Problems with babel loader in react-create-app

问题

The Problem

create-react-app initializes a repository where babel-loader is installed as an older version than needed.

LOG:

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:

  "babel-loader": "8.0.4"

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

  C:\Users\user\node_modules\babel-loader (version: 8.0.2)

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

If 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 "babel-loader" 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 C:\Users\User\node_modules\babel-loader is outside your project directory.
         For example, you might have accidentally installed something in your home folder.

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

    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! reg@0.1.0 start: `react-scripts start`
    npm ERR! Exit status 1
    npm ERR!
    npm ERR! Failed at the reg@0.1.0 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!     C:\Users\User\AppData\Roaming\npm-cache\_logs\2018-12-13T18_22_47_802Z-debug.log

After what it happened

$ npx create-react-app reg && cd reg && npm start

What I've tried

I tried to remove node_modules folder and package-lock.json, then run npm install.

Also installed yarn and ran yarn && yarn start.

I've recreated the app 3 times and got the same result.

Info that may be helpful

Node version: 10.8.0
NPM Version: 6.5.0
create-react-app / react-scripts: 2.1.1
babel-loader: 8.0.4
Global packages list (npm ls --depth=0 -g):

+-- create-react-app@2.1.1
+-- node-gyp@3.6.2
+-- npm@6.5.0
+-- yarn@1.12.3

package.json file:

{
  "name": "reg",
  "version": "0.1.0",
  "private": true,
  "dependencies": {
    "react": "^16.6.3",
    "react-dom": "^16.6.3",
    "react-scripts": "2.1.1"
  },
  "scripts": {
    "start": "react-scripts start",
    "build": "react-scripts build",
    "test": "react-scripts test",
    "eject": "react-scripts eject"
  },
  "eslintConfig": {
    "extends": "react-app"
  },
  "browserslist": [
    ">0.2%",
    "not dead",
    "not ie <= 11",
    "not op_mini all"
  ]
}

回答1:

Getting the same issue but given an hour on it get the solution When we run npm start then you got this kind of an error that is version related issues for this issue. Go to node_modules folder:

Project->node_modules->react-scripts->package.json

check the package.json file

there you got : "babel-loader": "8.0.4" first remove : babel-loader folder for Project->node_modules->babel-loader and then run npm i babel-loader@8.0.4 (it is depend on your version you can change it like : npm i babel-loader@8.0.5) after that may be you got webpack issue then follow same thing remvoe webpack from "Project->node_modules->webpack" and reinstall npm i webpack@4.19.1

4.19.1* webpack's version it may be change..

回答2:

Create a .env file in your project directory and include SKIP_PREFLIGHT_CHECK=true in the file.

回答3:

On Mac:

Remove the conflicting package from /Users/<yourusername>/node_modules

回答4:

However, a different version of babel-loader was detected higher up in the tree:

You should delete babel-loader package that was was detected higher up the tree. The output says there is a node_modules folder with babel-loader at..

C:\Users\user\node_modules\babel-loader (version: 8.0.2)

You may be able to delete the C:\Users\user\node_modules directory altogether as well, unless for some reason you have a project rooted there inside /Users/{user}

回答5:

You can momentarily downgrade react-scripts to 1.1.5 in the package.json file, then remove the node_modules folder and in the case of using NPM delete the package-lock.json file and in case Yarn delete the file yarn.lock. After that, reinstall the dependencies and start the development server with the yarn start or npm run start command.

回答6:

I was having this issue and just added in

"babel-loader": "8.0.4",

to my package.json in the dependencies and it seemed to fix the issue

回答7:

this means you install tow babel-loader

rm yarn.lock
run npm uninstall babel-loader@8.0.4

回答8:

I got the same problem. I solved it by removing folder node_modules in User/ and file package-lock.json (if exists). It should work perfectly then.

回答9:

I had this exact same issue. For anyone who finds this thread via Google and is a beginner like me. Here is exactly what to enter into your terminal(Mac User).

Say you're getting the same error that Paul was getting:

"The react-scripts package provided by Create React App requires a dependency: "babel-loader": "8.0.6"

Here's what I entered into the terminal. I could be wrong, but this is what worked for me (I am also a beginner):

Step 1: Delete the node_modules folder as well as the package_lock.json files.

Step 2: In your terminal, type cd - (we're just getting outside of our project folder and going into your home folder)

Step 3: In your terminal type in npm i "dependency-name@number" so for the above example it would be: npm i babel-loader@8.0.6

Step 4: Now in your terminal, navigate into your project folder and type: npm install or yarn install

Step 5: Try running npm start and if all the issues have been solved, it should start the development server.

Note: I had to do the above process twice, for babel-loader@8.0.6 as well as for Webpack.

回答10:

I have also problems after creating an app-project using the following commands:

create-react-app "project name"
create-react-app "project name" --use-npm
npx create-react-app. 

On all cases the result was the error specified right in the top:

[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.......][...]

watching on the error a line came with a small clue:

"/Users/john/node_modules/babel-loader (version: "7.1.5") -> was a version that creates conflict with above specified - version "babel-loader@8.0.6"

for me the solution was: following this path through my folders and delete the node_modules folder then restart again the project.

回答11:

 C:\Users\user\node_modules\babel-loader

Delete node_modules from \user\node_modules don't delete from your project

if you are using backend (nodejs) check if you are using webpack in your backend make sure your create-react-app webpack and backend webpack version same

来源：https://stackoverflow.com/questions/53768470/problems-with-babel-loader-in-react-create-app