Shorten the serialization of lists

This also helps prevent stack overflows when JSON.stringify large Elm
lists.

lib/result-cache-json.js

@@ -4,6 +4,34 @@ module.exports = {
 };
 
 function replacer(key, value) {
+  if (typeof value === 'object') {
+    // TODO Serialize Dicts also
+    // if (value.$ === -1) {
+    //   return {
+    //     $: '$D',
+    //     a: toDictProd(value, {})
+    //   };
+    // }
+    if (
+      value.$ === 1 &&
+      value.a !== undefined &&
+      value.b !== undefined &&
+      value.c === undefined
+    ) {
+      const list = prudent_List_toArray(value);
+      if (list === null) {
+        return value;
+      }
+
+      return {
+        $: '$L',
+        a: list
+      };
+    }
+
+    return value;
+  }
+
   if (Number.isNaN(value)) {
     return '$$elm-review$$NaN';
   }
@@ -19,9 +47,32 @@ function replacer(key, value) {
   return '$$elm-review$$+Inf';
 }
 
+
+function prudent_List_toArray(xs) {
+  const out = [];
+  for (; xs.b; xs = xs.b) {
+    if (xs.a === undefined || xs.c !== undefined) {
+      return null;
+    }
+
+    out.push(xs.a);
+  }
+
+  if (xs.$ !== 0 || xs.a !== undefined) {
+    return null;
+  }
+
+  return out;
+}
+
 function reviver(_, value) {
+  const type_ = typeof value;
+  if (type_ === 'object' && value.$ === '$L') {
+    return _List_fromArray_PROD(value.a);
+  }
+
   if (
-    typeof value !== 'string' ||
+    type_ !== 'string' ||
     value === null ||
     !value.startsWith('$$elm-review$$')
   ) {
@@ -39,3 +90,13 @@ function reviver(_, value) {
       return value;
   }
 }
+
+const _List_Nil_PROD = {$: 0};
+function _List_fromArray_PROD(array) {
+  let out = _List_Nil_PROD;
+  for (let i = array.length; i--; ) {
+    out = {$: 1, a: array[i], b: out};
+  }
+
+  return out;
+}