Columns exception, children of None variable #897

LukasKlement · 2019-07-12T13:16:00Z

I observe frequent exceptions with columned documents:

Request Method: | GET Django Version 2.2.3 AttributeError 'NoneType' object has no attribute 'children' /lib/python3.7/site-packages/weasyprint/layout/columns.py in columns_layout, line 165

The error is in:

/weasyprint/layout/columns.py in columns_layout new_box.children[-1].position_y - box.content_box_y() + new_box.children[-1].margin_height())

Basically, new_box = None hence the exception is thrown. I'm yet to produce a HTML document to reproduce this issue.

Edit: there are no floating elements

The text was updated successfully, but these errors were encountered:

smattheis · 2019-08-27T11:32:13Z

I encountered the same issue. An example to reproduce the bug is as follows:

Example file example.html:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8">
    <title>Example</title>
</head>
<body>
    <div style="position:absolute;">
        <div style="column-count: 2;">
            Lorem ipsum.
        </div>
    </div>
</body>
</html>

Bash on Mac OS X:

$ export LC_ALL=en_US.UTF-8; weasyprint example.html example.png
Traceback (most recent call last):
  File "/usr/local/bin/weasyprint", line 10, in <module>
    sys.exit(main())
  File "/usr/local/lib/python3.7/site-packages/weasyprint/__main__.py", line 190, in main
    getattr(html, 'write_' + format_)(output, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/weasyprint/__init__.py", line 290, in write_png
    font_config=font_config)
  File "/usr/local/lib/python3.7/site-packages/weasyprint/__init__.py", line 168, in render
    font_config)
  File "/usr/local/lib/python3.7/site-packages/weasyprint/document.py", line 377, in _render
    [Page(page_box, enable_hinting) for page_box in page_boxes],
  File "/usr/local/lib/python3.7/site-packages/weasyprint/document.py", line 377, in <listcomp>
    [Page(page_box, enable_hinting) for page_box in page_boxes],
  File "/usr/local/lib/python3.7/site-packages/weasyprint/layout/__init__.py", line 130, in layout_document
    pages = list(make_all_pages(context, root_box, html, pages, style_for))
  File "/usr/local/lib/python3.7/site-packages/weasyprint/layout/pages.py", line 798, in make_all_pages
    i, context, root_box, html, style_for)
  File "/usr/local/lib/python3.7/site-packages/weasyprint/layout/pages.py", line 736, in remake_page
    page_number, page_state)
  File "/usr/local/lib/python3.7/site-packages/weasyprint/layout/pages.py", line 561, in make_page
    absolute_layout(context, absolute_box, page, positioned_boxes)
  File "/usr/local/lib/python3.7/site-packages/weasyprint/layout/absolute.py", line 275, in absolute_layout
    absolute_box_layout(context, box, containing_block, fixed_boxes))
  File "/usr/local/lib/python3.7/site-packages/weasyprint/layout/absolute.py", line 300, in absolute_box_layout
    new_box = absolute_block(context, box, containing_block, fixed_boxes)
  File "/usr/local/lib/python3.7/site-packages/weasyprint/layout/absolute.py", line 214, in absolute_block
    adjoining_margins=None)
  File "/usr/local/lib/python3.7/site-packages/weasyprint/layout/blocks.py", line 519, in block_container_layout
    adjoining_margins)
  File "/usr/local/lib/python3.7/site-packages/weasyprint/layout/blocks.py", line 65, in block_level_layout
    adjoining_margins)
  File "/usr/local/lib/python3.7/site-packages/weasyprint/layout/blocks.py", line 81, in block_level_layout_switch
    adjoining_margins)
  File "/usr/local/lib/python3.7/site-packages/weasyprint/layout/blocks.py", line 110, in block_box_layout
    adjoining_margins)
  File "/usr/local/lib/python3.7/site-packages/weasyprint/layout/columns.py", line 165, in columns_layout
    new_box.children[-1].position_y - box.content_box_y() +
AttributeError: 'NoneType' object has no attribute 'children'

