Add script to compare namespace content for release cleanup (#51685)

Summary:
Usage explanation will be in the release note runbook.

This allows to generate diffs like:
```
Processing torch.nn
Things that were added:
{'quantizable', 'ChannelShuffle', 'LazyConvTranspose2d', 'LazyConv2d', 'LazyConvTranspose3d', 'LazyConv1d', 'GaussianNLLLoss', 'LazyConv3d', 'PixelUnshuffle', 'UninitializedParameter', 'LazyLinear', 'LazyConvTranspose1d'}

Things that were removed:
set()
```

This can then be shared with module owners along with the commits to help them validate that the namespace changes for their submodule is as expected.

Pull Request resolved: https://github.com/pytorch/pytorch/pull/51685

Reviewed By: zhangguanheng66

Differential Revision: D26260258

Pulled By: albanD

fbshipit-source-id: 40e40f86314e17246899d01ffa4b2631e93b52f7

.gitignore

@@ -109,6 +109,7 @@ torch/version.py
 # E.g., see .circleci/config.yaml
 env
 .circleci/scripts/COMMIT_MSG
+scripts/release_notes/*.json
 
 # IPython notebook checkpoints
 .ipynb_checkpoints

scripts/release_notes/namespace_check.py

@@ -0,0 +1,117 @@
+import argparse
+import torch
+from os import path
+import json
+
+# Import all utils so that getattr below can find them
+from torch.utils import bottleneck, checkpoint, model_zoo
+
+all_submod_list = [
+    "",
+    "nn",
+    "nn.functional",
+    "nn.init",
+    "optim",
+    "autograd",
+    "cuda",
+    "sparse",
+    "distributions",
+    "fft",
+    "linalg",
+    "jit",
+    "distributed",
+    "futures",
+    "onnx",
+    "random",
+    "utils.bottleneck",
+    "utils.checkpoint",
+    "utils.data",
+    "utils.model_zoo",
+]
+
+def get_content(submod):
+    mod = torch
+    if submod:
+        submod = submod.split(".")
+        for name in submod:
+            mod = getattr(mod, name)
+    content = dir(mod)
+    return content
+
+def namespace_filter(data):
+    out = set(d for d in data if d[0] != "_")
+    return out
+
+def run(args, submod):
+    print(f"## Processing torch.{submod}")
+    prev_filename = f"prev_data_{submod}.json"
+    new_filename = f"new_data_{submod}.json"
+
+    if args.prev_version:
+        content = get_content(submod)
+        with open(prev_filename, "w") as f:
+            json.dump(content, f)
+        print("Data saved for previous version.")
+    elif args.new_version:
+        content = get_content(submod)
+        with open(new_filename, "w") as f:
+            json.dump(content, f)
+        print("Data saved for new version.")
+    else:
+        assert args.compare
+        if not path.exists(prev_filename):
+            raise RuntimeError("Previous version data not collected")
+
+        if not path.exists(new_filename):
+            raise RuntimeError("New version data not collected")
+
+        with open(prev_filename, "r") as f:
+            prev_content = set(json.load(f))
+
+        with open(new_filename, "r") as f:
+            new_content = set(json.load(f))
+
+        if not args.show_all:
+            prev_content = namespace_filter(prev_content)
+            new_content = namespace_filter(new_content)
+
+        if new_content == prev_content:
+            print("Nothing changed.")
+            print("")
+        else:
+            print("Things that were added:")
+            print(new_content - prev_content)
+            print("")
+
+            print("Things that were removed:")
+            print(prev_content - new_content)
+            print("")
+
+def main():
+    parser = argparse.ArgumentParser(description='Tool to check namespace content changes')
+
+    group = parser.add_mutually_exclusive_group(required=True)
+    group.add_argument('--prev-version', action='store_true')
+    group.add_argument('--new-version', action='store_true')
+    group.add_argument('--compare', action='store_true')
+
+    group = parser.add_mutually_exclusive_group()
+    group.add_argument('--submod', default='', help='part of the submodule to check')
+    group.add_argument('--all-submod', action='store_true', help='collects data for all main submodules')
+
+    parser.add_argument('--show-all', action='store_true', help='show all the diff, not just public APIs')
+
+
+    args = parser.parse_args()
+
+    if args.all_submod:
+        submods = all_submod_list
+    else:
+        submods = [args.submod]
+
+    for mod in submods:
+        run(args, mod)
+
+
+if __name__ == '__main__':
+    main()