BUG: Fix deprecation warning on using PdfMerger (#891)

MasterOdin · web-flow · commit 68c9202a456c · 2022-05-23T13:27:38.000+02:00
Fixes a deprecation warning being raised when trying to use the PdfMerger class. This regression of #887 is caused by #889 which reversed the changes done to the PyPDF2/merger.py module so that it once again used the deprecated user-facing isString method as opposed to the internal _isString method. Additionally, this PR fixes the deprecation warning raised by referencing reader.namedDestinations as opposed to reader.named_destinations. Closes #890
diff --git a/PyPDF2/merger.py b/PyPDF2/merger.py
@@ -29,7 +29,7 @@
 from sys import version_info
 
 from PyPDF2._reader import PdfReader
-from PyPDF2._utils import DEPR_MSG, isString, str_
+from PyPDF2._utils import _isString, DEPR_MSG, str_
 from PyPDF2._writer import PdfWriter
 from PyPDF2.constants import PagesAttributes as PA
 from PyPDF2.generic import *
@@ -130,7 +130,7 @@ def merge(
         # BytesIO (or StreamIO) stream.
         # If fileobj is none of the above types, it is not modified
         decryption_key = None
-        if isString(fileobj):
+        if _isString(fileobj):
             fileobj = file(fileobj, "rb")
             my_file = True
         elif hasattr(fileobj, "seek") and hasattr(fileobj, "read"):
@@ -185,7 +185,7 @@ def merge(
         else:
             self.bookmarks += outline
 
-        dests = reader.namedDestinations
+        dests = reader.named_destinations
         trimmed_dests = self._trim_dests(reader, dests, pages)
         self.named_dests += trimmed_dests
 
@@ -241,7 +241,7 @@ def write(self, fileobj):
             file-like object.
         """
         my_file = False
-        if isString(fileobj):
+        if _isString(fileobj):
             fileobj = file(fileobj, "wb")
             my_file = True
 
