What to do if you get the error message "Don't try to install it manually: your package manager does it automatically. However, a different version of webpack was detected higher up in the tree:" when you do "npm start" Law

About this article

This article is for beginners. https://react-projects.netlify.app/ When implementing using React on this site, when I did ** npm start **, I got an error as the title says.

When you translate the error sentence of the title, it looks like this ** "Don't try to install manually. The package manager will install it automatically. However, a different version of webpack was detected at the top of the tree. "** In other words, ** "webpack is installed more than once in the upper directory" **, right?

Certainly my app directory contained "node_module", so it seems to be duplicated there. However, even if I deleted ** node_module, it didn't change, so I went to the last resort. ** **

Conclusion

Suddenly I came to the conclusion, but I solved it by creating a ".env" file directly under the application directory and adding the following line.

.env


SKIP_PREFLIGHT_CHECK=true

Error statement

By the way, the full text of the error statement is here I'm sorry it's long. .. ..


There might be a problem with the project dependency tree.
It is likely not a bug in Create React App, but something you need to fix locally.

The react-scripts package provided by Create React App requires a dependency:

  "webpack": "4.44.2"

Don't try to install it manually: your package manager does it automatically.
However, a different version of webpack was detected higher up in the tree:

  /Users/ishiwatahiroshishou/node_modules/webpack (version: 5.1.3) 

Manually installing incompatible versions is known to cause hard-to-debug issues.

If you would prefer to ignore this check, add SKIP_PREFLIGHT_CHECK=true to an .env file in your project.
That will permanently disable this message but you might encounter other issues.

To fix the dependency tree, try following the steps below in the exact order:

  1. Delete package-lock.json (not package.json!) and/or yarn.lock in your project folder.
  2. Delete node_modules in your project folder.
  3. Remove "webpack" from dependencies and/or devDependencies in the package.json file in your project folder.
  4. Run npm install or yarn, depending on the package manager you use.

In most cases, this should be enough to fix the problem.
If this has not helped, there are a few other things you can try:

  5. If you used npm, install yarn (http://yarnpkg.com/) and repeat the above steps with it instead.
     This may help because npm has known issues with package hoisting which may get resolved in future versions.

  6. Check if /Users/ishiwatahiroshishou/node_modules/webpack is outside your project directory.
     For example, you might have accidentally installed something in your home folder.

  7. Try running npm ls webpack in your project folder.
     This will tell you which other package (apart from the expected react-scripts) installed webpack.

If nothing else helps, add SKIP_PREFLIGHT_CHECK=true to an .env file in your project.
That would permanently disable this preflight check in case you want to proceed anyway.

P.S. We know this message is long but please read the steps above :-) We hope you find them helpful!

npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! [email protected] start: `react-scripts start`
npm ERR! Exit status 1
npm ERR! 
npm ERR! Failed at the [email protected] start script.
npm ERR! This is probably not a problem with npm. There is likely additional logging output above.

npm ERR! A complete log of this run can be found in:
npm ERR!     /Users/ishiwatahiroshishou/.npm/_logs/2020-11-03T10_08_18_340Z-debug.log

I paid attention to this line in this error statement.

If nothing else helps, add SKIP_PREFLIGHT_CHECK=true to an .env file in your project.

Translated, "Add SKIP_PREFLIGHT_CHECK = true to your project's .env file if nothing else helps." So you can use this as a last resort ...

** Add this to npm start !! **

Compiled with warnings.

src/App.js
  Line 1:17:  'useState' is defined but never used     no-unused-vars
  Line 2:8:   'SingleColor' is defined but never used  no-unused-vars
  Line 4:8:   'Values' is defined but never used       no-unused-vars

src/SingleColor.js
  Line 1:17:  'useState' is defined but never used   no-unused-vars
  Line 1:27:  'useEffect' is defined but never used  no-unused-vars
  Line 2:8:   'rgbToHex' is defined but never used   no-unused-vars

src/utils.js
  Line 3:21:  Expected '===' and instead saw '=='  eqeqeq

Search for the keywords to learn more about each warning.
To ignore, add // eslint-disable-next-line to the line before.

I was able to start! !! After that, you can check the startup by accessing localhost: 3000.

However, it doesn't make sense, so I'll try to deepen it in the future.

** Don't forget that it's a last resort! !! ** **

Recommended Posts

What to do if you get the error message "Don't try to install it manually: your package manager does it automatically. However, a different version of webpack was detected higher up in the tree:" when you do "npm start" Law
What to do if you get an "A server is already running." Error when you try to start the rails server
What to do if you get a wrong number of arguments error in binding.pry
What to do if you get a port error when docker-compose up on Mac
What to do if you don't see the test code error message in the terminal console
What to do if you get a "302" error in your controller unit test code in Rails
What to do if you get ActiveRecord :: StatementInvalid: Mysql2 :: Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near when you try to reset Heroku
What to do if you get a JNI shared library error when trying to build in Eclipse
What to do if you get a gcc error in Docker
What to do if you get a DISPLAY error in gym.render ()
What to do if you get the error message unrecognized selector send to instance "***"
What to do if you get To install the missing version, run `gem install bundler: 2.1.4`
What to do if you get an Argument Error: wrong number of arguments (given 2, expected 0) in your RSpec test
What to do if you can't get the text of an element in Selenium
What to do if you select a JRE in Eclipse and get "The selected JRE does not support the current compliance level 11"
[Rails] What to do if you accidentally install bundle in the production environment in your local environment
What to do if you get a "Cannot Pull Container Error" when starting ECS ​​Fargate
[Rails] What to do if you can't get an error message with the errors method
What to do if you get a java.io.IOException in GlassFish
What to do if you get an error saying Cannot find a valid baseurl for repo when you use yum -y install docker in a udemy course using CentOS7
What to do if you get a "Mysql2 :: Error: Operand should contain 1 column (s)" error in Rails
What to do if an error occurs when doing npm install axios in React + Typescript project
What to do if an error occurs in VS Code when importing a django module or your own module installed by pip install
I get a Ruby version error when I try to start Rails.
What to do if Operation not permitted is displayed when you execute a command in the terminal
[Rails] What to do if you get an error saying "Could not find a JavaScript runtime." When executing the rails s command on Catalina
What I did when I was addicted to the error "Could not find XXX in any of the sources" when I added a Gem and built it
What to do if you get a groovy warning in Thymeleaf Layout
What to do if you get a javax.net.ssl.SSLHandshakeException: Remote host closed connection during handshake in the IBM JDK
How to translate the error message into Japanese (What to do if you cannot log in for some reason)