Expression to be used to transform the string found with the 'include' option to a file name. Mostly useful to change "." to "/" for Java:

:setlocal includeexpr=substitute(v:fname,'\\.','/','g')

The "v:fname" variable will be set to the file name that was detected. Note the double backslash: the :set command first halves them, then one remains it the value, where "." matches a dot literally. For simple character replacements tr() avoids the need for escaping:

:setlocal includeexpr=tr(v:fname,'.','/')

Also used for the gf command if an unmodified file name can't be found. Allows doing "gf" on the name after an 'include' statement. Also used for <cfile>.

If the expression starts with s: or <SID>, then it is replaced with the script ID (local-function). Example:

setlocal includeexpr=s:MyIncludeExpr()
setlocal includeexpr=<SID>SomeIncludeExpr()

Otherwise, the expression is evaluated in the context of the script where the option was set, thus script-local items are available.

It is more efficient if the value is just a function call without arguments, see expr-option-function.

The expression will be evaluated in the sandbox when set from a modeline, see sandbox-option. This option cannot be set in a modeline when 'modelineexpr' is off.

It is not allowed to change text or jump to another window while evaluating 'includeexpr' textlock.

(default "")

not available when compiled without the +find_in_path or +eval features