internal: move WriteFormatted to internal/codegen

cmd/bpf2go/gen/output.go

@@ -18,6 +18,7 @@ import (
 	"github.com/cilium/ebpf/btf"
 	b2gInt "github.com/cilium/ebpf/cmd/bpf2go/internal"
 	"github.com/cilium/ebpf/internal"
+	"github.com/cilium/ebpf/internal/codegen"
 )
 
 //go:embed output.tpl
@@ -203,7 +204,7 @@ func Generate(args GenerateArgs) error {
 		return fmt.Errorf("can't generate types: %s", err)
 	}
 
-	return internal.WriteFormatted(buf.Bytes(), args.Output)
+	return codegen.WriteFormatted(buf.Bytes(), args.Output)
 }
 
 // sortTypes returns a list of types sorted by their (generated) Go type name.

internal/cmd/gentypes/main.go

@@ -17,6 +17,7 @@ import (
 
 	"github.com/cilium/ebpf/btf"
 	"github.com/cilium/ebpf/internal"
+	"github.com/cilium/ebpf/internal/codegen"
 	"github.com/cilium/ebpf/internal/sys"
 )
 
@@ -98,7 +99,7 @@ func run(args []string) error {
 	}
 	defer w.Close()
 
-	return internal.WriteFormatted(output, w)
+	return codegen.WriteFormatted(output, w)
 }
 
 func generateTypes(spec *btf.Spec) ([]byte, error) {

internal/codegen/format.go

@@ -0,0 +1,50 @@
+// Package codegen contains helpers for tools generating Go code.
+//
+// It is kept separate from package internal since go/format and its
+// dependencies would otherwise be linked and initialized in every binary
+// importing the library.
+package codegen
+
+import (
+	"bytes"
+	"errors"
+	"go/format"
+	"go/scanner"
+	"io"
+)
+
+// WriteFormatted outputs a formatted src into out.
+//
+// If formatting fails it returns an informative error message.
+func WriteFormatted(src []byte, out io.Writer) error {
+	formatted, err := format.Source(src)
+	if err == nil {
+		_, err = out.Write(formatted)
+		return err
+	}
+
+	var el scanner.ErrorList
+	if !errors.As(err, &el) {
+		return err
+	}
+
+	var nel scanner.ErrorList
+	for _, err := range el {
+		if !err.Pos.IsValid() {
+			nel = append(nel, err)
+			continue
+		}
+
+		buf := src[err.Pos.Offset:]
+		nl := bytes.IndexRune(buf, '\n')
+		if nl == -1 {
+			nel = append(nel, err)
+			continue
+		}
+
+		err.Msg += ": " + string(buf[:nl])
+		nel = append(nel, err)
+	}
+
+	return nel
+}

internal/output.go

@@ -1,11 +1,6 @@
 package internal
 
 import (
-	"bytes"
-	"errors"
-	"go/format"
-	"go/scanner"
-	"io"
 	"reflect"
 	"strings"
 	"unicode"
@@ -48,42 +43,6 @@ func Identifier(str string) string {
 	}, str)
 }
 
-// WriteFormatted outputs a formatted src into out.
-//
-// If formatting fails it returns an informative error message.
-func WriteFormatted(src []byte, out io.Writer) error {
-	formatted, err := format.Source(src)
-	if err == nil {
-		_, err = out.Write(formatted)
-		return err
-	}
-
-	var el scanner.ErrorList
-	if !errors.As(err, &el) {
-		return err
-	}
-
-	var nel scanner.ErrorList
-	for _, err := range el {
-		if !err.Pos.IsValid() {
-			nel = append(nel, err)
-			continue
-		}
-
-		buf := src[err.Pos.Offset:]
-		nl := bytes.IndexRune(buf, '\n')
-		if nl == -1 {
-			nel = append(nel, err)
-			continue
-		}
-
-		err.Msg += ": " + string(buf[:nl])
-		nel = append(nel, err)
-	}
-
-	return nel
-}
-
 // GoTypeName is like %T, but elides the package name.
 //
 // Pointers to a type are peeled off.