Optionally generate type prefixes and suffixes for python code (#7857)

* optionally generate type prefixes and suffixes for python code

* fix codegen error when qualified name is empty

* generated code updated

2 files changed, 47 insertions, 30 deletions

diff --git a/src/flatc.cpp b/src/flatc.cpp
index a5dd0b1f..0e20a2f7 100644
--- a/src/flatc.cpp
+++ b/src/flatc.cpp
@@ -250,6 +250,8 @@ const static FlatCOption flatc_options[] = {
   { "", "no-leak-private-annotation", "",
     "Prevents multiple type of annotations within a Fbs SCHEMA file. "
     "Currently this is required to generate private types in Rust" },
+  { "", "python-no-type-prefix-suffix", "",
+    "Skip emission of Python functions that are prefixed with typenames" },
   { "", "file-names-only", "",
     "Print out generated file names without writing to the files"},
 };
@@ -650,7 +652,9 @@ FlatCOptions FlatCompiler::ParseFromCommandLineArguments(int argc,
         opts.ts_no_import_ext = true;
       } else if (arg == "--no-leak-private-annotation") {
         opts.no_leak_private_annotations = true;
-      } else if (arg == "--annotate-sparse-vectors") {
+       } else if (arg == "--python-no-type-prefix-suffix") {
+        opts.python_no_type_prefix_suffix = true;
+     } else if (arg == "--annotate-sparse-vectors") {
         options.annotate_include_vector_contents = false;
       } else if (arg == "--annotate") {
         if (++argi >= argc) Error("missing path following: " + arg, true);
diff --git a/src/idl_gen_python.cpp b/src/idl_gen_python.cpp
index 5b5ce353..6c93b909 100644
--- a/src/idl_gen_python.cpp
+++ b/src/idl_gen_python.cpp
@@ -139,13 +139,15 @@ class PythonGenerator : public BaseGenerator {
     code += Indent + Indent + "return x\n";
     code += "\n";
 
-    // Add an alias with the old name
-    code += Indent + "@classmethod\n";
-    code += Indent + "def GetRootAs" + struct_type + "(cls, buf, offset=0):\n";
-    code +=
-        Indent + Indent +
-        "\"\"\"This method is deprecated. Please switch to GetRootAs.\"\"\"\n";
-    code += Indent + Indent + "return cls.GetRootAs(buf, offset)\n";
+    if (!parser_.opts.python_no_type_prefix_suffix) {
+      // Add an alias with the old name
+      code += Indent + "@classmethod\n";
+      code += Indent + "def GetRootAs" + struct_type + "(cls, buf, offset=0):\n";
+      code +=
+          Indent + Indent +
+          "\"\"\"This method is deprecated. Please switch to GetRootAs.\"\"\"\n";
+      code += Indent + Indent + "return cls.GetRootAs(buf, offset)\n";
+    }
   }
 
   // Initialize an existing object with other data, to avoid an allocation.
@@ -480,7 +482,10 @@ class PythonGenerator : public BaseGenerator {
     if (!nested) { return; }  // There is no nested flatbuffer.
 
     const std::string unqualified_name = nested->constant;
-    const std::string qualified_name = NestedFlatbufferType(unqualified_name);
+    std::string qualified_name = NestedFlatbufferType(unqualified_name);
+    if (qualified_name.empty()) {
+      qualified_name = nested->constant;
+    }
 
     auto &code = *code_ptr;
     GenReceiver(struct_def, code_ptr);
@@ -491,7 +496,7 @@ class PythonGenerator : public BaseGenerator {
     code += Indent + Indent + Indent;
     code += "from " + qualified_name + " import " + unqualified_name + "\n";
     code += Indent + Indent + Indent + "return " + unqualified_name;
-    code += ".GetRootAs" + unqualified_name;
+    code += ".GetRootAs";
     code += "(self._tab.Bytes, self._tab.Vector(o))\n";
     code += Indent + Indent + "return 0\n";
     code += "\n";
@@ -605,15 +610,18 @@ class PythonGenerator : public BaseGenerator {
     auto &code = *code_ptr;
     const auto struct_type = namer_.Type(struct_def);
     // Generate method with struct name.
-    code += "def " + struct_type + "Start(builder): ";
-    code += "builder.StartObject(";
+
+    const auto name = parser_.opts.python_no_type_prefix_suffix ? "Start" : struct_type + "Start";
+
+    code += "def " + name + "(builder):\n";
+    code += Indent + "return builder.StartObject(";
     code += NumToString(struct_def.fields.vec.size());
-    code += ")\n";
+    code += ")\n\n";
 
