lein-check-namespace-decls

A Leiningen plugin that lints source files in your Clojure project to check whether the ns declarations are cleaned the way refactor-nrepl and cljr-refactor would clean them (such as with the M-x cljr-clean-ns command in Emacs).

Checks the following:

• Namespaces and imports in the ns declaration are sorted
• No unused namespaces are present (configurable)
• :require forms are used instead of :use
• The top-level forms inside the ns form follow the conventional order: :gen-class, :refer-clojure, :require, :import
• Namespaces in :require use shared prefixes (e.g. (:require [clojure [string :as str] [data :as data]]))

For files with ns declarations that don't satisfy these rules, the linter tells you how to fix namespace declarations that aren't cleaned properly.

Example Usage

What happened? The linter detected an unused namespace, clojure.string, and removed it; it sorted the namespaces as well.

For each ns declaration it finds that isn't "clean" (i.e. not properly sorted or with unused namespaces), it will print a message like the one above; if any unclean namespaces were found, the linter will exit with a nonzero status.

Usage

Adding the dependency to :plugins

Add [lein-check-namespace-decls "1.0.2"] into the :plugins vector of your project.clj or ~/.lein/profiles.clj.

(defproject my-project
  :plugins [[lein-check-namespace-decls "1.0.2"]])

Running the linter

Run the linter like this:

lein check-namespace-decls

This will check ns declaration forms for all Clojure source files in the :source-paths of your project (usually ./src/).

Configuration

Add a :check-namespace-decls key to your project.clj to configure the way refactor-nrepl cleans namespaces. All options are passed directly to refactor-nrepl.

(defproject my-project
  :check-namespace-decls {:prefix-rewriting false})

The complete list of available options can be found here. The most interesting ones when using this as a linter are:

:prefix-rewriting

By setting {:prefix-rewriting false} the ns form will not be expected to use prefix lists when including several libs whose names have the same prefix. The default behavior uses prefixes:

;; Cleaned ns form with :prefix-rewriting true (default)
(ns my-project.core
  (:require [clojure.tools.namespace
             [find :as ns.find]
             [parse :as ns.parse]]))

Contrast this to ns forms without prefixes:

;; Cleaned ns form with :prefix-rewriting false
(ns my-project.core
  (:require [clojure.tools.namespace.find :as ns.find]
            [clojure.tools.namespace.parse :as ns.parse]))

Opinions on whether or not to use prefixes in :require forms vary in the Clojure community; I (@camsaul) personally like them, so I stuck with the default behavior of refactor-nrepl, which is to use them.

:ignore-paths

Specify a collection of regexes of filenames to ignore.

;; ignore any files ending in core.clj
(defproject my-project
  :check-namespace-decls {:ignore-paths [#".*core\.clj$"]})

:prune-ns-form

Whether to remove unused namespaces from the ns form. Defaults to true; if you don't want unused namespaces to be considered an error, set this to false.

Including or excluding source directories

lein-check-namespace-decls simply checks any Clojure source files it finds in :source-paths, excluding any that match a pattern in :ignore-paths.

To include or exclude entire directories from the linter you can modify or ^:replace :source-paths; the easiest way to do this without affecting the rest of your project is to add a profile for lein-check-namespace-decls and an alias that automatically applies it:

;; Check the sources under `./test/` in addition to the normal :source-paths (e.g. `./src/`)
(defproject my-project
  :aliases {"check-namespace-decls" ["with-profile" "+check-namespace-decls" "check-namespace-decls"]}
  :plugins [[lein-check-namespace-decls "1.0.2"]]
  :profiles {:check-namespace-decls {:source-paths ["test"]}})

If the above seems like black magic, the Leiningen documentation does a great job of explaining how Leiningen plugins work in more detail.

Verbose logging

Like Leiningen itself, setting the environment variable DEBUG=true will add additional log messages to linter output -- specifically, it will log messages about each file it checks and files that are skipped due to patterns in :ignore-paths (and the patterns that matched those files). This is useful for debugging which files are checked by the linter.

License

Copyright © 2021 Cam Saul.

Distributed under the Eclipse Public License, same as Clojure.