SOLR-2444 updated fl syntax and the SOLR-2719 regression, it would be useful to add some kind of validation regarding the field names you can use on Solr.
The objective would be adding consistency, allowing only field names that you can then use within fl, sorting etc.
The rules, taken from the actual StrParser behaviour, seem to be the following:
- same used for java identifiers (Character#isJavaIdentifierPart), plus the use of trailing '.' and '-'
- for the first character the rule is Character#isJavaIdentifierStart minus '$' (The dash can't be used as first character (SOLR-3191) for example)