BUG: Handle empty root outline (#2239)

Closes #2233

pypdf/_writer.py

@@ -295,13 +295,13 @@ def _replace_object(
         obj: PdfObject,
     ) -> PdfObject:
         if isinstance(indirect_reference, IndirectObject):
-            assert indirect_reference.pdf == self
+            if indirect_reference.pdf != self:
+                raise ValueError("pdf must be self")
             indirect_reference = indirect_reference.idnum
+        gen = self._objects[indirect_reference - 1].indirect_reference.generation  # type: ignore
         self._objects[indirect_reference - 1] = obj
+        obj.indirect_reference = IndirectObject(indirect_reference, gen, self)
         return self._objects[indirect_reference - 1]
-        if indirect_reference.pdf != self:
-            raise ValueError("pdf must be self")
-        return self._objects[indirect_reference.idnum - 1]
 
     def _add_page(
         self,
@@ -1623,6 +1623,10 @@ def get_outline_root(self) -> TreeObject:
         if CO.OUTLINES in self._root_object:
             # TABLE 3.25 Entries in the catalog dictionary
             outline = cast(TreeObject, self._root_object[CO.OUTLINES])
+            if not isinstance(outline, TreeObject):
+                t = TreeObject(outline)
+                self._replace_object(outline.indirect_reference.idnum, t)
+                outline = t
             idnum = self._objects.index(outline) + 1
             outline_ref = IndirectObject(idnum, 0, self)
             assert outline_ref.get_object() == outline
@@ -1718,7 +1722,7 @@ def getNamedDestRoot(self) -> ArrayObject:  # deprecated
 
     def add_outline_item_destination(
         self,
-        page_destination: Union[None, PageObject, TreeObject] = None,
+        page_destination: Union[None, IndirectObject, PageObject, TreeObject] = None,
         parent: Union[None, TreeObject, IndirectObject] = None,
         before: Union[None, TreeObject, IndirectObject] = None,
         is_open: bool = True,
@@ -1744,6 +1748,7 @@ def add_outline_item_destination(
             # argument is only Optional due to deprecated argument.
             raise ValueError("page_destination may not be None")
 
+        page_destination = cast(PageObject, page_destination.get_object())
         if isinstance(page_destination, PageObject):
             return self.add_outline_item_destination(
                 Destination(
@@ -1928,7 +1933,9 @@ def add_outline_item(
                     }
                 )
             )
-        outline_item = _create_outline_item(action_ref, title, color, italic, bold)
+        outline_item = self._add_object(
+            _create_outline_item(action_ref, title, color, italic, bold)
+        )
 
         if parent is None:
             parent = self.get_outline_root()

pypdf/generic/_data_structures.py

@@ -548,8 +548,10 @@ def readFromStream(
 
 
 class TreeObject(DictionaryObject):
-    def __init__(self) -> None:
+    def __init__(self, dct: Optional[DictionaryObject] = None) -> None:
         DictionaryObject.__init__(self)
+        if dct:
+            self.update(dct)
 
     def hasChildren(self) -> bool:  # deprecated
         deprecate_with_replacement("hasChildren", "has_children", "4.0.0")

tests/test_writer.py

@@ -4,6 +4,7 @@
 import subprocess
 from io import BytesIO
 from pathlib import Path
+from typing import Any
 
 import pytest
 
@@ -1861,6 +1862,86 @@ def test_object_contains_indirect_reference_to_self():
     writer.append(reader)
 
 
+@pytest.mark.enable_socket()
+def test_add_outlines_on_empty_dict():
+    """Cf #2233"""
+
+    def _get_parent_bookmark(current_indent, history_indent, bookmarks) -> Any:
+        """The parent of A is the nearest bookmark whose indent is smaller than A's"""
+        assert len(history_indent) == len(bookmarks)
+        if current_indent == 0:
+            return None
+        for i in range(len(history_indent) - 1, -1, -1):
+            # len(history_indent) - 1   ===>   0
+            if history_indent[i] < current_indent:
+                return bookmarks[i]
+        return None
+
+    bookmark_lines = """1 FUNDAMENTALS OF RADIATIVE TRANSFER 1
+1.1 The Electromagnetic Spectrum; Elementary Properties of Radiation 1
+1.2 Radiative Flux 2
+    Macroscopic Description of the Propagation of Radiation 2
+    Flux from an Isotropic Source-The Inverse Square Law 2
+1.3 The Specific Intensity and Its Moments 3
+    Definition of Specific Intensity or Brightness 3
+    Net Flux and Momentum Flux 4
+    Radiative Energy Density 5
+    Radiation Pressure in an Enclosure Containing an Isotropic Radiation Field 6
+    Constancy of Specific Zntensiw Along Rays in Free Space 7
+    Proof of the Inverse Square Law for a Uniformly Bright Sphere 7
+1.4 Radiative Transfer 8
+    Emission 9
+    Absorption 9
+    The Radiative Transfer Equation 11
+    Optical Depth and Source Function 12
+    Mean Free Path 14
+    Radiation Force 15
+1.5 Thermal Radiation 15
+    Blackbody Radiation 15
+    Kirchhof's Law for Thermal Emission 16
+    Thermodynamics of Blackbody Radiation 17
+    The Planck Spectrum 20
+    Properties of the Planck Law 23
+    Characteristic Temperatures Related to Planck Spectrum 25
+1.6 The Einstein Coefficients 27
+    Definition of Coefficients 27
+    Relations between Einstein Coefficients 29
+    Absorption and Emission Coefficients in Terms of Einstein Coefficients 30
+1.7 Scattering Effects; Random Walks 33
+    Pure Scattering 33
+    Combined Scattering and Absorption 36
+1.8 Radiative Diffusion 39
+    The Rosseland Approximation 39
+    The Eddington Approximation; Two-Stream Approximation 42
+PROBLEMS 45
+REFERENCES 50
+2 BASIC THEORY OF RADIATION FIELDS 51
+2.1 Review of Maxwell’s Equations 51
+2.2 Plane Electromagnetic Waves 55
+2.3 The Radiation Spectrum 58
+2.4 Polarization and Stokes Parameters 62
+    Monochromatic Waves 62
+    Quasi-monochromatic Waves 65
+2.5 Electromagnetic Potentials 69
+2.6 Applicability of Transfer Theory and the Geometrical Optics Limit 72
+PROBLEMS 74
+REFERENCES 76"""
+    url = "https://github.com/py-pdf/pypdf/files/12797067/test-12.pdf"
+    name = "iss2233.pdf"
+    reader = PdfReader(BytesIO(get_data_from_url(url, name=name)))
+    writer = PdfWriter(clone_from=reader)
+
+    bookmarks, history_indent = [], []
+    for line in bookmark_lines.split("\n"):
+        line2 = re.split(r"\s+", line.strip())
+        indent_size = len(line) - len(line.lstrip())
+        parent = _get_parent_bookmark(indent_size, history_indent, bookmarks)
+        history_indent.append(indent_size)
+        title, page = " ".join(line2[:-1]), int(line2[-1]) - 1
+        new_bookmark = writer.add_outline_item(title, page, parent=parent)
+        bookmarks.append(new_bookmark)
+
+
 def test_merging_many_temporary_files():
     def create_number_pdf(n) -> BytesIO:
         from fpdf import FPDF