feat: merge new extra resources into existing context

fn.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"context"
+	"maps"
 	"reflect"
 	"sort"
 
@@ -85,6 +86,15 @@ func (f *Function) RunFunction(_ context.Context, req *fnv1.RunFunctionRequest)
 		response.Fatal(rsp, errors.Wrapf(err, "cannot create new Struct from extra resources output"))
 		return rsp, nil
 	}
+
+	if in.Spec.Context.GetPolicy() == v1beta1.ContextPolicyMerge {
+		v, _ := request.GetContextKey(req, in.Spec.Context.GetKey())
+		if fields := v.GetStructValue().GetFields(); fields != nil {
+			maps.Copy(fields, s.GetFields())
+			s.Fields = fields
+		}
+	}
+
 	response.SetContextKey(rsp, in.Spec.Context.GetKey(), structpb.NewStructValue(s))
 
 	return rsp, nil

fn_test.go

@@ -230,6 +230,21 @@ func TestRunFunction(t *testing.T) {
 			args: args{
 				req: &fnv1.RunFunctionRequest{
 					Meta: &fnv1.RequestMeta{Tag: "hello"},
+					Context: &structpb.Struct{
+						Fields: map[string]*structpb.Value{
+							v1beta1.FunctionContextKeyExtraResources: structpb.NewStructValue(resource.MustStructJSON(`{
+								"previous": [
+									{
+										"apiVersion": "apiextensions.crossplane.io/v1beta1",
+										"kind": "EnvironmentConfig",
+										"metadata": {
+											"name": "previous"
+										}
+									}
+								]
+							}`)),
+						},
+					},
 					Observed: &fnv1.State{
 						Composite: &fnv1.Resource{
 							Resource: resource.MustStructJSON(`{
@@ -646,7 +661,7 @@ func TestRunFunction(t *testing.T) {
 									"apiVersion": "apiextensions.crossplane.io/v1beta1",
 									"type": "Reference",
 									"into": "obj-0",
-									"ref": {	
+									"ref": {
 										"name": "my-env-config"
 									}
 								}
@@ -688,6 +703,116 @@ func TestRunFunction(t *testing.T) {
 				},
 			},
 		},
+		"MergeContext": {
+			reason: "The Function should put resolved extra resources into existing context value when policy is Merge.",
+			args: args{
+				req: &fnv1.RunFunctionRequest{
+					Meta: &fnv1.RequestMeta{Tag: "hello"},
+					Context: &structpb.Struct{
+						Fields: map[string]*structpb.Value{
+							v1beta1.FunctionContextKeyExtraResources: structpb.NewStructValue(resource.MustStructJSON(`{
+								"previous": [
+									{
+										"apiVersion": "apiextensions.crossplane.io/v1beta1",
+										"kind": "EnvironmentConfig",
+										"metadata": {
+											"name": "previous"
+										}
+									}
+								]
+							}`)),
+						},
+					},
+					Observed: &fnv1.State{
+						Composite: &fnv1.Resource{
+							Resource: resource.MustStructJSON(`{
+								"apiVersion": "test.crossplane.io/v1alpha1",
+								"kind": "XR",
+								"metadata": {
+									"name": "my-xr"
+								}
+							}`),
+						},
+					},
+					RequiredResources: map[string]*fnv1.Resources{
+						"obj-0": {
+							Items: []*fnv1.Resource{
+								{
+									Resource: resource.MustStructJSON(`{
+									"apiVersion": "apiextensions.crossplane.io/v1beta1",
+									"kind": "EnvironmentConfig",
+									"metadata": {
+										"name": "my-env-config"
+									}
+								}`),
+								},
+							},
+						},
+					},
+					Input: resource.MustStructJSON(`{
+						"apiVersion": "extra-resources.fn.crossplane.io/v1beta1",
+						"kind": "Input",
+						"spec": {
+							"context": {
+								"policy": "Merge"
+							},
+							"extraResources": [
+								{
+									"kind": "EnvironmentConfig",
+									"apiVersion": "apiextensions.crossplane.io/v1beta1",
+									"type": "Reference",
+									"into": "obj-0",
+									"ref": {
+										"name": "my-env-config"
+									}
+								}
+							]
+						}
+					}`),
+				},
+			},
+			want: want{
+				rsp: &fnv1.RunFunctionResponse{
+					Meta:    &fnv1.ResponseMeta{Tag: "hello", Ttl: durationpb.New(response.DefaultTTL)},
+					Results: []*fnv1.Result{},
+					Requirements: &fnv1.Requirements{
+						Resources: map[string]*fnv1.ResourceSelector{
+							"obj-0": {
+								ApiVersion: "apiextensions.crossplane.io/v1beta1",
+								Kind:       "EnvironmentConfig",
+								Match: &fnv1.ResourceSelector_MatchName{
+									MatchName: "my-env-config",
+								},
+							},
+						},
+					},
+					Context: &structpb.Struct{
+						Fields: map[string]*structpb.Value{
+							v1beta1.FunctionContextKeyExtraResources: structpb.NewStructValue(resource.MustStructJSON(`{
+								"previous": [
+									{
+										"apiVersion": "apiextensions.crossplane.io/v1beta1",
+										"kind": "EnvironmentConfig",
+										"metadata": {
+											"name": "previous"
+										}
+									}
+								],
+								"obj-0": [
+									{
+										"apiVersion": "apiextensions.crossplane.io/v1beta1",
+										"kind": "EnvironmentConfig",
+										"metadata": {
+											"name": "my-env-config"
+										}
+									}
+								]
+							}`)),
+						},
+					},
+				},
+			},
+		},
 	}
 
