Add reflection support for python (#7026)

We already have the reflection.fbs file and the flatbuffers
python language support.

Adding this feature would give the python developers the
ability to parse the flatbuffers schema and write some tools.

Co-authored-by: Derek Bailey <derekbailey@google.com>

scripts/generate_code.py

@@ -82,6 +82,24 @@ def flatc(
     result = subprocess.run(cmd, cwd=str(cwd), check=True)
 
 
+# Generate the code for flatbuffers reflection schema
+def flatc_reflection(options, location, target):
+    full_options = ["--no-prefix"] + options
+    temp_dir = ".tmp"
+    flatc(
+        full_options,
+        prefix=temp_dir,
+        schema="reflection.fbs",
+        cwd=reflection_path,
+    )
+    new_reflection_path = Path(reflection_path, temp_dir, target)
+    original_reflection_path = Path(root_path, location, target)
+    if not filecmp.cmp(str(new_reflection_path), str(original_reflection_path)):
+        shutil.rmtree(str(original_reflection_path))
+        shutil.move(str(new_reflection_path), str(original_reflection_path))
+    shutil.rmtree(str(Path(reflection_path, temp_dir)))
+
+
 # Glob a pattern relative to file path
 def glob(path, pattern):
     return [str(p) for p in path.glob(pattern)]
@@ -422,22 +440,13 @@ flatc(
 )
 
 # Reflection
+
 # Skip generating the reflection if told too, as we run this script after
 # building flatc which uses the reflection_generated.h itself.
 if not args.skip_gen_reflection:
-    temp_dir = ".tmp"
-    flatc(
-        ["-c", "--cpp-std", "c++0x", "--no-prefix"],
-        prefix=temp_dir,
-        schema="reflection.fbs",
-        cwd=reflection_path,
-    )
-    new_reflection_file = Path(
-        reflection_path, temp_dir, "reflection_generated.h"
-    )
-    original_reflection_file = Path(
-        root_path, "include/flatbuffers/reflection_generated.h"
-    )
-    if not filecmp.cmp(str(new_reflection_file), str(original_reflection_file)):
-        shutil.move(str(new_reflection_file), str(original_reflection_file))
-    shutil.rmtree(str(Path(reflection_path, temp_dir)))
+  # C++ Reflection
+  flatc_reflection(["-c", "--cpp-std", "c++0x"], "include/flatbuffers",
+                   "reflection_generated.h")
+
+# Python Reflection
+flatc_reflection(["-p"], "python/flatbuffers", "reflection")