Related to #5730

Add support for custom autodiscovery plugin using WASM.

This feature leverage the WASM framework Extism which allows writing plugin using Rust, JS, Go, C#, F#, C, Haskell, and Zig

I also created this repository https://github.com/updatecli/plugins to host a plugin example.

A simple Updatecli manifest looks like
Where the autodiscovery crawler kind can be a file with the ".wasm" extension
At the moment it supports local files but we can envision supporting OCI artifacts in order to push/push plugins similar to Updatecli shared policies.

name: Test Custom autodiscovery plugin

autodiscovery:
  crawlers:
    "pkg/plugins/autodiscovery/plugin/testdata/demo.wasm":
      # The source code for this plugin is available autodiscovery
      # https://github.com/updatecli/plugins/tree/main/autodiscovery/demo
      spec:
        files:
          - pkg/plugins/autodiscovery/plugin/testdata/demo/data.txt

Please note that WASM comes with its own set of limitations.

• A WASM binary is executed within its own container so we need to mount any files that we need to manipulate from the host to the WASM container
• Depending on the programming language, we may have some limitations.

Test

To test this pull request, you can run the following commands:

cd pkg/plugins/autodiscovery/plugin/
go test .

go build -o bin/updatecli .
./bin/updatecli diff --config e2e/updatecli.d/success.d/autodiscovery/plugin/

Additional Information

Checklist

• I have updated the documentation via pull request in website repository.

Tradeoff

By default, a WASM container doesn't have access to the host local files. For that we need to allow list some path such as

  crawlers:
    "pkg/plugins/autodiscovery/plugin/testdata/demo.wasm":
      # The source code for this plugin is available autodiscovery
      # https://github.com/updatecli/plugins/tree/main/autodiscovery/demo
      spec:
        allowedpaths:
          - ".:/mnt"

If allowedpaths is unset, then I made the decision to automatically load the local directory or the scm directory if a scm configuration is specified, to reduce the amount of configuration needed in the Updatecli manifest.

By default, a WASM binary is executed from the directory /mnt

Potential improvement

• Right now the plugin must remain local to the Updatecli manifest file, it would be nice to also support fetching plugins from an OCI registry.