React and Vercel: Error: Command “npm run build” exited with 1?

Question

I am trying to deploy a simple create-react-app to vercel and keep getting this build log with the error in the title. Anyone know how to fix this? I forked and cloned two repos, one being a server and the other being a client app, and am trying to deploy the client app. Thanks!

19:02:29.808    Retrieving list of deployment files...
19:02:31.377    Downloading 45 deployment files...
19:02:32.197    Analyzing source code...
19:02:32.619    Installing build runtime...
19:02:34.651    Build runtime installed: 2031.231ms
19:02:36.331    Looking up build cache...
19:02:36.376    Build cache not found
19:02:37.053    Detected package.json
19:02:37.053    Installing dependencies...
19:02:37.517    npm WARN read-shrinkwrap This version of npm is compatible with lockfileVersion@1, but package-lock.json was generated for lockfileVersion@2. I'll try to do my best with it!
19:03:02.198    > core-js@2.6.12 postinstall /vercel/workpath0/node_modules/babel-runtime/node_modules/core-js
19:03:02.198    > node -e "try{require('./postinstall')}catch(e){}"
19:03:02.298    > core-js@3.10.1 postinstall /vercel/workpath0/node_modules/core-js
19:03:02.298    > node -e "try{require('./postinstall')}catch(e){}"
19:03:02.367    > core-js-pure@3.6.5 postinstall /vercel/workpath0/node_modules/core-js-pure
19:03:02.367    > node -e "try{require('./postinstall')}catch(e){}"
19:03:02.458    > ejs@2.7.4 postinstall /vercel/workpath0/node_modules/ejs
19:03:02.458    > node ./postinstall.js
19:03:04.533    npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@1.2.13 (node_modules/webpack-dev-server/node_modules/fsevents):
19:03:04.533    npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@1.2.13: wanted {"os":"darwin","arch":"any"} (current: {"os":"linux","arch":"x64"})
19:03:04.540    npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@1.2.13 (node_modules/watchpack-chokidar2/node_modules/fsevents):
19:03:04.541    npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@1.2.13: wanted {"os":"darwin","arch":"any"} (current: {"os":"linux","arch":"x64"})
19:03:04.549    npm WARN optional SKIPPING OPTIONAL DEPENDENCY: fsevents@2.3.2 (node_modules/fsevents):
19:03:04.549    npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for fsevents@2.3.2: wanted {"os":"darwin","arch":"any"} (current: {"os":"linux","arch":"x64"})
19:03:04.555    added 2207 packages from 769 contributors in 27.077s
19:03:05.692    137 packages are looking for funding
19:03:05.692      run `npm fund` for details
19:03:05.918    Running "npm run build"
19:03:06.121    > starter-constellations-client@0.1.0 build /vercel/workpath0
19:03:06.121    > react-scripts build
19:03:07.402    Creating an optimized production build...
19:03:12.854    Treating warnings as errors because process.env.CI = true.
19:03:12.854    Most CI servers set it automatically.
19:03:12.854    Failed to compile.
19:03:12.855    src/common/Header.jsx
19:03:12.855      Line 4:1:  Assign arrow function to a variable before exporting as module default  import/no-anonymous-default-export
19:03:12.855    src/common/Navigation.jsx
19:03:12.855      Line 3:1:  Assign arrow function to a variable before exporting as module default  import/no-anonymous-default-export
19:03:12.855    src/home/Constellation.jsx
19:03:12.855      Line 3:1:  Assign arrow function to a variable before exporting as module default  import/no-anonymous-default-export
19:03:12.855    src/home/ConstellationsList.jsx
19:03:12.855      Line 5:1:  Assign arrow function to a variable before exporting as module default  import/no-anonymous-default-export
19:03:12.855    src/home/NoConstellationsMessage.jsx
19:03:12.855      Line 3:1:  Assign arrow function to a variable before exporting as module default  import/no-anonymous-default-export
19:03:12.856    src/home/Search.jsx
19:03:12.856      Line 3:1:  Assign arrow function to a variable before exporting as module default  import/no-anonymous-default-export
19:03:12.882    npm ERR! code ELIFECYCLE
19:03:12.883    npm ERR! errno 1
19:03:12.886    npm ERR! starter-constellations-client@0.1.0 build: `react-scripts build`
19:03:12.886    npm ERR! Exit status 1
19:03:12.886    npm ERR! 
19:03:12.886    npm ERR! Failed at the starter-constellations-client@0.1.0 build script.
19:03:12.886    npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
19:03:12.891    npm ERR! A complete log of this run can be found in:
19:03:12.892    npm ERR!     /vercel/.npm/_logs/2021-04-08T00_03_12_886Z-debug.log
19:03:12.898    Error: Command "npm run build" exited with 1
19:03:15.563    Done with "package.json"

Answer 1

The logs show that the npm run build script is throwing an error because of lint warnings.

Here's how I mentally parse the logs ( ... means I skimmed over that section):

...
19:02:37.053    Installing dependencies...
...
19:03:05.918    Running "npm run build"
...
19:03:12.854    Treating warnings as errors because process.env.CI = true.
...
19:03:12.855    src/common/Header.jsx
19:03:12.855      Line 4:1:  Assign arrow function to a variable before exporting as module default  import/no-anonymous-default-export
...
19:03:12.898    Error: Command "npm run build" exited with 1
...

First, I noticed the message about warnings being treated as errors.

Second, I recognized the warnings as linter errors because of the format of the lint rule: import/no-anonymous-default-export .

---

You need to address the linter warnings in your source code or find a way to turn off the linter when running the build script ( related ).