Incorrect hypervisors and virtual Facts with Unsupported Container Runtime Warning in Docker

[molhamalnasr]

Describe the Bug

When running Puppet Facter inside a Docker container, the hypervisors and virtual facts are incorrectly set. Additionally, a warning is displayed:
Warning: Facter: Container runtime, 'docker', is unsupported, setting to, 'container_other'.

Example Output:

# facter -p hypervisors
[2024-11-27 13:49:35.972235 ] WARN Facter::Resolvers::Containers - Container runtime, 'docker', is unsupported, setting to, 'container_other'

# facter -p virtual
[2024-11-27 13:49:42.488042 ] WARN Facter::Resolvers::Containers - Container runtime, 'docker', is unsupported, setting to, 'container_other'
container_other

Expected Behavior

In previous versions (e.g., Tag 4.7.0), the hypervisors and virtual facts returned the correct values:

# facter -p hypervisors
{
  docker => {
    id => "<STRING_ID>"
  }
}

# facter -p virtual
docker

Steps to Reproduce

1. Run Puppet Agent/Facter inside a Docker container.
2. Execute the command facter -p hypervisors or facter -p virtual.

Environment

• Version: Puppet Agent 7.32.1
• Platform: Ubuntu 24.04
• Facter Version: 4.8.0

Additional Context

After debugging the repository, I identified the root cause in the following line within lib/facter/resolvers/containers.rb:

read_environ(fact_name) || read_cgroup(fact_name)

The call to read_environ(fact_name) always returns a value, which prevents read_cgroup(fact_name) from being executed. This causes the resolver to misidentify the container runtime and set incorrect values for the hypervisors and virtual facts.