-    if (!parser_.opts.one_file) {
+    if (!parser_.opts.one_file && !parser_.opts.python_no_type_prefix_suffix) {
       // Generate method without struct name.
       code += "def Start(builder):\n";
-      code += Indent + "return " + struct_type + "Start(builder)\n";
+      code += Indent + "return " + struct_type + "Start(builder)\n\n";
     }
   }
 
@@ -624,12 +632,14 @@ class PythonGenerator : public BaseGenerator {
     const std::string field_var = namer_.Variable(field);
     const std::string field_method = namer_.Method(field);
 
+    const auto name = parser_.opts.python_no_type_prefix_suffix ? "Add" + field_method : namer_.Type(struct_def) + "Add" + field_method;
+
     // Generate method with struct name.
-    code += "def " + namer_.Type(struct_def) + "Add" + field_method;
+    code += "def " + name;
     code += "(builder, ";
     code += field_var;
-    code += "): ";
-    code += "builder.Prepend";
+    code += "):\n";
+    code += Indent + "return builder.Prepend";
     code += GenMethod(field) + "Slot(";
     code += NumToString(offset) + ", ";
     if (!IsScalar(field.value.type.base_type) && (!struct_def.fixed)) {
@@ -646,16 +656,16 @@ class PythonGenerator : public BaseGenerator {
     } else {
       code += field.value.constant;
     }
-    code += ")\n";
+    code += ")\n\n";
 
-    if (!parser_.opts.one_file) {
+    if (!parser_.opts.one_file && !parser_.opts.python_no_type_prefix_suffix) {
       // Generate method without struct name.
       code += "def Add" + field_method + "(builder, " + field_var + "):\n";
       code +=
           Indent + "return " + namer_.Type(struct_def) + "Add" + field_method;
       code += "(builder, ";
       code += field_var;
-      code += ")\n";
+      code += ")\n\n";
     }
   }
 
@@ -667,20 +677,22 @@ class PythonGenerator : public BaseGenerator {
     const std::string field_method = namer_.Method(field);
 
     // Generate method with struct name.
-    code += "def " + struct_type + "Start" + field_method;
-    code += "Vector(builder, numElems): return builder.StartVector(";
+    const auto name = parser_.opts.python_no_type_prefix_suffix ? "Start" + field_method : struct_type + "Start" + field_method;
+    code += "def " + name;
+    code += "Vector(builder, numElems):\n";
+    code += Indent + "return builder.StartVector(";
     auto vector_type = field.value.type.VectorType();
     auto alignment = InlineAlignment(vector_type);
     auto elem_size = InlineSize(vector_type);
     code += NumToString(elem_size);
     code += ", numElems, " + NumToString(alignment);
-    code += ")\n";
+    code += ")\n\n";
 
-    if (!parser_.opts.one_file) {
+    if (!parser_.opts.one_file && !parser_.opts.python_no_type_prefix_suffix) {
       // Generate method without struct name.
       code += "def Start" + field_method + "Vector(builder, numElems):\n";
       code += Indent + "return " + struct_type + "Start";
-      code += field_method + "Vector(builder, numElems)\n";
+      code += field_method + "Vector(builder, numElems)\n\n";
     }
   }
 
@@ -725,15 +737,16 @@ class PythonGenerator : public BaseGenerator {
                            std::string *code_ptr) const {
     auto &code = *code_ptr;
 
+    const auto name = parser_.opts.python_no_type_prefix_suffix ? "End" : namer_.Type(struct_def) + "End";
     // Generate method with struct name.
-    code += "def " + namer_.Type(struct_def) + "End";
-    code += "(builder): ";
-    code += "return builder.EndObject()\n";
+    code += "def " + name + "(builder):\n";
+    code += Indent + "return builder.EndObject()\n\n";
 
-    if (!parser_.opts.one_file) {
+    if (!parser_.opts.one_file && !parser_.opts.python_no_type_prefix_suffix) {
       // Generate method without struct name.
       code += "def End(builder):\n";
       code += Indent + "return " + namer_.Type(struct_def) + "End(builder)";
+      code += "\n";
     }
   }