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Breaking changes to eieio in Emacs 27?

How to pass an argument to an object constructor that's NOT a slot?

2

Q: are there breaking changes to eieio in Emacs 27?

I just upgraded to the Emacs 27 snapshot, and I'm getting a
peculiar break in code that works in previous versions of Emacs.

walkthrough

Here's a toy class and a toy :after method:

(defclass simple-class ()

  ((value

    :initarg :value

    :initform nil

    :documentation "Test slot"))

  "Test class.")

This works:

(simple-class :value "some value") ;; ==> #s(simple-class "some value")

Now I'd like to define an :after method on initialize-instance:

(cl-defmethod initialize-instance :after ((sc simple-class) &key)

  (with-slots (value) sc

    (setf value (upcase value))))

Now it's broken:

(simple-class :value "some value") ;; ==> (error "Keyword argument nil not one of nil")

NB: it's nothing about the content of the :after method: I can
define an empty method and I get the same error.

(cl-defmethod initialize-instance :after ((sc simple-class) &key))

what happened?

So: have there been changes to eieio (specifically,
cl-defmethod) in Emacs 27 that break previous code? Or is there
something bizarre about the snapshot?

eieio emacs27

share|improve this question

edited 1 hour ago

Drew

49.5k465111

asked 8 hours ago

Dan♦Dan

21.6k653114

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Might be incorrect use of &key with no following arg name, I think Emacs got stricter about that. By the way, in 25.3, I get Lisp error: (wrong-type-argument char-or-string-p nil) after the cl-defmethod, did you mean (simple-class :value "some value")?
  
  – npostavs
  8 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Fixed the typos; sorry. Not sure how else one would define an after method without &keys here.
  
  – Dan♦
  7 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  what do you think &key means in an expression like (cl-defun foo (x &key) nil)?
  
  – npostavs
  7 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  We need the &key to maintain the same number of arguments. Removing &key throws an error to that effect.
  
  – Dan♦
  7 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  C-h n (view-emacs-news) is usually the starting point for "What's new?".
  
  – Drew
  1 hour ago
  

  
  
  
  

add a comment | 

2

Q: are there breaking changes to eieio in Emacs 27?

I just upgraded to the Emacs 27 snapshot, and I'm getting a
peculiar break in code that works in previous versions of Emacs.

walkthrough

Here's a toy class and a toy :after method:

(defclass simple-class ()

  ((value

    :initarg :value

    :initform nil

    :documentation "Test slot"))

  "Test class.")

This works:

(simple-class :value "some value") ;; ==> #s(simple-class "some value")

Now I'd like to define an :after method on initialize-instance:

(cl-defmethod initialize-instance :after ((sc simple-class) &key)

  (with-slots (value) sc

    (setf value (upcase value))))

Now it's broken:

(simple-class :value "some value") ;; ==> (error "Keyword argument nil not one of nil")

NB: it's nothing about the content of the :after method: I can
define an empty method and I get the same error.

(cl-defmethod initialize-instance :after ((sc simple-class) &key))

what happened?

So: have there been changes to eieio (specifically,
cl-defmethod) in Emacs 27 that break previous code? Or is there
something bizarre about the snapshot?

eieio emacs27

share|improve this question

edited 1 hour ago

Drew

49.5k465111

asked 8 hours ago

Dan♦Dan

21.6k653114

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Might be incorrect use of &key with no following arg name, I think Emacs got stricter about that. By the way, in 25.3, I get Lisp error: (wrong-type-argument char-or-string-p nil) after the cl-defmethod, did you mean (simple-class :value "some value")?
  
  – npostavs
  8 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Fixed the typos; sorry. Not sure how else one would define an after method without &keys here.
  
  – Dan♦
  7 hours ago
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  what do you think &key means in an expression like (cl-defun foo (x &key) nil)?
  
  – npostavs
  7 hours ago
  
  
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  We need the &key to maintain the same number of arguments. Removing &key throws an error to that effect.
  
  – Dan♦
  7 hours ago
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  C-h n (view-emacs-news) is usually the starting point for "What's new?".
  
  – Drew
  1 hour ago
  

  
  
  
  

add a comment | 

Q: are there breaking changes to eieio in Emacs 27?

I just upgraded to the Emacs 27 snapshot, and I'm getting a
peculiar break in code that works in previous versions of Emacs.

walkthrough

Here's a toy class and a toy :after method:

(defclass simple-class ()

  ((value

    :initarg :value

    :initform nil

    :documentation "Test slot"))

  "Test class.")

This works:

(simple-class :value "some value") ;; ==> #s(simple-class "some value")

Now I'd like to define an :after method on initialize-instance:

(cl-defmethod initialize-instance :after ((sc simple-class) &key)

  (with-slots (value) sc

    (setf value (upcase value))))

Now it's broken:

(simple-class :value "some value") ;; ==> (error "Keyword argument nil not one of nil")

NB: it's nothing about the content of the :after method: I can
define an empty method and I get the same error.

