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>

1 files changed, 14 insertions, 0 deletions

diff --git a/changelog.md b/changelog.md
index 2f7b584a3..3333a837b 100644
--- a/changelog.md
+++ b/changelog.md
@@ -4,6 +4,20 @@
 
 ## Standard library additions and changes
 
+- Added some enhancements to `std/jsonutils` module.
+  * Added a possibility to deserialize JSON arrays directly to `HashSet` and
+    `OrderedSet` types and respectively to serialize those types to JSON arrays
+    via `jsonutils.fromJson` and `jsonutils.toJson` procedures.
+  * Added a possibility to deserialize JSON `null` objects to Nim option objects
+    and respectively to serialize Nim option object to JSON object if `isSome`
+    or to JSON null object if `isNone` via `jsonutils.fromJson` and
+    `jsonutils.toJson` procedures.
+  * Added `Joptions` parameter to `jsonutils.fromJson` procedure currently
+    containing two boolean options `allowExtraKeys` and `allowMissingKeys`.
+    - If `allowExtraKeys` is `true` Nim's object to which the JSON is parsed is
+      not required to have a field for every JSON key.
+    - If `allowMissingKeys` is `true` Nim's object to which JSON is parsed is
+      allowed to have fields without corresponding JSON keys.
 - Added `bindParams`, `bindParam` to `db_sqlite` for binding parameters into a `SqlPrepared` statement.
 - Add `tryInsert`,`insert` procs to `db_*` libs accept primary key column name.
 - Added `xmltree.newVerbatimText` support create `style`'s,`script`'s text.