Add export schema Fusion CLI command

src/HotChocolate/Fusion/src/CommandLine/Commands/ExportCommand.cs

@@ -15,5 +15,6 @@ public ExportCommand() : base("export")
         Description = "Export commands.";
 
         AddCommand(new ExportGraphCommand());
+        AddCommand(new ExportSchemaCommand());
     }
 }

src/HotChocolate/Fusion/src/CommandLine/Commands/ExportGraphCommand.cs

@@ -46,7 +46,7 @@
                 packageFile = new FileInfo(Combine(packageFile.FullName, "gateway" + FusionPackage));
             }
             else if (!packageFile.Extension.EqualsOrdinal(FusionPackage) &&
-                !packageFile.Extension.EqualsOrdinal(ZipPackage))
+                     !packageFile.Extension.EqualsOrdinal(ZipPackage))
             {
                 packageFile = new FileInfo(packageFile.FullName + FusionPackage);
             }
@@ -65,7 +65,8 @@
         var graph = await package.GetFusionGraphAsync(cancellationToken);
         var options = new SyntaxSerializerOptions { Indented = true, MaxDirectivesPerLine = 0, };
 
-        await File.WriteAllTextAsync(graphFile.FullName, graph.ToString(options), Encoding.UTF8, cancellationToken);
+        await File.WriteAllTextAsync(graphFile.FullName, graph.ToString(options),
+            new UTF8Encoding(encoderShouldEmitUTF8Identifier: false, throwOnInvalidBytes: true), cancellationToken);
 
         return 0;
     }

src/HotChocolate/Fusion/src/CommandLine/Commands/ExportSchemaCommand.cs

@@ -0,0 +1,73 @@
+using System.CommandLine;
+using System.Text;
+using HotChocolate.Fusion.CommandLine.Helpers;
+using HotChocolate.Language;
+using HotChocolate.Language.Utilities;
+using HotChocolate.Utilities;
+
+namespace HotChocolate.Fusion.CommandLine.Commands;
+
+internal sealed class ExportSchemaCommand : Command
+{
+    public ExportSchemaCommand() : base("schema")
+    {
+        var fusionPackageFile = new Option<FileInfo?>("--package-file");
+        fusionPackageFile.AddAlias("--package");
+        fusionPackageFile.AddAlias("-p");
+
+        var schemaFile = new Option<FileInfo?>("--file");
+        schemaFile.AddAlias("-f");
+
+        AddOption(fusionPackageFile);
+        AddOption(schemaFile);
+
+        this.SetHandler(
+            ExecuteAsync,
+            Bind.FromServiceProvider<IConsole>(),
+            fusionPackageFile,
+            schemaFile,
+            Bind.FromServiceProvider<CancellationToken>());
+    }
+
+    private static async Task<int> ExecuteAsync(
+        IConsole console,
+        FileInfo? packageFile,
+        FileInfo? schemaFile,
+        CancellationToken cancellationToken)
+    {
+        packageFile ??=
+            new FileInfo(System.IO.Path.Combine(Environment.CurrentDirectory, "gateway" + Extensions.FusionPackage));
+
+        if (!packageFile.Exists)
+        {
+            if (Directory.Exists(packageFile.FullName))
+            {
+                packageFile =
+                    new FileInfo(System.IO.Path.Combine(packageFile.FullName, "gateway" + Extensions.FusionPackage));
+            }
+            else if (!packageFile.Extension.EqualsOrdinal(Extensions.FusionPackage) &&
+                     !packageFile.Extension.EqualsOrdinal(Extensions.ZipPackage))
+            {
+                packageFile = new FileInfo(packageFile.FullName + Extensions.FusionPackage);
+            }
+
+            if (!packageFile.Exists)
+            {
+                console.WriteLine($"The package file `{packageFile.FullName}` does not exist.");
+                return 1;
+            }
+        }
+
+        schemaFile ??= new FileInfo(System.IO.Path.Combine(packageFile.DirectoryName!, "schema.graphql"));
+
+        await using var package = FusionGraphPackage.Open(packageFile.FullName);
+
+        var schema = await package.GetSchemaAsync(cancellationToken);
+        var options = new SyntaxSerializerOptions { Indented = true, MaxDirectivesPerLine = 0, };
+
+        await File.WriteAllTextAsync(schemaFile.FullName, schema.ToString(options),
+            new UTF8Encoding(encoderShouldEmitUTF8Identifier: false, throwOnInvalidBytes: true), cancellationToken);
+
+        return 0;
+    }
+}