Syntax error causes yarn start to exit

[ianschmitz]

🐛 Bug Report

Accidentally introducing a syntax error in JSX code causes yarn start to exit completely. This is unexpected coming from other tools such as CRA, Next.JS, etc.

Have you read the Contributing Guidelines on issues?

👍

To Reproduce

1. yarn start
2. Introduce syntax error in JSX code within a mdx or js file
3. Save file
4. Observe error and subsequent exit of start script

Expected behavior

Watch mode continues to work, and fixing the error recovers correctly.

Actual Behavior

Client bundle compiled with errors therefore further build is impossible.
./docs/mobile/change-default-behaviour.mdx
Module build failed (from ./node_modules/@docusaurus/mdx-loader/src/index.js):
SyntaxError: unknown: Unexpected token (56:43)

  54 |         title="Commands and Operations"
  55 |         description="Learn more about commands and operations"
> 56 |         link="concepts-commands-operations",
     |                                            ^
  57 |     />
  58 |     <UseCaseCard
  59 |         title="Change Geocortex Mobile's Default Search Behaviour"
    at Object._raise (/home/ian/Code/dev-center/node_modules/@babel/parser/lib/index.js:742:17)
    at Object.raiseWithData (/home/ian/Code/dev-center/node_modules/@babel/parser/lib/index.js:735:17)
    at Object.raise (/home/ian/Code/dev-center/node_modules/@babel/parser/lib/index.js:729:17)
    at Object.unexpected (/home/ian/Code/dev-center/node_modules/@babel/parser/lib/index.js:8757:16)
    at Object.jsxParseIdentifier (/home/ian/Code/dev-center/node_modules/@babel/parser/lib/index.js:4388:12)
    at Object.jsxParseNamespacedName (/home/ian/Code/dev-center/node_modules/@babel/parser/lib/index.js:4398:23)
    at Object.jsxParseAttribute (/home/ian/Code/dev-center/node_modules/@babel/parser/lib/index.js:4482:22)
    at Object.jsxParseOpeningElementAfterName (/home/ian/Code/dev-center/node_modules/@babel/parser/lib/index.js:4503:28)
    at Object.jsxParseOpeningElementAt (/home/ian/Code/dev-center/node_modules/@babel/parser/lib/index.js:4496:17)
    at Object.jsxParseElementAt (/home/ian/Code/dev-center/node_modules/@babel/parser/lib/index.js:4528:33)
    at Object.jsxParseElementAt (/home/ian/Code/dev-center/node_modules/@babel/parser/lib/index.js:4544:32)
    at Object.jsxParseElementAt (/home/ian/Code/dev-center/node_modules/@babel/parser/lib/index.js:4544:32)
    at Object.jsxParseElement (/home/ian/Code/dev-center/node_modules/@babel/parser/lib/index.js:4602:17)
    at Object.parseExprAtom (/home/ian/Code/dev-center/node_modules/@babel/parser/lib/index.js:4609:19)
    at Object.parseExprSubscripts (/home/ian/Code/dev-center/node_modules/@babel/parser/lib/index.js:9602:23)
    at Object.parseMaybeUnary (/home/ian/Code/dev-center/node_modules/@babel/parser/lib/index.js:9582:21)
 @ ./.docusaurus/registry.js 1:2379-2448 1:2182-2329
 @ ./node_modules/@docusaurus/core/lib/client/exports/ComponentCreator.js
 @ ./.docusaurus/routes.js
 @ ./node_modules/@docusaurus/core/lib/client/clientEntry.js
 @ multi ./node_modules/react-dev-utils/webpackHotDevClient.js ./node_modules/@docusaurus/core/lib/client/clientEntry.js
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.

Your Environment

• Docusaurus version used: 2.0.0-alpha.48
• Environment name and version (e.g. Chrome 78.0.3904.108, Node.js 10.17.0): Node 12.13.0
• Operating system and version (desktop or mobile): Ubuntu 19.10

[lex111]

This is already fixed in #2437