Fix #794 - Filter out any preceding lines of Flow output which aren't JSON

1 files changed, 18 insertions, 2 deletions

diff --git a/ale_linters/javascript/flow.vim b/ale_linters/javascript/flow.vim
index 2e778c5a..f3e5deff 100644
--- a/ale_linters/javascript/flow.vim
+++ b/ale_linters/javascript/flow.vim
@@ -40,10 +40,26 @@ function! ale_linters#javascript#flow#GetCommand(buffer, version_lines) abort
     \   . ' --json --from ale %s'
 endfunction
 
+" Filter lines of flow output until we find the first line where the JSON
+" output starts.
+function! s:GetJSONLines(lines) abort
+    let l:start_index = 0
+
+    for l:line in a:lines
+        if l:line[:0] ==# '{'
+            break
+        endif
+
+        let l:start_index += 1
+    endfor
+
+    return a:lines[l:start_index :]
+endfunction
+
 function! ale_linters#javascript#flow#Handle(buffer, lines) abort
-    let l:str = join(a:lines, '')
+    let l:str = join(s:GetJSONLines(a:lines), '')
 
-    if l:str ==# ''
+    if empty(l:str)
         return []
     endif