feat: use PackageClauseOnly for parsing pkg name (gnolang#994)

gnovm/pkg/gnolang/nodes.go

@@ -2,6 +2,8 @@ package gnolang
 
 import (
 	"fmt"
+	"go/parser"
+	"go/token"
 	"io/ioutil"
 	"os"
 	"path/filepath"
@@ -1079,14 +1081,16 @@ type FileSet struct {
 	Files []*FileNode
 }
 
-// TODO replace with some more efficient method
-// that doesn't involve parsing the whole file.
-//
-// name could be anything,
-// it's only used to generate better error traces.
-func PackageNameFromFileBody(name string, body string) Name {
-	n := MustParseFile(name, body)
-	return n.PkgName
+// PackageNameFromFileBody extracts the package name from the given Gno code body.
+// The 'name' parameter is used for better error traces, and 'body' contains the Gno code.
+func PackageNameFromFileBody(name, body string) Name {
+	fset := token.NewFileSet()
+	astFile, err := parser.ParseFile(fset, name, body, parser.PackageClauseOnly)
+	if err != nil {
+		panic(err)
+	}
+
+	return Name(astFile.Name.Name)
 }
 
 // NOTE: panics if package name is invalid.
@@ -1096,7 +1100,6 @@ func ReadMemPackage(dir string, pkgPath string) *std.MemPackage {
 		panic(err)
 	}
 	memPkg := &std.MemPackage{Path: pkgPath}
-	var pkgName Name
 	allowedFiles := []string{ // make case insensitive?
 		"gno.mod",
 		"LICENSE",
@@ -1105,6 +1108,7 @@ func ReadMemPackage(dir string, pkgPath string) *std.MemPackage {
 	allowedFileExtensions := []string{
 		".gno",
 	}
+	var pkgName Name
 	for _, file := range files {
 		if file.IsDir() ||
 			strings.HasPrefix(file.Name(), ".") ||