feat: Add support for gzipped xrefmap that stored as local file

src/Docfx.Build/XRefMaps/XRefMapDownloader.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Diagnostics;
+using System.IO.Compression;
 using System.Net;
 using Docfx.Common;
 
@@ -119,6 +120,24 @@ private static async ValueTask<IXRefContainer> ReadLocalFileAsync(string filePat
             case ".zip":
                 return XRefArchive.Open(filePath, XRefArchiveMode.Read);
 
+            case ".gz":
+                {
+                    using var fileStream = File.OpenRead(filePath);
+                    using var stream = new GZipStream(fileStream, CompressionMode.Decompress);
+
+                    switch (Path.GetExtension(Path.GetFileNameWithoutExtension(filePath)).ToLowerInvariant())
+                    {
+                        case ".json":
+                            return await SystemTextJsonUtility.DeserializeAsync<XRefMap>(stream, token);
+                        case ".yml":
+                        default:
+                            {
+                                using var reader = new StreamReader(stream);
+                                return YamlUtility.Deserialize<XRefMap>(reader);
+                            };
+                    }
+                }
+
             case ".json":
                 {
                     using var stream = File.OpenRead(filePath);

test/Docfx.Build.Tests/XRefMapDownloaderTest.cs

@@ -51,6 +51,34 @@ public async Task ReadLocalXRefMapJsonFileTest()
         xrefMap.References.Should().HaveCount(1);
     }
 
+    [Fact]
+    public async Task ReadLocalXRefMapGZippedJsonFileTest()
+    {
+        // Arrange
+        var path = Path.Combine(Directory.GetCurrentDirectory(), "TestData", "xrefmap.json.gz");
+
+        XRefMapDownloader downloader = new XRefMapDownloader();
+        var xrefMap = await downloader.DownloadAsync(new Uri(path)) as XRefMap;
+
+        // Assert
+        xrefMap.Should().NotBeNull();
+        xrefMap.References.Should().HaveCount(1);
+    }
+
+    [Fact]
+    public async Task ReadLocalXRefMapGZippedYamlFileTest()
+    {
+        // Arrange
+        var path = Path.Combine(Directory.GetCurrentDirectory(), "TestData", "xrefmap.yml.gz");
+
+        XRefMapDownloader downloader = new XRefMapDownloader();
+        var xrefMap = await downloader.DownloadAsync(new Uri(path)) as XRefMap;
+
+        // Assert
+        xrefMap.Should().NotBeNull();
+        xrefMap.References.Should().HaveCount(1);
+    }
+
     /// <summary>
     /// XrefmapDownloader test for xrefmap that has no baseUrl and href is defined by relative path.
     /// </summary>