Topic on Help talk:Extension:ParserFunctions

I'm using replace to remove certain characters like "&" from strings like "One & Two". I'm replacing the character with nothing but I'm left with two consecutive spaces. This is causing issues with file names. Is there a way to replace multiple consecutive characters with one?

If you try using just the "#replace:" function, use it a second time to replace two spaces by one space, after replacing the "&" (assuming that it may or may not have a single leading space and/or a single trailing space).

Note that "#replace:" only performs simple substitutions of literal substring, not replacements by matching regexps.

However I think it is a bad idea to silently drop the ampersand to generate filenames, it would be better to replace it with a hyphen and keep spaces where they are. Beware also that such substitution may break strings containing numerical or named character references (frequenely needed and present in the wikitext, or automatically added by the Mediawiki text editors): you should only replace "&" not "&" alone.

As well, the ampersand character itself is authorized in Mediawiki filenames; but it must often be encoded as a character reference (in HTML text or wikilinks), or URL-encoded (when using it in a URL or in a query parameter). For URL-encoding, see the ParserFunction "urlencode:" (and select the correct form depending on the syntaxic type of target: PATH, QUERY...)

For stripping extra spaces (or underscores) in filenames, you can use the "#titleparts:", or "PAGENAME" functions (the later one also strips a leading ":" or recognized namespace prefix, but not a leading interwiki prefix).

The best method here would probably be to rewrite your template(s) as Scribunto modules, but if that isn't an option or practical for some reason, I'd probably approach it with multiple #replaces: remove the target character(s), replace all spaces with some character you're sure won't appear in the input, replace multiple space-replacement characters with a single one, and finally replace the replacement characters with spaces (these replaces can be reordered a little bit to your liking, e.g. removing the target characters can happen before or after replacing the spaces with a standin character). I might code this something like:

{{ #replace: {{ #replace: {{ #replace: {{ #replace: {{{1}}} | & }} | <!-- space --> | ¬ }} | ¬¬ | ¬ }} | ¬ | <nowiki/> <nowiki/> }}

For filenames specifically, speaking from personal experience, I'd recommend not to remove characters if you don't have to (though you might not have much choice if you're already dealing with a large collection of files that are named that way, of course).