fix module file detection (#1407)

The naming scheme for module files is [prefix.]MODULE.bazel:
https://bazel.build/rules/lib/globals/module#include

Author: novas0x2a

buildifier/utils/utils.go

@@ -37,7 +37,8 @@ func isStarlarkFile(name string) bool {
 	switch ext {
 	case ".bazel", ".oss":
 		// BUILD.bazel or BUILD.foo.bazel should be treated as Starlark files, same for WORSKSPACE and MODULE
-		return strings.HasPrefix(name, "BUILD.") || strings.HasPrefix(name, "WORKSPACE.") || strings.HasPrefix(name, "MODULE.")
+		// MODULE files flip the order: [prefix.]MODULE.bazel
+		return strings.HasPrefix(name, "BUILD.") || strings.HasPrefix(name, "WORKSPACE.") || strings.HasSuffix(name, "MODULE.bazel")
 	}
 
 	return name == "BUILD" || name == "WORKSPACE"

buildifier/utils/utils_test.go

@@ -129,6 +129,18 @@ func TestIsStarlarkFile(t *testing.T) {
 			filename: "foo.workspace",
 			ok:       false,
 		},
+		{
+			filename: "MODULE.bazel",
+			ok:       true,
+		},
+		{
+			filename: "my.MODULE.bazel",
+			ok:       true,
+		},
+		{
+			filename: "MODULE.bazel.other",
+			ok:       false,
+		},
 	}
 
 	for _, tc := range tests {