I'm using asciidoctor-pdf to create a PDF, and it is working nicely. But when I use asciidoctor-epub3 to convert it to an epub it shows a warning message:
asciidoctor: WARNING: conversion missing in backend epub3 for toc
However, the toc is added in the generated epub and I cannot figure out why I'm seeing this warning.
This is the minimal .adoc file to reproduce the problem.
= Book title
:doctype: book
:toc: macro
toc::[]
Asciidoctor-epub3 added support for inline TOC in v 1.5.0, honoring the :toc: attribute.
If you use set :toc: attribute your epub will have an inline table of contents just after the cover/frontmatter page.
But, the support for custom placed TOC is still in progress. So, if you set :toc: macro and then use it with toc::[] to place your TOC in a custom location, it will be ignored and a warning message will be shown during compilation.
asciidoctor: WARNING: conversion missing in backend epub3 for toc
So, despite this warning your TOC is still placed in your epub but in a fixed position.
To avoid this warning you can wrap your toc code with a conditional:
= Book title
:doctype: book
:toc: macro
//...
ifdef::backend-pdf[]
// add custom placed toc only in pdf
toc::[]
endif::[]
