Escape special characters in section name of editor config

src/Compilers/Core/CodeAnalysisTest/Analyzers/AnalyzerConfigTests.cs

@@ -57,6 +57,41 @@ public void SimpleCase()
             Assert.Equal("/bogus", config.NormalizedDirectory);
         }
 
+        [Fact]
+        public void ConfigWithEscapedValues()
+        {
+            var config = ParseConfigFile(@"is_global = true
+
+[c:/\{file1\}.cs]
+build_metadata.Compile.ToRetrieve = abc123
+
+[c:/file\#2.cs]
+build_metadata.Compile.ToRetrieve = def456
+
+[c:/file\[3\].cs]
+build_metadata.Compile.ToRetrieve = ghi789
+");
+
+            var namedSections = config.NamedSections;
+            Assert.Equal("c:/\\{file1\\}.cs", namedSections[0].Name);
+            AssertEx.Equal(
+                new[] { KeyValuePair.Create("build_metadata.compile.toretrieve", "abc123") },
+                namedSections[0].Properties
+            );
+
+            Assert.Equal("c:/file\\#2.cs", namedSections[1].Name);
+            AssertEx.Equal(
+                new[] { KeyValuePair.Create("build_metadata.compile.toretrieve", "def456") },
+                namedSections[1].Properties
+            );
+
+            Assert.Equal("c:/file\\[3\\].cs", namedSections[2].Name);
+            AssertEx.Equal(
+                new[] { KeyValuePair.Create("build_metadata.compile.toretrieve", "ghi789") },
+                namedSections[2].Properties
+            );
+        }
+
         [ConditionalFact(typeof(WindowsOnly))]
         public void WindowsPath()
         {

src/Compilers/Core/MSBuildTask/GenerateMSBuildEditorConfig.cs

@@ -78,7 +78,7 @@ public override bool Execute()
                 // write the section for this item
                 builder.AppendLine()
                        .Append("[")
-                       .Append(group.Key)
+                       .Append(EncodeString(group.Key))
                        .AppendLine("]");
 
                 foreach (var item in group)
@@ -101,6 +101,35 @@ public override bool Execute()
             return true;
         }
 
+        // Filenames with special characters like '#' and'{' get written
+        // into the section names in the resulting .editorconfig file. Later,
+        // when the file is parsed in configuration options these special
+        // characters are interpretted as invalid values and ignored by the
+        // processor. We encode the special characters in these strings
+        // before writing them here.
+
+        private static string EncodeString(string p)
+        {
+            StringBuilder builder = new StringBuilder();
+            for (var i = 0; i < p.Length; i++)
+            {
+                builder.Append(p[i] switch
+                {
+                    '*' => "\\*",
+                    '?' => "\\?",
+                    '{' => "\\{",
+                    ',' => "\\,",
+                    ';' => "\\;",
+                    '}' => "\\}",
+                    '[' => "\\[",
+                    ']' => "\\]",
+                    '#' => "\\#",
+                    var @default => @default
+                });
+            }
+            return builder.ToString();
+        }
+
         /// <remarks>
         /// Equivalent to Roslyn.Utilities.PathUtilities.NormalizeWithForwardSlash
         /// Both methods should be kept in sync.

src/Compilers/Core/MSBuildTaskTests/GenerateMSBuildEditorConfigTests.cs

@@ -97,6 +97,34 @@ public void MultipleItemMetaDataCreatesSections()
 ", result);
         }
 
+        [Fact]
+        public void MultipleSpecialCharacterItemMetaDataCreatesSections()
+        {
+            ITaskItem item1 = MSBuildUtil.CreateTaskItem("c:/{file1}.cs", new Dictionary<string, string> { { "ItemType", "Compile" }, { "MetadataName", "ToRetrieve" }, { "ToRetrieve", "abc123" } });
+            ITaskItem item2 = MSBuildUtil.CreateTaskItem("c:/file#2.cs", new Dictionary<string, string> { { "ItemType", "Compile" }, { "MetadataName", "ToRetrieve" }, { "ToRetrieve", "def456" } });
+            ITaskItem item3 = MSBuildUtil.CreateTaskItem("c:/file[3].cs", new Dictionary<string, string> { { "ItemType", "Compile" }, { "MetadataName", "ToRetrieve" }, { "ToRetrieve", "ghi789" } });
+
+            GenerateMSBuildEditorConfig configTask = new GenerateMSBuildEditorConfig()
+            {
+                MetadataItems = new[] { item1, item2, item3 }
+            };
+            configTask.Execute();
+
+            var result = configTask.ConfigFileContents;
+
+            Assert.Equal(@"is_global = true
+
+[c:/\{file1\}.cs]
+build_metadata.Compile.ToRetrieve = abc123
+
+[c:/file\#2.cs]
+build_metadata.Compile.ToRetrieve = def456
+
+[c:/file\[3\].cs]
+build_metadata.Compile.ToRetrieve = ghi789
+", result);
+        }
+
         [Fact]
         public void DuplicateItemSpecsAreCombinedInSections()
         {