Remove unused enum, and replace with a bool

(and clean up a teeny tiny bit)

Author: davidwengier

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/ProjectSystem/ProjectDifference.cs

@@ -1,7 +1,6 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the MIT license. See License.txt in the project root for license information.
 
-using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.IO;
@@ -20,11 +19,6 @@ namespace Microsoft.CodeAnalysis.Razor.ProjectSystem;
 // Internal tracker for DefaultProjectSnapshot
 internal class ProjectState
 {
-    private const ProjectDifference ClearDocumentCollectionVersionMask =
-        ProjectDifference.ConfigurationChanged |
-        ProjectDifference.DocumentAdded |
-        ProjectDifference.DocumentRemoved;
-
     private static readonly ImmutableDictionary<string, DocumentState> s_emptyDocuments = ImmutableDictionary.Create<string, DocumentState>(FilePathNormalizingComparer.Instance);
     private static readonly ImmutableDictionary<string, ImmutableArray<string>> s_emptyImportsToRelatedDocuments = ImmutableDictionary.Create<string, ImmutableArray<string>>(FilePathNormalizingComparer.Instance);
     private readonly object _lock;
@@ -63,7 +57,7 @@ private ProjectState(
 
     private ProjectState(
         ProjectState older,
-        ProjectDifference difference,
+        bool numberOfDocumentsMayHaveChanged,
         HostProject hostProject,
         ProjectWorkspaceState projectWorkspaceState,
         ImmutableDictionary<string, DocumentState> documents,
@@ -80,14 +74,14 @@ private ProjectState(
 
         _lock = new object();
 
-        if ((difference & ClearDocumentCollectionVersionMask) == 0)
+        if (numberOfDocumentsMayHaveChanged)
         {
-            // Document collection hasn't changed
-            DocumentCollectionVersion = older.DocumentCollectionVersion;
+            DocumentCollectionVersion = Version;
         }
         else
         {
-            DocumentCollectionVersion = Version;
+            // Document collection hasn't changed
+            DocumentCollectionVersion = older.DocumentCollectionVersion;
         }
 
         if (older._projectEngine != null &&
@@ -179,16 +173,6 @@ RazorProjectEngine CreateProjectEngine()
 
     public ProjectState WithAddedHostDocument(HostDocument hostDocument, TextLoader loader)
     {
-        if (hostDocument is null)
-        {
-            throw new ArgumentNullException(nameof(hostDocument));
-        }
-
-        if (loader is null)
-        {
-            throw new ArgumentNullException(nameof(loader));
-        }
-
         // Ignore attempts to 'add' a document with different data, we only
         // care about one, so it might as well be the one we have.
         if (Documents.ContainsKey(hostDocument.FilePath))
@@ -212,17 +196,12 @@ public ProjectState WithAddedHostDocument(HostDocument hostDocument, TextLoader
             }
         }
 
-        var state = new ProjectState(this, ProjectDifference.DocumentAdded, HostProject, ProjectWorkspaceState, documents, importsToRelatedDocuments);
+        var state = new ProjectState(this, numberOfDocumentsMayHaveChanged: true, HostProject, ProjectWorkspaceState, documents, importsToRelatedDocuments);
         return state;
     }
 
     public ProjectState WithRemovedHostDocument(HostDocument hostDocument)
     {
-        if (hostDocument is null)
-        {
-            throw new ArgumentNullException(nameof(hostDocument));
-        }
-
         if (!Documents.ContainsKey(hostDocument.FilePath))
         {
             return this;
@@ -244,17 +223,12 @@ public ProjectState WithRemovedHostDocument(HostDocument hostDocument)
         var importTargetPaths = GetImportDocumentTargetPaths(hostDocument);
         var importsToRelatedDocuments = RemoveFromImportsToRelatedDocuments(ImportsToRelatedDocuments, hostDocument, importTargetPaths);
 
-        var state = new ProjectState(this, ProjectDifference.DocumentRemoved, HostProject, ProjectWorkspaceState, documents, importsToRelatedDocuments);
+        var state = new ProjectState(this, numberOfDocumentsMayHaveChanged: true, HostProject, ProjectWorkspaceState, documents, importsToRelatedDocuments);
         return state;
     }
 
     public ProjectState WithChangedHostDocument(HostDocument hostDocument, SourceText sourceText, VersionStamp textVersion)
     {
-        if (hostDocument is null)
-        {
-            throw new ArgumentNullException(nameof(hostDocument));
-        }
-
         if (!Documents.TryGetValue(hostDocument.FilePath, out var document))
         {
             return this;
@@ -270,17 +244,12 @@ public ProjectState WithChangedHostDocument(HostDocument hostDocument, SourceTex
             }
         }
 
-        var state = new ProjectState(this, ProjectDifference.DocumentChanged, HostProject, ProjectWorkspaceState, documents, ImportsToRelatedDocuments);
+        var state = new ProjectState(this, numberOfDocumentsMayHaveChanged: false, HostProject, ProjectWorkspaceState, documents, ImportsToRelatedDocuments);
         return state;
     }
 
     public ProjectState WithChangedHostDocument(HostDocument hostDocument, TextLoader loader)
     {
-        if (hostDocument is null)
-        {
-            throw new ArgumentNullException(nameof(hostDocument));
-        }
-
         if (!Documents.TryGetValue(hostDocument.FilePath, out var document))
         {
             return this;
@@ -296,7 +265,7 @@ public ProjectState WithChangedHostDocument(HostDocument hostDocument, TextLoade
             }
         }
 
-        var state = new ProjectState(this, ProjectDifference.DocumentChanged, HostProject, ProjectWorkspaceState, documents, ImportsToRelatedDocuments);
+        var state = new ProjectState(this, numberOfDocumentsMayHaveChanged: false, HostProject, ProjectWorkspaceState, documents, ImportsToRelatedDocuments);
         return state;
     }
 
@@ -320,7 +289,7 @@ public ProjectState WithHostProjectAndWorkspaceState(HostProject hostProject, Pr
             importsToRelatedDocuments = AddToImportsToRelatedDocuments(importsToRelatedDocuments, document.Value.HostDocument.FilePath, importTargetPaths);
         }
 
-        var state = new ProjectState(this, ProjectDifference.ConfigurationChanged, hostProject, projectWorkspaceState, documents, importsToRelatedDocuments);
+        var state = new ProjectState(this, numberOfDocumentsMayHaveChanged: true, hostProject, projectWorkspaceState, documents, importsToRelatedDocuments);
         return state;
     }
 
@@ -333,7 +302,7 @@ internal static ImmutableDictionary<string, ImmutableArray<string>> AddToImports
         {
             if (!importsToRelatedDocuments.TryGetValue(importTargetPath, out var relatedDocuments))
             {
-                relatedDocuments = ImmutableArray.Create<string>();
+                relatedDocuments = [];
             }
 
             relatedDocuments = relatedDocuments.Add(documentFilePath);