Improve documentation for custom :options

* doc/lispref/customize.texi (Variable Definitions):
Mention that re-evaluating a defcustom form doesn't reset custom
options (bug#30101).

diff --git a/doc/lispref/customize.texi b/doc/lispref/customize.texi
index 2a72276bc5612df1aa272739318fb142ed11f71f..b9c9130a9209c8e8cae752e3072b70bea20f5bd1 100644 (file)
--- a/doc/lispref/customize.texi
+++ b/doc/lispref/customize.texi
@@ -358,6 +358,10 @@ This is meaningful only for certain types, currently including
 @code{hook}, @code{plist} and @code{alist}.  See the definition of the
 individual types for a description of how to use @code{:options}.
 
+Re-evaluating a @code{defcustom} form with a different @code{:options}
+value does not clear the values added by previous evaluations, or
+added by calls to @code{custom-add-frequent-value} (see below).
+
 @item :set @var{setfunction}
 @kindex set@r{, @code{defcustom} keyword}
 Specify @var{setfunction} as the way to change the value of this
@@ -485,6 +489,10 @@ list of reasonable values.
 
 The precise effect of adding a value depends on the customization type
 of @var{symbol}.
+
+Since evaluating a @code{defcustom} form does not clear values added
+previously, Lisp programs can use this function to add values for user
+options not yet defined.
 @end defun
 
 Internally, @code{defcustom} uses the symbol property