refactor(lint): modularize json linters

README.md

@@ -121,6 +121,7 @@ Consult the [builtin tools](https://github.com/nvimdev/guard.nvim/tree/main/lua%
 #### Linters
 
 - [clang-tidy](https://clang.llvm.org/extra/clang-tidy/)
+- [luacheck](https://github.com/lunarmodules/luacheck)
 - [pylint](https://github.com/PyCQA/pylint)
 - [rubocop](https://github.com/rubocop/rubocop)
 - [shellcheck](https://github.com/koalaman/shellcheck)

lua/guard/tools/linter/luacheck.lua

@@ -0,0 +1,39 @@
+local diag_fmt = require('guard.lint').diag_fmt
+return {
+  cmd = 'luacheck',
+  args = { '--formatter', 'plain', '--codes', '-', '--filename' },
+  fname = true,
+  stdin = true,
+  output_fmt = function(result, buf)
+    local lines = vim.split(result, '\n', { trimempty = true })
+
+    if #lines < 1 then
+      return {}
+    end
+
+    -- For each line, substring between parentheses contains
+    -- three digit issue code, prefixed with E for errors and W for warnings.
+    -- https://luacheck.readthedocs.io/en/stable/cli.html
+    local severities = {
+      E = 1,
+      W = 2,
+    }
+
+    local diags = {}
+
+    vim.tbl_map(function(line)
+      local lnum, col, severity, code, message = line:match('(%d+):(%d+):%s%((%a)(%w+)%) (.+)')
+
+      diags[#diags + 1] = diag_fmt(
+        buf,
+        tonumber(lnum) - 1,
+        tonumber(col) - 1,
+        message .. ' [' .. code .. ']',
+        severities[severity] or 4,
+        'luacheck'
+      )
+    end, lines)
+
+    return diags
+  end,
+}