elixir: add flycheck support for mix compile

layers/+lang/elixir/README.org

@@ -5,6 +5,8 @@
 * Table of Contents                                         :TOC_4_gh:noexport:
  - [[#description][Description]]
  - [[#install][Install]]
+ - [[#configuration][Configuration]]
+   - [[#flycheck-support-for-mix-compile][Flycheck support for mix compile]]
  - [[#key-bindings][Key bindings]]
    - [[#refcard][Refcard]]
    - [[#help][Help]]
@@ -18,7 +20,6 @@
    - [[#code-definition-jump][Code Definition Jump]]
 
 * Description
-
 This layer adds support for [[http://elixir-lang.org/][Elixir]] .
 
 [[https://github.com/tonini/alchemist.el][Alchemist]] brings the Elixir tooling to Emacs and comes with a bunch of
@@ -32,16 +33,38 @@ features like:
 - Smart code completion
 - Elixir project management
 - Integration with [[http://company-mode.github.io/][company-mode]]
+- Flycheck support for mix compile
 
 * Install
 To use this configuration layer, add it to your =~/.spacemacs=. You will need to
 add =elixir= to the existing =dotspacemacs-configuration-layers= list in this
 file.
 
+* Configuration
+** Flycheck support for mix compile
+*Important:*
+Elixir compilation is based on macros and is unsafe since arbitrary code can
+be run during compilation. Therefore Spacemacs disable compilation flycheck
+support by default.
+
+To enable flycheck support for =mix compile= *globally* the variable
+=elixir-enable-compilation-checking= must be explicitly set to =t= in your
+dotfile.
+
+It is recommended to use directory local variables instead. These variables are
+stored in a file named =.dit-local.el= at the root of your project. Their values
+are applied only for the project and not outside. To easily add a directory
+local variable used ~SPC f v d~ and provide the mode =elixir-mode= then the
+variable name =elixir-enable-compilation-checking= and its value.
+
+Spacemacs marks the variable =elixir-enable-compilation-checking= as safe so
+Emacs won't ask you if the variable is safe whenever an elixir file is opened.
+
+Remember that you can check the flycheck checkers enabled with ~SPC e v~.
+
 * Key bindings
 
 ** Refcard
-
 You find and overview of all the key-bindings on the [[file:alchemist-refcard.pdf][Alchemist-Refcard]].
 
 ** Help

layers/+lang/elixir/config.el

@@ -11,5 +11,11 @@
 
 ;; Variables
 
+(defvar elixir-enable-compilation-checking nil
+  "If non-nil syntax checking is enable for compilation.
+Default is nil because Elixir compilation is based on macros and thus it
+is unsafe. Activate this option only for trusted code, usage of a
+directory variable is recommended.")
+
 (spacemacs|defvar-company-backends elixir-mode)
 (spacemacs|defvar-company-backends alchemist-iex-mode)

layers/+lang/elixir/funcs.el

@@ -14,3 +14,14 @@
     (newline-and-indent)
     (forward-line -1)
     (indent-according-to-mode)))
+
+(defun spacemacs//elixir-enable-compilation-checking ()
+  "Enable compile checking if `elixir-enable-compilation-checking' is non nil."
+  (message "djeoifhwfwfjegweifh")
+  (hack-dir-local-variables)
+  (let ((enabled (cdr (assq 'elixir-enable-compilation-checking
+                            file-local-variables-alist))))
+    (message "---> %s" (assq 'elixir-enable-compilation-checking
+                        file-local-variables-alist))
+    (when (or enabled elixir-enable-compilation-checking)
+      (elixir-flycheck-mix-compile-setup))))

layers/+lang/elixir/local/elixir-flycheck-mix-compile/elixir-flycheck-mix-compile.el

@@ -0,0 +1,62 @@
+;;; elixir-flycheck-mix-compile.el --- Elixir flycheck integration -*- lexical-binding: t; -*-
+
+;; Copyright (C) 2016  Tomasz Kowal
+
+;; Author: Tomasz Kowal <tomekowal@gmail.com>
+;; Keywords: Elixir flycheck mix
+;; Version: 0.0.1
+
+;; This program is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation, either version 3 of the License, or
+;; (at your option) any later version.
+
+;; This program is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+;;; Commentary:
+
+;; This package should be distributed with =mix_compile_helper=.
+;; Make sure it is in your PATH
+
+;;; Code:
+(require 'flycheck)
+
+;; :command uses source-original, source-inplace copies the file
+;; which makes mix throw errors
+(flycheck-define-checker
+ elixir-mix-compile
+ "Defines a checker for elixir with mix compile"
+ :command ("mix_compile_helper" source-original)
+ :error-patterns
+ ((warning line-start
+            (file-name)
+            ":"
+            line
+            ": warning: "
+            (message)
+            line-end)
+   (error line-start
+          "** ("
+          (one-or-more word)
+          "Error) "
+          (file-name)
+          ":"
+          line
+          ": "
+          (message)
+          line-end))
+ :modes (elixir-mode))
+
+;;;###autoload
+(defun elixir-flycheck-mix-compile-setup ()
+  "Setup Flycheck for Elixir."
+  (add-to-list 'flycheck-checkers 'elixir-mix-compile))
+
+(provide 'elixir-flycheck-mix-compile)
+;;; elixir-flycheck-mix-compile.el ends here

