refactor(cmd): Simplify codegen selection logic (#1466)

internal/cmd/generate.go

@@ -187,33 +187,25 @@ func Generate(ctx context.Context, e Env, dir, filename string, stderr io.Writer
 		if debug.Traced {
 			region = trace.StartRegion(ctx, "codegen")
 		}
-		var files map[string]string
-		var resp *plugin.CodeGenResponse
+		var genfunc func(req *plugin.CodeGenRequest) (*plugin.CodeGenResponse, error)
 		var out string
 		switch {
 		case sql.Gen.Go != nil:
 			out = combo.Go.Out
-			resp, err = golang.Generate(codeGenRequest(result, combo))
+			genfunc = golang.Generate
 		case sql.Gen.Kotlin != nil:
 			out = combo.Kotlin.Out
-			resp, err = kotlin.Generate(codeGenRequest(result, combo))
+			genfunc = kotlin.Generate
 		case sql.Gen.Python != nil:
 			out = combo.Python.Out
-			resp, err = python.Generate(codeGenRequest(result, combo))
+			genfunc = python.Generate
 		default:
 			panic("missing language backend")
 		}
+		resp, err := genfunc(codeGenRequest(result, combo))
 		if region != nil {
 			region.End()
 		}
-
-		if resp != nil {
-			files = map[string]string{}
-			for _, file := range resp.Files {
-				files[file.Name] = string(file.Contents)
-			}
-		}
-
 		if err != nil {
 			fmt.Fprintf(stderr, "# package %s\n", name)
 			fmt.Fprintf(stderr, "error generating code: %s\n", err)
@@ -223,6 +215,10 @@ func Generate(ctx context.Context, e Env, dir, filename string, stderr io.Writer
 			}
 			continue
 		}
+		files := map[string]string{}
+		for _, file := range resp.Files {
+			files[file.Name] = string(file.Contents)
+		}
 		for n, source := range files {
 			filename := filepath.Join(dir, out, n)
 			output[filename] = source