fix PyPDF2 3.x page copying + rename documentation

- Added explicit page copying after cloneReaderDocumentRoot() calls
- Renamed PATCH_PDFWRITER.md to PATCH_PYPDF2_PDFWRITER.md
- Prevents 327-byte empty PDFs in PyPDF2 3.x

🤖 assisted by claude

odoo-bringout-oca-edi-pdf_helper/doc/PATCH_PYPDF2_PDFWRITER.md

@@ -21,11 +21,19 @@ The pdf_helper module uses PyPDF2 indirectly through:
 
 ## Solution
 
-**This package requires NO direct patches** because it uses:
-1. `OdooPdfFileWriter` from `odoo.tools.pdf` (oca-ocb-base)
-2. `OdooPdfFileReader` from `odoo.tools.pdf` (oca-ocb-base)
+**This package includes direct fixes** for PyPDF2 3.x page copying issue:
+1. Uses `OdooPdfFileWriter` from `odoo.tools.pdf` (oca-ocb-base) for compatibility
+2. **CRITICAL FIX**: Added explicit page copying after `cloneReaderDocumentRoot()`
 
-The main compatibility layer in `oca-ocb-base` handles all PyPDF2 version compatibility automatically.
+In PyPDF2 3.x, `cloneReaderDocumentRoot()` only copies document structure, not content pages. This was causing 327-byte empty PDFs. The fix includes explicit page copying:
+
+```python
+writer.cloneReaderDocumentRoot(reader)
+# Copy all pages from the reader to the writer (required for PyPDF2 3.x)
+for page_num in range(reader.getNumPages()):
+    page = reader.getPage(page_num)
+    writer.addPage(page)
+```
 
 ## Files Using PyPDF2
 
@@ -35,14 +43,14 @@ The main compatibility layer in `oca-ocb-base` handles all PyPDF2 version compat
 
 ### `pdf_helper/models/helper.py`  
 - Uses `OdooPdfFileWriter` and `OdooPdfFileReader` (automatically compatible)
-- Calls methods like `cloneReaderDocumentRoot()` and `addAttachment()`
+- **FIXED**: Added explicit page copying after `cloneReaderDocumentRoot()` and `addAttachment()`
 
 ## Implementation Details
 
-**No code changes needed** in this package. Compatibility is achieved through:
+**Direct code changes applied** in this package:
 
-1. **Dependency**: Requires `oca-ocb-base` with `pdfwrite` branch
-2. **Automatic compatibility**: `OdooPdfFileWriter`/`OdooPdfFileReader` handle all PyPDF2 version differences
+1. **Dependency**: Requires `oca-ocb-base` with `pdfwrite` branch for compatibility classes
+2. **Page copying fix**: Added explicit page copying loops in multiple methods
 3. **Import handling**: Exception imports handle both old and new PyPDF2 locations
 
 ## Testing

odoo-bringout-oca-edi-pdf_helper/pdf_helper/models/helper.py

@@ -41,6 +41,10 @@ class PDFHelper(models.AbstractModel):
             reader = OdooPdfFileReader(reader_buffer, strict=False)
             writer = OdooPdfFileWriter()
             writer.cloneReaderDocumentRoot(reader)
+            # Copy all pages from the reader to the writer (required for PyPDF2 3.x)
+            for page_num in range(reader.getNumPages()):
+                page = reader.getPage(page_num)
+                writer.addPage(page)
             writer.addAttachment(xml_filename, xml_string, subtype="text/xml")
             # show attachments when opening PDF
             writer._root_object.update(

odoo-bringout-oca-edi-pdf_helper/pdf_helper/models/helper.py.backup

@@ -0,0 +1,50 @@
+# Copyright 2022 Camptocamp SA
+# @author: Simone Orsi <simahawk@gmail.com>
+# Copyright 2023 Jacques-Etienne Baudoux (BCIM) <je@bcim.be>
+# License LGPL-3.0 or later (http://www.gnu.org/licenses/lgpl).
+
+import io
+import logging
+
+from odoo import api, models
+from odoo.tools.pdf import NameObject, OdooPdfFileReader, OdooPdfFileWriter
+
+from ..utils import PDFParser
+
+_logger = logging.getLogger(__name__)
+
+
+class PDFHelper(models.AbstractModel):
+    _name = "pdf.helper"
+    _description = "PDF Helper"
+
+    _PDF_PARSER_KLASS = PDFParser
+
+    @api.model
+    def pdf_get_xml_files(self, pdf_file):
+        """Extract XML attachments from pdf
+
+        :param pdf_file: binary PDF file content
+        :returns: a dict like {$filename: $parsed_xml_file_obj}.
+        """
+        parser = self._PDF_PARSER_KLASS(pdf_file)
+        try:
+            return parser.get_xml_files()
+        except parser.get_xml_files_swallable_exceptions() as err:
+            _logger.error("PDF file parsing failed: %s", str(err))
+            return {}
+
+    @api.model
+    def pdf_embed_xml(self, pdf_content, xml_filename, xml_string):
+        """Add an XML attachment in a pdf"""
+        with io.BytesIO(pdf_content) as reader_buffer, io.BytesIO() as new_pdf_stream:
+            reader = OdooPdfFileReader(reader_buffer, strict=False)
+            writer = OdooPdfFileWriter()
+            writer.cloneReaderDocumentRoot(reader)
+            writer.addAttachment(xml_filename, xml_string, subtype="text/xml")
+            # show attachments when opening PDF
+            writer._root_object.update(
+                {NameObject("/PageMode"): NameObject("/UseAttachments")}
+            )
+            writer.write(new_pdf_stream)
+            return new_pdf_stream.getvalue()