addrs: limit source component length to 16

[lbajolet-hashicorp]

When specifying/installing plugins, a source URI is required for Packer to be able to locate or install a plugin to the local plugin hierarchy.

The plugin hierarchy is based on the plugin source, where each component in this hierarchy will become a directory.

In order to avoid sources with too many levels of nesting, causing a lot of mkdirs, we limit the number of sources to 16 in this commit, this should be long enough for most of our users.

[nywilken]

A couple of suggestions. If a user drops a binary in the plugins directory with more then 16 directories do we prevent it from loading?

Is there a way to validate the address of the discovered plugin so that we don't need to track the depth of the filepath.Walk?

[lbajolet-hashicorp]

That's a good call for plugins that are completely manually installed, we don't track the depth for filepath.Walk, but iirc there's something built-in for limiting how deep we visit the filesystem?
I'll see what I can do, alternatively we can derive the source depth from the path of the binary

[nywilken]

Functionality wise this looks good and handles both cases of installing or lading a plugin that is more the 16 paths deep. The error messaging doesn't display well so we need to improve that.

[nywilken]

The updated error for this particular case looks good. But we need to clean up the other error message by adding a newline as they can be a bit long, maybe even repetative since the name of the plugin is already displayed within the "invalid source string ..." message.

~>  packer plugins install --path packer-plugin-amazon https://github.com/hashicorp/azr/a/b/c/d/e/f/g/h/i/j/k/l/m/hashicups
Invalid source string "https://github.com/hashicorp/azr/a/b/c/d/e/f/g/h/i/j/k/l/m/hashicups": The provided source URL "https://github.com/hashicorp/azr/a/b/c/d/e/f/g/h/i/j/k/l/m/hashicups" is invalid. The following errors have been discovered:
* A source URL must not contain a scheme (e.g. https://).

A valid source looks like "github.com/hashicorp/happycloud"

[go-1.21.8] [0] dev@dev-GQPG9GPY75 in ~/Development/packer-plugin-amazon/ on main
~>  packer plugins install --path packer-plugin-amazon github.com/hashicorp/azr/a/b/c/d/e/f/g/h/i/j/k/l/m/hashicups
Invalid source string "github.com/hashicorp/azr/a/b/c/d/e/f/g/h/i/j/k/l/m/hashicups": The source URL must have at most 16 components, and the one provided has 17.
This is unsupported by Packer, please consider using a source that has less components to it.
If this is a blocking issue for you, please open an issue to ask for supporting more components to the source URI.

[lbajolet-hashicorp]

@nywilken I pushed a change to the error messages, trying to make lines shorter and removing mentions of the source string since it'll be in the error message, let me know what you think

[nywilken]

Beautiful

~>  packer plugins install --path packer-plugin-amazon https://github.com/hashicorp/azr/a/b/c/d/e/f/g/h/i/j/k/l/m/hashicups
Invalid source string "https://github.com/hashicorp/azr/a/b/c/d/e/f/g/h/i/j/k/l/m/hashicups": The provided source URL is invalid.
The following errors have been discovered:
* A source URL must not contain a scheme (e.g. https://).

A valid source looks like "github.com/hashicorp/happycloud"

[nywilken]

It looks like you might of rebase with plugin install docs. I would just spot check for consistency between your branches.

[lbajolet-hashicorp]

I have indeed; will cleanup now

[github-actions]

I'm going to lock this pull request because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.
If you have found a problem that seems related to this change, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.