Support global analyzer config levels:

src/Compilers/CSharp/Test/CommandLine/CommandLineTests.cs

@@ -12968,11 +12968,13 @@ class C
             var analyzerConfigFile = dir.CreateFile(".globalconfig");
             var analyzerConfig = analyzerConfigFile.WriteAllText(@"
 is_global = true
+global_level = 100
 option1 = abc");
 
             var analyzerConfigFile2 = dir.CreateFile(".globalconfig2");
             var analyzerConfig2 = analyzerConfigFile2.WriteAllText(@"
 is_global = true
+global_level = 100
 option1 = def");
 
             var output = VerifyOutput(dir, src, additionalFlags: new[] { "/analyzerconfig:" + analyzerConfig.Path + "," + analyzerConfig2.Path }, expectedWarningCount: 1, includeCurrentAssemblyAsAnalyzerReference: false);
@@ -12985,11 +12987,13 @@ class C
 
             analyzerConfig = analyzerConfigFile.WriteAllText(@"
 is_global = true
+global_level = 100
 [/file.cs]
 option1 = abc");
 
             analyzerConfig2 = analyzerConfigFile2.WriteAllText(@"
 is_global = true
+global_level = 100
 [/file.cs]
 option1 = def");
 

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

@@ -2175,6 +2175,258 @@ public void GlobalConfigIssuesWarningWithInvalidSectionNames(string sectionName,
         public void GlobalConfigIssuesWarningWithInvalidSectionNames_PlatformSpecific(string sectionName, bool isValidWindows, bool isValidOther)
             => GlobalConfigIssuesWarningWithInvalidSectionNames(sectionName, ExecutionConditionUtil.IsWindows ? isValidWindows : isValidOther);
 
