Fix #3278 - Handle UTF-8 in URI encoding/decoding

autoload/ale/uri.vim

@@ -1,9 +1,18 @@
-" This probably doesn't handle Unicode characters well.
+function! s:EncodeChar(char) abort
+    let l:result = ''
+
+    for l:index in range(strlen(a:char))
+        let l:result .= printf('%%%02x', char2nr(a:char[l:index]))
+    endfor
+
+    return l:result
+endfunction
+
 function! ale#uri#Encode(value) abort
     return substitute(
     \   a:value,
     \   '\([^a-zA-Z0-9\\/$\-_.!*''(),]\)',
-    \   '\=printf(''%%%02x'', char2nr(submatch(1)))',
+    \   '\=s:EncodeChar(submatch(1))',
     \   'g'
     \)
 endfunction
@@ -12,7 +21,7 @@ function! ale#uri#Decode(value) abort
     return substitute(
     \   a:value,
     \   '%\(\x\x\)',
-    \   '\=nr2char(''0x'' . submatch(1))',
+    \   '\=printf("%c", str2nr(submatch(1), 16))',
     \   'g'
     \)
 endfunction