Fix zlib.Decompress.flush error handling

Author: msimacek

graalpython/com.oracle.graal.python.cext/zlib/zlib.c

@@ -1108,13 +1108,6 @@ int zlib_Decompress_flush(zlib_stream *zst, ssize_t length) {
             error_occurred(zst, INFLATE_END_ERROR);
             return err;
         }
-    } else if (err != Z_OK && err != Z_BUF_ERROR) {
-        /* We will only get Z_BUF_ERROR if the output buffer was full
-           but there wasn't more output when we tried again, so it is
-           not an error condition.
-        */
-        error_occurred(zst, INFLATE_FLUSH_ERROR);
-        return err;
     }
     if (zst->output->size) {
         zst->output_size = zst->zst.next_out - zst->output->buf;

graalpython/com.oracle.graal.python.test/src/tests/test_zlib.py

@@ -164,6 +164,12 @@ def test_custom_bufsize(self):
         compressed = zlib.compress(data, 1)
         self.assertEqual(zlib.decompress(compressed, 15, CustomInt()), data)
 
+    def test_decoding_flush_ignore_error(self):
+        d = zlib.decompressobj()
+        self.assertRaises(zlib.error, d.decompress, b"asdf")
+        d.flush()
+
+
 HAMLET_SCENE = b"""
 LAERTES
 

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/modules/zlib/ZlibDecompressBuiltins.java

@@ -73,6 +73,7 @@
 import com.oracle.graal.python.runtime.NFIZlibSupport;
 import com.oracle.graal.python.runtime.NativeLibrary;
 import com.oracle.graal.python.runtime.PythonContext;
+import com.oracle.graal.python.runtime.exception.PException;
 import com.oracle.graal.python.runtime.object.PythonObjectFactory;
 import com.oracle.graal.python.util.PythonUtils;
 import com.oracle.truffle.api.dsl.Cached;
@@ -253,7 +254,13 @@ PBytes doit(ZLibCompObject.NativeZlibCompObject self, int length,
         PBytes doit(ZLibCompObject.JavaZlibCompObject self, int length,
                         @Cached ZlibNodes.JavaDecompressNode decompressNode,
                         @Cached BytesNodes.ToBytesNode toBytes) {
-            byte[] res = decompressNode.execute(self, toBytes.execute(self.getUnconsumedTail()), 0, length, factory());
+            byte[] res;
+            try {
+                res = decompressNode.execute(self, toBytes.execute(self.getUnconsumedTail()), 0, length, factory());
+            } catch (PException e) {
+                // CPython ignores errors here
+                res = PythonUtils.EMPTY_BYTE_ARRAY;
+            }
             self.setUninitialized();
             return factory().createBytes(res);
         }