Give a resumed download's progress the whole file's size as its total.

The total was "length + have or size or 0", which is the part file's size when a resumed answer names no length:
the bar ran past its end. It is now the expected size, else the server's length plus the part, else unknown.

Co-Authored-By: Claude Fable 5.2 <noreply@anthropic.com>

launcher/net.py

@@ -262,7 +262,12 @@ def download(url, dest, sha256=None, size=None, progress=None, cancel=None, head
                 status = getattr(r, 'status', 200)
                 if have and status != 206:   # the server ignores Range: start over
                     have = 0
-                total = int(r.headers.get('Content-Length') or 0) + have or size or 0
+                # The whole file's size for progress: the expected one, else what the server says is still to come
+                # plus what the part file holds, else unknown (0: progress then gets the bytes so far as the total).
+                # "length + have or size or 0" took the part file's size for the whole when a resumed answer named
+                # no length, and the bar ran past its end.
+                coming = int(r.headers.get('Content-Length') or 0)
+                total = size or (coming + have if coming else 0)
                 with open(part, 'ab' if have else 'wb') as f:
                     done = have
                     while True:

tests/launcher_test.py

@@ -657,6 +657,42 @@ class NetTest(Tmp):
         with self.assertRaises(net.DownloadError):
             net.download(srv.url + 'missing.bin', self.tmp / 'out' / 'm.bin')
 
+    def test_the_download_total(self):
+        """progress gets the whole file's size as its total: the expected size, else the length the server names
+        plus what the part file holds, else the bytes so far. A resumed answer without a length gave the part
+        file's size as the total, so the bar passed 100 %."""
+        data = os.urandom(2 * net.CHUNK + 500)
+        have = 1000
+
+        class Answer(io.BytesIO):   # what net.request returns: the rest of the file after a Range request
+            status = 206
+            length = None
+
+            def __init__(self, headers):
+                super().__init__(data[have:])
+                self.headers = headers
+
+        def fetch(headers, **kw):
+            dest = self.tmp / 'total' / 'f.bin'
+            shutil.rmtree(dest.parent, ignore_errors=True)
+            dest.parent.mkdir()
+            dest.with_name('f.bin.part').write_bytes(data[:have])
+            seen = []
+            with mock.patch.object(net, 'request', lambda url, h, timeout, version: Answer(headers)):
+                net.download('https://example.invalid/f.bin', dest, progress=lambda d, t: seen.append((d, t)), **kw)
+            self.assertEqual(dest.read_bytes(), data)
+            self.assertEqual(seen[-1][0], len(data))
+            return seen
+
+        for d, t in fetch({}):                                            # no length, no expected size
+            self.assertEqual(t, d)                                        # (the part's 1000 bytes as the total before)
+        for d, t in fetch({'Content-Length': str(len(data) - have)}):     # the length of the rest
+            self.assertEqual(t, len(data))
+        for d, t in fetch({}, size=len(data)):                            # the expected size, whatever the server says
+            self.assertEqual(t, len(data))
+        for d, t in fetch({'Content-Length': '7'}, size=len(data)):
+            self.assertEqual(t, len(data))
+
     def test_plain_http_redirects_and_oversize(self):
         with self.assertRaises(net.DownloadError):                        # refused before any connection
             net.request('http://example.invalid/f.bin')