Improve couch_js_tests

There are a few minor improvements:

- Add more tests to check sandboxing resets, and that docs are "frozen".

- Remove the extra `\n` and `"` around function body lines. Erlang can do
  multi-line binaries just fine. Mark the sections with %erlfmt-ignore to the
  formatter doesn't complain.

- Generalize `should_create_sandbox` test to check for the `not defined` string
  only. Experimenting with QuickJS noticed that it uses single quotes
  around`'Object.foo' is not defined` and SM doesn't. So check for `not
  defined` part only as it's obvious enough what the check is about.

- Make sure to return test procs back to the pool. Previously, none of the
  tests returned the processes back into the pool, and when the tests ended,
  they were forcibly killed which resulted in log noise that looked like:

```
erl_child_setup: failed with error 32 on line 265
erl_child_setup: failed with error 32 on line 265
...
```

src/couch/test/eunit/couch_js_tests.erl

@@ -22,6 +22,8 @@ couch_js_test_() ->
             fun test_util:stop_couch/1,
             [
                 fun should_create_sandbox/0,
+                fun should_reset_properly/0,
+                fun should_freeze_doc_object/0,
                 fun should_roundtrip_utf8/0,
                 fun should_roundtrip_modified_utf8/0,
                 fun should_replace_broken_utf16/0,
@@ -31,72 +33,117 @@ couch_js_test_() ->
         }
     }.
 
+%% erlfmt-ignore
 should_create_sandbox() ->
     % Try and detect whether we can see out of the
     % sandbox or not.
-    Src = <<
-        "function(doc) {\n"
-        "  try {\n"
-        "    emit(false, typeof(Couch.compile_function));\n"
-        "  } catch (e) {\n"
-        "    emit(true, e.message);\n"
-        "  }\n"
-        "}\n"
-    >>,
+    Src = <<"
+        function(doc) {
+            try {
+                emit(false, typeof(Couch.compile_function));
+            } catch (e) {
+                emit(true, e.message);
+            }
+        }
+    ">>,
+    Proc = couch_query_servers:get_os_process(<<"javascript">>),
+    true = couch_query_servers:proc_prompt(Proc, [<<"add_fun">>, Src]),
+    Result = couch_query_servers:proc_prompt(Proc, [<<"map_doc">>, {[]}]),
+    ?assertMatch([[[true, <<_/binary>>]]], Result),
+    [[[true, ErrMsg]]] = Result,
+    ?assertNotEqual([], binary:matches(ErrMsg, <<"not defined">>)),
+    couch_query_servers:ret_os_process(Proc).
+
+%% erlfmt-ignore
+should_reset_properly() ->
+    Src = <<"
+        function(doc) {
+            var a = [0,1,2];
+            emit(a.indexOf(0), Object.foo);
+            Object.foo = 43;
+            [].constructor.prototype.indexOf = function(x) {return 42;};
+        }
+    ">>,
     Proc = couch_query_servers:get_os_process(<<"javascript">>),
     true = couch_query_servers:proc_prompt(Proc, [<<"add_fun">>, Src]),
-    Result = couch_query_servers:proc_prompt(Proc, [<<"map_doc">>, <<"{}">>]),
-    ?assertEqual([[[true, <<"Couch is not defined">>]]], Result).
+    Doc = {[]},
+    Result1 = couch_query_servers:proc_prompt(Proc, [<<"map_doc">>, Doc]),
+    ?assertEqual([[[0, null]]], Result1),
+    Result2 = couch_query_servers:proc_prompt(Proc, [<<"map_doc">>, Doc]),
+    ?assertEqual([[[42, 43]]], Result2),
+    true = couch_query_servers:proc_prompt(Proc, [<<"reset">>]),
+    true = couch_query_servers:proc_prompt(Proc, [<<"add_fun">>, Src]),
+    Result3 = couch_query_servers:proc_prompt(Proc, [<<"map_doc">>, Doc]),
+    ?assertEqual([[[0, null]]], Result3),
+    couch_query_servers:ret_os_process(Proc).
 
+%% erlfmt-ignore
+should_freeze_doc_object() ->
+    Src = <<"
+        function(doc) {
+            emit(doc.foo, doc.bar);
+            doc.foo = 1042;
+            doc.bar = 1043;
+            emit(doc.foo, doc.bar);
+        }
+    ">>,
+    Proc = couch_query_servers:get_os_process(<<"javascript">>),
+    true = couch_query_servers:proc_prompt(Proc, [<<"add_fun">>, Src]),
+    Doc = {[{<<"bar">>, 1041}]},
+    Result1 = couch_query_servers:proc_prompt(Proc, [<<"map_doc">>, Doc]),
+    ?assertEqual([[[null, 1041], [null, 1041]]], Result1),
+    Result2 = couch_query_servers:proc_prompt(Proc, [<<"map_doc">>, Doc]),
+    ?assertEqual([[[null, 1041], [null, 1041]]], Result2),
+    couch_query_servers:ret_os_process(Proc).
+
+%% erlfmt-ignore
 should_roundtrip_utf8() ->
     % Try round tripping UTF-8 both directions through
     % couchjs. These tests use hex encoded values of
     % Ä (C384) and Ü (C39C) so as to avoid odd editor/Erlang encoding
     % strangeness.
     Src = <<
-        "function(doc) {\n"
-        "  emit(doc.value, \"",
-        16#C3,
-        16#9C,
-        "\");\n"
-        "}\n"
-    >>,
+        "function(doc) {
+          emit(doc.value, \"", 16#C3,  16#9C, "\");
+        }
+    ">>,
     Proc = couch_query_servers:get_os_process(<<"javascript">>),
     true = couch_query_servers:proc_prompt(Proc, [<<"add_fun">>, Src]),
     Doc =
         {[
             {<<"value">>, <<16#C3, 16#84>>}
         ]},
     Result = couch_query_servers:proc_prompt(Proc, [<<"map_doc">>, Doc]),
-    ?assertEqual([[[<<16#C3, 16#84>>, <<16#C3, 16#9C>>]]], Result).
+    ?assertEqual([[[<<16#C3, 16#84>>, <<16#C3, 16#9C>>]]], Result),
+    couch_query_servers:ret_os_process(Proc).
 
