master 945af4d9d11 5/6: eieio-core.el: Always put a parent in the parents of a class

[Stefan Monnier]

branch: master
commit 945af4d9d11192d262f4fabbc66ee83f5beefc86
Author: Stefan Monnier <monnier@iro.umontreal.ca>
Commit: Stefan Monnier <monnier@iro.umontreal.ca>

    eieio-core.el: Always put a parent in the parents of a class
    
    * lisp/emacs-lisp/eieio-core.el (eieio-defclass-internal):
    Always put a parent in the `parents` slot of the class.
    
    * lisp/emacs-lisp/eieio.el (eieio-class-parents): Remove the
    `eieio-default-superclass` if it's the only parent.
    (child-of-class-p): Handle all classes in the parents.
    (eieio-default-superclass): Adjust docstring.
---
 lisp/emacs-lisp/eieio-core.el | 31 +++++++++++--------------------
 lisp/emacs-lisp/eieio.el      | 12 ++++++++----
 2 files changed, 19 insertions(+), 24 deletions(-)

diff --git a/lisp/emacs-lisp/eieio-core.el b/lisp/emacs-lisp/eieio-core.el
index 9c526f67204..9945e19c65c 100644
--- a/lisp/emacs-lisp/eieio-core.el
+++ b/lisp/emacs-lisp/eieio-core.el
@@ -293,8 +293,7 @@ See `defclass' for more information."
                    ;; reloading the file that does the `defclass', we don't
                    ;; want to create a new class object.
                    (eieio--class-make cname)))
-        (groups nil) ;; list of groups id'd from slots
-        (clearparent nil))
+        (groups nil)) ;; list of groups id'd from slots
 
     ;; If this class already existed, and we are updating its structure,
     ;; make sure we keep the old child list.  This can cause bugs, but
@@ -317,6 +316,9 @@ See `defclass' for more information."
           (setf (eieio--class-children newc) children)
          (remhash cname eieio-defclass-autoload-map))))
 
+    (unless (or superclasses (eq cname 'eieio-default-superclass))
+      (setq superclasses '(eieio-default-superclass)))
+
     (if superclasses
        (progn
          (dolist (p superclasses)
@@ -336,16 +338,13 @@ See `defclass' for more information."
                   (push c (eieio--class-parents newc))))))
          ;; Reverse the list of our parents so that they are prioritized in
          ;; the same order as specified in the code.
-         (cl-callf nreverse (eieio--class-parents newc)))
-      ;; If there is nothing to loop over, then inherit from the
-      ;; default superclass.
-      (unless (eq cname 'eieio-default-superclass)
-       ;; adopt the default parent here, but clear it later...
-       (setq clearparent t)
-        ;; save new child in parent
-        (cl-pushnew cname (eieio--class-children eieio-default-superclass))
-        ;; save parent in child
-        (setf (eieio--class-parents newc) (list eieio-default-superclass))))
+         (cl-callf nreverse (eieio--class-parents newc))
+         ;; Before adding new slots, let's add all the methods and classes
+         ;; in from the parent class.
+         (eieio-copy-parents-into-subclass newc))
+
+      (cl-assert (eq cname 'eieio-default-superclass))
+      (setf (eieio--class-parents newc) (list (cl--find-class 'record))))
 
     ;; turn this into a usable self-pointing symbol;  FIXME: Why?
     (when eieio-backward-compatibility
@@ -376,10 +375,6 @@ See `defclass' for more information."
                              cname)
                        "25.1")))
 
-    ;; Before adding new slots, let's add all the methods and classes
-    ;; in from the parent class.
-    (eieio-copy-parents-into-subclass newc)
-
     ;; Store the new class vector definition into the symbol.  We need to
     ;; do this first so that we can call defmethod for the accessor.
     ;; The vector will be updated by the following while loop and will not
@@ -512,10 +507,6 @@ See `defclass' for more information."
     ;; Set up the options we have collected.
     (setf (eieio--class-options newc) options)
 
-    ;; if this is a superclass, clear out parent (which was set to the
-    ;; default superclass eieio-default-superclass)
-    (if clearparent (setf (eieio--class-parents newc) nil))
-
     ;; Create the cached default object.
     (let ((cache (make-record newc
                               (+ (length (eieio--class-slots newc))
diff --git a/lisp/emacs-lisp/eieio.el b/lisp/emacs-lisp/eieio.el
index fba69a36a97..74f5e21db7d 100644
--- a/lisp/emacs-lisp/eieio.el
+++ b/lisp/emacs-lisp/eieio.el
@@ -449,7 +449,12 @@ If EXTRA, include that in the string returned to represent 
the symbol."
 (defun eieio-class-parents (class)
   ;; FIXME: What does "(overload of variable)" mean here?
   "Return parent classes to CLASS.  (overload of variable)."
-  (eieio--class-parents (eieio--full-class-object class)))
+  ;; (declare (obsolete cl--class-parents "30.1"))
+  (let ((parents (eieio--class-parents (eieio--full-class-object class))))
+    (if (and (null (cdr parents))
+             (eq (car parents) (cl--find-class 'eieio-default-superclass)))
+        nil
+      parents)))
 
 (define-obsolete-function-alias 'class-parents #'eieio-class-parents "24.4")
 
@@ -497,7 +502,7 @@ If EXTRA, include that in the string returned to represent 
the symbol."
         (setq class (eieio--class-object class))
         (cl-check-type class eieio--class)
         (while (and child (not (eq child class)))
-          (setq p (append p (eieio--class-parents child))
+          (setq p (append p (cl--class-parents child))
                 child (pop p)))
         (if child t))))
 
@@ -680,8 +685,7 @@ If SLOT is unbound, do nothing."
 (defclass eieio-default-superclass nil
   nil
   "Default parent class for classes with no specified parent class.
-Its slots are automatically adopted by classes with no specified parents.
-This class is not stored in the `parent' slot of a class vector."
+Its slots are automatically adopted by classes with no specified parents."
   :abstract t)
 
 (setq eieio-default-superclass (cl--find-class 'eieio-default-superclass))