test: repro #840 (#842)

ppx/test/hover.t

@@ -0,0 +1,76 @@
+Test some locations in reason-react components, reproduces #840
+
+  $ cat >dune-project <<EOF
+  > (lang dune 3.13)
+  > (using melange 0.1)
+  > EOF
+
+  $ cat >dune <<EOF
+  > (melange.emit
+  >  (alias foo)
+  >  (target foo)
+  >  (libraries reason-react)
+  >  (emit_stdlib false)
+  >  (preprocess
+  >   (pps melange.ppx reason-react-ppx)))
+  > EOF
+
+  $ cat >component.ml <<EOF
+  > let[@react.component] make ~foo ~bar =
+  >   (div
+  >      ~children:[ React.string foo; bar |> string_of_int |> React.string ]
+  >      () [@JSX])
+  > EOF
+  $ dune build @foo
+
+Let's test hovering over parts of the component
+
+`React.string`:
+
+  $ ocamlmerlin single type-enclosing -position 3:25 -verbosity 0 \
+  > -filename component.ml < component.ml | jq '.value'
+  [
+    {
+      "start": {
+        "line": 3,
+        "col": 17
+      },
+      "end": {
+        "line": 3,
+        "col": 29
+      },
+      "type": "string -> React.element",
+      "tail": "no"
+    },
+    {
+      "start": {
+        "line": 1,
+        "col": 0
+      },
+      "end": {
+        "line": 4,
+        "col": 15
+      },
+      "type": "< bar : int; foo : string > Js.t -> React.element",
+      "tail": "no"
+    }
+  ]
+
+The `foo` variable inside the component body
+
+  $ ocamlmerlin single type-enclosing -position 3:31 -verbosity 0 \
+  > -filename component.ml < component.ml | jq '.value'
+  [
+    {
+      "start": {
+        "line": 1,
+        "col": 0
+      },
+      "end": {
+        "line": 4,
+        "col": 15
+      },
+      "type": "< bar : int; foo : string > Js.t -> React.element",
+      "tail": "no"
+    }
+  ]