Allow for alternate versions of documents to be semantically highlighted

src/OmniSharp.Abstractions/Models/v2/SemanticHighlight/SemanticHighlightRequest.cs

@@ -7,10 +7,15 @@ namespace OmniSharp.Models.SemanticHighlight
     public class SemanticHighlightRequest : Request
     {
         /// <summary>
-        ///   Specifies the range to highlight.
-        ///   If none is given, highlight the entire
-        ///   file.
+        ///   Specifies the range to highlight. If none is given, highlight the entire file.
         /// </summary>
         public Range Range { get; set; }
+
+        /// <summary>
+        ///   Optionally provide the text for a different version of the document to be highlighted.
+        ///   This property works differently than the Buffer property, since it is only used for
+        ///   highlighting and will not update the document in the CurrentSolution.
+        /// </summary>
+        public string VersionedText { get; set; }
     }
 }

src/OmniSharp.Roslyn.CSharp/Services/SemanticHighlight/SemanticHighlightService.cs

@@ -33,7 +33,12 @@ public async Task<SemanticHighlightResponse> Handle(SemanticHighlightRequest req
             foreach (var document in documents)
             {
                 var project = document.Project.Name;
-                var text = await document.GetTextAsync();
+
+                var highlightDocument = request.VersionedText != null
+                    ? document.WithText(SourceText.From(request.VersionedText))
+                    : document;
+
+                var text = await highlightDocument.GetTextAsync();
 
                 TextSpan textSpan;
                 if (request.Range is object)
@@ -55,7 +60,7 @@ public async Task<SemanticHighlightResponse> Handle(SemanticHighlightRequest req
                     textSpan = new TextSpan(0, text.Length);
                 }
 
-                results.AddRange((await Classifier.GetClassifiedSpansAsync(document, textSpan))
+                results.AddRange((await Classifier.GetClassifiedSpansAsync(highlightDocument, textSpan))
                     .Select(span => new ClassifiedResult()
                     {
                         Span = span,

tests/OmniSharp.Roslyn.CSharp.Tests/SemanticHighlightFacts.cs

@@ -31,7 +31,7 @@ class C1 { int n = true; }
 ");
 
             var line = -1;
-            var highlights = await GetSemanticHighlightsForLineAsync(testFile, line);
+            var highlights = await GetSemanticHighlightsForLineAsync(testFile, line, versionedText: null);
 
             Assert.Empty(highlights);
         }
@@ -47,7 +47,7 @@ class C1 { int n = true; }
 ");
 
             var line = 3;
-            var highlights = await GetSemanticHighlightsForLineAsync(testFile, line);
+            var highlights = await GetSemanticHighlightsForLineAsync(testFile, line, versionedText: null);
 
             AssertSyntax(highlights, testFile.Content.Code, line,
                 Keyword("class"),
@@ -90,6 +90,42 @@ class C1 { int n = true; }
             );
         }
 
+        [Fact]
+        public async Task SemanticHighlightEntireFileWithVersionedText()
+        {
+            var testFile = new TestFile("a.cs", @"
+namespace N1
+{
+    class C1 { int n = true; }
+}
+");
+            var versionedText = @"
+namespace N1
+{
+    class C { int n = false; }
+}
+";
+
+            var highlights = await GetSemanticHighlightsForFileAsync(testFile, versionedText);
+
+            AssertSyntax(highlights, versionedText, 0,
+                Keyword("namespace"),
+                NamespaceName("N1"),
+                Punctuation("{"),
+                Keyword("class"),
+                ClassName("C"),
+                Punctuation("{"),
+                Keyword("int"),
+                Field("n"),
+                Operator("="),
+                Keyword("false"),
+                Punctuation(";"),
+                Punctuation("}"),
+                Punctuation("}")
+            );
+        }
+
+
         [Fact]
         public async Task SemanticHighlightStringInterpolation()
         {
@@ -317,28 +353,34 @@ record struct R1(string S, int I);
 
         private Task<SemanticHighlightSpan[]> GetSemanticHighlightsForFileAsync(TestFile testFile)
         {
-            return GetSemanticHighlightsAsync(testFile, range: null);
+            return GetSemanticHighlightsAsync(testFile, range: null, versionedText: null);
+        }
+
+        private Task<SemanticHighlightSpan[]> GetSemanticHighlightsForFileAsync(TestFile testFile, string versionedText)
+        {
+            return GetSemanticHighlightsAsync(testFile, range: null, versionedText);
         }
 
-        private Task<SemanticHighlightSpan[]> GetSemanticHighlightsForLineAsync(TestFile testFile, int line)
+        private Task<SemanticHighlightSpan[]> GetSemanticHighlightsForLineAsync(TestFile testFile, int line, string versionedText)
         {
             var range = new Range()
             {
                 Start = new Point() { Column = 0, Line = line },
                 End = new Point() { Column = 0, Line = line + 1 }
             };
 
-            return GetSemanticHighlightsAsync(testFile, range);
+            return GetSemanticHighlightsAsync(testFile, range, versionedText);
         }
 
-        private async Task<SemanticHighlightSpan[]> GetSemanticHighlightsAsync(TestFile testFile, Range range)
+        private async Task<SemanticHighlightSpan[]> GetSemanticHighlightsAsync(TestFile testFile, Range range, string versionedText)
         {
             SharedOmniSharpTestHost.AddFilesToWorkspace(testFile);
             var requestHandler = GetRequestHandler(SharedOmniSharpTestHost);
             var request = new SemanticHighlightRequest
             {
                 FileName = testFile.FileName,
-                Range = range
+                Range = range,
+                VersionedText = versionedText,
             };
 
             var response = await requestHandler.Handle(request);