Note that it does NOT crash if the content is completely empty and also NOT if the content spans two columns:

Example file example.html:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="utf-8">
    <title>Example</title>
</head>
<body>
    <div style="position:absolute;">
        <div style="column-count: 2;">
            Lorem ipsum dolor sit amet, consetetur sadipscing elitr, sed diam nonumy eirmod tempor invidunt ut labore et dolore magna aliquyam erat, sed diam voluptua.
        </div>
    </div>
</body>
</html>

This produces the following example.png:

liZe · 2019-09-04T14:26:23Z

The bug is fixed, but the rendering can be different from what browsers do, because:

The width of the absolute div fits the content in WeasyPrint, but it takes the whole width of the container in browsers. I don't know what this width should be.
Browsers don't respect widows and orphans, but the spec explicitly says that widows and orphans must be respected.
Feel free to open new issues if there's anything wrong.

Version 50 ---------- Released on 2019-09-19. New features: * `#209 <https://github.com/Kozea/WeasyPrint/issues/209>`_: Make ``break-*`` properties work inside tables * `#661 <https://github.com/Kozea/WeasyPrint/issues/661>`_: Make blocks with ``overflow: auto`` grow to include floating children Bug fixes: * `#945 <https://github.com/Kozea/WeasyPrint/issues/945>`_: Don't break pages between a list item and its marker * `#727 <https://github.com/Kozea/WeasyPrint/issues/727>`_: Avoid tables lost between pages * `#831 <https://github.com/Kozea/WeasyPrint/issues/831>`_: Ignore auto margins on flex containers * `#923 <https://github.com/Kozea/WeasyPrint/issues/923>`_: Fix a couple of crashes when splitting a line twice * `#896 <https://github.com/Kozea/WeasyPrint/issues/896>`_: Fix skip stack order when using a reverse flex direction Contributors: - grewn0uille - Guillaume Ayoub Version 49 ---------- Released on 2019-09-11. Performance: * Speed and memory use have been largely improved. New features: * `#700 <https://github.com/Kozea/WeasyPrint/issues/700>`_: Handle ``::marker`` pseudo-selector * `135dc06c <https://github.com/Kozea/WeasyPrint/commit/135dc06c>`_: Handle ``recto`` and ``verso`` parameters for page breaks * `#907 <https://github.com/Kozea/WeasyPrint/pull/907>`_: Provide a clean way to build layout contexts Bug fixes: * `#937 <https://github.com/Kozea/WeasyPrint/issues/937>`_: Fix rendering of tables with empty lines and rowspans * `#897 <https://github.com/Kozea/WeasyPrint/issues/897>`_: Don't crash when small columns are wrapped in absolute blocks * `#913 <https://github.com/Kozea/WeasyPrint/issues/913>`_: Fix a test about gradient colors * `#924 <https://github.com/Kozea/WeasyPrint/pull/924>`_: Fix title for document with attachments * `#917 <https://github.com/Kozea/WeasyPrint/issues/917>`_: Fix tests with Pango 1.44 * `#919 <https://github.com/Kozea/WeasyPrint/issues/919>`_: Fix padding and margin management for column flex boxes * `#901 <https://github.com/Kozea/WeasyPrint/issues/901>`_: Fix width of replaced boxes with no intrinsic width * `#906 <https://github.com/Kozea/WeasyPrint/issues/906>`_: Don't respect table cell width when content doesn't fit * `#927 <https://github.com/Kozea/WeasyPrint/pull/927>`_: Don't use deprecated ``logger.warn`` anymore * `a8662794 <https://github.com/Kozea/WeasyPrint/commit/a8662794>`_: Fix margin collapsing between caption and table wrapper * `87d9e84f <https://github.com/Kozea/WeasyPrint/commit/87d9e84f>`_: Avoid infinite loops when rendering columns * `789b80e6 <https://github.com/Kozea/WeasyPrint/commit/789b80e6>`_: Only use in flow children to set columns height * `615e298a <https://github.com/Kozea/WeasyPrint/commit/615e298a>`_: Don't include floating elements each time we try to render a column * `48d8632e <https://github.com/Kozea/WeasyPrint/commit/48d8632e>`_: Avoid not in flow children to compute column height * `e7c452ce <https://github.com/Kozea/WeasyPrint/commit/e7c452ce>`_: Fix collapsing margins for columns * `fb0887cf <https://github.com/Kozea/WeasyPrint/commit/fb0887cf>`_: Fix crash when using currentColor in gradients * `f66df067 <https://github.com/Kozea/WeasyPrint/commit/f66df067>`_: Don't crash when using ex units in word-spacing in letter-spacing * `c790ff20 <https://github.com/Kozea/WeasyPrint/commit/c790ff20>`_: Don't crash when properties needing base URL use var functions * `d63eac31 <https://github.com/Kozea/WeasyPrint/commit/d63eac31>`_: Don't crash with object-fit: non images with no intrinsic size Documentation: * `#900 <https://github.com/Kozea/WeasyPrint/issues/900>`_: Add documentation about semantic versioning * `#692 <https://github.com/Kozea/WeasyPrint/issues/692>`_: Add a snippet about PDF magnification * `#899 <https://github.com/Kozea/WeasyPrint/pull/899>`_: Add .NET wrapper link * `#893 <https://github.com/Kozea/WeasyPrint/pull/893>`_: Fixed wrong nested list comprehension example * `#902 <https://github.com/Kozea/WeasyPrint/pull/902>`_: Add ``state`` to the ``make_bookmark_tree`` documentation * `#921 <https://github.com/Kozea/WeasyPrint/pull/921>`_: Fix typos in the documentation * `#328 <https://github.com/Kozea/WeasyPrint/issues/328>`_: Add CSS sample for forms Contributors: - grewn0uille - Guillaume Ayoub - Raphael Gaschignard - Stani - Szmen - Thomas Dexter - Tontyna Version 48 ---------- Released on 2019-07-08. Dependencies: * CairoSVG 2.4.0+ is now needed New features: * `#891 <https://github.com/Kozea/WeasyPrint/pull/891>`_: Handle ``text-overflow`` * `#878 <https://github.com/Kozea/WeasyPrint/pull/878>`_: Handle ``column-span`` * `#855 <https://github.com/Kozea/WeasyPrint/pull/855>`_: Handle all the ``text-decoration`` features * `#238 <https://github.com/Kozea/WeasyPrint/issues/238>`_: Don't repeat background images when it's not needed * `#875 <https://github.com/Kozea/WeasyPrint/issues/875>`_: Handle ``object-fit`` and ``object-position`` * `#870 <https://github.com/Kozea/WeasyPrint/issues/870>`_: Handle ``bookmark-state`` Bug fixes: * `#686 <https://github.com/Kozea/WeasyPrint/issues/686>`_: Fix column balance when children are not inline * `#885 <https://github.com/Kozea/WeasyPrint/issues/885>`_: Actually use the content box to resolve flex items percentages * `#867 <https://github.com/Kozea/WeasyPrint/issues/867>`_: Fix rendering of KaTeX output, including (1) set row baseline of tables when no cells are baseline-aligned, (2) set baseline for inline tables, (3) don't align lines larger than their parents, (4) force CairoSVG to respect image size defined by CSS. * `#873 <https://github.com/Kozea/WeasyPrint/issues/873>`_: Set a minimum height for empty list elements with outside marker * `#811 <https://github.com/Kozea/WeasyPrint/issues/811>`_: Don't use translations to align flex items * `#851 <https://github.com/Kozea/WeasyPrint/issues/851>`_, `#860 <https://github.com/Kozea/WeasyPrint/issues/860>`_: Don't cut pages when content