Fix duplicate diagnostics caused by DidChange handler (#1079)

Author: TylerLeonhardt

src/PowerShellEditorServices/Services/TextDocument/Handlers/TextDocumentHandler.cs

@@ -4,7 +4,6 @@
 //
 
 using System;
-using System.Collections.Generic;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.Extensions.Logging;
@@ -52,23 +51,19 @@ public TextDocumentHandler(
 
         public Task<Unit> Handle(DidChangeTextDocumentParams notification, CancellationToken token)
         {
-            List<ScriptFile> changedFiles = new List<ScriptFile>();
+            ScriptFile changedFile = _workspaceService.GetFile(notification.TextDocument.Uri.ToString());
 
             // A text change notification can batch multiple change requests
             foreach (TextDocumentContentChangeEvent textChange in notification.ContentChanges)
             {
-                ScriptFile changedFile = _workspaceService.GetFile(notification.TextDocument.Uri.ToString());
-
                 changedFile.ApplyChange(
                     GetFileChangeDetails(
                         textChange.Range,
                         textChange.Text));
-
-                changedFiles.Add(changedFile);
             }
 
             // TODO: Get all recently edited files in the workspace
-            _analysisService.RunScriptDiagnosticsAsync(changedFiles.ToArray());
+            _analysisService.RunScriptDiagnosticsAsync(new ScriptFile[] { changedFile });
             return Unit.Task;
         }
 

test/PowerShellEditorServices.Test.E2E/LanguageServerProtocolMessageTests.cs

@@ -145,6 +145,43 @@ public async Task CanReceiveDiagnosticsFromFileOpen()
             Assert.Equal("PSUseDeclaredVarsMoreThanAssignments", diagnostic.Code);
         }
 
+        [Fact]
+        public async Task CanReceiveDiagnosticsFromFileChanged()
+        {
+            string filePath = NewTestFile("$a = 4");
+            await WaitForDiagnostics();
+            Diagnostics.Clear();
+
+            LanguageClient.SendNotification("textDocument/didChange", new DidChangeTextDocumentParams
+            {
+                // Include several content changes to test against duplicate Diagnostics showing up.
+                ContentChanges = new Container<TextDocumentContentChangeEvent>(new []
+                {
+                    new TextDocumentContentChangeEvent
+                    {
+                        Text = "$a = 5"
+                    },
+                    new TextDocumentContentChangeEvent
+                    {
+                        Text = "$a = 6"
+                    },
+                    new TextDocumentContentChangeEvent
+                    {
+                        Text = "$a = 7"
+                    }
+                }),
+                TextDocument = new VersionedTextDocumentIdentifier
+                {
+                    Version = 4,
+                    Uri = new Uri(filePath)
+                }
+            });
+
+            await WaitForDiagnostics();
+            Diagnostic diagnostic = Assert.Single(Diagnostics);
+            Assert.Equal("PSUseDeclaredVarsMoreThanAssignments", diagnostic.Code);
+        }
+
         [Fact]
         public async Task CanReceiveDiagnosticsFromConfigurationChange()
         {