Lazy loading pdf.js library (#9371)

* Lazy loading pdf.js library

* Removing pdfjs lib from plugins/export

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

components/pdf_preview.jsx

@@ -3,7 +3,6 @@
 
 import PropTypes from 'prop-types';
 import React from 'react';
-import PDFJS from 'pdfjs-dist';
 import debounce from 'lodash/debounce';
 
 import {getFileDownloadUrl} from 'mattermost-redux/utils/file_utils';
@@ -147,7 +146,10 @@ export default class PDFPreview extends React.PureComponent {
     }
 
     getPdfDocument = () => {
-        PDFJS.getDocument(this.props.fileUrl).then(this.onDocumentLoad).catch(this.onDocumentLoadError);
+        import('pdfjs-dist').then((PDFJS) => {
+            PDFJS.disableWorker = true;
+            PDFJS.getDocument(this.props.fileUrl).then(this.onDocumentLoad).catch(this.onDocumentLoadError);
+        });
     }
 
     onDocumentLoad = (pdf) => {

plugins/export.js

@@ -29,7 +29,6 @@ window.ReactRedux = require('react-redux');
 window.ReactBootstrap = require('react-bootstrap');
 window.ReactRouterDom = require('react-router-dom');
 window.PropTypes = require('prop-types');
-window.PDFJS = require('pdfjs-dist');
 window.Luxon = require('luxon');
 
 // Functions exposed on window for plugins to use.

root.jsx

@@ -6,8 +6,6 @@ import './entry.js';
 import React from 'react';
 import ReactDOM from 'react-dom';
 
-import PDFJS from 'pdfjs-dist';
-
 import {logError} from 'mattermost-redux/actions/errors';
 
 // Import our styles
@@ -20,8 +18,6 @@ import {isDevMode, setCSRFFromCookie} from 'utils/utils';
 import store from 'stores/redux_store.jsx';
 import App from 'components/app';
 
-PDFJS.disableWorker = true;
-
 // This is for anything that needs to be done for ALL react components.
 // This runs before we start to render anything.
 function preRenderSetup(callwhendone) {