feat(handlebars plugin): adding handlebars helpers for common math op…

…erations (#20648)

* feat(plugin-chart-handlebars): add common helpers

* add import

* add declare module

Co-authored-by: Ville Brofeldt <ville.v.brofeldt@gmail.com>

superset-frontend/plugins/plugin-chart-handlebars/package.json

@@ -26,7 +26,8 @@
     "access": "public"
   },
   "dependencies": {
-    "handlebars": "^4.7.7"
+    "handlebars": "^4.7.7",
+    "just-handlebars-helpers": "^1.0.19"
   },
   "peerDependencies": {
     "@superset-ui/chart-controls": "*",
@@ -39,8 +40,8 @@
     "react-dom": "^16.13.1"
   },
   "devDependencies": {
-    "@types/lodash": "^4.14.149",
     "@types/jest": "^26.0.0",
+    "@types/lodash": "^4.14.149",
     "jest": "^26.0.1"
   }
 }

superset-frontend/plugins/plugin-chart-handlebars/src/components/Handlebars/HandlebarsViewer.tsx

@@ -21,6 +21,7 @@ import Handlebars from 'handlebars';
 import moment from 'moment';
 import React, { useMemo, useState } from 'react';
 import { isPlainObject } from 'lodash';
+import Helpers from 'just-handlebars-helpers';
 
 export interface HandlebarsViewerProps {
   templateSource: string;
@@ -73,3 +74,5 @@ Handlebars.registerHelper('stringify', (obj: any, obj2: any) => {
     throw Error('Please call with an object. Example: `stringify myObj`');
   return isPlainObject(obj) ? JSON.stringify(obj) : String(obj);
 });
+
+Helpers.registerHelpers(Handlebars);

superset-frontend/plugins/plugin-chart-handlebars/types/external.d.ts

@@ -20,3 +20,5 @@ declare module '*.png' {
   const value: any;
   export default value;
 }
+
+declare module 'just-handlebars-helpers';