[REL] v1.4.7

v1.4.7

fix: memory leak in some templates

README.md

@@ -124,7 +124,7 @@ npm install @odoo/owl
 
 If you want to use a simple `<script>` tag, the last release can be downloaded here:
 
-- [owl-1.4.5](https://github.com/odoo/owl/releases/tag/v1.4.5)
+- [owl-1.4.7](https://github.com/odoo/owl/releases/tag/v1.4.7)
 
 ## License
 

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@odoo/owl",
-  "version": "1.4.5",
+  "version": "1.4.7",
   "description": "Odoo Web Library (OWL)",
   "main": "dist/owl.cjs.js",
   "browser": "dist/owl.iife.js",

roadmap.md

@@ -1,6 +1,6 @@
 # 🦉 OWL Roadmap 🦉
 
-- Current version: 1.4.5
+- Current version: 1.4.7
 - Status: stable
 
 This roadmap is only an attempt at predicting Owl's future.  Everything may

src/component/component.ts

@@ -400,6 +400,7 @@ export class Component<Props extends {} = any, T extends Env = Env> {
     if (currentFiber && !currentFiber.isRendered && !currentFiber.isCompleted) {
       return scheduler.addFiber(currentFiber.root);
     }
+
     // if we aren't mounted at this point, it implies that there is a
     // currentFiber that is already rendered (isRendered is true), so we are
     // about to be mounted
@@ -505,7 +506,6 @@ export class Component<Props extends {} = any, T extends Env = Env> {
     const __owl__ = this.__owl__;
 
     __owl__.status = STATUS.MOUNTED;
-    __owl__.currentFiber = null;
     this.mounted();
     if (__owl__.mountedCB) {
       __owl__.mountedCB();

src/component/fiber.ts

@@ -198,6 +198,7 @@ export class Fiber {
     // build patchQueue
     const patchQueue: Fiber[] = [];
     const doWork: (Fiber) => Fiber | null = function (f) {
+      f.component.__owl__.currentFiber = null;
       patchQueue.push(f);
       return f.child;
     };
@@ -255,10 +256,6 @@ export class Fiber {
           component.__owl__.pvnode!.elm = component.__owl__.vnode!.elm;
         }
       }
-      const compOwl = component.__owl__;
-      if (fiber === compOwl.currentFiber) {
-        compOwl.currentFiber = null;
-      }
     }
 
     // insert into the DOM (mount case)

src/config.ts

@@ -28,8 +28,6 @@ Object.defineProperty(config, "mode", {
 
 This is not suitable for production use.
 See https://github.com/odoo/owl/blob/master/doc/reference/config.md#mode for more information.`);
-    } else {
-      console.log(`Owl is now running in 'prod' mode.`);
     }
   },
 });

src/qweb/base_directives.ts

@@ -326,7 +326,8 @@ QWeb.addDirective({
     ctx.addLine(`if (!_${arrayID}) { throw new Error('QWeb error: Invalid loop expression')}`);
     let keysID = ctx.generateID();
     let valuesID = ctx.generateID();
-    ctx.addLine(`let _${keysID} = _${valuesID} = _${arrayID};`);
+    ctx.addLine(`let _${keysID} = _${arrayID};`);
+    ctx.addLine(`let _${valuesID} = _${arrayID};`);
     ctx.addIf(`!(_${arrayID} instanceof Array)`);
     ctx.addLine(`_${keysID} = Object.keys(_${arrayID});`);
     ctx.addLine(`_${valuesID} = Object.values(_${arrayID});`);

