unikernel/duniverse/dune_/test/blackbox-tests/test-cases/loop.t/dune

@@ -0,0 +1,11 @@
+(rule (copy %{read:x} a))
+(rule (copy %{read:y} b))
+
+(rule (progn (run true) (with-stdout-to x (echo b))))
+(rule (progn (run true) (with-stdout-to y (echo a))))
+
+(rule (progn
+       (write-file result1 "")
+       (copy input result2)))
+
+(rule (copy result2 input))

unikernel/duniverse/dune_/test/blackbox-tests/test-cases/loop.t/dune-project

@@ -0,0 +1 @@
+(lang dune 1.0)

unikernel/duniverse/dune_/test/blackbox-tests/test-cases/loop.t/run.t

@@ -0,0 +1,26 @@
+  $ dune build a
+  Error: Dependency cycle between:
+     _build/default/a
+  -> _build/default/b
+  -> _build/default/a
+  [1]
+
+This second example is slightly more complicated as we request result1
+but the cycle doesn't involve result1. We must make sure the output
+does show a cycle.
+
+  $ dune build result1
+  Error: Dependency cycle between:
+     _build/default/input
+  -> _build/default/result2
+  -> _build/default/input
+  -> required by _build/default/result1
+  [1]
+
+  $ dune build result1 --debug-dependency-path
+  Error: Dependency cycle between:
+     _build/default/input
+  -> _build/default/result2
+  -> _build/default/input
+  -> required by _build/default/result1
+  [1]