+%% erlfmt-ignore
 should_roundtrip_modified_utf8() ->
     % Mimicking the test case from the mailing list
-    Src = <<
-        "function(doc) {\n"
-        "  emit(doc.value.toLowerCase(), \"",
-        16#C3,
-        16#9C,
-        "\");\n"
-        "}\n"
-    >>,
+    Src = <<"
+        function(doc) {
+          emit(doc.value.toLowerCase(), \"", 16#C3, 16#9C, "\");
+        }
+    ">>,
     Proc = couch_query_servers:get_os_process(<<"javascript">>),
     true = couch_query_servers:proc_prompt(Proc, [<<"add_fun">>, Src]),
     Doc =
         {[
             {<<"value">>, <<16#C3, 16#84>>}
         ]},
     Result = couch_query_servers:proc_prompt(Proc, [<<"map_doc">>, Doc]),
-    ?assertEqual([[[<<16#C3, 16#A4>>, <<16#C3, 16#9C>>]]], Result).
+    ?assertEqual([[[<<16#C3, 16#A4>>, <<16#C3, 16#9C>>]]], Result),
+    couch_query_servers:ret_os_process(Proc).
 
+%% erlfmt-ignore
 should_replace_broken_utf16() ->
     % This test reverse the surrogate pair of
     % the Boom emoji U+1F4A5
-    Src = <<
-        "function(doc) {\n"
-        "  emit(doc.value.split(\"\").reverse().join(\"\"), 1);\n"
-        "}\n"
-    >>,
+    Src = <<"
+        function(doc) {
+            emit(doc.value.split(\"\").reverse().join(\"\"), 1);
+        }
+    ">>,
     Proc = couch_query_servers:get_os_process(<<"javascript">>),
     true = couch_query_servers:proc_prompt(Proc, [<<"add_fun">>, Src]),
     Doc =
@@ -107,8 +154,10 @@ should_replace_broken_utf16() ->
     % Invalid UTF-8 gets replaced with the 16#FFFD replacement
     % marker
     Markers = list_to_binary(xmerl_ucs:to_utf8([16#FFFD, 16#FFFD])),
-    ?assertEqual([[[Markers, 1]]], Result).
+    ?assertEqual([[[Markers, 1]]], Result),
+    couch_query_servers:ret_os_process(Proc).
 
+%% erlfmt-ignore
 should_allow_js_string_mutations() ->
     % This binary corresponds to this string: мама мыла раму
     % Which I'm told translates to: "mom was washing the frame"
@@ -142,21 +191,21 @@ should_allow_js_string_mutations() ->
     >>,
     Mom = <<16#D0, 16#BC, 16#D0, 16#B0, 16#D0, 16#BC, 16#D0, 16#B0>>,
     Washed = <<16#D0, 16#BC, 16#D1, 16#8B, 16#D0, 16#BB, 16#D0, 16#B0>>,
-    Src1 = <<
-        "function(doc) {\n"
-        "  emit(\"length\", doc.value.length);\n"
-        "}\n"
-    >>,
-    Src2 = <<
-        "function(doc) {\n"
-        "  emit(\"substring\", doc.value.substring(5, 9));\n"
-        "}\n"
-    >>,
-    Src3 = <<
-        "function(doc) {\n"
-        "  emit(\"slice\", doc.value.slice(0, 4));\n"
-        "}\n"
-    >>,
+    Src1 = <<"
+        function(doc) {
+          emit(\"length\", doc.value.length);
+        }
+    ">>,
+    Src2 = <<"
+        function(doc) {
+          emit(\"substring\", doc.value.substring(5, 9));
+        }
+    ">>,
+    Src3 = <<"
+        function(doc) {
+          emit(\"slice\", doc.value.slice(0, 4));
+        }
+    ">>,
     Proc = couch_query_servers:get_os_process(<<"javascript">>),
     true = couch_query_servers:proc_prompt(Proc, [<<"add_fun">>, Src1]),
     true = couch_query_servers:proc_prompt(Proc, [<<"add_fun">>, Src2]),
@@ -168,19 +217,21 @@ should_allow_js_string_mutations() ->
         [[<<"substring">>, Washed]],
         [[<<"slice">>, Mom]]
     ],
-    ?assertEqual(Expect, Result).
+    ?assertEqual(Expect, Result),
+    couch_query_servers:ret_os_process(Proc).
 
+%% erlfmt-ignore
 should_exit_on_oom() ->
-    Src = <<
-        "var state = [];\n"
-        "function(doc) {\n"
-        "  var val = \"0123456789ABCDEF\";\n"
-        "  for(var i = 0; i < 665535; i++) {\n"
-        "    state.push([val, val]);\n"
-        "    emit(null, null);\n"
-        "  }\n"
-        "}\n"
-    >>,
+    Src = <<"
+        var state = [];
+        function(doc) {
+            var val = \"0123456789ABCDEF\";
+            for(var i = 0; i < 665535; i++) {
+                state.push([val, val]);
+                emit(null, null);
+             }
+        }
+    ">>,
     Proc = couch_query_servers:get_os_process(<<"javascript">>),
     true = couch_query_servers:proc_prompt(Proc, [<<"add_fun">>, Src]),
     trigger_oom(Proc).