NextJS collecting page data fails with status code 500

Question

I have a NextJS application which builds an optimised front end. npm run build is now throwing this error:

> [email protected] build C:\git\MyApp\MyApp-UI\src
> next build

info  - Loaded env from C:\git\MyApp\MyApp-UI\src\.env.local
info  - Loaded env from C:\git\MyApp\MyApp-UI\src\.env.production
(node:15540) Warning: Setting the NODE_TLS_REJECT_UNAUTHORIZED environment variable to '0' makes TLS connections and HTTPS requests insecure by disabling certificate verification.
(Use `node --trace-warnings ...` to show where the warning was created)
info  - Checking validity of types
info  - Creating an optimized production build
info  - Compiled successfully

When it gets to this point I see this:

info  - Collecting page data ..

But a moment later that line disappears and I see this:

> Build error occurred
Error: Request failed with status code 500
    at createError (C:\git\MyApp\MyApp-UI\src\node_modules\axios\lib\core\createError.js:16:15)
    at settle (C:\git\MyApp\MyApp-UI\src\node_modules\axios\lib\core\settle.js:17:12)
    at IncomingMessage.handleStreamEnd (C:\git\MyApp\MyApp-UI\src\node_modules\axios\lib\adapters\http.js:293:11)
    at IncomingMessage.emit (events.js:387:35)
    at endReadableNT (internal/streams/readable.js:1317:12)
    at processTicksAndRejections (internal/process/task_queues.js:82:21) {
  type: 'Error',
  config: {
    transitional: {
      silentJSONParsing: true,
      forcedJSONParsing: true,
      clarifyTimeoutError: false
    },
    transformRequest: [ null ],
    transformResponse: [ null ],
    timeout: 0,
    xsrfCookieName: 'XSRF-TOKEN',
    xsrfHeaderName: 'X-XSRF-TOKEN',
    maxContentLength: -1,
    maxBodyLength: -1,
    headers: { Accept: 'application/json', 'User-Agent': 'axios/0.23.0' },
    method: 'get',
    url: 'http://localhost:8080/api/v1/catalog/en-GB/pages',
    data: null,
    withCredentials: false
  },
  status: 500
}
info  - Collecting page data .npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! [email protected] build: `next build`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the [email protected] build script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

The package.json contains this:

  "scripts": {
    "dev": "next dev",
    "build": "next build",
    "start": "next start",
    "lint": "eslint ./ --ext js,jsx,ts,tsx",
    "export": "next export",
    "gzip": "gzipper compress --gzip-level 9 --verbose --output-file-format [filename].[ext] ./out ./zipped",
    "sitemap": "node ./sitemap-generator/sitemap-gen.js",
    "sitemap-index": "node ./sitemap-generator/sitemap-index-gen.js"
  },

The URL at 8080 which provides the build-time data returns sensible content when I drop it into a browser. As far as I can see, there is no error there.

The basic question is, what would be causing this and where should I look to identify the source?

If this is something to do with the NODE_TLS_REJECT_UNAUTHORIZED environment variable, where/what do I need to adjust and what is that? (I can't find that variable in the solution.)

Answer 1

Turns out there was an error in the solution which was being called but due to errors being ignored I had not seen it get caught in the debugger.