How to combine buildpacks from builder and local file system?

[jsamoocha]

I'm trying to build an image using the heroku/python and heroku-community/apt buildpacks. The first is included in the heroku/buildpacks builder (which I set as default builder). I git-cloned the second to a local path.

When trying pack build [NAME]:[TAG] --buildpack [LOCAL_PATH_TO_heroku-buildpack-apt] --buildpack heroku/python, build fails as follows:

Using default builder image heroku/buildpacks
Pulling image index.docker.io/heroku/buildpacks:latest
latest: Pulling from heroku/buildpacks
Digest: sha256:ebe9cac86cf5aff48e18e085d02ab259d188446c57d211b74eb2ae5e0a81827d
Status: Image is up to date for heroku/buildpacks:latest
Selected run image heroku/pack:18 from builder
Pulling image heroku/pack:18
18: Pulling from heroku/pack
Digest: sha256:ed100d5a3005613e368b97c41eb6e1b6b42aef361de7056ae836176965d98326
Status: Image is up to date for heroku/pack:18
No version for [LOCAL_PATH_TO_heroku-buildpack-apt] buildpack provided, will use [LOCAL_PATH_TO_heroku-buildpack-apt]@latest
No version for heroku/python buildpack provided, will use heroku/python@latest
setting custom order

ERROR: failed to set custom buildpack order: no versions of buildpack [LOCAL_PATH_TO_heroku-buildpack-apt] were found on the builder

where [LOCAL_PATH_TO_heroku-buildpack-apt] is an absolute path.

Obviously, the custom buildpack heroku-buildpack-apt is not in the builder. How can I specify that this buildpack is on the local file system?

[jromero]

What version of pack are you running? If you are using the latest released version then the associated code to differentiate between a directory and an image name is here. This has further been improved in master.

Either implementations would use the requirement for buildpacks to have a buildpack.toml, along with other strategies, to determine if it's a local compatible buildpack. This file is missing from heroku-buildpack-apt making it incompatible. Maybe @jkutner or @hone can provide some more insight here.

[jsamoocha]

Pack version is v0.2.1. Thanks for pointing to the relevant docs and code - it made me realize my mistake, i.e. confusing Cloud Native buildpacks with Heroku buildpacks.

As you suggested, adding a minimal buildpack.toml to heroku-buildpack-apt resolved the initial failure. However, because of other incompatibilities in that buildpack, it just results in other errors. Eventually, the heroku-buildpack-apt (or something equivalent) should be transformed into a cloud native version...

[fagiani]

Hello @jsamoocha!

I had a similar requirement and ended up creating a CNB apt-based buildpack off the heroku-buildpack-apt called fagiani/apt... You can check more details here.

Any feedback would be highly appreciated as it is the first buildpack I created pretty much to get a deeper understanding of how it works.

I hope it becomes helpful to others in the future.

[jsamoocha]

At the time, I worked around the issue using a totally different approach, not requiring any build packs. So I'm afraid I'm not in the position to provide meaningful feedback on your solution.

[enricorotundo]

Hey @fagiani is there any guide out there on how to convert heroku-buildpacks to CNB buildpacks? I see you've been through this journey as well. I'm a bit confused.... isn't heroku supposed to be using the official buildpacks standard?

[fagiani]

@enricorotundo There are other versions of buildpacks as you can see below:

If I understand it correctly, heroku still uses it's V2 buildpacks.

I've spent some time to understand how both work in order to transition them to current CNB ones... If you're looking to convert any specific buildpacks and think I can be of help, please feel free to reach out!

Keep Rocking!