Add dollar variable for the global template context

README.md

@@ -290,6 +290,12 @@ For more information, see the example in [recursive](example/recursive).
 | [`setResourceNameAnnotation`](example/inline)                    | Returns the special resource-name annotation with given name |
 | [`include`](example/functions/include)                           | Outputs template as a string                                 |
 
+## Additional variables
+
+| Name | Description                                                                                     |
+| ---- | ----------------------------------------------------------------------------------------------- |
+| `$`  | As for Helm, the `$` variable will always point to the root context, thus the function request. |
+
 ## Developing this function
 
 This function uses [Go][go], [Docker][docker], and the [Crossplane CLI][cli] to

fn.go

@@ -49,6 +49,8 @@ const (
 	annotationKeyReady                   = "gotemplating.fn.crossplane.io/ready"
 
 	metaApiVersion = "meta.gotemplating.fn.crossplane.io/v1alpha1"
+
+	itemDollar = "$"
 )
 
 // RunFunction runs the Function.
@@ -82,6 +84,7 @@ func (f *Function) RunFunction(_ context.Context, req *fnv1beta1.RunFunctionRequ
 		response.Fatal(rsp, errors.Wrap(err, "cannot convert request to map"))
 		return rsp, nil
 	}
+	reqMap[itemDollar] = &reqMap
 
 	f.log.Debug("constructed request map", "request", reqMap)
 

fn_test.go

@@ -23,6 +23,7 @@ import (
 var (
 	cd                    = `{"apiVersion":"example.org/v1","kind":"CD","metadata":{"annotations":{"gotemplating.fn.crossplane.io/composition-resource-name":"cool-cd"},"name":"cool-cd"}}`
 	cdTmpl                = `{"apiVersion":"example.org/v1","kind":"CD","metadata":{"annotations":{"gotemplating.fn.crossplane.io/composition-resource-name":"cool-cd"},"name":"cool-cd","labels":{"belongsTo":{{.observed.composite.resource.metadata.name|quote}}}}}`
+	cdTmplWithDollar      = `{"apiVersion":"example.org/v1","kind":"CD","metadata":{"annotations":{"gotemplating.fn.crossplane.io/composition-resource-name":"cool-cd"},"name":"cool-cd","labels":{"belongsTo":{{ $.observed.composite.resource.metadata.name|quote}}}}}`
 	cdWrongTmpl           = `{"apiVersion":"example.org/v1","kind":"CD","metadata":{"name":"cool-cd","labels":{"belongsTo":{{.invalid-key}}}}}`
 	cdMissingKind         = `{"apiVersion":"example.org/v1"}`
 	cdMissingResourceName = `{"apiVersion":"example.org/v1","kind":"CD","metadata":{"name":"cool-cd"}}`
@@ -316,6 +317,44 @@ func TestRunFunction(t *testing.T) {
 				},
 			},
 		},
+		"ResponseIsReturnedWithTemplatingFromGlobalContext": {
+			reason: "The Function should be able to template by accessing the global context from the dollar variable.",
+			args: args{
+				req: &fnv1beta1.RunFunctionRequest{
+					Meta: &fnv1beta1.RequestMeta{Tag: "templates"},
+					Input: resource.MustStructObject(
+						&v1beta1.GoTemplate{
+							Source: v1beta1.InlineSource,
+							Inline: &v1beta1.TemplateSourceInline{Template: cdTmplWithDollar},
+						}),
+					Observed: &fnv1beta1.State{
+						Composite: &fnv1beta1.Resource{
+							Resource: resource.MustStructJSON(xr),
+						},
+					},
+					Desired: &fnv1beta1.State{
+						Composite: &fnv1beta1.Resource{
+							Resource: resource.MustStructJSON(xr),
+						},
+					},
+				},
+			},
+			want: want{
+				rsp: &fnv1beta1.RunFunctionResponse{
+					Meta: &fnv1beta1.ResponseMeta{Tag: "templates", Ttl: durationpb.New(response.DefaultTTL)},
+					Desired: &fnv1beta1.State{
+						Composite: &fnv1beta1.Resource{
+							Resource: resource.MustStructJSON(xr),
+						},
+						Resources: map[string]*fnv1beta1.Resource{
+							"cool-cd": {
+								Resource: resource.MustStructJSON(`{"apiVersion": "example.org/v1","kind":"CD","metadata":{"annotations":{},"name":"cool-cd","labels":{"belongsTo":"cool-xr"}}}`),
+							},
+						},
+					},
+				},
+			},
+		},
 		"UpdateDesiredCompositeStatus": {
 			reason: "The Function should update the desired composite resource status.",
 			args: args{