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Theia Tree Editor

The Theia Tree Editor integrates JSON Forms with the Theia IDE.

This component is not meant to be used standalone but instead enables the usage of the TreeWithDetail component of JSONForms within Theia.

NOTE: This project is currently WIP and it's very likely that we'll be able to cut down the boilerplate, so bear with us :)


You’ll need node in version 8:

curl -o- | bash
nvm install 8

and yarn

npm install -g yarn

Also make sure your python --version points to a Python 2.x installation. Run the following command in your terminal.

python --version

Additionally, also install yeoman and the theia extension generator for project scaffolding:

npm install -g yo generator-theia-extension    

Getting started

In this section we will walk you through the process of creating a very minimalistic extension based on the theia tree editor extension and an example schema from the JSON schema homepage, which can be found under the Miscellaneous Examples section. We'll call our editor veggie-editor.

First, let's scaffold a basic extension with the theia generator extension:

mkdir veggie-editor && cd veggie-editor
yo theia-extension veggie-editor
cd veggie-editor-extension

Let's add a couple of dependencies with yarn (TODO: we shouldn't need that many deps, e.g. recompose, lodash etc.):

yarn add
yarn add @jsonforms/material-tree-renderer
yarn add @jsonforms/material-renderers
yarn add react-redux
yarn add lodash
yarn add recompose
yarn add lodash

JSON Schema

Next, we'll add a basic JSON schema which describes the instances we want to work with. For this example we'll use the Array of things example schema from the JSON Schema examples section.

TODO (this might change soon): Unfortunately, we have to modify the schema a bit in order to allow JSON Forms mapping subschemas. Therefore, we have to set $id properties for each definition we want to reference from within JSON Forms.

In this case, we'll replace the id property with $id and give it a value of #fruitsOrVeggies and we'll also add an additional $id to the veggie definition with the value of #veggie. We save the modified schema in a file called schema.ts, within the veggie-editor-extension/src folder:


export default {
  $id: "#fruitsOrVeggies",
  $schema: "",
  description: "A representation of a person, company, organization, or place",
  type: "object",
  properties: {
    fruits: {
      type: "array",
      items: { type: "string" }
    vegetables: {
      type: "array",
      items: { $ref: "#/definitions/veggie" }
  definitions: {
    veggie: {
      $id: "#veggie",
      type: "object",
      required: [ "veggieName", "veggieLike" ],
      properties: {
        veggieName: {
          type: "string",
          description: "The name of the vegetable."
        veggieLike: {
          type: "boolean",
          description: "Do I like this vegetable?"


Next up, we need to set-up a configuration object which describes a few additional properties of the schema. All of the following will be goes into a file name config.ts with in veggie-editor-extension/src folder.

For determining the labels that are to be displayed within the master view of the tree renderer, we set up a labels object . The format follows the convention of key-value pairs, where the key is the $id value of sub schema and the value is the label to be shown. The label value is either a plain string or an object with a property field. In the latter case the given property will be used to determine the label of the object to be displayed, which allows for dynamic labels. Specifying a constant property is the same as specifying a plain string.


export const labels = {
	"#fruitsOrVeggies": {
		constant: "Fruits/Vegetables"
	"#veggie": {
		property: "veggieName"

In this example, we display a static string for the top node and a dynamic one for the objects that conform to the veggie schema.



Model mapping

The modelMapping describes how instances can be mapped to their corresponding schema. The first property, attribute, determines which property should be used for identification purposes while the mapping property maps possible value of the attribute property to the respective $ids of the sub schemas.

// TODO: rename?
export const modelMapping = {
	attribute: 'type',
 	mapping: {
		fruitsOrVeggies: '#fruitsOrVeggies',
		veggies: '#veggies'

Detail UI schemas

The uischemas object holds a mapping of schema ID to its respective UI schema, which should be used while rendering the detail view of the TreeWithDetail renderer.

export const uischemas = {
  '#fruitsOrVeggies': {
    type: 'VerticalLayout',
    elements: [
        type: 'Control',
        scope: '#/properties/fruits'
        type: 'Control',
        scope: '#/properties/vegetables'
  '#veggie': {
    type: 'HorizontalLayout',
    elements: [
        type: 'Control',
        scope: '#/properties/veggieName'
        type: 'Control',
        scope: '#/properties/veggieLike'

You can save and close config.ts now. We'll use it when we set up the Editor component.

