autobuilder: Use -mod=mod for vendor directories wihtout modules.txt

Author: Sauyon Lee

extractor/cli/go-autobuilder/go-autobuilder.go

@@ -244,7 +244,10 @@ func main() {
 	// skip the dependency installation step and run the extractor with `-mod=vendor`
 	if util.FileExists("vendor/modules.txt") {
 		modMode = ModVendor
+	} else if util.DirExists("vendor") {
+		modMode = modModIfSupported()
 	}
+
 	if modMode == ModVendor {
 		// fix go vendor issues with go versions >= 1.14 when no go version is specified in the go.mod
 		// if this is the case, and dependencies were vendored with an old go version (and therefore

extractor/util/util.go

@@ -91,3 +91,12 @@ func FileExists(filename string) bool {
 	}
 	return err == nil && !info.IsDir()
 }
+
+// DirExists tests whether `filename` exists and is a directory.
+func DirExists(filename string) bool {
+	info, err := os.Stat(filename)
+	if err != nil && !os.IsNotExist(err) {
+		log.Printf("Unable to stat %s: %s\n", filename, err.Error())
+	}
+	return err == nil && info.IsDir()
+}