Fixes # Deprecation Warning in console about UNSAFE_componentWillUpdate which "promotes unsafe coding practices" -React Blog

Additional description

WhileUNSAFE_componentWillUpdate is called right before render,getSnapshotBeforeUpdate is called right before mutating the DOM. According to theReact Documentation, the combination ofgetSnapshotBeforeUpdate andcomponentDidUpdateshould cover all use cases for the legacycomponentWillUpdate.

In this case since the purpose of usingUNSAFE_componentWillUpdate appeared to be resetting the interactive elements for the datatable if the props differed, I moved this logic intogetSnapshotBeforeUpdate. However, sincegetSnapshotBeforeUpdate gets the previous props rather than the next props, the if-statement had to be slightly adjusted. Additionally, becausegetSnapshotBeforeUpdate must contain a return statement(the return is passed as the third parameter tocomponentDidUpdate), it simply returns null. This change avoid the deprecation warning and enables the same behavior as withUNSAFE_componentWillUpdate.

CONTRIBUTOR checklist (do not remove)

Please complete for every pull request

• First-time contributors should sign the Contributor License Agreement. It's a fancy way of saying that you are giving away your contribution to this project. If you haven't before, wait a few minutes and a bot will comment on this pull request with instructions.
• npm run lint:fix has been run and linting passes.
• Mocha, Jest (Storyshots), andcomponents/component-docs.json CI tests pass (npm test).
• Tests have been added for new props to prevent regressions in the future. Seereadme. -Not Applicable
• Review the appropriate Storybook stories. Openhttp://localhost:9001/.
• Review tests are passing in the browser. Openhttp://localhost:8001/. -2 tests for SLDSCombobox fail("selects a menu item and scrolls when a letter key is pressed in read-only mode" and "selects menu items and scrolls when the down/up keys are pressed"), but they also did not pass after a clean install.
• Review markup conforms toSLDS by looking atDOM snapshot strings. -Not Applicable

REVIEWER checklist (do not remove)

• CircleCI tests pass. This includes linting, Mocha, Jest, Storyshots, andcomponents/component-docs.json tests.
• Tests have been added for new props to prevent regressions in the future. Seereadme.
• Review the appropriate Storybook stories. Openhttp://localhost:9001/.
• The Accessibility panel of each Storybook story has 0 violations (aXe). Openhttp://localhost:9001/.
• Review tests are passing in the browser. Openhttp://localhost:8001/.
• Review markup conforms toSLDS by looking atDOM snapshot strings.

Required only if there are markup / UX changes

• Add year-first date and commit SHA tolast-slds-markup-review inpackage.json and push.
• Request a review of the deployed Heroku app by the Salesforce UX Accessibility Team.
• Add year-first review date, and commit SHA,last-accessibility-review, topackage.json and push.
• While the contributor's branch is checked out, runnpm run local-update within locally clonedsite repo to confirm the site will function correctly at the next release.