overflows a very little bit * `#862 <https://github.com/Kozea/WeasyPrint/issues/862>`_: Don't crash when using UTC dates in metadata Documentation: * `#854 <https://github.com/Kozea/WeasyPrint/issues/854>`_: Add a "Tips & Tricks" section Contributors: - Gabriel Corona - Guillaume Ayoub - Manuel Barkhau - Nathan de Maestri - grewn0uille - theopeek Version 47 ---------- Released on 2019-04-12. New features: * `#843 <https://github.com/Kozea/WeasyPrint/pull/843>`_: Handle CSS variables * `#846 <https://github.com/Kozea/WeasyPrint/pull/846>`_: Handle ``:nth()`` page selector * `#847 <https://github.com/Kozea/WeasyPrint/pull/847>`_: Allow users to use a custom SSL context for HTTP requests Bug fixes: * `#797 <https://github.com/Kozea/WeasyPrint/issues/797>`_: Fix underlined justified text * `#836 <https://github.com/Kozea/WeasyPrint/issues/836>`_: Fix crash when flex items are replaced boxes * `#835 <https://github.com/Kozea/WeasyPrint/issues/835>`_: Fix ``margin-break: auto`` Version 46 ---------- Released on 2019-03-20. New features: * `#771 <https://github.com/Kozea/WeasyPrint/issues/771>`_: Handle ``box-decoration-break`` * `#115 <https://github.com/Kozea/WeasyPrint/issues/115>`_: Handle ``margin-break`` * `#821 <https://github.com/Kozea/WeasyPrint/issues/821>`_: Continuous integration includes tests on Windows Bug fixes: * `#765 <https://github.com/Kozea/WeasyPrint/issues/765>`_, `#754 <https://github.com/Kozea/WeasyPrint/issues/754>`_, `#800 <https://github.com/Kozea/WeasyPrint/issues/800>`_: Fix many crashes related to the flex layout * `#783 <https://github.com/Kozea/WeasyPrint/issues/783>`_: Fix a couple of crashes with strange texts * `#827 <https://github.com/Kozea/WeasyPrint/pull/827>`_: Named strings and counters are case-sensitive * `#823 <https://github.com/Kozea/WeasyPrint/pull/823>`_: Shrink min/max-height/width according to box-sizing * `#728 <https://github.com/Kozea/WeasyPrint/issues/728>`_, `#171 <https://github.com/Kozea/WeasyPrint/issues/171>`_: Don't crash when fixed boxes are nested * `#610 <https://github.com/Kozea/WeasyPrint/issues/610>`_, `#828 <https://github.com/Kozea/WeasyPrint/issues/828>`_: Don't crash when preformatted text lines end with a space * `#808 <https://github.com/Kozea/WeasyPrint/issues/808>`_, `#387 <https://github.com/Kozea/WeasyPrint/issues/387>`_: Fix position of some images * `#813 <https://github.com/Kozea/WeasyPrint/issues/813>`_: Don't crash when long preformatted text lines end with ``\n`` Documentation: * `#815 <https://github.com/Kozea/WeasyPrint/pull/815>`_: Add documentation about custom ``url_fetcher``

liZe added the crash Problems preventing documents from being rendered label Jul 12, 2019

liZe added this to the 49 milestone Sep 4, 2019

liZe closed this as completed in 4dc0b11 Sep 4, 2019

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Columns exception, children of None variable #897

Columns exception, children of None variable #897

LukasKlement commented Jul 12, 2019 •

edited

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smattheis commented Aug 27, 2019

liZe commented Sep 4, 2019

Columns exception, children of None variable #897

Columns exception, children of None variable #897

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LukasKlement commented Jul 12, 2019 • edited Loading

smattheis commented Aug 27, 2019

liZe commented Sep 4, 2019

LukasKlement commented Jul 12, 2019 •

edited

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