 	for name, tc := range cases {

input/v1beta1/resource_select.go

@@ -48,6 +48,13 @@ type Context struct {
 	// standard functions such as Function Patch and Transform.
 	// +kubebuilder:default=apiextensions.crossplane.io/extra-resources
 	Key *string `json:"key,omitempty"`
+
+	// Policy specifies how to handle the context's potentially existing value.
+	// Replace replaces the existing context key with the new extra resources.
+	// Merge merges the extra resources into the context key's existing value.
+	// +kubebuilder:default=Replace
+	// +kubebuilder:validation:Enum=Replace;Merge
+	Policy *ContextPolicy `json:"policy,omitempty"`
 }
 
 // GetKey returns the key of the context, defaulting to
@@ -59,6 +66,25 @@ func (i *Context) GetKey() string {
 	return *i.Key
 }
 
+// ContextPolicy specifies how to handle the context's potentially existing value.
+type ContextPolicy string
+
+const (
+	// ContextPolicyReplace replaces the context key.
+	ContextPolicyReplace ContextPolicy = "Replace"
+	// ContextPolicyMerge merges into the context key.
+	ContextPolicyMerge ContextPolicy = "Merge"
+)
+
+// GetPolicy returns the policy of the context, defaulting to Replace if not
+// specified.
+func (i *Context) GetPolicy() ContextPolicy {
+	if i == nil || i.Policy == nil {
+		return ContextPolicyReplace
+	}
+	return *i.Policy
+}
+
 // Policy represents the Resolution policy of Reference instance.
 type Policy struct {
 	// Resolution specifies whether resolution of this reference is required.

package/input/extra-resources.fn.crossplane.io_inputs.yaml

@@ -52,6 +52,16 @@ spec:
                       E.g. 'apiextensions.crossplane.io/environment', the environment used in
                       standard functions such as Function Patch and Transform.
                     type: string
+                  policy:
+                    default: Replace
+                    description: |-
+                      Policy specifies how to handle the context's potentially existing value.
+                      Replace replaces the existing context key with the new extra resources.
+                      Merge merges the extra resources into the context key's existing value.
+                    enum:
+                    - Replace
+                    - Merge
+                    type: string
                 type: object
               extraResources:
                 description: |-