Improve documentation of 'read-command'

* src/minibuf.c (Fread_command): Document the return value
when DEFAULT-VALUE is nil and the user enters nothing.
* doc/lispref/minibuf.texi (High-Level Completion): Document
the printed representation of a symbol whose name is empty.
(Bug#3522)

2 files changed, 4 insertions, 2 deletions

diff --git a/doc/lispref/minibuf.texi b/doc/lispref/minibuf.texi
index 796be07ef14..3a2a9d82e97 100644
--- a/doc/lispref/minibuf.texi
+++ b/doc/lispref/minibuf.texi
@@ -1327,7 +1327,8 @@ is a string, @code{read-command} interns it before returning it.
 If it is a list, @code{read-command} interns the first element of this list.
 If @var{default} is @code{nil}, that means no default has been
 specified; then if the user enters null input, the return value is
-@code{(intern "")}, that is, a symbol whose name is an empty string.
+@code{(intern "")}, that is, a symbol whose name is an empty string,
+and whose printed representation is @code{##} (@pxref{Symbol Type}).
 
 @example
 (read-command "Command name? ")
diff --git a/src/minibuf.c b/src/minibuf.c
index 6964f350ffe..a33ddf40a1c 100644
--- a/src/minibuf.c
+++ b/src/minibuf.c
@@ -1054,7 +1054,8 @@ the current input method and the setting of`enable-multibyte-characters'.  */)
 DEFUN ("read-command", Fread_command, Sread_command, 1, 2, 0,
        doc: /* Read the name of a command and return as a symbol.
 Prompt with PROMPT.  By default, return DEFAULT-VALUE or its first element
-if it is a list.  */)
+if it is a list.  If DEFAULT-VALUE is omitted or nil, and the user enters
+null input, return a symbol whose name is an empty string.  */)
   (Lisp_Object prompt, Lisp_Object default_value)
 {
   Lisp_Object name, default_string;