Fixes #26: Loop control in workflows

internal/step/dummy/provider.go

@@ -24,6 +24,9 @@ func (p *dummyProvider) Kind() string {
 type dummyProvider struct {
 }
 
+func (p *dummyProvider) Register(_ step.Registry) {
+}
+
 func (p *dummyProvider) ProviderSchema() map[string]*schema.PropertySchema {
 	// We don't need any steps to set up the provider.
 	return map[string]*schema.PropertySchema{}
@@ -64,7 +67,7 @@ func (p *dummyProvider) Lifecycle() step.Lifecycle[step.LifecycleStage] {
 	}
 }
 
-func (p *dummyProvider) LoadSchema(_ map[string]any) (step.RunnableStep, error) {
+func (p *dummyProvider) LoadSchema(_ map[string]any, _ map[string][]byte) (step.RunnableStep, error) {
 	return &runnableStep{}, nil
 }
 

internal/step/dummy/provider_test.go

@@ -42,7 +42,7 @@ func (s *stageChangeHandler) OnStepComplete(
 func TestProvider(t *testing.T) {
 	provider := dummy.New()
 	assert.Equals(t, provider.Kind(), "dummy")
-	runnable, err := provider.LoadSchema(map[string]any{})
+	runnable, err := provider.LoadSchema(map[string]any{}, map[string][]byte{})
 	assert.NoError(t, err)
 
 	handler := &stageChangeHandler{

internal/step/foreach/README.md

@@ -0,0 +1,26 @@
+# Foreach step provider
+
+This provider allows you to loop over a list of inputs and execute (potentially parallel) workflows for each item. The subworkflows must only have one possible output named "success" and this output will be collected into a list as a result.
+
+## Usage
+
+```yaml
+steps:
+  your_step:
+    kind: foreach
+    workflow: some_workflow_file.yaml # This must be in the workflow directory
+    items: !expr $.input.some_list_of_items
+    parallelism: 5 # How many workflows to run in parallel
+output:
+  result: !expr $.steps.your_step.outputs.success.data # This will be a list of result objects
+```
+
+### Handling errors
+
+In case one or more subworkflows exit with an error, you can also recover.
+
+```yaml
+output:
+  result: !expr $.steps.your_step.failed.error.data # This will be a map of int keys to provide the subworkflows with a successful execution.
+  errors: !expr $.steps.your_step.failed.error.messages # This will be a map of int to error messages for the subworkflows that failed.
+```

internal/step/foreach/doc.go

@@ -0,0 +1,2 @@
+// Package foreach provides the ability to loop over items.
+package foreach