Failed to push some refs in Heroku - node.js

Question

`I tried to push my web application to Heroku but it gave me this error. I searched for similar problems but it didn't help me. I did this before and it worked but when I tried to do it again it failed and I don't know why.
How can I resolve this error?
PS D:\react application> git push heroku master
Enumerating objects: 125, done.
Counting objects: 100% (125/125), done.
Delta compression using up to 4 threads
Compressing objects: 100% (116/116), done.
Writing objects: 100% (125/125), 2.56 MiB | 31.00 KiB/s, done.
Total 125 (delta 29), reused 0 (delta 0)
remote: Compressing source files... done.
remote: Building source:
remote:
remote: -----> Node.js app detected
remote:
remote: -----> Build failed
remote: ! Two different lockfiles found: package-lock.json and yarn.lock
remote:
remote: Both npm and yarn have created lockfiles for this application,
remote: but only one can be used to install dependencies. Installing
remote: dependencies using the wrong package manager can result in missing
remote: packages or subtle bugs in production.
remote:
remote: - To use npm to install your application's dependencies please delete
remote: the yarn.lock file.
remote:
remote: $ git rm yarn.lock
remote:
remote: - To use yarn to install your application's dependences please delete
remote: the package-lock.json file.
remote:
remote: $ git rm package-lock.json
remote:
remote: https://kb.heroku.com/why-is-my-node-js-build-failing-because-of-conflicting-lock-files
remote:
remote: ! Push rejected, failed to compile Node.js app.
remote:
remote: ! Push failed
remote: Verifying deploy...
remote:
remote: ! Push rejected to heroku-react-app-3.
remote:
To https://git.heroku.com/heroku-react-app-3.git
! [remote rejected] master -> master (pre-receive hook declined)
error: failed to push some refs to 'https://git.heroku.com/heroku-react-app-3.git'
Here's my application code:
const path = require('path');
const express = require('express');
const app = express();
const publicPath = path.join(__dirname, '..','public');
const port = process.env.PORT || 3000;
app.use(express.static(publicPath));
app.get('*', (req,res) => {
res.sendFile(path.join(publicPath,'index.html'))
});
app.listen(port, () => {
console.log('Server is up');
});
after deleting yarn.lock
PS D:\react application> git push heroku master
Enumerating objects: 130, done.
Counting objects: 100% (130/130), done.
Delta compression using up to 4 threads
Compressing objects: 100% (121/121), done.
Writing objects: 100% (130/130), 2.56 MiB | 33.00 KiB/s, done.
Total 130 (delta 32), reused 0 (delta 0)
remote: Compressing source files... done.
remote: Building source:
remote:
remote: -----> Node.js app detected
remote:
remote: -----> Creating runtime environment
remote:
remote: NPM_CONFIG_LOGLEVEL=error
remote: NODE_ENV=production
remote: NODE_MODULES_CACHE=true
remote: NODE_VERBOSE=false
remote:
remote: -----> Installing binaries
remote: engines.node (package.json): 10.16.0
remote: engines.npm (package.json): unspecified (use default)
remote:
remote: Resolving node version 10.16.0...
remote: Downloading and installing node 10.16.0...
remote: Using default npm version: 6.9.0
remote:
remote: -----> Installing dependencies
remote: Installing node modules (package.json + package-lock)
remote:
remote: > node-sass#4.12.0 install /tmp/build_fa4b97b82e26e28c8efaef8a02fd356e/node_modules/node-sass
remote: > node scripts/install.js
remote:
remote: Downloading binary from https://github.com/sass/node-sass/releases/download/v4.12.0/linux-x64-64_binding.node
remote: Download complete
remote: Binary saved to /tmp/build_fa4b97b82e26e28c8efaef8a02fd356e/node_modules/node-sass/vendor/linux-x64-64/binding.node
remote: Caching binary to /tmp/npmcache.jQpTT/node-sass/4.12.0/linux-x64-64_binding.node
remote:
remote: > core-js#2.6.9 postinstall /tmp/build_fa4b97b82e26e28c8efaef8a02fd356e/node_modules/core-js
remote: > node scripts/postinstall || echo "ignore"
remote:
remote:
remote: > uglifyjs-webpack-plugin#0.4.6 postinstall /tmp/build_fa4b97b82e26e28c8efaef8a02fd356e/node_modules/uglifyjs-webpack-plugin
remote: > node lib/post_install.js
remote:
remote:
remote: > node-sass#4.12.0 postinstall /tmp/build_fa4b97b82e26e28c8efaef8a02fd356e/node_modules/node-sass
remote: > node scripts/build.js
remote:
remote: Binary found at /tmp/build_fa4b97b82e26e28c8efaef8a02fd356e/node_modules/node-sass/vendor/linux-x64-64/binding.node
remote: Testing binary
remote: Binary is fine
remote: added 1139 packages from 774 contributors and audited 16655 packages in 26.036s
remote: found 36 vulnerabilities (31 low, 2 moderate, 3 high)
remote: run `npm audit fix` to fix them, or `npm audit` for details
remote:
remote: -----> Build
remote: Detected both "build" and "heroku-postbuild" scripts
remote: Running heroku-postbuild
remote:
remote: > expensify#1.0.0 heroku-postbuild /tmp/build_fa4b97b82e26e28c8efaef8a02fd356e
remote: > yarn run build:prod
remote:
remote: sh: 1: yarn: not found
remote: npm ERR! file sh
remote: npm ERR! code ELIFECYCLE
remote: npm ERR! errno ENOENT
remote: npm ERR! syscall spawn
remote: npm ERR! expensify#1.0.0 heroku-postbuild: `yarn run build:prod`
remote: npm ERR! spawn ENOENT
remote: npm ERR!
remote: npm ERR! Failed at the expensify#1.0.0 heroku-postbuild script.
remote: npm ERR! This is probably not a problem with npm. There is likely additional logging output above.
remote:
remote: npm ERR! A complete log of this run can be found in:
remote: npm ERR! /tmp/npmcache.jQpTT/_logs/2019-06-11T22_03_49_679Z-debug.log
remote:
remote: -----> Build failed
remote:
remote: We're sorry this build is failing! You can troubleshoot common issues here:
remote: https://devcenter.heroku.com/articles/troubleshooting-node-deploys
remote:
remote: If you're stuck, please submit a ticket so we can help:
remote: https://help.heroku.com/
remote:
remote: Love,
remote: Heroku
remote:
remote: ! Push rejected, failed to compile Node.js app.
remote:
remote: ! Push failed
remote: Verifying deploy...
remote:
remote: ! Push rejected to heroku-react-app-3.
remote:
To https://git.heroku.com/heroku-react-app-3.git
! [remote rejected] master -> master (pre-receive hook declined)
error: failed to push some refs to 'https://git.heroku.com/heroku-react-app-3.git'
my scripts
"engines": {
"node":"10.16.0"
},
"scripts": {
"serve": "live-server public/",
"build": "webpack",
"build:dev": "webpack",
"build:prod": "webpack -p --env production",
"dev-server": "webpack-dev-server",
"test": "jest --config=jest.config.json",
"start": "node server/server.js",
"heroku-postbuild": "yarn run build:prod"
}

Answer 1

As given the problem is that you are having both package-lock.json and yarn.lock
The heroku uses other servers to deploy your app hence it needs to download the dependencies on that remote server.
As you have two dependencies files so heroku can not decide which one to use to download dependencies hence the error.
Delete the one that you are not using(generally yarn.json) and your app will be good to go.