🐛 Bug Report: "ReferenceError: $RefreshReg$ is not defined" when starting local backend plugin

📜 Description

I’m upgrading a local plugin + Backstage app to 1.7, and started seeing the following error when I run yarn workspace backend start.

ReferenceError: $RefreshReg$ is not defined

It appears to be related to react-refresh and/or react-refresh-webpack-plugin? I’m at a bit of a loss on how to debug this - I’ve been trying re-installing all my node modules, cleaning the workspace, etc, but nothing seems to be working. I was surprised that anything related to react-refresh would run on a backend plugin. My only wild guess is that the backstage-cli is not excluding react-refresh-webpack-plugin for backend plugins after this work? https://github.com/backstage/backstage/pull/10394

👍 Expected behavior

yarn workspace backend start successfully starts.

👎 Actual Behavior with Screenshots

Full error:

/code/aws-for-backstage/personal-backstage-app/packages/backend/dist/main.js:422
/******/ 			throw e;
         			^

ReferenceError: $RefreshReg$ is not defined
    at eval (webpack-internal:///../../plugins/aws-proton-backend/dist/index.cjs.js:206:1)
    at Object.../../plugins/aws-proton-backend/dist/index.cjs.js (/code/aws-for-backstage/personal-backstage-app/packages/backend/dist/main.js:118:1)
    at __webpack_require__ (/code/aws-for-backstage/personal-backstage-app/packages/backend/dist/main.js:419:33)
    at fn (/code/aws-for-backstage/personal-backstage-app/packages/backend/dist/main.js:579:21)
    at eval (webpack-internal:///./src/plugins/scaffolder.ts:11:102)
    at Module../src/plugins/scaffolder.ts (/code/aws-for-backstage/personal-backstage-app/packages/backend/dist/main.js:85:1)
    at __webpack_require__ (/code/aws-for-backstage/personal-backstage-app/packages/backend/dist/main.js:419:33)
    at fn (/code/aws-for-backstage/personal-backstage-app/packages/backend/dist/main.js:579:21)
    at eval (webpack-internal:///./src/index.ts:11:77)
    at Module../src/index.ts (/code/aws-for-backstage/personal-backstage-app/packages/backend/dist/main.js:19:1)

Relevant snippet from packages/backend/dist/main.js where I found RefreshReg:

var Router__default = /*#__PURE__*/ _interopDefaultLegacy(Router);\n_c = Router__default;\nvar fs__default = /*#__PURE__*/ _interopDefaultLegacy(fs);\nclass AwsProtonApi {....ctx.logger.info(`Successfully created service ${resp.service.arn}`);\n                ctx.output(\"arn\", `${resp.service.arn}`);\n            }\n        }\n    });\n};\nexports.createAwsProtonServiceAction = createAwsProtonServiceAction;\nexports.createRouter = createRouter; //# sourceMappingURL=index.cjs.js.map\nvar _c;\n$RefreshReg$(_c, \"Router__default\");

Relevant snippet from plugins/aws-proton-backend/dist/index.cjs.js:

function _interopDefaultLegacy (e) { return e && typeof e === 'object' && 'default' in e ? e : { 'default': e }; }

var express__default = /*#__PURE__*/_interopDefaultLegacy(express);
var Router__default = /*#__PURE__*/_interopDefaultLegacy(Router);
var fs__default = /*#__PURE__*/_interopDefaultLegacy(fs);

class AwsProtonApi {
....
        ctx.logger.info(`Successfully created service ${resp.service.arn}`);
        ctx.output("arn", `${resp.service.arn}`);
      }
    }
  });
};

exports.createAwsProtonServiceAction = createAwsProtonServiceAction;
exports.createRouter = createRouter;
//# sourceMappingURL=index.cjs.js.map

👟 Reproduction steps

If it helps, this is how I’m setting up my workspace: https://github.com/awslabs/aws-proton-plugins-for-backstage/blob/main/docs/developing.md

📃 Provide the context for the Bug.

