Composer installation - Support Devel 4.0.0

The issue is already tested with the latest stable versions of the mentioned above module:

composer require drupal/devel drupal/search_kint drupal/devel_debug_log

and we get them without any kind of issue:

  - Installing symfony/polyfill-php80 (v1.17.0): Downloading (100%)         
  - Installing symfony/var-dumper (v4.4.10): Downloading (100%)         
  - Installing drupal/devel (2.1.0): Loading from cache
  - Installing drupal/search_kint (1.0.0): Downloading (100%)  
  - Installing drupal/kint (2.1.0)
  - Installing drupal/devel_debug_log (1.0.0-beta2): Downloading (100%) 

Please review that we got "drupal/devel:2.1" by default.

I change the issue category to Support request.

Might this part of the composer.json perhaps cause the problems?

    "require-dev": {
        "drupal/devel": "^2.0"
    }

I just ran into a similar problem when testing it out with Drupal 9:

Your requirements could not be resolved to an installable set of packages.

Problem 1
- drupal/kint 1.0.0-alpha1 requires drupal/devel 1.0.0-alpha1 -> satisfiable by drupal/devel[1.0.0-alpha1] but these conflict with your requirements or minimum-stability.
- drupal/kint 1.0.0-beta1 requires drupal/devel 1.0.0-beta1 -> satisfiable by drupal/devel[1.0.0-beta1] but these conflict with your requirements or minimum-stability.
- drupal/kint 1.0.0-rc1 requires drupal/devel 1.0.0-rc1 -> satisfiable by drupal/devel[1.0.0-rc1] but these conflict with your requirements or minimum-stability.
- drupal/kint 1.0.0-rc2 requires drupal/devel 1.0.0-rc2 -> satisfiable by drupal/devel[1.0.0-rc2] but these conflict with your requirements or minimum-stability.
- drupal/kint 1.0.0 requires drupal/devel 1.0.0 -> satisfiable by drupal/devel[1.0.0] but these conflict with your requirements or minimum-stability.
- drupal/kint 1.1.0 requires drupal/devel 1.1.0 -> satisfiable by drupal/devel[1.1.0] but these conflict with your requirements or minimum-stability.
- drupal/kint 1.2.0 requires drupal/devel 1.2.0 -> satisfiable by drupal/devel[1.2.0] but these conflict with your requirements or minimum-stability.
- drupal/kint 2.0.0 requires drupal/devel 2.0.0 -> satisfiable by drupal/devel[2.0.0] but these conflict with your requirements or minimum-stability.
- drupal/kint 2.1.0 requires drupal/devel 2.1.0 -> satisfiable by drupal/devel[2.1.0] but these conflict with your requirements or minimum-stability.
- Installation request for drupal/devel_debug_log 1.x-dev@dev -> satisfiable by drupal/devel_debug_log[1.x-dev].
- Conclusion: don't install drupal/devel 3.0.0-beta1
- Conclusion: remove drupal/devel 3.x-dev
- drupal/devel_debug_log 1.x-dev requires drupal/kint * -> satisfiable by drupal/kint[2.1.0, dev-2.x, 2.x-dev, 2.0.0, 1.2.0, 1.1.0, 1.0.0, 1.0.0-rc2, 1.0.0-rc1, 1.0.0-beta1, 1.0.0-alpha1, dev-1.x, 1.x-dev].
- drupal/kint dev-1.x requires drupal/devel dev-1.x -> satisfiable by drupal/devel[dev-1.x].
- drupal/kint 1.x-dev requires drupal/devel == 1.9999999.9999999.9999999-dev -> satisfiable by drupal/devel[1.x-dev].
- drupal/kint dev-2.x requires drupal/devel dev-2.x -> satisfiable by drupal/devel[dev-2.x].
- drupal/kint 2.x-dev requires drupal/devel == 2.9999999.9999999.9999999-dev -> satisfiable by drupal/devel[2.x-dev].
- Can only install one of: drupal/devel[3.x-dev, dev-1.x].
- Can only install one of: drupal/devel[3.x-dev, 1.x-dev].
- Can only install one of: drupal/devel[3.x-dev, dev-2.x].
- Can only install one of: drupal/devel[3.x-dev, 2.x-dev].
- Installation request for drupal/devel ^3.0 -> satisfiable by drupal/devel[3.x-dev, 3.0.0-beta1].

So for me devel_debug_log is NOT usable under Drupal 9 currently.

Setting Active as of #6 + #7

I'd suggest a new 3.x release for Devel 3.x and Drupal 9 compatibility.

Might this part of the composer.json perhaps cause the problems?

"require-dev": {
"drupal/devel": "^2.0"
}

Only when it is in the composer.json of the project (site) as it is root-only.

On a Drupal 9 install I just tried composer require drupal/devel_debug_log which should install the module and its dependencies, but instead I got the composer errors shown in the original post and #7.

I agree with the comment in #7, the issue appears to be the version of devel that is stated as a requirement in this module's composer.json.

The bigger issue for Drupal 9 is that version 4.0.0 of devel no longer includes kint as a submodule, so it's impossible to use devel_debug_log with Drupal 9, as the 8.x-2.1 version of devel is not compatible with Drupal 9.

While devel_kint has been removed from the devel module in 4.0.0, as long as the kint library is present devel debug log continues to work with devel 4 on D9. As long as you can install it, that is.

Attached is a patch that removes the devel_kint module dependency, adds a requirement for kint in the composer.json, and adds a minimum version of 4.0.0 for devel.

Dependency issues are resolved with patch #11. The Kint library will only be installed via composer, this is a devel module, so that should not be a problem.

I can also confirm that #11 is solving the problem. But unfortunately this does not seem to be fixable by using composer patches. I suppose because composer checks the requirements before patches are applied. So one need to manually download devel_debug_log and patch it there. Therefore it would be very nice if this patch does get incorporated with a new release.

We need a proper Drupal 9 version. Composer patches are NOT compatible.