Merge branch 'main' into reader-minor-sty

docs/user/metadata.md

@@ -76,6 +76,30 @@ writer.add_metadata(
     }
 )
 
+# Clear all data but keep the entry in PDF
+writer.metadata = {}
+
+# Replace all entries with new set of entries
+writer.metadata = {
+    "/Author": "Martin",
+    "/Producer": "Libre Writer",
+}
+
+# Save the new PDF to a file
+with open("meta-pdf.pdf", "wb") as f:
+    writer.write(f)
+```
+
+## Removing metadata entry
+
+```python
+from pypdf import PdfWriter
+
+writer = PdfWriter("example.pdf")
+
+# Remove Metadata (/Info entry)
+writer.metadata = None
+
 # Save the new PDF to a file
 with open("meta-pdf.pdf", "wb") as f:
     writer.write(f)

pypdf/_cmap.py

@@ -7,8 +7,8 @@
 from .generic import (
     DecodedStreamObject,
     DictionaryObject,
-    NullObject,
     StreamObject,
+    is_null_or_none,
 )
 
 
@@ -468,7 +468,7 @@ def compute_space_width(
                         cpt += 1
                 sp_width = m / max(1, cpt) / 2
 
-    if sp_width is None or isinstance(sp_width, NullObject):
+    if is_null_or_none(sp_width):
         sp_width = 0.0
     return sp_width
 
@@ -482,8 +482,9 @@ def type1_alternative(
     if "/FontDescriptor" not in ft:
         return map_dict, space_code, int_entry
     ft_desc = cast(DictionaryObject, ft["/FontDescriptor"]).get("/FontFile")
-    if ft_desc is None:
+    if is_null_or_none(ft_desc):
         return map_dict, space_code, int_entry
+    assert ft_desc is not None, "mypy"
     txt = ft_desc.get_object().get_data()
     txt = txt.split(b"eexec\n")[0]  # only clear part
     txt = txt.split(b"/Encoding")[1]  # to get the encoding part

pypdf/_doc_common.py

@@ -85,6 +85,7 @@
     TreeObject,
     ViewerPreferences,
     create_string_object,
+    is_null_or_none,
 )
 from .types import OutlineType, PagemodeType
 from .xmp import XmpInformation
@@ -761,7 +762,7 @@ def _get_inherited(obj: DictionaryObject, key: str) -> Any:
             field = cast(DictionaryObject, field.indirect_reference.get_object())  # type: ignore
         except Exception as exc:
             raise ValueError("field type is invalid") from exc
-        if _get_inherited(field, "/FT") is None:
+        if is_null_or_none(_get_inherited(field, "/FT")):
             raise ValueError("field is not valid")
         ret = []
         if field.get("/Subtype", "") == "/Widget":
@@ -852,7 +853,7 @@ def _get_outline(
                     return outline
 
                 # §12.3.3 Document outline, entries in the outline dictionary
-                if lines is not None and "/First" in lines:
+                if not is_null_or_none(lines) and "/First" in lines:
                     node = cast(DictionaryObject, lines["/First"])
             self._namedDests = self._get_named_destinations()