Allow EditorConfigFile to be used in-memory without access or use of physical file system.

src/EditorConfig.Core/ConfigSection.cs

@@ -70,6 +70,8 @@ public ConfigSection(string name, IEditorConfigFile origin, Dictionary<string, s
 
 		private static string FixGlob(string glob, string directory)
 		{
+			if (string.IsNullOrEmpty(directory)) return glob;
+
 			switch (glob.IndexOf('/'))
 			{
 				case -1: glob = "**/" + glob; break;

src/EditorConfig.Core/EditorConfigFile.cs

@@ -62,25 +62,49 @@ public class EditorConfigFile : IEditorConfigFile
 		/// <inheritdoc cref="IEditorConfigFile.IsRoot"/>
 		public bool IsRoot => _isRoot;
 
-		internal EditorConfigFile(string path, string cacheKey = null)
+		private EditorConfigFile(
+			string fileName,
+			string directory,
+			TextReader reader,
+			string cacheKey = null)
 		{
-			Directory = Path.GetDirectoryName(path);
-			FileName = Path.GetFileName(path);
+			Directory = directory;
+			FileName = fileName;
 			CacheKey = cacheKey;
-			Parse(path);
+			ReadAndParse(reader);
 
 			if (_globalDict.TryGetValue("root", out var value))
 				bool.TryParse(value, out _isRoot);
 		}
 
-		private void Parse(string file)
+		/// <summary> Parses EditorConfig file from the file path. </summary>
+		/// <param name="path"> File path in a physical file system. </param>
+		/// <returns> Parsed EditorConfig file. </returns>
+		public static EditorConfigFile Parse(string path) => Parse(path, cacheKey: null);
+
+		/// <summary> Parses EditorConfig file from the text reader. </summary>
+		/// <param name="reader"> Text reader. </param>
+		/// <param name="directory"> EditorConfig base directory to match file sections to. Default is null. </param>
+		/// <param name="fileName"> EditorConfig file name. Default is '.editorconfig'. </param>
+		/// <returns> Parsed EditorConfig file. </returns>
+		public static EditorConfigFile Parse(TextReader reader, string directory = null, string fileName = ".editorconfig") =>
+			new(fileName, directory, reader);
+
+		internal static EditorConfigFile Parse(string path, string cacheKey)
 		{
-			var lines = File.ReadLines(file);
+			using var file = File.OpenRead(path);
+			using var reader = new StreamReader(file);
+			return new EditorConfigFile(
+				Path.GetFileName(path), Path.GetDirectoryName(path),
+				reader, cacheKey);
+		}
 
+		private void ReadAndParse(TextReader reader)
+		{
 			var activeDict = _globalDict;
 			var sectionName = string.Empty;
 			var reset = false;
-			foreach (var line in lines)
+			while (reader.ReadLine() is { } line)
 			{
 				if (string.IsNullOrWhiteSpace(line)) continue;
 

src/EditorConfig.Core/EditorConfigFileCache.cs

@@ -28,9 +28,9 @@ private static string GetFileHash(string filename)
 	/// <returns></returns>
 	public static EditorConfigFile GetOrCreate(string file)
 	{
-		if (!File.Exists(file)) return new EditorConfigFile(file);
+		if (!File.Exists(file)) return EditorConfigFile.Parse(file);
 
 		var key = $"{file}_{GetFileHash(file)}";
-		return FileCache.GetOrAdd(key, _ => new EditorConfigFile(file, key));
+		return FileCache.GetOrAdd(key, _ => EditorConfigFile.Parse(file, key));
 	}
 }

src/EditorConfig.Core/EditorConfigParser.cs

@@ -41,7 +41,7 @@ public class EditorConfigParser
 		/// <param name="configFileName">The name of the file(s) holding the editorconfiguration values</param>
 		/// <param name="developmentVersion">Only used in testing, development to pass an older version to the parsing routine</param>
 		public EditorConfigParser(string configFileName = ".editorconfig", Version developmentVersion = null)
-			: this(f => new EditorConfigFile(f), configFileName, developmentVersion)
+			: this(EditorConfigFile.Parse, configFileName, developmentVersion)
 		{
 
 		}
@@ -91,13 +91,13 @@ public FileConfiguration Parse(string fileName, IEnumerable<EditorConfigFile> ed
 			var sections =
 				from configFile in editorConfigFiles
 				from section in configFile.Sections
-				where IsMatch(section.Glob, fullPath, configFile.Directory)
+				where IsMatch(section.Glob, fullPath)
 				select section;
 
 			return new FileConfiguration(ParseVersion, file, sections.ToList());
 		}
 
-		private bool IsMatch(string glob, string fileName, string directory)
+		private bool IsMatch(string glob, string fileName)
 		{
 			var matcher = GlobMatcher.Create(glob, _globOptions);
 			var isMatch = matcher.IsMatch(fileName);

src/EditorConfig.Tests/InMemory/InMemoryConfigTests.cs

@@ -0,0 +1,58 @@
+using System.IO;
+using EditorConfig.Core;
+using FluentAssertions;
+using Microsoft.VisualBasic;
+using NUnit.Framework;
+
+namespace EditorConfig.Tests.InMemory
+{
+	[TestFixture]
+	public class CachingTests : EditorConfigTestBase
+	{
+		[Test]
+		public void InMemoryConfigIsUsable()
+		{
+			var configContent = @"""
+			                    root = true
+
+			                    [*.cs]
+			                    end_of_line = lf
+			                    """;
+			var stringReader = new StringReader(configContent);
+			var editorConfigFile = EditorConfigFile.Parse(stringReader);
+
+			var parser = new EditorConfigParser();
+			var config = parser.Parse("myfile.cs", new[] { editorConfigFile });
+
+			config.EditorConfigFiles.Should().ContainSingle(f => f.IsRoot);
+			config.EndOfLine.Should().Be(EndOfLine.LF);
+		}
+
+		[Test]
+		public void InMemoryConfigIsUsableWithVirtualPath()
+		{
+			var virtualDirectory = Path.Combine(Directory.GetDirectoryRoot("."), "VirtualPath");
+
+			var configContent = @"""
+			                    root = true
+
+			                    [*.cs]
+			                    end_of_line = lf
+			                    """;
+			var stringReader = new StringReader(configContent);
+			var editorConfigFile = EditorConfigFile.Parse(stringReader, virtualDirectory);
+
+			var parser = new EditorConfigParser();
+
+			var file = Path.Combine(virtualDirectory, "myfile.cs");
+			var config1 = parser.Parse(file, new[] { editorConfigFile });
+			config1.EditorConfigFiles.Should().ContainSingle(f => f.IsRoot);
+			config1.EndOfLine.Should().Be(EndOfLine.LF);
+
+			var directoryOutOfScope = Path.Combine(Directory.GetDirectoryRoot("."), "DifferentDirectory");
+			var fileOutOfScope = Path.Combine(directoryOutOfScope, "myfile.cs");
+			var config2 = parser.Parse(fileOutOfScope, new[] { editorConfigFile });
+			config2.EditorConfigFiles.Should().BeEmpty();
+		}
+	}
+}