add joker handler for clojure

Adds new linter for clojure using joker

https://github.com/candid82/joker

fixes #975
ref #544 #1040

ale_linters/clojure/joker.vim

@@ -0,0 +1,32 @@
+" Author: Nic West <nicwest@mailbox.org>
+" Description: linter for clojure using joker https://github.com/candid82/joker
+
+function! ale_linters#clojure#joker#HandleJokerFormat(buffer, lines) abort
+    " output format
+    " <filename>:<line>:<column>: <issue type>: <message>
+    let l:pattern = '\v^[a-zA-Z]?:?[^:]+:(\d+):(\d+):? ((Read error|Parse error|Parse warning|Exception): ?(.+))$'
+    let l:output = []
+
+    for l:match in ale#util#GetMatches(a:lines, l:pattern)
+        let l:type = 'E'
+        if l:match[4] is? 'Parse warning'
+          let l:type = 'W'
+        endif
+        call add(l:output, {
+        \   'lnum': l:match[1] + 0,
+        \   'col': l:match[2] + 0,
+        \   'text': l:match[3],
+        \   'type': l:type,
+        \})
+    endfor
+
+    return l:output
+endfunction
+
+call ale#linter#Define('clojure', {
+\   'name': 'joker',
+\   'output_stream': 'stderr',
+\   'executable': 'joker',
+\   'command': 'joker --lint %t',
+\   'callback': 'ale_linters#clojure#joker#HandleJokerFormat',
+\})