Debugging PDFKit and WKHTMLToPDF

When PDFKit errors out with an unhelpful error like: RuntimeError (command failed (exitstatus=1): /bin/wkhtmltopdf --page-size A4 - -):, try the following:

• Add config.verbose = true to its configuration
• Add load_error_handling: 'ignore' to its config.default_options
• Save the rendered HTML to a file by modifying pdfkit.rb’s to_pdf method with this just before the invoke declaration.

open('/tmp/pdfkit-source.html', 'a') { |f| f.puts @source.to_s }

Once you’ve got the html saved, you can inspect it for errors, and manually run wkhtmltopdf on the CLI using it as input like so:

cat /tmp/pdfkit-source.html | <the wkhtmltopdfbin command that is failing> out.pdf

Hopefully one of these techniques can highlight where your problems lie, and get you to a resolution.