Add nix checker

CHANGES.rst

@@ -10,6 +10,7 @@
 
   - Protobuf with ``protoc`` [GH-1125]
   - systemd-analyze with ``systemd-analyze`` [GH-1135]
+  - Nix with ``nix-instantiate`` [GH-1164]
   - Dockerfile with ``hadolint`` [GH-1194]
   - AsciiDoc with ``asciidoctor`` [GH-1167]
   - CSS/SCSS/LESS with ``stylelint`` [GH-903]

Cask

@@ -32,6 +32,7 @@
  (depends-on "lua-mode")
  (depends-on "markdown-mode")
  (depends-on "mmm-mode")
+ (depends-on "nix-mode")
  (depends-on "php-mode")
  (depends-on "processing-mode")
  (depends-on "protobuf-mode")

doc/languages.rst

@@ -693,6 +693,14 @@ to view the docstring of the syntax checker.  Likewise, you may use
 
       .. syntax-checker-config-file:: flycheck-markdown-mdl-style
 
+.. supported-language:: Nix
+
+   .. syntax-checker:: nix
+
+      Check Nix with nix-instantiate_.
+
+      .. _nix-instantiate: https://nixos.org/nix/manual/#sec-nix-instantiate
+
 .. supported-language:: Perl
 
    Flycheck checks Perl with `perl` and `perl-perlcritic`.

flycheck.el

@@ -221,6 +221,7 @@ attention to case differences."
     racket
     rpm-rpmlint
     markdown-mdl
+    nix
     rst-sphinx
     rst
     ruby-rubocop
@@ -8709,6 +8710,17 @@ See URL `https://github.com/mivok/markdownlint'."
      (flycheck-remove-error-file-names "(stdin)" errors)))
   :modes (markdown-mode gfm-mode))
 
+(flycheck-define-checker nix
+  "Nix checker using nix-instantiate.
+
+See URL `https://nixos.org/nix/manual/#sec-nix-instantiate'."
+  :command ("nix-instantiate" "--parse" source-inplace)
+  :error-patterns
+  ((error line-start
+          "error: " (message) " at " (file-name) ":" line ":" column
+          line-end))
+  :modes nix-mode)
+
 (defun flycheck-locate-sphinx-source-directory ()
   "Locate the Sphinx source directory for the current buffer.
 

test/flycheck-test.el

@@ -3766,6 +3766,11 @@ Why not:
    "language/markdown.md" 'markdown-mode
    '(1 nil error "First header should be a h1 header" :id "MD002" :checker markdown-mdl)))
 
+(flycheck-ert-def-checker-test nix nix nil
+  (flycheck-ert-should-syntax-check
+   "language/nix.nix" 'nix-mode
+   '(3 1 error "syntax error, unexpected IN, expecting ';'," :checker nix)))
+
 (ert-deftest flycheck-locate-sphinx-source-directory/not-in-a-sphinx-project ()
   :tags '(language-rst)
   (flycheck-ert-with-resource-buffer "language/rst/errors.rst"

test/resources/language/nix.nix

@@ -0,0 +1,4 @@
+let
+  number = 42
+in
+  number * 10