Strapi + Heroku deployment failed:npm ERR! code ERESOLVE - heroku

Question

I'm following this tutorial to deploy the Strapi app to Heroku.
I have set up to auto-deploy from my Github repo.
After pushing to Github, I get the notification of build failure with the following message.
build log
-----> Building on the Heroku-20 stack
-----> Node.js app detected
-----> Creating runtime environment
NPM_CONFIG_LOGLEVEL=error
NODE_VERBOSE=false
NODE_ENV=production
NODE_MODULES_CACHE=true
-----> Installing binaries
engines.node (package.json): >=10.16.0 <=14.x.x
engines.npm (package.json): >=6.0.0
Resolving node version >=10.16.0 <=14.x.x...
Downloading and installing node 14.15.4...
Bootstrapping npm >=6.0.0 (replacing 6.14.10)...
npm >=6.0.0 installed
-----> Installing dependencies
Installing node modules (package.json)
npm ERR! code ERESOLVE
npm ERR! ERESOLVE unable to resolve dependency tree
npm ERR!
npm ERR! While resolving: drkang-strapi#0.1.0
npm ERR! Found: knex#0.19.5
npm ERR! node_modules/knex
npm ERR! knex#"<0.20.0" from the root project
npm ERR!
npm ERR! Could not resolve dependency:
npm ERR! peer knex#"^0.20.0" from strapi-connector-bookshelf#3.4.6
npm ERR! node_modules/strapi-connector-bookshelf
npm ERR! strapi-connector-bookshelf#"3.4.6" from the root project
npm ERR!
npm ERR! Fix the upstream dependency conflict, or retry
npm ERR! this command with --force, or --legacy-peer-deps
npm ERR! to accept an incorrect (and potentially broken) dependency resolution.
npm ERR!
npm ERR! See /tmp/npmcache.9OnCF/eresolve-report.txt for a full report.
npm ERR! A complete log of this run can be found in:
npm ERR! /tmp/npmcache.9OnCF/_logs/2021-02-04T02_14_54_807Z-debug.log
-----> Build failed
We're sorry this build is failing! You can troubleshoot common issues here:
https://devcenter.heroku.com/articles/troubleshooting-node-deploys
Some possible problems:
- Dangerous semver range (>) in engines.node
https://devcenter.heroku.com/articles/nodejs-support#specifying-a-node-js-version
Love,
Heroku
! Push rejected, failed to compile Node.js app.
! Push failed
What should I do here? Any help would be appreciated.

Answer 1

I had the same issue today. It appears to me that the problem has to do with the version of knex not being compatible with the version of nodejs. After looking into it more, Strapi isn't compatible with nodejs over v.14 or npm over v.6 (Heroku was trying to build my Strapi app with node v.15). To resolve it, I updated the package.json file to make sure that Heroku uses the versions that are compatible. Here is what I added, it worked for me and I hope it works for you.
In the package.json file, update the versions of node and npm like this:
"engines": {
"node": "<=14.x.x",
"npm": "<=6.x.x"
}

Answer 2

In my case .npmrc solved this,
create .npmrc in the root of the project and allow legacy peer dependencies
legacy-peer-deps=true

Answer 3

Jryke's way solved my problem:
I added these lines to package.json and the problem fixed:
"engines": {
"node": "16.x",
"npm": "8.5.5"
},
And again thanks to Jryke :-) yes I use "knex" module in my code and yes I use "heroku" also.