tests/component/__snapshots__/component.test.ts.snap

@@ -51,7 +51,8 @@ exports[`basic widget properties reconciliation alg works for t-foreach in t-for
     let vn1 = h('div', p1, c1);
     let _2 = scope['state'].s;
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);
@@ -68,7 +69,8 @@ exports[`basic widget properties reconciliation alg works for t-foreach in t-for
         let key1 = i1;
         let _6 = scope['section'].blips;
         if (!_6) { throw new Error('QWeb error: Invalid loop expression')}
-        let _7 = _8 = _6;
+        let _7 = _6;
+        let _8 = _6;
         if (!(_6 instanceof Array)) {
             _7 = Object.keys(_6);
             _8 = Object.values(_6);
@@ -309,7 +311,8 @@ exports[`composition sub components with some state rendered in a loop 1`] = `
     let vn1 = h('div', p1, c1);
     let _2 = scope['state'].numbers;
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);
@@ -597,7 +600,8 @@ exports[`other directives with t-component t-on expression captured in t-foreach
     scope.iter = 0;
     let _2 = scope['arr'];
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);
@@ -639,7 +643,8 @@ exports[`other directives with t-component t-on expression in t-foreach 1`] = `
     let vn1 = h('div', p1, c1);
     let _2 = scope['state'].values;
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);
@@ -691,7 +696,8 @@ exports[`other directives with t-component t-on expression in t-foreach with t-s
     scope.bossa = 'nova';
     let _2 = scope['state'].values;
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);
@@ -744,7 +750,8 @@ exports[`other directives with t-component t-on method call in t-foreach 1`] = `
     let vn1 = h('div', p1, c1);
     let _2 = scope['state'].values;
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);
@@ -1410,7 +1417,8 @@ exports[`other directives with t-component t-set outside modified in t-foreach 1
     scope.iter = 0;
     let _2 = scope['state'].values;
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);
@@ -1560,7 +1568,8 @@ exports[`random stuff/miscellaneous t-on with handler bound to dynamic argument
     let vn1 = h('div', p1, c1);
     let _2 = scope['items'];
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);
@@ -1838,7 +1847,8 @@ exports[`t-model directive in a t-foreach 1`] = `
     let vn1 = h('div', p1, c1);
     let _2 = scope['state'];
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);
@@ -1878,7 +1888,8 @@ exports[`t-model directive in a t-foreach, part 2 1`] = `
     let vn1 = h('div', p1, c1);
     let _2 = scope['state'];
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);

tests/component/__snapshots__/slots.test.ts.snap

@@ -414,7 +414,8 @@ exports[`t-slot directive slots are rendered with proper context, part 2 2`] = `
     c1.push(vn2);
     let _3 = scope['state'].users;
     if (!_3) { throw new Error('QWeb error: Invalid loop expression')}
-    let _4 = _5 = _3;
+    let _4 = _3;
+    let _5 = _3;
     if (!(_3 instanceof Array)) {
         _4 = Object.keys(_3);
         _5 = Object.values(_3);
@@ -512,7 +513,8 @@ exports[`t-slot directive slots are rendered with proper context, part 3 2`] = `
     c1.push(vn2);
     let _3 = scope['state'].users;
     if (!_3) { throw new Error('QWeb error: Invalid loop expression')}
-    let _4 = _5 = _3;
+    let _4 = _3;
+    let _5 = _3;
     if (!(_3 instanceof Array)) {
         _4 = Object.keys(_3);
         _5 = Object.values(_3);
@@ -645,7 +647,8 @@ exports[`t-slot directive slots in t-foreach in t-foreach 1`] = `
     let vn1 = h('div', p1, c1);
     let _2 = scope['tree'];
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);
@@ -672,7 +675,8 @@ exports[`t-slot directive slots in t-foreach in t-foreach 1`] = `
         c1.push(vn8);
         let _9 = scope['node1'].nodes;
         if (!_9) { throw new Error('QWeb error: Invalid loop expression')}
-        let _10 = _11 = _9;
+        let _10 = _9;
+        let _11 = _9;
         if (!(_9 instanceof Array)) {
             _10 = Object.keys(_9);
             _11 = Object.values(_9);

tests/component/async.test.ts

@@ -1388,6 +1388,62 @@ describe("async rendering", () => {
     expect(fixture.innerHTML).toBe("<span>4</span>");
   });
 
+  test("calling render in destroy", async () => {
+    let a: any = null;
+    let c: any = null;
+
+    class C extends Component {
+      static template = xml`
+        <div>
+          <t t-esc="props.fromA"/>
+        </div>`;
+    }
+
+    let flag = false;
+    class B extends Component {
+      static template = xml`<C fromA="props.fromA"/>`;
+      static components = { C };
+
+      setup() {
+        c = this;
+      }
+
+      mounted() {
+        if (flag) {
+          this.render();
+        } else {
+          flag = true;
+        }
+      }
+      willUnmount() {
+        c.render();
+      }
+    }
+
+    class A extends Component {
+      static template = xml`<B t-key="key" fromA="state"/>`;
+      static components = { B };
+      state = "a";
+      key = 1;
+
+      setup() {
+        a = this;
+      }
+    }
+
+    const parent = new A();
+    await parent.mount(fixture);
+    expect(fixture.innerHTML).toBe("<div>a</div>");
+
+    a.state = "A";
+    a.key = 2;
+    await a.render();
+    // this nextTick is critical, otherwise jest may silently swallow errors
+    await nextTick();
+
+    expect(fixture.innerHTML).toBe("<div>A</div>");
+  });
+
   test("change state and call manually render: no unnecessary rendering", async () => {
     class Widget extends Component {
       static template = xml`<div><t t-esc="state.val"/></div>`;

