Conform on-the-fly to PEP8 using flycheck on emacs

Question

I unpack flycheck to ~/. and put the following lines in ~/.emacs:

;; (package-initialize)
(setq load-path (cons "~/flycheck-20170415.1006" load-path))
(require 'flycheck)
(add-hook 'after-init-hook #'global-flycheck-mode)

Starting Emacs 24.5.1 I get:

File error: Cannot open load file, no such file or directory, let-alist

With Emacs 25.1.1 I get:

File error: Cannot open load file, No such file or directory, dash

(These errors do not change if I uncomment (package-initialize). Emacs 25 now inserts (package-initialize), nudging those of us with a long setup to adapt.)

My (subsequent) aim is to conform Python code on-the-fly to PEP8. Once the problem above is resolved, I'll add

(setq exec-path (append exec-path '("/opt/local/Library/Frameworks/Python.framework/Versions/2.7/bin")))

to this brief ~/.emacs (/opt/..2.7/bin is where MacPorts put flake8), but there is apparently an issue before I even specify the programming language.

Update

This is far more painful than I expected. Flycheck is heavy-handed about being installed through packages, and incorporating the steps described here to my usual ~/.emacs leads to the notorious

load-with-code-conversion: Symbol’s value as variable is void: <!DOCTYPE

error. (I'm pretty sure I have no HTML files hiding under a .el extension.)

Update2

Uh.. I stand corrected! Some dash.el made its way to my usual elisp directory, and flycheck depends on it, but it was indeed an HTML file.

What do you see when you do `M-x flycheck-verify-setup` in a Python buffer? — elethan, Apr 21 '17 at 02:20
@elethan Thanks. Once again I am reminded that it's pointless to attempt to debug an Emacs problem without working with an isolated and minimal `.emacs`. Running `eval-region` on a few lines is misleading. I've revised the question. — Calaf, Apr 21 '17 at 08:00

Calaf · Accepted Answer · 2017-04-21T18:13:51.987

Flycheck depends on dash, let-alist, and seq.

Download the files

  84766  dash.el
 381142  flycheck.el
   6136  let-alist.el
  17589  seq-24.el
  17684  seq-25.el
   1540  seq.el

and put them in ~/.concise-elisp. You need three files for seq because it has alternative implementations for Emacs 24 & 25.

Put the following lines in your ~/.emacs:

;; Even if you are not using packages, you need the following
;; commented-out line, or else Emacs 25 will insert one for you.
;; (package-initialize)

(setq load-path (cons "~/.concise-elisp" load-path))
(require 'flycheck)
(add-hook 'after-init-hook #'global-flycheck-mode)
(setq exec-path (append exec-path '("/opt/local/Library/Frameworks/Python.framework/Versions/2.7/bin")))

The last line points to where MacPorts would have put flake8. Flake8 is one of the programs to which flycheck delegates PEP8 checking.

Next exercise: Hook flycheck just for Python (and perhaps C/C++/Java/JS/..). In particular, don't worry about making elisp files kosher. Selectively activate flycheck for languages as needed.

Conform on-the-fly to PEP8 using flycheck on emacs

1 Answers1