ENH: Allow to pass input file without named argument (#2576)

pypdf/_writer.py

@@ -168,7 +168,7 @@ def is_encrypted(self) -> bool:
 
     def __init__(
         self,
-        fileobj: StrByteType = "",
+        fileobj: Union[None, PdfReader, StrByteType, Path] = "",
         clone_from: Union[None, PdfReader, StrByteType, Path] = None,
     ) -> None:
         self._header = b"%PDF-1.3"
@@ -213,12 +213,41 @@ def __init__(
         )
         self._root = self._add_object(self._root_object)
 
+        def _get_clone_from(
+            fileobj: Union[None, PdfReader, str, Path, IO[Any], BytesIO],
+            clone_from: Union[None, PdfReader, str, Path, IO[Any], BytesIO],
+        ) -> Union[None, PdfReader, str, Path, IO[Any], BytesIO]:
+            if not isinstance(fileobj, (str, Path, IO, BytesIO)) or (
+                fileobj != "" and clone_from is None
+            ):
+                cloning = True
+                if not (
+                    not isinstance(fileobj, (str, Path))
+                    or (
+                        Path(str(fileobj)).exists()
+                        and Path(str(fileobj)).stat().st_size > 0
+                    )
+                ):
+                    cloning = False
+                if isinstance(fileobj, (IO, BytesIO)):
+                    t = fileobj.tell()
+                    fileobj.seek(-1, 2)
+                    if fileobj.tell() == 0:
+                        cloning = False
+                    fileobj.seek(t, 0)
+                if cloning:
+                    clone_from = fileobj
+            return clone_from
+
+        clone_from = _get_clone_from(fileobj, clone_from)
+        # to prevent overwriting
+        self.temp_fileobj = fileobj
+        self.fileobj = ""
+        self.with_as_usage = False
         if clone_from is not None:
             if not isinstance(clone_from, PdfReader):
                 clone_from = PdfReader(clone_from)
             self.clone_document_from_reader(clone_from)
-        self.fileobj = fileobj
-        self.with_as_usage = False
 
         self._encryption: Optional[Encryption] = None
         self._encrypt_entry: Optional[DictionaryObject] = None
@@ -268,7 +297,10 @@ def xmp_metadata(self, value: Optional[XmpInformation]) -> None:
 
     def __enter__(self) -> "PdfWriter":
         """Store that writer is initialized by 'with'."""
+        t = self.temp_fileobj
+        self.__init__()  # type: ignore
         self.with_as_usage = True
+        self.fileobj = t  # type: ignore
         return self
 
     def __exit__(

tests/test_writer.py

@@ -2196,3 +2196,24 @@ def test_mime_jupyter():
     writer = PdfWriter(clone_from=reader)
     assert reader._repr_mimebundle_(("include",), ("exclude",)) == {}
     assert writer._repr_mimebundle_(("include",), ("exclude",)) == {}
+
+
+def test_init_without_named_arg():
+    """Test to use file_obj argument and not clone_from"""
+    pdf_path = RESOURCE_ROOT / "crazyones.pdf"
+    reader = PdfReader(pdf_path)
+    writer = PdfWriter(clone_from=reader)
+    nb = len(writer._objects)
+    writer = PdfWriter(reader)
+    assert len(writer._objects) == nb
+    with open(pdf_path, "rb") as f:
+        writer = PdfWriter(f)
+        f.seek(0, 0)
+        by = BytesIO(f.read())
+    assert len(writer._objects) == nb
+    writer = PdfWriter(pdf_path)
+    assert len(writer._objects) == nb
+    writer = PdfWriter(str(pdf_path))
+    assert len(writer._objects) == nb
+    writer = PdfWriter(by)
+    assert len(writer._objects) == nb