Bug/652 markdown lint hook fails with unexpected output

CHANGELOG.md

@@ -7,6 +7,7 @@
 * Relax `childprocess` dependency to allow version 1.x
 * Add `CodeSpellCheck` pre-commit hook
 * Fix deadlock which was more likely to occur when setting `parallelize` on a hook to `false`
+* Fix `Mdl` hook to use JSON output and not fail on unexpected output
 
 ## 0.48.1
 

config/default.yml

@@ -486,6 +486,7 @@ PreCommit:
     enabled: false
     description: 'Analyze markdown files with mdl'
     required_executable: 'mdl'
+    flags: ['--json']
     install_command: 'gem install mdl'
     include: '**/*.md'
 

lib/overcommit/hook/pre_commit/mdl.rb

@@ -5,8 +5,6 @@ module Overcommit::Hook::PreCommit
   #
   # @see https://github.com/mivok/markdownlint
   class Mdl < Base
-    MESSAGE_REGEX = /^(?<file>(?:\w:)?[^:]+):(?<line>\d+):\s(?<msg>.+)/
-
     def run
       result = execute(command, args: applicable_files)
       output = result.stdout.chomp
@@ -15,11 +13,17 @@ def run
       return [:fail, result.stderr] unless result.stderr.empty?
 
       # example message:
-      #   path/to/file.md:1: MD001 Error message
-      extract_messages(
-        output.split("\n"),
-        MESSAGE_REGEX
-      )
+      #   [{"filename":"file1.md","line":1,"rule":"MD013","aliases":["line-length"],
+      #   "description":"Line length"}]
+      json_messages = JSON.parse(output)
+      json_messages.map do |message|
+        Overcommit::Hook::Message.new(
+          :error,
+          message[:filename],
+          message[:line],
+          message[:description]
+        )
+      end
     end
   end
 end

spec/overcommit/hook/pre_commit/mdl_spec.rb

@@ -27,7 +27,10 @@
     let(:success) { false }
 
     context 'and it reports an error' do
-      let(:stdout) { 'file1.md:1: MD013 Line length' }
+      let(:stdout) do
+        '[{"filename":"file1.md","line":1,"rule":"MD013","aliases":["line-length"],'\
+        '"description":"Line length"}]'
+      end
       let(:stderr) { '' }
 
       it { should fail_hook }