fix: retry a file list the network cut short

install.ps1

@@ -8,7 +8,7 @@ param(
 
 $ErrorActionPreference = "Stop"
 $defaultInstallUrl = "https://raw.githubusercontent.com/Abdess/retrobios/main/install.py"
-$defaultInstallSha256 = "546d190d17449d7b25bcf981bd396645c194364f363a2d315380a043ca101e38"
+$defaultInstallSha256 = "e57aa03a8f581b6bf02cb1d3161af6da19719425383790da0ed5f761afaf436c"
 $maximumInstallerBytes = 2MB
 $installerExit = 0
 $installer = if ($PSScriptRoot) { Join-Path $PSScriptRoot "install.py" } else { $null }

install.py

@@ -1257,18 +1257,31 @@ def normalize_platform(name: str) -> str:
 def _read_limited_json(
     response: http.client.HTTPResponse, limit: int, label: str
 ) -> object:
-    """Read a bounded UTF-8 JSON response."""
+    """Read a bounded UTF-8 JSON response.
+
+    A body shorter than its Content-Length is a dropped connection, raised
+    as one so the caller retries: parsed, the cut read as an invalid file
+    list and the run ended without the network advice.
+    """
     raw_length = response.headers.get("Content-Length") if response.headers else None
+    expected: int | None = None
     if raw_length:
         try:
-            if int(raw_length) > limit:
-                raise ValueError(f"{label} exceeds {limit} bytes")
-        except ValueError as exc:
-            if "exceeds" in str(exc):
-                raise
-    payload = response.read(limit + 1)
+            expected = int(raw_length)
+        except ValueError:
+            expected = None
+        if expected is not None and expected > limit:
+            raise ValueError(f"{label} exceeds {limit} bytes")
+    try:
+        payload = response.read(limit + 1)
+    except http.client.IncompleteRead as exc:
+        raise ConnectionError(
+            f"{label} cut after {len(exc.partial)} bytes"
+        ) from exc
     if len(payload) > limit:
         raise ValueError(f"{label} exceeds {limit} bytes")
+    if expected is not None and len(payload) < expected:
+        raise ConnectionError(f"{label} cut after {len(payload)} of {expected} bytes")
     try:
         return json.loads(payload.decode("utf-8"))
     except (UnicodeDecodeError, json.JSONDecodeError) as exc:

install.sh

@@ -18,7 +18,7 @@ esac
 TEMP_INSTALLER=""
 TEMP_DIRECTORY=""
 DEFAULT_INSTALL_URL="https://raw.githubusercontent.com/Abdess/retrobios/main/install.py"
-DEFAULT_INSTALL_SHA256="546d190d17449d7b25bcf981bd396645c194364f363a2d315380a043ca101e38"
+DEFAULT_INSTALL_SHA256="e57aa03a8f581b6bf02cb1d3161af6da19719425383790da0ed5f761afaf436c"
 MAX_INSTALLER_BYTES=2097152
 
 cleanup() {

tests/test_install.py

@@ -2446,5 +2446,34 @@ class QuitMeansNoAtTheLastQuestion(unittest.TestCase):
                 self.assertIs(install._confirm("? "), expected)
 
 
+
+class ACutFileListIsRetried(unittest.TestCase):
+    """Wi-Fi dropped mid install/batocera.json: the short body parsed as an
+    invalid file list, no retry, no network advice."""
+
+    class _Response(io.BytesIO):
+        def __init__(self, body: bytes, length: int):
+            super().__init__(body)
+            self.headers = {"Content-Length": str(length)}
+
+        def __enter__(self):
+            return self
+
+        def __exit__(self, *exc):
+            return False
+
+    def test_the_second_attempt_succeeds(self):
+        full = json.dumps({"a": 1}).encode()
+        answers = iter([self._Response(full[:4], len(full)), self._Response(full, len(full))])
+        with unittest.mock.patch.object(install.urllib.request, "urlopen",
+                                        lambda *a, **k: next(answers)), \
+                unittest.mock.patch.object(install.time, "sleep"):
+            self.assertEqual(install._fetch_json("https://x/y.json", 1000, "manifest"), {"a": 1})
+
+    def test_a_short_body_is_a_connection_error(self):
+        with self.assertRaises(ConnectionError):
+            install._read_limited_json(self._Response(b'{"a"', 10), 1000, "manifest")
+
+
 if __name__ == "__main__":
     unittest.main()