Add some enhancements to `jsonutils.nim` (#15133)

* Add some enhancements to `jsonutils.nim`

* Use `jsonutils.nim` hookable API to add a possibility to deserialize
  JSON arrays directly to `HashSet` and `OrderedSet` types and
  respectively to serialize those types to JSON arrays.

* Also add a possibility to deserialize JSON `null` objects to Nim
  option objects and respectively to serialize Nim option object to JSON
  object if some or to JSON `null` object if none.

* Move serialization/deserialization functionality for `Table` and
  `OrderedTable` types from `jsonutils.nim` to `tables.nim` via the
  hookable API.

* Add object `jsonutils.Joptions` and parameter from its type to
  `jsonutils.fromJson` procedure to control whether to allow
  deserializing JSON objects to Nim objects when the JSON has some
  extra or missing keys.

* Add unit tests for the added functionalities to `tjsonutils.nim`.

* improve fromJsonFields

* Add changelog entry for the jsonutils enhancements

* Add TODO in `jsonutils.nim`

* Added an entry to "Future directions" section in `jsonutils.nim` as
  suggestion for future support of serialization and de-serialization of
  nested variant objects.

* Added currently disabled test case in `tjsonutils.nim` for testing
  serialization and de-serialization of nested variant objects.

* Move JSON hooks to `jsonutils.nim`

Move `fromJsonHook` and `toJsonHook` procedures for different types to
`jsonutils.nim` module to avoid a dependency of collections modules to
the `json.nim` module.

The hooks are removed from the following modules:

  * `tables.nim`

  * `sets.nim`

  * `options.nim`

  * `strtabs.nim`

* Add some tests about `StringTableRef`

Add tests for `StringTableRef`'s `fromJsonHook` and `toJsonHook` to
`tjsonutils.nim`.

* Disable a warning in `jsonutils.nim`

Mark `fun` template in `jsonutils` module with `{.used.}` pragma in
order to disable `[XDeclaredButNotUsed]` hint. The template is actually
used by the `initCaseObject` macro in the same module.

Co-authored-by: Timothee Cour <timothee.cour2@gmail.com>

2 files changed, 2 insertions, 6 deletions

diff --git a/lib/pure/collections/sets.nim b/lib/pure/collections/sets.nim
index b019da2a7..67e407576 100644
--- a/lib/pure/collections/sets.nim
+++ b/lib/pure/collections/sets.nim
@@ -80,6 +80,8 @@ type
     ## <#initOrderedSet,int>`_ before calling other procs on it.
     data: OrderedKeyValuePairSeq[A]
     counter, first, last: int
+  SomeSet*[A] = HashSet[A] | OrderedSet[A]
+    ## Type union representing `HashSet` or `OrderedSet`.
 
 const
   defaultInitialSize* = 64
@@ -907,8 +909,6 @@ iterator pairs*[A](s: OrderedSet[A]): tuple[a: int, b: A] =
   forAllOrderedPairs:
     yield (idx, s.data[h].key)
 
-
-
 # -----------------------------------------------------------------------
 
 
diff --git a/lib/pure/collections/tables.nim b/lib/pure/collections/tables.nim
index 6d79638c2..dc21c0539 100644
--- a/lib/pure/collections/tables.nim
+++ b/lib/pure/collections/tables.nim
@@ -1750,10 +1750,6 @@ iterator mvalues*[A, B](t: var OrderedTable[A, B]): var B =
     yield t.data[h].val
     assert(len(t) == L, "the length of the table changed while iterating over it")
 
-
-
-
-
 # ---------------------------------------------------------------------------
 # --------------------------- OrderedTableRef -------------------------------
 # ---------------------------------------------------------------------------