Tests and fix a bug with the img2pdf functionality

src/paperless/parsers/tesseract.py

@@ -393,13 +393,13 @@ class RasterisedDocumentParser:
 
         plain_pdf_path = Path(self.tempdir) / "image_plain.pdf"
         try:
-            layout_fun = None
+            convert_kwargs: dict = {}
             if self.settings.image_dpi is not None:
-                layout_fun = img2pdf.get_fixed_dpi_layout_fun(
+                convert_kwargs["layout_fun"] = img2pdf.get_fixed_dpi_layout_fun(
                     (self.settings.image_dpi, self.settings.image_dpi),
                 )
             plain_pdf_path.write_bytes(
-                img2pdf.convert(str(document_path), layout_fun=layout_fun),
+                img2pdf.convert(str(document_path), **convert_kwargs),
             )
         except Exception as e:
             raise ParseError(

src/paperless/tests/parsers/test_convert_image_to_pdfa.py

@@ -0,0 +1,141 @@
+"""
+Tests for RasterisedDocumentParser._convert_image_to_pdfa.
+
+The method converts an image to a PDF/A-2b file using img2pdf (wrapping)
+then pikepdf (PDF/A metadata stamping), with a fallback to plain PDF when
+pikepdf stamping fails.  No Tesseract or Ghostscript is invoked.
+
+These are unit/integration tests: img2pdf and pikepdf run for real; only
+error-path branches mock the respective library call.
+"""
+
+from __future__ import annotations
+
+from pathlib import Path
+from typing import TYPE_CHECKING
+
+import img2pdf
+import magic
+import pikepdf
+import pytest
+
+from documents.parsers import ParseError
+
+if TYPE_CHECKING:
+    from pytest_mock import MockerFixture
+
+    from paperless.parsers.tesseract import RasterisedDocumentParser
+
+
+class TestConvertImageToPdfa:
+    """_convert_image_to_pdfa: output shape, error paths, DPI handling."""
+
+    def test_valid_png_produces_pdf_bytes(
+        self,
+        tesseract_parser: RasterisedDocumentParser,
+        simple_png_file: Path,
+    ) -> None:
+        """
+        GIVEN: a valid PNG with DPI metadata
+        WHEN: _convert_image_to_pdfa is called
+        THEN: the returned file is non-empty and begins with the PDF magic bytes
+        """
+        result = tesseract_parser._convert_image_to_pdfa(simple_png_file)
+
+        assert result.exists()
+        assert magic.from_file(str(result), mime=True) == "application/pdf"
+
+    def test_output_path_is_archive_pdf_in_tempdir(
+        self,
+        tesseract_parser: RasterisedDocumentParser,
+        simple_png_file: Path,
+    ) -> None:
+        """
+        GIVEN: any valid image
+        WHEN: _convert_image_to_pdfa is called
+        THEN: the returned path is exactly <tempdir>/archive.pdf
+        """
+        result = tesseract_parser._convert_image_to_pdfa(simple_png_file)
+
+        assert result == Path(tesseract_parser.tempdir) / "archive.pdf"
+
+    def test_img2pdf_failure_raises_parse_error(
+        self,
+        mocker: MockerFixture,
+        tesseract_parser: RasterisedDocumentParser,
+        simple_png_file: Path,
+    ) -> None:
+        """
+        GIVEN: img2pdf.convert raises an exception
+        WHEN: _convert_image_to_pdfa is called
+        THEN: a ParseError is raised that mentions "img2pdf conversion failed"
+        """
+        mocker.patch.object(img2pdf, "convert", side_effect=Exception("boom"))
+
+        with pytest.raises(ParseError, match="img2pdf conversion failed"):
+            tesseract_parser._convert_image_to_pdfa(simple_png_file)
+
+    def test_pikepdf_stamping_failure_falls_back_to_plain_pdf(
+        self,
+        mocker: MockerFixture,
+        tesseract_parser: RasterisedDocumentParser,
+        simple_png_file: Path,
+    ) -> None:
+        """
+        GIVEN: pikepdf.open raises during PDF/A metadata stamping
+        WHEN: _convert_image_to_pdfa is called
+        THEN: no exception is raised and the returned file is still a valid PDF
+              (plain PDF bytes are used as fallback)
+        """
+        mocker.patch.object(pikepdf, "open", side_effect=Exception("pikepdf boom"))
+
+        result = tesseract_parser._convert_image_to_pdfa(simple_png_file)
+
+        assert result.exists()
+        assert magic.from_file(str(result), mime=True) == "application/pdf"
+
+    def test_image_dpi_setting_applies_fixed_dpi_layout(
+        self,
+        mocker: MockerFixture,
+        tesseract_parser: RasterisedDocumentParser,
+        simple_no_dpi_png_file: Path,
+    ) -> None:
+        """
+        GIVEN: parser.settings.image_dpi = 150
+        WHEN: _convert_image_to_pdfa is called with a no-DPI PNG
+        THEN: img2pdf.get_fixed_dpi_layout_fun is called with (150, 150)
+              and the output is still a valid PDF
+        """
+        spy = mocker.patch.object(
+            img2pdf,
+            "get_fixed_dpi_layout_fun",
+            wraps=img2pdf.get_fixed_dpi_layout_fun,
+        )
+        tesseract_parser.settings.image_dpi = 150
+
+        result = tesseract_parser._convert_image_to_pdfa(simple_no_dpi_png_file)
+
+        spy.assert_called_once_with((150, 150))
+        assert magic.from_file(str(result), mime=True) == "application/pdf"
+
+    def test_no_image_dpi_setting_skips_fixed_dpi_layout(
+        self,
+        mocker: MockerFixture,
+        tesseract_parser: RasterisedDocumentParser,
+        simple_png_file: Path,
+    ) -> None:
+        """
+        GIVEN: parser.settings.image_dpi is None (default)
+        WHEN: _convert_image_to_pdfa is called
+        THEN: img2pdf.get_fixed_dpi_layout_fun is never called
+        """
+        spy = mocker.patch.object(
+            img2pdf,
+            "get_fixed_dpi_layout_fun",
+            wraps=img2pdf.get_fixed_dpi_layout_fun,
+        )
+        tesseract_parser.settings.image_dpi = None
+
+        tesseract_parser._convert_image_to_pdfa(simple_png_file)
+
+        spy.assert_not_called()