print aeson warning to stderr, not stdout …

1 files changed, 2 insertions, 1 deletions

diff --git a/src/Main.hs b/src/Main.hs
index 0315be4..d115660 100644
--- a/src/Main.hs
+++ b/src/Main.hs
@@ -21,6 +21,7 @@ import           LintConfig               (LintConfig (..), patch)
 import           Types                    (Level (..))
 import           Util                     (printPretty)
 import           WriteRepo                (writeAdjustedRepository)
+import System.IO (hPutStrLn, stderr)
 
 -- | the options this cli tool can take
 data Options = Options
@@ -87,7 +88,7 @@ printLB a = putStrLn $ C8.unpack $ LB.toStrict a
 -- cf. https://frasertweedale.github.io/blog-fp/posts/2021-10-12-aeson-hash-flooding-protection.html
 aesonWarning :: IO ()
 aesonWarning = case coercionToHashMap of
-  Just _ -> putStrLn
+  Just _ -> hPutStrLn stderr
     "Warning: this program was compiled using an older version of the Aeson Library\n\
     \used for parsing JSON, which is susceptible to hash flooding attacks.\n\
     \n\