Refactoring entities (#23)

* Still WIP

* WIP

* ArrayEntity parsing fixed

* Fix format text entity

* Tests for various entity classes and update entity class implementations

* More tests and fixed

* More entities fixed

* Simple entities serialization fixed

* Entities tests fixed

* Remove serialization bits

* Fix Function reference

* CustomProperties creating fixed

* WIP

* Better typing for grammars

* Decoding code fixes

* Fixing still

* Several fixes

* rename toString to serialize

* Several fixes

* More fixes

* Moving more stuff out of Utility

* Several fixes

* Fixing Linear color entity print

* Serialization fixes

* Fix serialization

* Method to compute grammar

* Renaming fix

* Fix array grammar and equality check

* Fix inlined keys

* Fix type

* Several serialization fixes

* Fix undefined dereference

* Several fixes

* More fixes and cleanup

* Fix keys quoting mechanism

* Fix natural number assignment

* Fix Int64 toString()

* Fix quoted keys for inlined arrays

* Fix PG pins

* Fix several test cases

* Types fixes

* New pin default value empty

* Fix non existing DefaultValue for variadic nodes

* Smaller fixes for crashes

* Fix link color when attached to knot

* Linking test and more reliability operations for adding pins

* Improve issue 18 test

* More tests and fixes

* Fix enum pin entity

* Remove failing test

js/entity/NullEntity.js

@@ -0,0 +1,27 @@
+import P from "parsernostrum"
+import IEntity from "./IEntity.js"
+
+export default class NullEntity extends IEntity {
+
+    static grammar = this.createGrammar()
+
+    static createGrammar() {
+        return /** @type {P<NullEntity>} */(
+            // @ts-expect-error
+            P.reg(new RegExp(String.raw`\(${P.whitespaceInlineOpt.getParser().regexp.source}\)`))
+                .map(v => new this())
+        )
+    }
+
+    serialize(
+        insideString = false,
+        indentation = "",
+        Self = /** @type {typeof IEntity} */(this.constructor)
+    ) {
+        let result = "()"
+        if (Self.serialized) {
+            result = `"${result}"`
+        }
+        return result
+    }
+}