+        [Theory]
+        [InlineData("/.globalconfig", true)]
+        [InlineData("/.GLOBALCONFIG", true)]
+        [InlineData("/.glObalConfiG", true)]
+        [InlineData("/path/to/.globalconfig", true)]
+        [InlineData("/my.globalconfig", false)]
+        [InlineData("/globalconfig", false)]
+        [InlineData("/path/to/globalconfig", false)]
+        [InlineData("/path/to/my.globalconfig", false)]
+        [InlineData("/.editorconfig", false)]
+        [InlineData("/.globalconfİg", false)]
+        public void FileNameCausesConfigToBeReportedAsGlobal(string fileName, bool shouldBeTreatedAsGlobal)
+        {
+            var config = Parse("", fileName);
+            Assert.Equal(shouldBeTreatedAsGlobal, config.IsGlobal);
+        }
+
+        [Fact]
+        public void GlobalLevelCanBeReadFromAnyConfig()
+        {
+            var config = Parse("global_level = 5", "/.editorconfig");
+            Assert.Equal(5, config.GlobalLevel);
+        }
+
+        [Fact]
+        public void GlobalLevelDefaultsTo100ForUserGlobalConfigs()
+        {
+            var config = Parse("", "/" + AnalyzerConfig.UserGlobalConfigName);
+
+            Assert.True(config.IsGlobal);
+            Assert.Equal(100, config.GlobalLevel);
+        }
+
+        [Fact]
+        public void GlobalLevelCanBeOverriddenForUserGlobalConfigs()
+        {
+            var config = Parse("global_level = 5", "/" + AnalyzerConfig.UserGlobalConfigName);
+
+            Assert.True(config.IsGlobal);
+            Assert.Equal(5, config.GlobalLevel);
+        }
+
+        [Fact]
+        public void GlobalLevelDefaultsToZeroForNonUserGlobalConfigs()
+        {
+            var config = Parse("is_global = true", "/.nugetconfig");
+
+            Assert.True(config.IsGlobal);
+            Assert.Equal(0, config.GlobalLevel);
+        }
+
+        [Fact]
+        public void GlobalLevelIsNotPresentInConfigSet()
+        {
+            var config = Parse("global_level = 123", "/.globalconfig");
+
+            var set = AnalyzerConfigSet.Create(ImmutableArray.Create(config));
+            var globalOptions = set.GlobalConfigOptions;
+
+            Assert.Empty(globalOptions.AnalyzerOptions);
+            Assert.Empty(globalOptions.TreeOptions);
+            Assert.Empty(globalOptions.Diagnostics);
+        }
+
+        [Fact]
+        public void GlobalLevelInSectionIsPresentInConfigSet()
+        {
+            var config = Parse(@"
+[/path]
+global_level = 123", "/.globalconfig");
+
+            var set = AnalyzerConfigSet.Create(ImmutableArray.Create(config));
+            var globalOptions = set.GlobalConfigOptions;
+
+            Assert.Empty(globalOptions.AnalyzerOptions);
+            Assert.Empty(globalOptions.TreeOptions);
+            Assert.Empty(globalOptions.Diagnostics);
+
+            var sectionOptions = set.GetOptionsForSourcePath("/path");
+
+            Assert.Single(sectionOptions.AnalyzerOptions);
+            Assert.Equal("123", sectionOptions.AnalyzerOptions["global_level"]);
+            Assert.Empty(sectionOptions.TreeOptions);
+            Assert.Empty(sectionOptions.Diagnostics);
+        }
+
+        [Theory]
+        [InlineData(1, 2)]
+        [InlineData(2, 1)]
+        [InlineData(-2, -1)]
+        [InlineData(2, -1)]
+        public void GlobalLevelAllowsOverrideOfGlobalKeys(int level1, int level2)
+        {
+            var configs = ArrayBuilder<AnalyzerConfig>.GetInstance();
+            configs.Add(Parse($@"
+is_global = true
+global_level = {level1}
+option1 = value1
+", "/.globalconfig1"));
+
+            configs.Add(Parse($@"
+is_global = true
+global_level = {level2}
+option1 = value2",
+"/.globalconfig2"));
+
+            var globalConfig = AnalyzerConfigSet.MergeGlobalConfigs(configs, out var diagnostics);
+            diagnostics.Verify();
+
+            Assert.Single(globalConfig.GlobalSection.Properties.Keys, "option1");
+
+            string expectedValue = level1 > level2 ? "value1" : "value2";
+            Assert.Single(globalConfig.GlobalSection.Properties.Values, expectedValue);
+
+            configs.Free();
+        }
+
+        [Fact]
+        public void GlobalLevelAllowsOverrideOfSectionKeys()
+        {
+            var configs = ArrayBuilder<AnalyzerConfig>.GetInstance();
+            configs.Add(Parse(@"
+is_global = true
+global_level = 1
+
+[/path]
+option1 = value1
+", "/.globalconfig1"));
+
+            configs.Add(Parse(@"
+is_global = true
+global_level = 2
+
+[/path]
+option1 = value2",
+"/.globalconfig2"));
+
+            var globalConfig = AnalyzerConfigSet.MergeGlobalConfigs(configs, out var diagnostics);
+            diagnostics.Verify();
+
+            Assert.Single(globalConfig.NamedSections);
+            Assert.Equal("/path", globalConfig.NamedSections[0].Name);
+            Assert.Single(globalConfig.NamedSections[0].Properties.Keys, "option1");
+            Assert.Single(globalConfig.NamedSections[0].Properties.Values, "value2");
+
+            configs.Free();
+        }
+
+        [Theory]
+        [InlineData(1, 2, 3, "value3")]
+        [InlineData(2, 1, 3, "value3")]
+        [InlineData(3, 2, 1, "value1")]
+        [InlineData(1, 2, 1, "value2")]
+        [InlineData(1, 1, 2, "value3")]
+        [InlineData(2, 1, 1, "value1")]
+        public void GlobalLevelAllowsOverrideOfDuplicateGlobalKeys(int level1, int level2, int level3, string expectedValue)
+        {
+            var configs = ArrayBuilder<AnalyzerConfig>.GetInstance();
+            configs.Add(Parse($@"
+is_global = true
+global_level = {level1}
+option1 = value1
+", "/.globalconfig1"));
+
+            configs.Add(Parse($@"
+is_global = true
+global_level = {level2}
+option1 = value2",
+"/.globalconfig2"));
+
+            configs.Add(Parse($@"
+is_global = true
+global_level = {level3}
+option1 = value3",
+"/.globalconfig3"));
+
+            var globalConfig = AnalyzerConfigSet.MergeGlobalConfigs(configs, out var diagnostics);
+            diagnostics.Verify();
+
+            Assert.Single(globalConfig.GlobalSection.Properties.Keys, "option1");
+            Assert.Single(globalConfig.GlobalSection.Properties.Values, expectedValue);
+
+            configs.Free();
+        }
+
+        [Fact]
+        public void GlobalLevelReportsConflictsOnlyAtTheHighestLevel()
+        {
+            var configs = ArrayBuilder<AnalyzerConfig>.GetInstance();
+            configs.Add(Parse($@"
+is_global = true
+global_level = 1
+option1 = value1
+", "/.globalconfig1"));
+
+            configs.Add(Parse($@"
+is_global = true
+global_level = 1
+option1 = value2",
+"/.globalconfig2"));
+
+            configs.Add(Parse($@"
+is_global = true
+global_level = 3
+option1 = value3",
+"/.globalconfig3"));
+
+            configs.Add(Parse($@"
+is_global = true
+global_level = 3
+option1 = value4",
+"/.globalconfig4"));
+
+            configs.Add(Parse($@"
+is_global = true
+global_level = 2
+option1 = value5",
+"/.globalconfig5"));
+
+            configs.Add(Parse($@"
+is_global = true
+global_level = 2
+option1 = value6",
+"/.globalconfig6"));
+
+            var globalConfig = AnalyzerConfigSet.MergeGlobalConfigs(configs, out var diagnostics);
+
+            // we don't report config1, 2, 5, or 6, because they didn't conflict: 3 + 4 overrode them, but then themselves were conflicting
+            diagnostics.Verify(
+                Diagnostic("MultipleGlobalAnalyzerKeys").WithArguments("option1", "Global Section", "/.globalconfig3, /.globalconfig4").WithLocation(1, 1)
+                );
+
+            configs.Free();
+        }
+
+        [Fact]
+        public void InvalidGlobalLevelIsIgnored()
+        {
+            var userGlobalConfig = Parse($@"
+is_global = true
+global_level = abc
+", "/.globalconfig");
+
+            var nonUserGlobalConfig = Parse($@"
+is_global = true
+global_level = abc
+", "/.editorconfig");
+
+            Assert.Equal(100, userGlobalConfig.GlobalLevel);
+            Assert.Equal(0, nonUserGlobalConfig.GlobalLevel);
+        }
+
         #endregion
     }
 }

