From 10087d701236277626d7d037e21420d38f50ad7a Mon Sep 17 00:00:00 2001
From: Etienne Millon <me@emillon.org>
Date: Mon, 27 Jun 2022 09:50:27 +0200
Subject: [PATCH] Make warning always fire, fatal in 3.4

Signed-off-by: Etienne Millon <me@emillon.org>
---
 src/dune_rules/dune_env.ml                    | 20 +++++++++----------
 .../test-cases/env/env-unused.t               | 15 +++++++++++---
 2 files changed, 22 insertions(+), 13 deletions(-)

diff --git a/src/dune_rules/dune_env.ml b/src/dune_rules/dune_env.ml
index 806c3b47d40a..065fa7799601 100644
--- a/src/dune_rules/dune_env.ml
+++ b/src/dune_rules/dune_env.ml
@@ -227,18 +227,18 @@ module Stanza = struct
        (pat, configs))
 
   let check_rules ~version ~loc rules =
-    let has_after_any l =
-      let is_any = function
-        | Any, _ -> true
-        | Profile _, _ -> false
-      in
-      List.split_while l ~f:is_any |> snd |> List.is_non_empty
+    let rec has_after_any = function
+      | [ (Any, _) ] -> false
+      | (Any, _) :: _ :: _ -> true
+      | (Profile _, _) :: rules -> has_after_any rules
+      | [] -> false
     in
-    if version >= (3, 4) && has_after_any rules then
-      User_warning.emit ~loc
+    if has_after_any rules then
+      let is_error = version >= (3, 4) in
+      User_warning.emit ~loc ~is_error
         [ Pp.text
-            "This stanza contains rules after a wildcard rule. These are going \
-             to be ignored."
+            "This env stanza contains rules after a wildcard rule. These are \
+             going to be ignored."
         ]
 
   let decode =
diff --git a/test/blackbox-tests/test-cases/env/env-unused.t b/test/blackbox-tests/test-cases/env/env-unused.t
index ef722d710c39..de818b175370 100644
--- a/test/blackbox-tests/test-cases/env/env-unused.t
+++ b/test/blackbox-tests/test-cases/env/env-unused.t
@@ -14,10 +14,18 @@
   >  (dev (env-vars (VAR specific))))
   > EOF
 
+A warning is displayed when there are unreachable cases.
+
   $ dune runtest
+  File "dune", line 5, characters 0-71:
+  5 | (env
+  6 |  (_   (env-vars (VAR default )))
+  7 |  (dev (env-vars (VAR specific))))
+  Warning: This env stanza contains rules after a wildcard rule. These are
+  going to be ignored.
   default
 
-In 3.4, a warning is added for that case:
+In 3.4, this warning becomes fatal.
 
   $ cat > dune-project << EOF
   > (lang dune 3.4)
@@ -28,5 +36,6 @@ In 3.4, a warning is added for that case:
   5 | (env
   6 |  (_   (env-vars (VAR default )))
   7 |  (dev (env-vars (VAR specific))))
-  Warning: This stanza contains rules after a wildcard rule. These are going to
-  be ignored.
+  Error: This env stanza contains rules after a wildcard rule. These are going
+  to be ignored.
+  [1]