No response

🖥️ Your Environment

$ yarn backstage-cli info
yarn run v1.22.18
$ /home/ANT.AMAZON.COM/liguori/code/aws-for-backstage/personal-backstage-app/node_modules/.bin/backstage-cli info
OS:   Linux 5.15.0-52-generic - linux/x64
node: v14.21.0
yarn: 1.22.18
cli:  0.20.0 (installed)
backstage:  1.7.1

Dependencies:
  @backstage/app-defaults                          1.0.7
  @backstage/backend-common                        0.15.2
  @backstage/backend-plugin-api                    0.1.3
  @backstage/backend-tasks                         0.3.6
  @backstage/catalog-client                        1.1.1
  @backstage/catalog-model                         1.1.2
  @backstage/cli-common                            0.1.10
  @backstage/cli                                   0.20.0
  @backstage/config-loader                         1.1.5
  @backstage/config                                1.0.3
  @backstage/core-app-api                          1.1.1
  @backstage/core-components                       0.11.2
  @backstage/core-plugin-api                       1.0.7
  @backstage/dev-utils                             1.0.7
  @backstage/errors                                1.1.2
  @backstage/integration-react                     1.1.5
  @backstage/integration                           1.3.2
  @backstage/plugin-api-docs                       0.8.10
  @backstage/plugin-app-backend                    0.3.37
  @backstage/plugin-auth-backend                   0.17.0
  @backstage/plugin-auth-node                      0.2.6
  @backstage/plugin-catalog-backend                1.5.0
  @backstage/plugin-catalog-common                 1.0.7
  @backstage/plugin-catalog-graph                  0.2.22
  @backstage/plugin-catalog-import                 0.9.0
  @backstage/plugin-catalog-node                   1.2.0
  @backstage/plugin-catalog-react                  1.2.0
  @backstage/plugin-catalog                        1.6.0
  @backstage/plugin-github-actions                 0.5.10
  @backstage/plugin-org                            0.5.10
  @backstage/plugin-permission-common              0.7.0
  @backstage/plugin-permission-node                0.7.0
  @backstage/plugin-permission-react               0.4.6
  @backstage/plugin-proxy-backend                  0.2.31
  @backstage/plugin-scaffolder-backend             1.7.0
  @backstage/plugin-scaffolder-common              1.2.1
  @backstage/plugin-scaffolder                     1.7.0
  @backstage/plugin-search-backend-module-pg       0.4.1
  @backstage/plugin-search-backend-node            1.0.3
  @backstage/plugin-search-backend                 1.1.0
  @backstage/plugin-search-common                  1.1.0
  @backstage/plugin-search-react                   1.2.0
  @backstage/plugin-search                         1.0.3
  @backstage/plugin-tech-radar                     0.5.17
  @backstage/plugin-techdocs-backend               1.4.0
  @backstage/plugin-techdocs-module-addons-contrib 1.0.5
  @backstage/plugin-techdocs-node                  1.4.1
  @backstage/plugin-techdocs-react                 1.0.5
  @backstage/plugin-techdocs                       1.3.3
  @backstage/plugin-user-settings                  0.5.0
  @backstage/release-manifests                     0.0.6
  @backstage/test-utils                            1.2.1
  @backstage/theme                                 0.2.16
  @backstage/types                                 1.0.0
  @backstage/version-bridge                        1.0.1

👀 Have you spent some time to check if this bug has been raised before?

• I checked and didn’t find similar issue

🏢 Have you read the Code of Conduct?

• I have read the Code of Conduct

Are you willing to submit PR?

No response

[clareliguori]

That did indeed fix the issue, thanks!

[clareliguori]

Ahhhhhh thank you for finding that! This repo went through a LOT of hacking to try to get things working initially, so I think it’s probably just left over from that. Will confirm that removing that fixes things