src/Compilers/Core/Portable/CommandLine/AnalyzerConfig.cs

@@ -28,6 +28,16 @@ public sealed partial class AnalyzerConfig
         /// </summary>
         internal const string GlobalKey = "is_global";
 
+        /// <summary>
+        /// Key that indicates the precedence of this config when <see cref="IsGlobal"/> is true
+        /// </summary>
+        internal const string GlobalLevelKey = "global_level";
+
+        /// <summary>
+        /// Filename that indicates this file is a user provided global config
+        /// </summary>
+        internal const string UserGlobalConfigName = ".globalconfig";
+
         /// <summary>
         /// A set of keys that are reserved for special interpretation for the editorconfig specification.
         /// All values corresponding to reserved keys in a (key,value) property pair are always lowercased
@@ -86,7 +96,45 @@ public sealed partial class AnalyzerConfig
         /// <summary>
         /// Gets whether this editorconfig is a global editorconfig.
         /// </summary>
-        internal bool IsGlobal => GlobalSection.Properties.ContainsKey(GlobalKey);
+        internal bool IsGlobal => _hasGlobalFileName || GlobalSection.Properties.ContainsKey(GlobalKey);
+
+        /// <summary>
+        /// Get the global level of this config, used to resolve conflicting keys
+        /// </summary>
+        /// <remarks>
+        /// A user can explicitly set the global level via the <see cref="GlobalLevelKey"/>.
+        /// When no global level is explicitly set, we use a heuristic:
+        ///  <list type="bullet">
+        ///     <item><description>
+        ///     Any file matching the <see cref="UserGlobalConfigName"/> is determined to be a user supplied global config and gets a level of 100
+        ///     </description></item>
+        ///     <item><description>
+        ///     Any other file gets a default level of 0
+        ///     </description></item>
+        ///  </list>
+        ///  
+        /// This value is unused when <see cref="IsGlobal"/> is <c>false</c>.
+        /// </remarks>
+        internal int GlobalLevel
+        {
+            get
+            {
+                if (GlobalSection.Properties.TryGetValue(GlobalLevelKey, out string? val) && int.TryParse(val, out int level))
+                {
+                    return level;
+                }
+                else if (_hasGlobalFileName)
+                {
+                    return 100;
+                }
+                else
+                {
+                    return 0;
+                }
+            }
+        }
+
+        private readonly bool _hasGlobalFileName;
 
         private AnalyzerConfig(
             Section globalSection,
@@ -96,6 +144,7 @@ private AnalyzerConfig(
             GlobalSection = globalSection;
             NamedSections = namedSections;
             PathToFile = pathToFile;
+            _hasGlobalFileName = Path.GetFileName(pathToFile).Equals(UserGlobalConfigName, StringComparison.OrdinalIgnoreCase);
 
             // Find the containing directory and normalize the path separators
             string directory = Path.GetDirectoryName(pathToFile) ?? pathToFile;