From 1c6e288428c6b90178fc498fc874db03646d32c5 Mon Sep 17 00:00:00 2001
From: Dale Phurrough <dale@hidale.com>
Date: Wed, 25 Aug 2021 02:14:48 +0200
Subject: [PATCH 1/2] another fix opencv/opencv#20575

---
 testdata/dnn/download_models.py | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/testdata/dnn/download_models.py b/testdata/dnn/download_models.py
index 6eca15c29..c1d325aa4 100755
--- a/testdata/dnn/download_models.py
+++ b/testdata/dnn/download_models.py
@@ -82,7 +82,12 @@ def get(self):
 
         print(' done')
         print(' file {}'.format(self.filename))
-        return self.verify()
+        candidate_verify = self.verify()
+        if not candidate_verify:
+            if os.path.exists(self.filename):
+                print('  deleting invalid file')
+                os.remove(self.filename)
+        return candidate_verify
 
     def download(self):
         try:

From 778223b5dd74bb7bec1f03ac8b0f3f124a88c735 Mon Sep 17 00:00:00 2001
From: Alexander Alekhin <alexander.a.alekhin@gmail.com>
Date: Mon, 30 Aug 2021 18:36:37 +0000
Subject: [PATCH 2/2] download_models: rename downloaded content for further
 investigation

---
 testdata/dnn/download_models.py | 28 ++++++++++++++++++++++++----
 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/testdata/dnn/download_models.py b/testdata/dnn/download_models.py
index c1d325aa4..7cbbd4d40 100755
--- a/testdata/dnn/download_models.py
+++ b/testdata/dnn/download_models.py
@@ -51,7 +51,8 @@ def verify(self):
                         break
                     sha.update(buf)
             print('  actual {}'.format(sha.hexdigest()))
-            return self.sha == sha.hexdigest()
+            self.sha_actual = sha.hexdigest()
+            return self.sha == self.sha_actual
         except Exception as e:
             print('  catch {}'.format(e))
 
@@ -84,9 +85,7 @@ def get(self):
         print(' file {}'.format(self.filename))
         candidate_verify = self.verify()
         if not candidate_verify:
-            if os.path.exists(self.filename):
-                print('  deleting invalid file')
-                os.remove(self.filename)
+            self.handle_bad_download()
         return candidate_verify
 
     def download(self):
@@ -117,6 +116,27 @@ def save(self, r):
                 print('>', end='')
                 sys.stdout.flush()
 
+    def handle_bad_download(self):
+        if os.path.exists(self.filename):
+            # rename file for further investigation
+            try:
+                # NB: using `self.sha_actual` may create unbounded number of files
+                rename_target = self.filename + '.invalid'
+                # TODO: use os.replace (Python 3.3+)
+                try:
+                    if os.path.exists(rename_target):  # avoid FileExistsError on Windows from os.rename()
+                        os.remove(rename_target)
+                finally:
+                    os.rename(self.filename, rename_target)
+                    print('  renaming invalid file to ' + rename_target)
+            except:
+                import traceback
+                traceback.print_exc()
+            finally:
+                if os.path.exists(self.filename):
+                    print('  deleting invalid file')
+                    os.remove(self.filename)
+
 
 def GDrive(gid):
     def download_gdrive(dst):