So is there a way to make AjaxSearch index content coming from snippets?
Not with the current version (1.8.1).
A solution could be :
1/avoid to strip snippet calls (cached or uncached call) read from the content field
2/ analyse the snippet call in order to get the snippet name and snippet parameters
3/ on fly, change the id of the current document by the id of the document analysed
4/ execute the snippet and get the output : $output = $modx->runSnippet($snippet_name, $snippet_params);
5/ restore the content id of the document where the search occurs
5/ replace the snippet call by the output inside the content value
6/ search into this "interpreted" content value, the search terms requested
This is not simple, not implemented. And I am not sure that it could be work
Is the indexing of the snippet output an important feature, requested by lot of people ?