From 8df9e1ecf28396497f1a60e255467b9bdc0133c6 Mon Sep 17 00:00:00 2001
From: Alex Bezzubov <bzz@apache.org>
Date: Thu, 16 Feb 2023 17:47:44 +0100
Subject: [PATCH] code-gen: improve ability to debug failures

Code generation failres were hard to identify and undertand

 * avoid unnececary re-formating & memory allocation
 * return clear formatting errors
---
 .../code-generator/generator/generator.go     | 22 ++++++-------------
 internal/code-generator/main.go               |  2 +-
 2 files changed, 8 insertions(+), 16 deletions(-)

diff --git a/internal/code-generator/generator/generator.go b/internal/code-generator/generator/generator.go
index ce0bdd4..b081d47 100644
--- a/internal/code-generator/generator/generator.go
+++ b/internal/code-generator/generator/generator.go
@@ -3,7 +3,6 @@
 package generator
 
 import (
-	"bytes"
 	"fmt"
 	"go/format"
 	"io"
@@ -22,12 +21,15 @@ type File func(fileToParse, samplesDir, outPath, tmplPath, tmplName, commit stri
 func formatedWrite(outPath string, source []byte) error {
 	formatedSource, err := format.Source(source)
 	if err != nil {
-		return err
+		err = fmt.Errorf("'go fmt' fails on %v", err)
+		// write un-formatter source to simplify debugging
+		formatedSource = source
 	}
+
 	if err := ioutil.WriteFile(outPath, formatedSource, 0666); err != nil {
 		return err
 	}
-	return nil
+	return err
 }
 
 func executeTemplate(w io.Writer, name, path, commit string, fmap template.FuncMap, data interface{}) error {
@@ -51,20 +53,10 @@ func executeTemplate(w io.Writer, name, path, commit string, fmap template.FuncM
 	headerPath := filepath.Join(filepath.Dir(path), headerTmpl)
 
 	h := template.Must(template.New(headerTmpl).Funcs(fmap).ParseFiles(headerPath))
-	buf := bytes.NewBuffer(nil)
-	if err := h.Execute(buf, data); err != nil {
+	if err := h.Execute(w, data); err != nil {
 		return err
 	}
 
 	t := template.Must(template.New(name).Funcs(fmap).ParseFiles(path))
-	if err := t.Execute(buf, data); err != nil {
-		return err
-	}
-
-	src, err := format.Source(buf.Bytes())
-	if err != nil {
-		return err
-	}
-	_, err = w.Write(src)
-	return err
+	return t.Execute(w, data)
 }
diff --git a/internal/code-generator/main.go b/internal/code-generator/main.go
index 5eda1da..4fa40f4 100644
--- a/internal/code-generator/main.go
+++ b/internal/code-generator/main.go
@@ -134,7 +134,7 @@ func main() {
 
 	for _, file := range fileList {
 		if err := file.generate(file.fileToParse, file.samplesDir, file.outPath, file.tmplPath, file.tmplName, file.commit); err != nil {
-			log.Fatalf("error generating template %q to %q: %+v", file.tmplPath, file.outPath, err)
+			log.Fatalf("failed to generate %q from %q - %+v", file.outPath, file.tmplPath, err)
 		}
 	}
 }