[Python] Avoid include own type (#8625)

This prevents the include of the type defined in the pyi,
otherwise this leads to error message like this:
error: Name XYZ already defined (possibly by an import)  [no-redef]

include/codegen/python.cc

@@ -59,5 +59,21 @@ const python::Import &python::Imports::Import(const std::string &module,
   imports.push_back(std::move(import));
   return imports.back();
 }
+
+const python::Import &python::Imports::Export(const std::string &module) {
+  python::Import import;
+  import.module = module;
+  exports.push_back(std::move(import));
+  return exports.back();
+}
+
+const python::Import &python::Imports::Export(const std::string &module,
+                                              const std::string &name) {
+  python::Import import;
+  import.module = module;
+  import.name = name;
+  exports.push_back(std::move(import));
+  return exports.back();
+}
 }  // namespace python
 }  // namespace flatbuffers

include/codegen/python.h

@@ -85,7 +85,12 @@ struct Imports {
   const python::Import &Import(const std::string &module,
                                const std::string &name);
 
+  const python::Import &Export(const std::string &module);
+  const python::Import &Export(const std::string &module,
+                               const std::string &name);
+
   std::vector<python::Import> imports;
+  std::vector<python::Import> exports;
 };
 }  // namespace python
 }  // namespace flatbuffers

src/idl_gen_python.cpp

@@ -290,6 +290,7 @@ class PythonStubGenerator {
   void GenerateObjectStub(std::stringstream &stub, const StructDef *struct_def,
                           Imports *imports) const {
     std::string name = namer_.ObjectType(*struct_def);
+    imports->Export(ModuleFor(struct_def), namer_.Type(*struct_def));
 
     stub << "class " << name;
     if (version_.major != 3) stub << "(object)";
@@ -327,6 +328,7 @@ class PythonStubGenerator {
   void GenerateStructStub(std::stringstream &stub, const StructDef *struct_def,
                           Imports *imports) const {
     std::string type = namer_.Type(*struct_def);
+    imports->Export(ModuleFor(struct_def), namer_.Type(*struct_def));
 
     stub << "class " << type;
     if (version_.major != 3) stub << "(object)";
@@ -545,6 +547,7 @@ class PythonStubGenerator {
   void GenerateEnumStub(std::stringstream &stub, const EnumDef *enum_def,
                         Imports *imports) const {
     stub << "class " << namer_.Type(*enum_def);
+    imports->Export(ModuleFor(enum_def), namer_.Type(*enum_def));
 
     if (version_.major == 3){
       imports->Import("enum", "IntEnum");
@@ -589,18 +592,32 @@ class PythonStubGenerator {
       }
     }
 
+    // Remove imports from exports
+    for (const Import &import : imports.exports) {
+      if (import.name == "") {
+        modules.erase(import.module);
+      } else {
+        auto search = names_by_module.find(import.module);
+        if (search != names_by_module.end()) {
+          search->second.erase(import.name);
+        }
+      }
+    }
+
     for (const std::string &module : modules) {
       ss << "import " << module << '\n';
     }
     for (const auto &import : names_by_module) {
-      ss << "from " << import.first << " import ";
-      size_t i = 0;
-      for (const std::string &name : import.second) {
-        if (i > 0) ss << ", ";
-        ss << name;
-        ++i;
+      if (!import.second.empty()) {
+        ss << "from " << import.first << " import ";
+        size_t i = 0;
+        for (const std::string &name : import.second) {
+          if (i > 0) ss << ", ";
+          ss << name;
+          ++i;
+        }
+        ss << '\n';
       }
-      ss << '\n';
     }
   }
 

tests/MyGame/Example/ArrayStruct.pyi

@@ -5,7 +5,6 @@ import numpy as np
 
 import flatbuffers
 import typing
-from MyGame.Example.ArrayStruct import ArrayStruct
 from MyGame.Example.NestedStruct import NestedStruct, NestedStructT
 from MyGame.Example.TestEnum import TestEnum
 

tests/MyGame/Example/ArrayTable.pyi

@@ -6,7 +6,6 @@ import numpy as np
 import flatbuffers
 import typing
 from MyGame.Example.ArrayStruct import ArrayStruct, ArrayStructT
-from MyGame.Example.ArrayTable import ArrayTable
 
 uoffset: typing.TypeAlias = flatbuffers.number_types.UOffsetTFlags.py_type
 

tests/MyGame/Example/NestedStruct.pyi

@@ -5,7 +5,6 @@ import numpy as np
 
 import flatbuffers
 import typing
-from MyGame.Example.NestedStruct import NestedStruct
 from MyGame.Example.TestEnum import TestEnum
 
 uoffset: typing.TypeAlias = flatbuffers.number_types.UOffsetTFlags.py_type

tests/MyGame/Example/NestedUnion/Any.pyi

@@ -5,7 +5,6 @@ import numpy as np
 
 import flatbuffers
 import typing
-from MyGame.Example.NestedUnion.Any import Any
 from MyGame.Example.NestedUnion.TestSimpleTableWithEnum import TestSimpleTableWithEnum
 from MyGame.Example.NestedUnion.Vec3 import Vec3
 from flatbuffers import table

tests/MyGame/Example/NestedUnion/NestedUnionTest.pyi

@@ -6,7 +6,6 @@ import numpy as np
 import flatbuffers
 import typing
 from MyGame.Example.NestedUnion.Any import Any
-from MyGame.Example.NestedUnion.NestedUnionTest import NestedUnionTest
 from MyGame.Example.NestedUnion.TestSimpleTableWithEnum import TestSimpleTableWithEnumT
 from MyGame.Example.NestedUnion.Vec3 import Vec3T
 from flatbuffers import table

tests/MyGame/Example/NestedUnion/Test.pyi

@@ -5,7 +5,6 @@ import numpy as np
 
 import flatbuffers
 import typing
-from MyGame.Example.NestedUnion.Test import Test
 
 uoffset: typing.TypeAlias = flatbuffers.number_types.UOffsetTFlags.py_type
 

tests/MyGame/Example/NestedUnion/TestSimpleTableWithEnum.pyi

@@ -6,7 +6,6 @@ import numpy as np
 import flatbuffers
 import typing
 from MyGame.Example.NestedUnion.Color import Color
-from MyGame.Example.NestedUnion.TestSimpleTableWithEnum import TestSimpleTableWithEnum
 
 uoffset: typing.TypeAlias = flatbuffers.number_types.UOffsetTFlags.py_type
 

tests/MyGame/Example/NestedUnion/Vec3.pyi

@@ -7,7 +7,6 @@ import flatbuffers
 import typing
 from MyGame.Example.NestedUnion.Color import Color
 from MyGame.Example.NestedUnion.Test import Test, TestT
-from MyGame.Example.NestedUnion.Vec3 import Vec3
 
 uoffset: typing.TypeAlias = flatbuffers.number_types.UOffsetTFlags.py_type
 

tests/MyGame/MonsterExtra.pyi

@@ -5,7 +5,6 @@ import numpy as np
 
 import flatbuffers
 import typing
-from MyGame.MonsterExtra import MonsterExtra
 
 uoffset: typing.TypeAlias = flatbuffers.number_types.UOffsetTFlags.py_type