import { indentexpr } from "https://deno.land/x/denops_std@v6.4.0/option/mod.ts";
Expression which is evaluated to obtain the proper indent for a line.
It is used when a new line is created, for the = operator and
in Insert mode as specified with the 'indentkeys' option.
When this option is not empty, it overrules the 'cindent' and
'smartindent' indenting. When 'lisp' is set, this option is
is only used when 'lispoptions' contains "expr:1".
When 'paste' is set this option is not used for indenting.
The expression is evaluated with v:lnum set to the line number for
which the indent is to be computed. The cursor is also in this line
when the expression is evaluated (but it may be moved around).
If the expression starts with s: or <SID>, then it is replaced with
the script ID (local-function). Example:
set indentexpr=s:MyIndentExpr()
set indentexpr=<SID>SomeIndentExpr()
Otherwise, the expression is evaluated in the context of the script where the option was set, thus script-local items are available.
The advantage of using a function call without arguments is that it is
faster, see expr-option-function.
The expression must return the number of spaces worth of indent. It
can return "-1" to keep the current indent (this means 'autoindent' is
used for the indent).
Functions useful for computing the indent are indent(), cindent()
and lispindent().
The evaluation of the expression must not have side effects! It must
not change the text, jump to another window, etc. Afterwards the
cursor position is always restored, thus the cursor may be moved.
Normally this option would be set to call a function:
:set indentexpr=GetMyIndent()
Error messages will be suppressed, unless the 'debug' option contains
"msg".
See indent-expression.
NOTE: This option is set to "" when 'compatible' is set.
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 'indentexpr' textlock.
(default "")
not available when compiled without the +eval feature