-interfaces"))
     var shouldEnableParseableModuleInterfaces: Bool = false

Sources/Commands/SwiftTool.swift

@@ -795,7 +795,7 @@ public class SwiftTool {
                 shouldLinkStaticSwiftStdlib: options.shouldLinkStaticSwiftStdlib,
                 sanitizers: options.enabledSanitizers,
                 enableCodeCoverage: options.shouldEnableCodeCoverage,
-                indexStoreMode: options.indexStore,
+                indexStoreMode: options.indexStoreMode.indexStoreMode,
                 enableParseableModuleInterfaces: options.shouldEnableParseableModuleInterfaces,
                 emitSwiftModuleSeparately: options.emitSwiftModuleSeparately,
                 useIntegratedSwiftDriver: options.useIntegratedSwiftDriver,