Added --python-fields-snake-case option

include/flatbuffers/idl.h

@@ -729,6 +729,9 @@ struct IDLOptions {
   // Whether to generate numpy helpers.
   bool python_gen_numpy;
 
+  // Use snake-case for field names in the Python object API.
+  bool python_fields_snake_case;
+
   bool ts_omit_entrypoint;
   ProtoIdGapAction proto_id_gap_action;
 
@@ -856,6 +859,7 @@ struct IDLOptions {
         python_no_type_prefix_suffix(false),
         python_typing(false),
         python_gen_numpy(true),
+        python_fields_snake_case(false),
         ts_omit_entrypoint(false),
         proto_id_gap_action(ProtoIdGapAction::WARNING),
         mini_reflect(IDLOptions::kNone),

src/flatc.cpp

@@ -266,6 +266,8 @@ const static FlatCOption flatc_options[] = {
     {"", "python-decode-obj-api-strings", "",
      "Decode bytes to strings for the Python Object API"},
     {"", "python-gen-numpy", "", "Whether to generate numpy helpers."},
+    {"", "python-fields-snake-case", "",
+      "Generate Python fields using snake_case naming convention."},
     {"", "ts-omit-entrypoint", "",
      "Omit emission of namespace entrypoint file"},
     {"", "file-names-only", "",
@@ -708,6 +710,8 @@ FlatCOptions FlatCompiler::ParseFromCommandLineArguments(int argc,
       } else if (arg == "--no-python-gen-numpy" ||
                  arg == "--python-gen-numpy=false") {
         opts.python_gen_numpy = false;
+      } else if (arg == "--python-fields-snake-case") {
+        opts.python_fields_snake_case = true;
       } else if (arg == "--ts-omit-entrypoint") {
         opts.ts_omit_entrypoint = true;
       } else if (arg == "--annotate-sparse-vectors") {

src/idl_gen_python.cpp

@@ -48,12 +48,22 @@ typedef std::set<ImportMapEntry> ImportMap;
 static const CommentConfig def_comment = {nullptr, "#", nullptr};
 static const std::string Indent = "    ";
 
+inline Namer::Config PythonNamerConfig(const Namer::Config& input,
+                                       const IDLOptions& opts,
+                                       const std::string& path) {
+  auto cfg = WithFlagOptions(input, opts, path);
+  if (opts.python_fields_snake_case) {
+    cfg.fields = Case::kSnake;
+  }
+  return cfg;
+}
+
 class PythonStubGenerator {
  public:
   PythonStubGenerator(const Parser& parser, const std::string& path,
                       const Version& version)
       : parser_{parser},
-        namer_{WithFlagOptions(kStubConfig, parser.opts, path),
+        namer_{PythonNamerConfig(kStubConfig, parser.opts, path),
                Keywords(version)},
         version_(version) {}
 
@@ -698,7 +708,7 @@ class PythonGenerator : public BaseGenerator {
       : BaseGenerator(parser, path, file_name, "" /* not used */,
                       "" /* not used */, "py"),
         float_const_gen_("float('nan')", "float('inf')", "float('-inf')"),
-        namer_(WithFlagOptions(kConfig, parser.opts, path), Keywords(version)) {
+        namer_(PythonNamerConfig(kConfig, parser.opts, path), Keywords(version)) {
   }
 
   // Most field accessors need to retrieve and test the field offset first,
@@ -1321,7 +1331,7 @@ class PythonGenerator : public BaseGenerator {
         } else {
           code += IsArray(field_type) ? "    " : "";
           code += indent + "    builder.Prepend" + GenMethod(field) + "(";
-          code += nameprefix + namer_.Variable(field);
+          code += nameprefix + namer_.Field(field);
           size_t array_cnt = index + (IsArray(field_type) ? 1 : 0);
           for (size_t i = 0; in_array && i < array_cnt; i++) {
             code += "[_idx" + NumToString(i) + "-1]";