Update tsconfig.json

We need to update the generated tsconfig.json in order to support writing React extensions. Add the following properties to tsconfig.json:

"compilerOptions": {
   // ...
   "strict": false,
   "jsx": "react"
"exclude": [

NOTE: turning of strict mode should be necessary of course, we need to fix the current issues


With the configuration in place we can set up the App component, which will only act as a wrapper around JSON Form's TreeWithDetail renderer. The code for the entire component looks as follows and should be saved within veggie-editor-extension/src/VeggieEditor.tsx.

import * as React from 'react';
import _ as _ from 'lodash';
import { TreeWithDetailRenderer } from '@jsonforms/material-tree-renderer';
import { connect } from 'react-redux';
import {
} from 'theia-tree-editor';

class VeggieEditor extends React.Component<TreeEditorProps, {}> {
  componentDidUpdate(prevProps) {
    if (!_.isEqual(this.props.rootData, prevProps.rootData)) {
      this.props.saveable.dirty = true;

  render() {
    return (
      <TreeWithDetailRenderer {...this.props} />

export default connect(mapStateToTreeEditorProps)(VeggieEditor);


Now let's put our editor component to use. To do so, we import our Editor component and wire it up with the configuration with defined previously. We also need to take care of setting up the store.

The relevant code to do so is given below and should be placed into veggie-editor-extension/src/App.tsx:

import { defaultProps } from 'recompose';
import { combineReducers, createStore, Store } from 'redux';
import { materialFields, materialRenderers } from '@jsonforms/material-renderers';
import {
} from '@jsonforms/core';
import {
} from '@jsonforms/material-tree-renderer';
import { calculateLabel, filterPredicate } from 'theia-tree-editor';

import schema from './schema';

import {labels, modelMapping, uischemas} from './config';
import VeggieEditor from './VeggieEditor';

const imageGetter = (schemaId: string) => 'icon-test';
// !_.isEmpty(imageProvider) ? `icon ${imageProvider[schemaId]}` : '';

export const initStore = async() => {
  const uischema = {
    'type': 'TreeWithDetail',
    'scope': '#'
  const renderers: { tester: RankedTester, renderer: any}[] = materialRenderers;
  const fields: { tester: RankedTester, field: any}[] = materialFields;
  const jsonforms: any = {
    jsonforms: {
      treeWithDetail: {
        // imageMapping: imageProvider,
        labelMapping: labels,
        uiSchemata: uischemas

  const store: Store<any> = createStore(
        jsonforms: jsonformsReducer(
            treeWithDetail: treeWithDetailReducer
    { ...jsonforms }

  store.dispatch(Actions.init({}, schema, uischema));
  store.dispatch(setContainerProperties(findAllContainerProperties(schema, schema)));

  return store;

export default defaultProps(
    'filterPredicate': filterPredicate,
    'labelProvider': calculateLabel(labels),
    'imageProvider': imageGetter

Frontend module

Finally, open the frontend module in veggie-editor-extension/src/browser/veggie-editor-frontend-module.ts which already has been generated by the extension generator and add the following binding:

NOTE: explain what's going on here

Add the following imports:

  // necessary imports
  import { WidgetFactory } from "@theia/core/lib/browser";
  import { ResourceProvider } from "@theia/core/lib/common";
  import { TheiaTreeEditorContribution, TreeEditorWidget, TreeEditorWidgetOptions } from "theia-tree-editor";
  import URI from "@theia/core/lib/common/uri";
  import App, {initStore} from "../App";

Then add the bindings (TODO: is the ID correct?). If you want to use another implementation of the TheiaTreeEditorContribution replace the imports with your version of it:

  bind<WidgetFactory>(WidgetFactory).toDynamicValue(ctx => ({
    id: 'theia-tree-editor',
    async createWidget(uri: string): Promise<TreeEditorWidget> {
      const { container } = ctx;
      const resource = await container.get<ResourceProvider>(ResourceProvider)(new URI(uri));
      const store = await initStore();
      const child = container.createChild();
        .toConstantValue({ resource, store, EditorComponent: App, fileName: new URI(uri).path.base});
      return child.get(TreeEditorWidget);
  [CommandContribution, MenuContribution, OpenHandler].forEach(serviceIdentifier =>

That's it, we are finally good to go!

Running the extension

  1. Run yarn start within browser-app directory
  2. Run yarn watch --mode development within browser-app directory
  3. Run yarn watch within the directory of your extension

This will cause your extension and the browser-app to be rebuilt upon each change you do in the extension and also start a webserver on http://localhost:3000. Note however, that a refresh is not triggered automatically.

Within the browser, navigate to the File Menu, open an empty JSON file or, alternatively, create one. Right click JSON file and select Open With and your extension should be listed.