(cl-defmethod initialize-instance :after ((sc simple-class) &key))

what happened?

So: have there been changes to eieio (specifically,
cl-defmethod) in Emacs 27 that break previous code? Or is there
something bizarre about the snapshot?

eieio emacs27

share|improve this question

edited 1 hour ago

Drew

49.5k465111

asked 8 hours ago

Dan♦Dan

21.6k653114

(defclass simple-class ()

  ((value

    :initarg :value

    :initform nil

    :documentation "Test slot"))

  "Test class.")

(simple-class :value "some value") ;; ==> #s(simple-class "some value")

(cl-defmethod initialize-instance :after ((sc simple-class) &key)

  (with-slots (value) sc

    (setf value (upcase value))))

(simple-class :value "some value") ;; ==> (error "Keyword argument nil not one of nil")

(cl-defmethod initialize-instance :after ((sc simple-class) &key))

share|improve this question

edited 1 hour ago

Drew

49.5k465111

asked 8 hours ago

Dan♦Dan

21.6k653114

share|improve this question

edited 1 hour ago

Drew

49.5k465111

asked 8 hours ago

Dan♦Dan

21.6k653114

edited 1 hour ago

Drew

49.5k465111

edited 1 hour ago

Drew

49.5k465111

asked 8 hours ago

Dan♦Dan

21.6k653114

asked 8 hours ago

Dan♦Dan

21.6k653114

1 Answer
1

active

oldest

votes

2

So: have there been changes to eieio (specifically, cl-defmethod) in Emacs 27 that break previous code?

It's not a change in eieio or cl-defmethod directly; what's changed is the handling of the &key symbol in cl-def* macros.

(cl-defmethod initialize-instance :after ((sc simple-class) &key))

In Emacs 26 and earlier this produces a function which accepts any number of arguments. In Emacs 27 it produces a function which accepts only one argument (sc). The correct argument list for initialize-instance would be like this:

(cl-defmethod initialize-instance :after ((sc simple-class) &optional slots))

As told by <f1> f initialize-instance RET:

initialize-instance is a compiled Lisp function in ‘eieio.el’.



(initialize-instance THIS &optional SLOTS)

share|improve this answer

answered 6 hours ago

npostavsnpostavs

7,05611237

add a comment | 

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2

So: have there been changes to eieio (specifically, cl-defmethod) in Emacs 27 that break previous code?

It's not a change in eieio or cl-defmethod directly; what's changed is the handling of the &key symbol in cl-def* macros.

(cl-defmethod initialize-instance :after ((sc simple-class) &key))

In Emacs 26 and earlier this produces a function which accepts any number of arguments. In Emacs 27 it produces a function which accepts only one argument (sc). The correct argument list for initialize-instance would be like this:

(cl-defmethod initialize-instance :after ((sc simple-class) &optional slots))

As told by <f1> f initialize-instance RET:

initialize-instance is a compiled Lisp function in ‘eieio.el’.



(initialize-instance THIS &optional SLOTS)

share|improve this answer

answered 6 hours ago

npostavsnpostavs

7,05611237

add a comment | 

2

So: have there been changes to eieio (specifically, cl-defmethod) in Emacs 27 that break previous code?

It's not a change in eieio or cl-defmethod directly; what's changed is the handling of the &key symbol in cl-def* macros.

(cl-defmethod initialize-instance :after ((sc simple-class) &key))

In Emacs 26 and earlier this produces a function which accepts any number of arguments. In Emacs 27 it produces a function which accepts only one argument (sc). The correct argument list for initialize-instance would be like this:

(cl-defmethod initialize-instance :after ((sc simple-class) &optional slots))

As told by <f1> f initialize-instance RET:

initialize-instance is a compiled Lisp function in ‘eieio.el’.



(initialize-instance THIS &optional SLOTS)

share|improve this answer

answered 6 hours ago

npostavsnpostavs

7,05611237

add a comment | 

So: have there been changes to eieio (specifically, cl-defmethod) in Emacs 27 that break previous code?

It's not a change in eieio or cl-defmethod directly; what's changed is the handling of the &key symbol in cl-def* macros.

(cl-defmethod initialize-instance :after ((sc simple-class) &key))

In Emacs 26 and earlier this produces a function which accepts any number of arguments. In Emacs 27 it produces a function which accepts only one argument (sc). The correct argument list for initialize-instance would be like this:

(cl-defmethod initialize-instance :after ((sc simple-class) &optional slots))

As told by <f1> f initialize-instance RET:

initialize-instance is a compiled Lisp function in ‘eieio.el’.



(initialize-instance THIS &optional SLOTS)

share|improve this answer

answered 6 hours ago

npostavsnpostavs

7,05611237

(cl-defmethod initialize-instance :after ((sc simple-class) &optional slots))

share|improve this answer

answered 6 hours ago

npostavsnpostavs

7,05611237

answered 6 hours ago

npostavsnpostavs

7,05611237

answered 6 hours ago

npostavsnpostavs

7,05611237