[TS] Add Obj API (#5788)

* added basic code

* backup work

* got class property to work

* backup progress

* implementented fmt for creating code

* added docs for genFieldUtils

* back up work

* added base helper js func

* added union js code

* added unpackTo and base for pack

* added pack code

* added null check for packing struct list

* passes compile test

* fixed some spacing of generated functions

* added annotations for constructors

* added obj api unpack test

* tested pack to work

* merge branch

* separated js and ts test

* fixed union signature to include string

* fixed generator to support string union

* hardcoded fb builder name

* refactored struct vector creation

* work around createLong

* handle default value in constructor

* update typescript docs

* added notes about import flag

* fixed formatting stuffs

* undo TypescriptTest change

* refactored fmt

* updated generated code

* remove ignoring union_vector for js

* revert changes for .project

* revert changes for package.json

* don't generate js in ts test

* fixed android project file

* removed unused js function

* removed package-lock.json

* adjust createObjList to new signature

* changed regex to callback style

* fixed package.json

* used existing func for generating annotation

* changed ternary to !!

* added return type for lambda

* removed callback style for obj api generator

* fixed js file indentation

* removed unused header

* added tests for string only union

* handle string only union and refactor union conv func

* updated generated ts files

* renamed union conv func

* made js test create files like other languages

* removed union string only handling

* don't allow null in createObjectOffsetList

* updated generated ts code

* changed the line that triggers Windows build errors

* hopefully fix CI error

js/flatbuffers.js

@@ -54,6 +54,15 @@ flatbuffers.FILE_IDENTIFIER_LENGTH = 4;
  */
 flatbuffers.SIZE_PREFIX_LENGTH = 4;
 
+/**
+ * @param {number} low
+ * @param {number} high
+ * @returns {flatbuffers.Long}
+ */
+flatbuffers.createLong = function(low, high) {
+  return flatbuffers.Long.create(low, high);
+};
+
 /**
  * @enum {number}
  */
@@ -830,6 +839,52 @@ flatbuffers.Builder.prototype.createString = function(s) {
 flatbuffers.Builder.prototype.createLong = function(low, high) {
   return flatbuffers.Long.create(low, high);
 };
+
+/**
+ * A helper function to pack an object
+ * 
+ * @returns offset of obj
+ */
+flatbuffers.Builder.prototype.createObjectOffset = function(obj) {
+  if(obj === null) {
+    return 0
+  }
+
+  if(typeof obj === 'string') {
+    return this.createString(obj);
+  } else {
+    return obj.pack(this);
+  }
+}
+
+/**
+ * A helper function to pack a list of object
+ * 
+ * @returns list of offsets of each non null object
+ */
+flatbuffers.Builder.prototype.createObjectOffsetList = function(list) {
+  let ret = [];
+
+  for(let i = 0; i < list.length; ++i) {
+    let val = list[i];
+
+    if(val !== null) {
+      ret.push(this.createObjectOffset(val));
+    } else {
+      throw new Error(
+        'FlatBuffers: Argument for createObjectOffsetList cannot contain null.'); 
+    }
+  }
+  
+  return ret;
+};
+
+flatbuffers.Builder.prototype.createStructOffsetList = function(list, startFunc) {
+  startFunc(this, list.length);
+  this.createObjectOffsetList(list);
+  return this.endVector();
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 /// @cond FLATBUFFERS_INTERNAL
 /**
@@ -1195,6 +1250,24 @@ flatbuffers.ByteBuffer.prototype.__string = function(offset, opt_encoding) {
   return result;
 };
 
+/**
+ * Handle unions that can contain string as its member, if a Table-derived type then initialize it, 
+ * if a string then return a new one
+ * 
+ * WARNING: strings are immutable in JS so we can't change the string that the user gave us, this 
+ * makes the behaviour of __union_with_string different compared to __union
+ *
+ * @param {flatbuffers.Table|string} o
+ * @param {number} offset
+ * @returns {flatbuffers.Table|string}
+ */
+flatbuffers.ByteBuffer.prototype.__union_with_string = function(o, offset) {
+  if(typeof o === 'string') {
+    return this.__string(offset);
+  } 
+  return this.__union(o, offset);
+};
+
 /**
  * Retrieve the relative offset stored at "offset"
  * @param {number} offset
@@ -1252,6 +1325,48 @@ flatbuffers.ByteBuffer.prototype.createLong = function(low, high) {
   return flatbuffers.Long.create(low, high);
 };
 
+/**
+ * A helper function for generating list for obj api
+ * @param listAccessor function that accepts an index and return data at that index
+ * @param {number} listLength
+ * @returns {any[]}
+ */
+flatbuffers.ByteBuffer.prototype.createScalarList = function(listAccessor, listLength) {
+  let ret = [];
+  for(let i = 0; i < listLength; ++i) {
+    if(listAccessor(i) !== null) {
+      ret.push(listAccessor(i));
+    }
+  }
+
+  return ret;
+};
+
+/**
+ * This function is here only to get around typescript type system
+ */
+flatbuffers.ByteBuffer.prototype.createStringList = function(listAccessor, listLength) {
+  return this.createScalarList(listAccessor, listLength);
+};
+
+/**
+ * A helper function for generating list for obj api
+ * @param listAccessor function that accepts an index and return data at that index
+ * @param listLength {number} listLength
+ * @param res any[] result list
+ */
+flatbuffers.ByteBuffer.prototype.createObjList = function(listAccessor, listLength) {
+  let ret = [];
+  for(let i = 0; i < listLength; ++i) {
+    let val = listAccessor(i);
+    if(val !== null) {
+      ret.push(val.unpack());
+    }
+  }
+  
+  return ret;
+};
+
 // Exports for Node.js and RequireJS
 this.flatbuffers = flatbuffers;