cmd/vfsgendev: Simplify lookupSource to lookupNameAndComment.

This is cleaner and more readable code, better separated by the
responsibilities.

Rename imported source package to "sourcepkg". This makes the generated
script easier to read, and also safer (avoids any possible package name
conflicts).

cmd/vfsgendev/generate.go

@@ -6,8 +6,11 @@ import (
 )
 
 type data struct {
-	source
-	BuildTags string
+	ImportPath      string
+	PackageName     string
+	BuildTags       string
+	VariableName    string
+	VariableComment string
 }
 
 var generateTemplate = template.Must(template.New("").Funcs(template.FuncMap{
@@ -21,11 +24,11 @@ import (
 
 	"github.com/shurcooL/vfsgen"
 
-	{{.ImportPath | quote}}
+	sourcepkg {{.ImportPath | quote}}
 )
 
 func main() {
-	err := vfsgen.Generate({{.PackageName}}.{{.VariableName}}, vfsgen.Options{
+	err := vfsgen.Generate(sourcepkg.{{.VariableName}}, vfsgen.Options{
 		PackageName:     {{.PackageName | quote}},
 		BuildTags:       {{.BuildTags | quote}},
 		VariableName:    {{.VariableName | quote}},

cmd/vfsgendev/main.go

@@ -52,13 +52,19 @@ func run() error {
 
 	bctx := build.Default
 	bctx.BuildTags = []string{tag}
-	source, err := lookupSource(bctx, importPath, variableName)
+	packageName, variableComment, err := lookupNameAndComment(bctx, importPath, variableName)
 	if err != nil {
 		return err
 	}
 
 	var buf bytes.Buffer
-	err = generateTemplate.Execute(&buf, data{source: source, BuildTags: "!" + tag})
+	err = generateTemplate.Execute(&buf, data{
+		ImportPath:      importPath,
+		PackageName:     packageName,
+		BuildTags:       "!" + tag,
+		VariableName:    variableName,
+		VariableComment: variableComment,
+	})
 	if err != nil {
 		return err
 	}

cmd/vfsgendev/parse.go

@@ -55,37 +55,24 @@ func stringValue(e ast.Expr) (string, error) {
 	return strconv.Unquote(lit.Value)
 }
 
-type source struct {
-	ImportPath      string
-	PackageName     string
-	VariableName    string
-	VariableComment string
-}
-
-// lookupSource imports package using provided build context, and returns the
-// import path, package name, variable name and variable comment.
-func lookupSource(bctx build.Context, importPath, variableName string) (source, error) {
+// lookupNameAndComment imports package using provided build context, and
+// returns the package name and variable comment.
+func lookupNameAndComment(bctx build.Context, importPath, variableName string) (packageName, variableComment string, err error) {
 	bpkg, err := bctx.Import(importPath, "", 0)
 	if err != nil {
-		return source{}, fmt.Errorf("can't import package %q: %v", importPath, err)
+		return "", "", fmt.Errorf("can't import package %q: %v", importPath, err)
 	}
 	dpkg, err := docPackage(bpkg)
 	if err != nil {
-		return source{}, fmt.Errorf("can't get godoc of package %q: %v", importPath, err)
+		return "", "", fmt.Errorf("can't get godoc of package %q: %v", importPath, err)
 	}
-	var variableComment string
 	for _, v := range dpkg.Vars {
 		if len(v.Names) == 1 && v.Names[0] == variableName {
 			variableComment = strings.TrimSuffix(v.Doc, "\n")
 			break
 		}
 	}
-	return source{
-		ImportPath:      bpkg.ImportPath,
-		PackageName:     bpkg.Name,
-		VariableName:    variableName,
-		VariableComment: variableComment,
-	}, nil
+	return bpkg.Name, variableComment, nil
 }
 
 // TODO: Keep in sync or unify with github.com/shurcooL/cmd/gorepogen/docpackage.go.