tests/qweb/__snapshots__/qweb.test.ts.snap

@@ -429,7 +429,8 @@ exports[`foreach does not pollute the rendering context 1`] = `
     let vn1 = h('div', p1, c1);
     let _2 = [1];
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);
@@ -464,7 +465,8 @@ exports[`foreach iterate on items (on a element node) 1`] = `
     let vn1 = h('div', p1, c1);
     let _2 = [1,2];
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);
@@ -502,7 +504,8 @@ exports[`foreach iterate on items 1`] = `
     let vn1 = h('div', p1, c1);
     let _2 = [3,2,1];
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);
@@ -549,7 +552,8 @@ exports[`foreach iterate, dict param 1`] = `
     let vn1 = h('div', p1, c1);
     let _2 = scope['value'];
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);
@@ -596,7 +600,8 @@ exports[`foreach iterate, position 1`] = `
     let vn1 = h('div', p1, c1);
     let _2 = Array(5);
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);
@@ -641,7 +646,8 @@ exports[`foreach t-call with body in t-foreach in t-foreach 1`] = `
     let vn1 = h('div', p1, c1);
     let _2 = scope['numbers'];
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);
@@ -658,7 +664,8 @@ exports[`foreach t-call with body in t-foreach in t-foreach 1`] = `
         let key1 = i1;
         let _6 = scope['letters'];
         if (!_6) { throw new Error('QWeb error: Invalid loop expression')}
-        let _7 = _8 = _6;
+        let _7 = _6;
+        let _8 = _6;
         if (!(_6 instanceof Array)) {
             _7 = Object.keys(_6);
             _8 = Object.values(_6);
@@ -729,7 +736,8 @@ exports[`foreach t-call without body in t-foreach in t-foreach 1`] = `
     let vn1 = h('div', p1, c1);
     let _2 = scope['numbers'];
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);
@@ -746,7 +754,8 @@ exports[`foreach t-call without body in t-foreach in t-foreach 1`] = `
         let key1 = i1;
         let _6 = scope['letters'];
         if (!_6) { throw new Error('QWeb error: Invalid loop expression')}
-        let _7 = _8 = _6;
+        let _7 = _6;
+        let _8 = _6;
         if (!(_6 instanceof Array)) {
             _7 = Object.keys(_6);
             _8 = Object.values(_6);
@@ -811,7 +820,8 @@ exports[`foreach t-foreach in t-forach 1`] = `
     let vn1 = h('div', p1, c1);
     let _2 = scope['numbers'];
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);
@@ -828,7 +838,8 @@ exports[`foreach t-foreach in t-forach 1`] = `
         let key1 = i1;
         let _6 = scope['letters'];
         if (!_6) { throw new Error('QWeb error: Invalid loop expression')}
-        let _7 = _8 = _6;
+        let _7 = _6;
+        let _8 = _6;
         if (!(_6 instanceof Array)) {
             _7 = Object.keys(_6);
             _8 = Object.values(_6);
@@ -871,7 +882,8 @@ exports[`foreach warn if no key in some case 1`] = `
     let vn1 = h('div', p1, c1);
     let _2 = [1,2];
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);
@@ -940,7 +952,8 @@ exports[`misc global 1`] = `
     let vn1 = h('div', p1, c1);
     let _2 = [4,5,6];
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);
@@ -1666,7 +1679,8 @@ exports[`t-call (template calling recursive template, part 2 2`] = `
     }
     let _6 = scope['node'].children||[];
     if (!_6) { throw new Error('QWeb error: Invalid loop expression')}
-    let _7 = _8 = _6;
+    let _7 = _6;
+    let _8 = _6;
     if (!(_6 instanceof Array)) {
         _7 = Object.keys(_6);
         _8 = Object.values(_6);
@@ -1746,7 +1760,8 @@ exports[`t-call (template calling recursive template, part 3 2`] = `
     }
     let _6 = scope['node'].children||[];
     if (!_6) { throw new Error('QWeb error: Invalid loop expression')}
-    let _7 = _8 = _6;
+    let _7 = _6;
+    let _8 = _6;
     if (!(_6 instanceof Array)) {
         _7 = Object.keys(_6);
         _8 = Object.values(_6);
@@ -1832,7 +1847,8 @@ exports[`t-call (template calling recursive template, part 4: with t-set recursi
     }
     let _6 = scope['node'].children||[];
     if (!_6) { throw new Error('QWeb error: Invalid loop expression')}
-    let _7 = _8 = _6;
+    let _7 = _6;
+    let _8 = _6;
     if (!(_6 instanceof Array)) {
         _7 = Object.keys(_6);
         _8 = Object.values(_6);
@@ -1998,7 +2014,8 @@ exports[`t-call (template calling t-call with t-set inside and outside 1`] = `
     let vn1 = h('div', p1, c1);
     let _2 = scope['list'];
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);
@@ -2775,7 +2792,8 @@ exports[`t-key t-key directive in a list 1`] = `
     let vn1 = h('ul', p1, c1);
     let _2 = scope['beers'];
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);
@@ -2879,7 +2897,8 @@ exports[`t-on can bind handlers with loop variable as argument 1`] = `
     let vn1 = h('ul', p1, c1);
     let _2 = ['someval'];
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);
@@ -3161,7 +3180,8 @@ exports[`t-on t-on with prevent modifier in t-foreach 1`] = `
     let vn1 = h('div', p1, c1);
     let _2 = scope['projects'];
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);
@@ -3432,7 +3452,8 @@ exports[`t-ref refs in a loop 1`] = `
     let vn1 = h('div', p1, c1);
     let _2 = scope['items'];
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);
@@ -3676,7 +3697,8 @@ exports[`t-set t-set should reuse variable if possible 1`] = `
     scope.v = 1;
     let _2 = scope['list'];
     if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
-    let _3 = _4 = _2;
+    let _3 = _2;
+    let _4 = _2;
     if (!(_2 instanceof Array)) {
         _3 = Object.keys(_2);
         _4 = Object.values(_2);

