unikernel/duniverse/dune_/test/blackbox-tests/test-cases/promote/dep-on-promoted-target.t

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+Depending on a promoted file works.
+
+  $ cat > dune-project <<EOF
+  > (lang dune 2.0)
+  > EOF
+
+  $ cat > dune <<EOF
+  > (rule
+  >   (mode promote)
+  >   (deps original)
+  >   (target promoted)
+  >   (action (copy %{deps} %{target})))
+  > (rule
+  >   (deps promoted)
+  >   (target result)
+  >   (action (bash "cat promoted promoted > result")))
+  > EOF
+
+  $ echo hi > original
+  $ dune build result
+  $ cat promoted
+  hi
+  $ cat _build/default/result
+  hi
+  hi
+
+Now change the [original] and rebuild.
+
+  $ echo bye > original
+  $ dune build result
+  $ cat promoted
+  bye
+  $ cat _build/default/result
+  bye
+  bye
+
+Now switch the mode to standard. Dune reports an error about multiple rules for
+[_build/default/promoted], as expected.
+
+  $ cat > dune <<EOF
+  > (rule
+  >   (mode standard)
+  >   (deps original)
+  >   (target promoted)
+  >   (action (copy %{deps} %{target})))
+  > (rule
+  >   (deps promoted)
+  >   (target result)
+  >   (action (bash "cat promoted promoted > result")))
+  > EOF
+
+  $ dune build result
+  Error: Multiple rules generated for _build/default/promoted:
+  - dune:1
+  - file present in source tree
+  Hint: rm -f promoted
+  [1]
+
+We use the hint and it starts to work.
+
+  $ rm -f promoted
+  $ dune build result
+  $ cat promoted
+  cat: promoted: No such file or directory
+  [1]
+  $ cat _build/default/promoted
+  bye
+  $ cat _build/default/result
+  bye
+  bye
+
+Now use [fallback] to override the rule that generates [promoted].
+
+  $ cat > dune <<EOF
+  > (rule
+  >   (mode fallback)
+  >   (deps original)
+  >   (target promoted)
+  >   (action (copy %{deps} %{target})))
+  > (rule
+  >   (deps promoted)
+  >   (target result)
+  >   (action (bash "cat promoted promoted > result")))
+  > EOF
+
+At first, we don't have the source, so the rule is used.
+
+  $ dune build result
+  $ cat promoted
+  cat: promoted: No such file or directory
+  [1]
+  $ cat _build/default/promoted
+  bye
+  $ cat _build/default/result
+  bye
+  bye
+
+Now we create the source file and it overrides the rule.
+
+  $ echo hi > promoted
+  $ dune build result
+  $ cat promoted
+  hi
+  $ cat _build/default/promoted
+  hi
+  $ cat _build/default/result
+  hi
+  hi