layers/+lang/elixir/local/elixir-flycheck-mix-compile/mix_compile_helper

@@ -0,0 +1,71 @@
+#!/usr/bin/env elixir
+defmodule :mix_compile_helper do
+  def run() do
+    project_root = get_project_root()
+
+    if project_root do
+      {stdout, exit_status} =
+        System.cmd "mix", ["compile", "--ignore-module-conflict"],
+        cd: project_root, stderr_to_stdout: true
+      stdout
+      |> String.split("\n")
+      |> Enum.map(&(make_paths_absolute(&1, project_root)))
+      |> Enum.join("\n")
+      |> IO.puts
+      exit({:shutdown, exit_status})
+    else
+      usage(:root_not_found)
+    end
+  end
+
+  def usage(:general) do
+    file = __ENV__.file |> Path.split |> List.last
+    IO.puts "Usage:"
+    IO.puts "Make sure executable is in the path. Run inside mix project"
+    IO.puts "    #{file}"
+  end
+  def usage(:root_not_found) do
+    IO.puts "mix.exs not detected in the directory structure"
+    usage(:general)
+  end
+
+  defp make_paths_absolute(line, root) do
+    line
+    |> make_error_paths_absolute(root)
+    |> make_warning_paths_absolute(root)
+  end
+
+  defp make_error_paths_absolute(line, root) do
+    replace_at_position_if_pattern(line, "CompileError", 2, root)
+  end
+
+  defp make_warning_paths_absolute(line, root) do
+    replace_at_position_if_pattern(line, "warning:", 0, root)
+  end
+
+  defp replace_at_position_if_pattern(line, pattern, position, root) do
+    if String.contains?(line, pattern) do
+      line
+      |> String.split(" ")
+      |> List.update_at(position, &(Path.absname(&1, root)))
+      |> Enum.join(" ")
+    else
+      line
+    end
+  end
+
+  def get_project_root do
+    System.cwd
+    |> Path.split
+    |> Enum.reverse
+    |> get_project_root
+  end
+  def get_project_root([]), do: nil
+  def get_project_root([_|rest] = reversed_path) do
+    current_path = reversed_path |> Enum.reverse |> Path.join()
+    mix_file = Path.join(current_path, "mix.exs")
+    if File.exists?(mix_file), do: current_path, else: get_project_root(rest)
+  end
+end
+
+:mix_compile_helper.run

layers/+lang/elixir/packages.el

@@ -13,11 +13,19 @@
   '(
     alchemist
     company
+    (elixir-flycheck-mix-compile
+     :location local
+     :toggle (configuration-layer/package-usedp 'flycheck))
     elixir-mode
+    flycheck
     popwin
     smartparens
     ))
 
+(defun elixir/post-init-company ()
+  (spacemacs|add-company-hook elixir-mode)
+  (spacemacs|add-company-hook alchemist-iex-mode))
+
 (defun elixir/init-alchemist ()
   (use-package alchemist
     :defer t
@@ -109,9 +117,35 @@
       (evil-define-key 'normal mode
         (kbd "q") 'quit-window))))
 
-(defun elixir/post-init-company ()
-  (spacemacs|add-company-hook elixir-mode)
-  (spacemacs|add-company-hook alchemist-iex-mode))
+(defun elixir/init-elixir-flycheck-mix-compile ()
+  (use-package elixir-flycheck-mix-compile
+    :commands (elixir-flycheck-mix-compile-setup)
+    :init
+    (progn
+      (add-to-list 'safe-local-variable-values
+                   (cons 'elixir-enable-compilation-checking nil))
+      (add-to-list 'safe-local-variable-values
+                   (cons 'elixir-enable-compilation-checking t))
+      (add-hook 'elixir-mode-hook
+                'spacemacs//elixir-enable-compilation-checking t))
+    :config
+    ;; enable mix_compile_helper executable
+    (let ((layer-path (configuration-layer/get-layer-path 'elixir)))
+      (add-to-list 'exec-path
+                   (concat layer-path
+                           "elixir/local/elixir-flycheck-mix-compile")))))
+
+(defun elixir/init-elixir-mode ()
+  (use-package elixir-mode
+    :defer t))
+
+(defun elixir/post-init-flycheck ()
+  (add-hook 'elixir-mode-hook 'flycheck-mode))
+
+(defun elixir/pre-init-popwin ()
+  (spacemacs|use-package-add-hook popwin
+    :post-config
+    (push '("*mix*" :tail t :noselect t) popwin:special-display-config)))
 
 (defun elixir/post-init-smartparens ()
   (spacemacs|use-package-add-hook smartparens
@@ -129,13 +163,3 @@
          :when '(("SPC" "RET"))
          :post-handlers '(:add spacemacs//elixir-do-end-close-action)
          :actions '(insert))))))
-
-(defun elixir/init-elixir-mode ()
-  (use-package elixir-mode
-    :defer t))
-
-(defun elixir/pre-init-popwin ()
-  (spacemacs|use-package-add-hook popwin
-    :post-config
-    (push '("*mix*" :tail t :noselect t) popwin:special-display-config)))
-