unikernel/duniverse/ppxlib/test/migrations/run.t

@@ -0,0 +1,22 @@
+Ppxlib applies migrations to the AST. In some cases, especially when applying
+downward migrations, extra information must be encoded in the AST in order to
+be able to properly re-encode the AST when migrating back up.
+
+This means that sometimes the extra information is left in the AST especially
+when printing the code as source of the current compiler (where the current
+compiler is less than the internal AST version).
+
+Therefore we must clean the produced AST to remove ppxlib.migration attributes.
+
+  $ touch file.ml
+  $ ./driver.exe file.ml
+  let f a = fun b -> a + b
+  module F = (F)(struct  end)
+
+Now we ensure no attributes are left in the AST after we force a downard
+migration using the --use-compiler-pp flag.
+
+  $ ./driver.exe --use-compiler-pp file.ml
+  let f a b = a + b
+  module F = (F)(struct  end)
+