How I Found a Hidden Bug in Wagtail-Localize

I am working on a GSoC proposal for Wagtail CMS. As part of my preparation, I set up a multilingual demo site using wagtail-localize. I learned a lot about how Wagtail handles translations and found a bug along the way. What I Was Doing I extended Wagtail's Bakery Demo with three languages: English, Spanish, and French. For Spanish, I translated pages one by one. For French, I used the "Include subtree" option to translate an entire section at once. The Spanish pages worked fine, but the French pages had a strange problem. What Went Wrong After translating the French subtree, I could not see any child pages in the admin panel. The pages existed in the database. They had content. But the admin explorer showed nothing under the French homepage. I got "Page not found" errors when I visited the child page URLs directly, even though the pages exist. How I Diagnosed It I wrote a small script to check the page tree data. Every Wagtail page stores a field called numchild. This tells the admin