Make empty generated source files descriptive

Sources/GRPCCodeGen/Internal/Translator/IDLToStructuredSwiftTranslator.swift

@@ -72,13 +72,23 @@ struct IDLToStructuredSwiftTranslator: Translator {
       }
     }
 
-    let fileDescription = FileDescription(
-      topComment: .preFormatted(codeGenerationRequest.leadingTrivia),
-      imports: try self.makeImports(
+    let imports: [ImportDescription]
+    if codeBlocks.isEmpty {
+      imports = []
+      codeBlocks.append(
+        CodeBlock(comment: .inline("This file contained no services."))
+      )
+    } else {
+      imports = try self.makeImports(
         dependencies: codeGenerationRequest.dependencies,
         accessLevel: accessLevel,
         accessLevelOnImports: accessLevelOnImports
-      ),
+      )
+    }
+
+    let fileDescription = FileDescription(
+      topComment: .preFormatted(codeGenerationRequest.leadingTrivia),
+      imports: imports,
       codeBlocks: codeBlocks
     )
 

Sources/GRPCCodeGen/SourceGenerator.swift

@@ -94,6 +94,7 @@ public struct SourceGenerator: Sendable {
       client: self.config.client,
       server: self.config.server
     )
+
     let sourceFile = try textRenderer.render(structured: structuredSwiftRepresentation)
 
     return sourceFile

Tests/GRPCCodeGenTests/Internal/Translator/IDLToStructuredSwiftTranslatorSnippetBasedTests.swift

@@ -298,6 +298,25 @@ final class IDLToStructuredSwiftTranslatorSnippetBasedTests: XCTestCase {
     )
   }
 
+  func testEmptyFileGeneration() throws {
+    let expectedSwift =
+      """
+      /// Some really exciting license header 2023.
+
+
+      // This file contained no services.
+      """
+    try self.assertIDLToStructuredSwiftTranslation(
+      codeGenerationRequest: makeCodeGenerationRequest(
+        services: [],
+        dependencies: []
+      ),
+      expectedSwift: expectedSwift,
+      accessLevel: .public,
+      server: true
+    )
+  }
+
   private func assertIDLToStructuredSwiftTranslation(
     codeGenerationRequest: CodeGenerationRequest,
     expectedSwift: String,