Support Env-based SDP part 2: Add resolve method to SynthesizerRef struct in API

api/v1/composition.go

@@ -1,6 +1,8 @@
 package v1
 
 import (
+	"context"
+	"errors"
 	"fmt"
 	"strconv"
 
@@ -58,6 +60,82 @@ type CompositionSpec struct {
 	SynthesisEnv []EnvVar `json:"synthesisEnv,omitempty"`
 }
 
+// Sentinel errors for synthesizer resolution.
+var (
+	// ErrNoMatchingSelector is returned when no synthesizers match the label selector.
+	ErrNoMatchingSelector = errors.New("no synthesizers match the label selector")
+
+	// ErrMultipleMatches is returned when more than one synthesizer matches the label selector.
+	ErrMultipleMatches = errors.New("multiple synthesizers match the label selector")
+)
+
+// ResolveSynthesizer resolves the Composition's SynthesizerRef to a concrete Synthesizer.
+//
+// Precedence behavior: When both Name and LabelSelector are set in the ref,
+// LabelSelector takes precedence and Name is ignored. This allows for more
+// flexible matching when needed while maintaining backwards compatibility
+// with name-based resolution.
+//
+// If the ref has a labelSelector, it lists all synthesizers matching the selector.
+// Exactly one synthesizer must match; if zero match, ErrNoMatchingSelector is returned,
+// and if more than one match, ErrMultipleMatches is returned.
+//
+// If labelSelector is not set, it uses the name field to get the synthesizer directly.
+//
+// Returns:
+//   - The resolved Synthesizer if found
+//   - nil, ErrNoMatchingSelector if no synthesizers match the label selector
+//   - nil, ErrMultipleMatches if more than one synthesizer matches the label selector
+//   - nil, error if there was an error during resolution
+func (c *Composition) ResolveSynthesizer(ctx context.Context, cl client.Reader) (*Synthesizer, error) {
+	ref := &c.Spec.Synthesizer
+	// LabelSelector takes precedence over name
+	if ref.LabelSelector != nil {
+		return c.resolveSynthesizerByLabel(ctx, cl)
+	}
+
+	// Fallback to name-based resolution
+	synth := &Synthesizer{}
+	synth.Name = ref.Name
+
+	return synth, cl.Get(ctx, client.ObjectKeyFromObject(synth), synth)
+}
+
+// resolveSynthesizerByLabel resolves a Synthesizer using a label selector.
+// It lists all synthesizers matching the selector and returns the matching one.
+// Exactly one synthesizer must match the selector.
+//
+// Returns:
+//   - The resolved Synthesizer if exactly one matches
+//   - nil, ErrNoMatchingSelector if no synthesizers match the selector
+//   - nil, ErrMultipleMatches if more than one synthesizer matches the selector
+//   - nil, error if there was an error during resolution
+func (c *Composition) resolveSynthesizerByLabel(ctx context.Context, cl client.Reader) (*Synthesizer, error) {
+	ref := &c.Spec.Synthesizer
+	// Convert metav1.LabelSelector to labels.Selector
+	selector, err := metav1.LabelSelectorAsSelector(ref.LabelSelector)
+	if err != nil {
+		return nil, fmt.Errorf("converting label selector: %w", err)
+	}
+
+	// List all synthesizers matching the selector
+	synthList := &SynthesizerList{}
+	err = cl.List(ctx, synthList, client.MatchingLabelsSelector{Selector: selector})
+	if err != nil {
+		return nil, fmt.Errorf("listing synthesizers by label selector: %w", err)
+	}
+
+	// Handle results based on match count
+	switch len(synthList.Items) {
+	case 0:
+		return nil, ErrNoMatchingSelector
+	case 1:
+		return &synthList.Items[0], nil
+	default:
+		return nil, ErrMultipleMatches
+	}
+}
+
 type CompositionStatus struct {
 	Simplified        *SimplifiedStatus `json:"simplified,omitempty"`
 	InFlightSynthesis *Synthesis        `json:"inFlightSynthesis,omitempty"`

api/v1/synthesizer.go

@@ -75,3 +75,4 @@ type SynthesizerRef struct {
 	Name          string                `json:"name,omitempty"`
 	LabelSelector *metav1.LabelSelector `json:"labelSelector,omitempty"`
 }
+