formatting ns forms

[expez]

For refactor-nrepl I made the terrible mistake of trying to write my own pretty-printing code to output the newly-cleaned ns form. This started out as just a few lines of code which worked in 95% of cases, but has now grown to a a huge mess which badly needs to be rewritten, or preferably thrown out altogether.

Will it ever be in the scope of cljfmt to format an ns form nicely?

[weavejester]

I don't see why not.

cljfmt can already correct the indentation of an ns form, but doesn't currently order the namespaces or insert linebreaks when necessary. However, both those things would come under formatting in my book.

[expez]

Glad to hear you consider this in-scope for cljfmt.

Here's what the clean-ns op in clj-refactor does:

• Eliminate :use clauses
• Sort required libraries, imports and vectors of referred symbols
• Rewrite to favor prefix form, e.g. [clojure [string test]] instead of two separate libspecs
• Raise errors if any inconsistencies are found (e.g. a libspec with more than one alias.
• Remove any unused namespaces, referred symbols or imported classes.
• Remove any duplication in the :require and :import form.

In the interest of not duplication any code I researched the following solutions when I needed to format the ns. Some of this might interest to you:

clojure.core/pprint Has a small amount of special handling for pretty-printing the ns form, but not enough. The relevant code is here

fipp which is a pretty-printer construction kit didn't work out of the box, but I now regret trying to hack my own code instead of relying on this lib.

slamhound has its code for pretty-printing the ns form here.

The rewriting to use prefix form drove some of these issues I had. I find the prefix form easier to read, but it's a pain to manage manually (which is why I think it isn't used more widely). I'd like libspecs that aren't vectors to be printed on their own line(s), but breaking at line 80:

(:require [clojure data edn xml
           [instant :as inst]
           [pprint :refer [pprint]]])

I'll likely write an op for clj-refactor to call out to cljfmt once it's a bit more mature.

[weavejester]

I'm not sure how much of that is in scope for cljfmt. Currently it just affects whitespace, and doesn't change the meaning of the source code. If cljfmt were to affect more, I think it would have to be controlled by an optional flag.

[expez]

Perhaps I was unclear: I just want cljfmt to format the ns nicely, the rest clj-refactor can handle (like eliminating duplication and rewriting to use prefix form). I'm hoping that if just dump the entire ns form on a single line cljfmt will insert newlines in it in a sensible way.

[weavejester]

Oh I see. Yes, that's perfectly within scope of cljfmt.

[bbatsov]

I'll likely write an op for clj-refactor to call out to cljfmt once it's a bit more mature.

Actually we might add this directly to CIDER (I can imaged commands like format-buffer and format-region (or rather format-form). clj-rewrite deps shouldn't be problematic for most people.

[expez]

👍

[bbatsov]

And now we have cider commands for cljfmt. :-) See clojure-emacs/cider@b661d10

The initial support is pretty basic, but will cover the needs of most people.

[expez]

Very cool!

[xpe]

@expez Is your issue still open? Or has it been resolved?

[expez]

@xpe this issue is still open

I've written some refactorings for moving files and directories of clj files for clj-refactor. Right now I parse and update the ns form of all affected namespaces but then I have to use emacs and clojure-mode to visit the files afterwards to get right indentation of the ns form.

Needless to say I'd be quite happy to skip that last step. Not only because it makes it easier but because the op becomes slow when a large amount of files are affected.

[expez]

@weavejester is this likely to get solved? I realize this isn't the most sexy problem to spend limited time on :/

[weavejester]

When someone submits a pull request for it.

It's not something I personally need, and isn't a bug but a new feature, so it's fairly far down my list of priorities.

[expez]

Hi, I see this was closed in a commit that mentions ns sorting. Has the formatting / pretty-printing (proper indentation, breaking of long lines in sensible places etc) been solved previously?

Many thanks for your tireless and consistent maintenance of you open source projects @weavejester 🙇