fix: ensure single trailing newline for raw generated files

internal/codegen/file.go

@@ -81,12 +81,13 @@ func (f *File) Write(p []byte) (int, error) {
 	return n, err // nolint: wrapcheck // false positive
 }
 
-func (f *File) Bytes() []byte {
-	return f.buf.Bytes()
+// RawContent returns the raw content of the file.
+func (f *File) RawContent() []byte {
+	return append(bytes.TrimSpace(f.buf.Bytes()), '\n')
 }
 
-// Content returns the formatted Go source of the file.
-func (f *File) Content() (_ []byte, err error) {
+// GoContent returns the formatted Go source of the file.
+func (f *File) GoContent() (_ []byte, err error) {
 	if f.err != nil {
 		return nil, fmt.Errorf("content of %s: %w", f.cfg.Filename, f.err)
 	}

sg/generate.go

@@ -80,7 +80,7 @@ func genMakefiles(ctx context.Context, mks ...Makefile) {
 	if err := generateInitFile(initFile, pkg); err != nil {
 		panic(err)
 	}
-	initFileContent, err := initFile.Content()
+	initFileContent, err := initFile.GoContent()
 	if err != nil {
 		panic(err)
 	}
@@ -105,8 +105,7 @@ func genMakefiles(ctx context.Context, mks ...Makefile) {
 		if err := generateMakefile(ctx, mk, pkg, v, mks...); err != nil {
 			panic(err)
 		}
-		// Remove trailing whitespace with len
-		if err := os.WriteFile(v.Path, mk.Bytes()[:len(mk.Bytes())-1], 0o600); err != nil {
+		if err := os.WriteFile(v.Path, mk.RawContent(), 0o600); err != nil {
 			panic(err)
 		}
 	}

sg/makefile.go

@@ -1,7 +1,6 @@
 package sg
 
 import (
-	"bytes"
 	"context"
 	"fmt"
 	"go/ast"
@@ -18,22 +17,16 @@ func generateMakefile(ctx context.Context, g *codegen.File, pkg *doc.Package, mk
 	if err != nil {
 		return err
 	}
-	cmd := Command(context.Background(), "go", "list", "-m")
-	var b bytes.Buffer
-	cmd.Stdout = &b
-	if err := cmd.Run(); err != nil {
-		return err
-	}
 	dependencies := fmt.Sprintf("%s/go.mod %s/*.go", includePath, includePath)
-	if strings.TrimSpace(b.String()) == "go.einride.tech/sage" {
+	if strings.TrimSpace(Output(Command(ctx, "go", "list", "-m"))) == "go.einride.tech/sage" {
 		dependencies = fmt.Sprintf("%s/go.mod $(shell find %s/.. -type f -name '*.go')", includePath, includePath)
 	}
 	g.P("# To learn more, see ", includePath, "/sagefile.go and https://github.com/einride/sage.")
-	g.P()
 	if len(mk.defaultTargetName()) != 0 {
-		g.P(".DEFAULT_GOAL := ", toMakeTarget(mk.defaultTargetName()))
 		g.P()
+		g.P(".DEFAULT_GOAL := ", toMakeTarget(mk.defaultTargetName()))
 	}
+	g.P()
 	g.P("sagefile := ", filepath.Join(includePath, BinDir, SageFileBinary))
 	g.P()
 	g.P("$(sagefile): ", dependencies)
@@ -76,10 +69,8 @@ func generateMakefile(ctx context.Context, g *codegen.File, pkg *doc.Package, mk
 			g.P(".PHONY: ", toMakeTarget(i.namespaceName()))
 			g.P(toMakeTarget(i.namespaceName()), ":")
 			g.P("\t$(MAKE) -C ", mkPath, " -f ", filepath.Base(i.Path))
-			g.P()
 		}
 	}
-	g.P()
 	return nil
 }