Variables in Workflows

When running locally, variables are shared in-memory between targets. In CI/CD workflows, targets may run in separate jobs on different machines. Atom bridges this gap by mapping variables to the platform's native output/variable mechanism.

How It Works

1. A target declares .ProducesVariable(nameof(BuildVersion)) and writes it with WriteVariable.
2. A downstream target declares .ConsumesVariable(nameof(SetupVersion), nameof(BuildVersion)).
3. Locally: the variable is persisted to a job-scoped JSON file and loaded back into the consuming target.
4. In CI: the WorkflowResolver detects the dependency, creates a job boundary if needed, and the platform module maps the variable to:
   • GitHub Actions: job outputs (${{ needs.job.outputs.var }})
   • Azure DevOps: pipeline variables

Platform Variable Providers

Each platform module registers an IVariableProvider:

Module	Provider	Mechanism
Invex.Atom.Module.GithubWorkflows	GithubVariableProvider	Writes to $GITHUB_OUTPUT, reads from job outputs
Invex.Atom.Module.DevopsWorkflows	DevopsVariableProvider	Uses Azure DevOps pipeline variables

The built-in AtomVariableProvider handles local execution.

Example

A variable is always backed by a [ParamDefinition] property of the same name. The producing target writes the value; consuming targets read it back through that parameter (the executor loads consumed variables automatically before the target runs):

[ParamDefinition("build-version", "The computed build version")]
string? BuildVersion => GetParam(() => BuildVersion);

Target SetupVersion => t => t
    .ProducesVariable(nameof(BuildVersion))
    .Executes(async ct =>
    {
        await WriteVariable(nameof(BuildVersion), "1.2.3", ct);
    });

Target Pack => t => t
    .DependsOn(SetupVersion)
    .ConsumesVariable(nameof(SetupVersion), nameof(BuildVersion))
    .Executes(() =>
    {
        // BuildVersion resolves to the value written by SetupVersion
        Logger.LogInformation("Packing version {Version}", BuildVersion);
    });

In the generated YAML, SetupVersion and Pack will be in separate jobs with the variable passed as a job output.

Next Steps

→ Debugging Workflows