Fix Quick Info nullability display for backing fields (#77240)

Co-authored-by: Cyrus Najmabadi <[email protected]>
dotnet · Feb 19, 2025 · c84d249 · c84d249
1 parent 51f74e4
commit c84d249
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Showing 3 changed files with 160 additions and 2 deletions.
diff --git a/src/Compilers/CSharp/Test/Symbol/SymbolDisplay/SymbolDisplayTests.cs b/src/Compilers/CSharp/Test/Symbol/SymbolDisplay/SymbolDisplayTests.cs
@@ -2164,6 +2164,121 @@ class C {
                 SymbolDisplayPartKind.Keyword);
         }
 
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/77219")]
+        public void TestPropertyBackingField_Minimal_01()
+        {
+            var text = @"
+#nullable enable
+class C {
+    string P { get; set; } }
+";
+
+            Func<NamespaceSymbol, Symbol> findSymbol = global =>
+                global.GetTypeMembers("C", 0).Single().
+                GetMembers("<P>k__BackingField").Single();
+
+            var format = new SymbolDisplayFormat(
+                memberOptions:
+                    SymbolDisplayMemberOptions.IncludeExplicitInterface);
+
+            TestSymbolDescription(
+                text,
+                findSymbol,
+                format,
+                "P.field",
+                SymbolDisplayPartKind.PropertyName,
+                SymbolDisplayPartKind.Punctuation,
+                SymbolDisplayPartKind.Keyword);
+        }
+
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/77219")]
+        public void TestPropertyBackingField_Minimal_02()
+        {
+            var text = @"
+#nullable enable
+
+interface I {
+    string P { get; set; }
+}
+
+class C : I {
+    string I.P { get; set; } }
+";
+
+            Func<NamespaceSymbol, Symbol> findSymbol = global =>
+                global.GetTypeMembers("C", 0).Single().
+                GetMembers("<I.P>k__BackingField").Single();
+
+            var format = new SymbolDisplayFormat(
+                memberOptions:
+                    SymbolDisplayMemberOptions.IncludeExplicitInterface);
+
+            TestSymbolDescription(
+                text,
+                findSymbol,
+                format,
+                "I.P.field",
+                SymbolDisplayPartKind.InterfaceName,
+                SymbolDisplayPartKind.Punctuation,
+                SymbolDisplayPartKind.PropertyName,
+                SymbolDisplayPartKind.Punctuation,
+                SymbolDisplayPartKind.Keyword);
+        }
+
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/77219")]
+        public void TestPropertyBackingField_Minimal_03()
+        {
+            var text = @"
+#nullable enable
+
+interface I {
+    string P { get; set; }
+}
+
+class C : I {
+    string I.P { get; set; } }
+";
+
+            Func<NamespaceSymbol, Symbol> findSymbol = global =>
+                global.GetTypeMembers("C", 0).Single().
+                GetMembers("<I.P>k__BackingField").Single();
+
+            var format = new SymbolDisplayFormat();
+
+            TestSymbolDescription(
+                text,
+                findSymbol,
+                format,
+                "P.field",
+                SymbolDisplayPartKind.PropertyName,
+                SymbolDisplayPartKind.Punctuation,
+                SymbolDisplayPartKind.Keyword);
+        }
+
+        [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/77219")]
+        public void TestOrdinaryField_Minimal()
+        {
+            var text = @"
+#nullable enable
+
+class C {
+    string F;
+";
+
+            Func<NamespaceSymbol, Symbol> findSymbol = global =>
+                global.GetTypeMembers("C", 0).Single().
+                GetMembers("F").Single();
+
+            var format = new SymbolDisplayFormat();
+
+            TestSymbolDescription(
+                text,
+                findSymbol,
+                format,
+                "F",
+                SymbolDisplayPartKind.FieldName);
+        }
+
         [Fact]
         public void TestPropertyBackingFieldFromCompilationReference()
         {

diff --git a/src/EditorFeatures/CSharpTest/QuickInfo/SemanticQuickInfoSourceTests.cs b/src/EditorFeatures/CSharpTest/QuickInfo/SemanticQuickInfoSourceTests.cs
@@ -7998,6 +7998,44 @@ void N()
             NullabilityAnalysis(string.Format(FeaturesResources._0_is_not_null_here, "s")));
     }
 
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/77219")]
+    public async Task NullableBackingFieldThatIsMaybeNull()
+    {
+        await TestWithOptionsAsync(TestOptions.RegularPreview,
+            """
+            #nullable enable
+
+            class X
+            {
+                string? P
+                {
+                    get => $$field;
+                }
+            }
+            """,
+            MainDescription($"({FeaturesResources.field}) string? X.P.field"),
+            NullabilityAnalysis(string.Format(FeaturesResources._0_may_be_null_here, "P.field")));
+    }
+
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/77219")]
+    public async Task NullableBackingFieldThatIsNotNull()
+    {
+        await TestWithOptionsAsync(TestOptions.RegularPreview,
+            """
+            #nullable enable
+
+            class X
+            {
+                string P
+                {
+                    get => $$field;
+                } = "a";
+            }
+            """,
+            MainDescription($"({FeaturesResources.field}) string X.P.field"),
+            NullabilityAnalysis(string.Format(FeaturesResources._0_is_not_null_here, "P.field")));
+    }
+
     [Fact]
     public async Task NullablePropertyThatIsMaybeNull()
     {

diff --git a/src/Features/Core/Portable/QuickInfo/QuickInfoUtilities.cs b/src/Features/Core/Portable/QuickInfo/QuickInfoUtilities.cs
@@ -18,6 +18,11 @@ namespace Microsoft.CodeAnalysis.QuickInfo;
 
 internal static class QuickInfoUtilities
 {
+    /// <summary>
+    /// Display variable name only.
+    /// </summary>
+    private static readonly SymbolDisplayFormat s_nullableDisplayFormat = new SymbolDisplayFormat();
+
     public static Task<QuickInfoItem> CreateQuickInfoItemAsync(SolutionServices services, SemanticModel semanticModel, TextSpan span, ImmutableArray<ISymbol> symbols, SymbolDescriptionOptions options, CancellationToken cancellationToken)
         => CreateQuickInfoItemAsync(services, semanticModel, span, symbols, supportedPlatforms: null, showAwaitReturn: false, flowState: NullableFlowState.None, options, onTheFlyDocsInfo: null, cancellationToken);
 
@@ -136,8 +141,8 @@ public static async Task<QuickInfoItem> CreateQuickInfoItemAsync(
 
         var nullableMessage = flowState switch
         {
-            NullableFlowState.MaybeNull => string.Format(FeaturesResources._0_may_be_null_here, symbol.Name),
-            NullableFlowState.NotNull => string.Format(FeaturesResources._0_is_not_null_here, symbol.Name),
+            NullableFlowState.MaybeNull => string.Format(FeaturesResources._0_may_be_null_here, symbol.ToDisplayString(s_nullableDisplayFormat)),
+            NullableFlowState.NotNull => string.Format(FeaturesResources._0_is_not_null_here, symbol.ToDisplayString(s_nullableDisplayFormat)),
             _ => null
         };