Hi, I was running into an issue where webp files would not load due to texture.source being undefined. The source, in case of a webp file seems to be under 'texture.extensions.EXT_texture_webp.source'. To address this, I wrote a small function that searches for the 'source' key. I do not know if this is the 'right' fix, but it did fix my problem of webp's not loading.
This issue appears to be discussing a feature request or bug report related to the repository. Based on the content, it seems to be resolved. The issue was opened by MatsErdkamp and has received 2 comments.