tests/qweb/__snapshots__/qweb_memory.test.ts.snap

@@ -0,0 +1,37 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`memory t-foreach does not leak stuff in global scope 1`] = `
+"function anonymous(context, extra
+) {
+    // Template name: \\"test\\"
+    let scope = Object.create(context);
+    let h = this.h;
+    let c1 = [], p1 = {key:1};
+    let vn1 = h('p', p1, c1);
+    let _2 = [3,2,1];
+    if (!_2) { throw new Error('QWeb error: Invalid loop expression')}
+    let _3 = _2;
+    let _4 = _2;
+    if (!(_2 instanceof Array)) {
+        _3 = Object.keys(_2);
+        _4 = Object.values(_2);
+    }
+    let _length3 = _3.length;
+    let _origScope5 = scope;
+    scope = Object.create(scope);
+    for (let i1 = 0; i1 < _length3; i1++) {
+        scope.item_first = i1 === 0
+        scope.item_last = i1 === _length3 - 1
+        scope.item_index = i1
+        scope.item = _3[i1]
+        scope.item_value = _4[i1]
+        let key1 = i1;
+        let _6 = scope['item'];
+        if (_6 != null) {
+            c1.push({text: _6});
+        }
+    }
+    scope = _origScope5;
+    return vn1;
+}"
+`;

tests/qweb/qweb_memory.test.ts

@@ -0,0 +1,14 @@
+import { QWeb } from "../../src/qweb/index";
+import { renderToString } from "../helpers";
+
+describe("memory", () => {
+  test("t-foreach does not leak stuff in global scope", () => {
+    let qweb = new QWeb();
+    const initialNumberOfGlobals = Object.keys(window).length;
+    qweb.addTemplate("test", `<p><t t-foreach="[3, 2, 1]" t-as="item"><t t-esc="item"/></t></p>`);
+    const result = renderToString(qweb, "test");
+    const expected = `<p>321</p>`;
+    expect(result).toBe(expected);
+    expect(Object.keys(window).length).toBe(initialNumberOfGlobals);
+  });
+});

tsconfig.json

@@ -13,8 +13,8 @@
   // "compileOnSave": false,                                    // Signals to the IDE to generate all files for a given tsconfig.json upon saving.
   "compilerOptions": {
                                                                 // Main options
-    "target": "esnext",                                         // Specify ECMAScript target version: 'es3' (default), 'es5', 'es2015', 'es2016', 'es2017','es2018' or 'esnext'.
-    "module": "esnext",                                         // Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'.
+    "target": "es2017",                                         // Specify ECMAScript target version: 'es3' (default), 'es5', 'es2015', 'es2016', 'es2017','es2018' or 'esnext'.
+    "module": "es6",                                         // Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', or 'ESNext'.
     // "lib": ["esnext", "dom"],                                // Specify library files to be included in the compilation.
     // "allowJs": false,                                        // Allow javascript files to be compiled.
     // "checkJs": false,                                        // Report errors in .js files.