Add custom find_operation support (#454)

Issue: aws-controllers-k8s/community#1827

Description of changes:
This change allow to implement custom find function. The name of the function could be written in generator.yaml as 'find_operation: <name-of-function>' similar to update_operation. And generated code for sdkFind() would call this custom find function. The find function itself could be written in hooks.go.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

Author: nnbu

pkg/config/resource.go

@@ -63,6 +63,18 @@ type ResourceConfig struct {
 	// very little consistency to the APIs that we can use to instruct the code
 	// generator :(
 	UpdateOperation *UpdateOperationConfig `json:"update_operation,omitempty"`
+	// ReadOperation contains instructions for the code generator to generate
+	// Go code for the read operation for the resource. For some resources,
+	// there is no describe/find/list apis. However, it is possible to write
+	// `read` function for such resources using another resource's (say,
+	// resource B) `read` function. Then, one could write custom code to find
+	// the relevant resource from the response of resource B's read function.
+	//
+	// Additionally, if the `read` function for a resource is not available
+	// then reconciler's progression is stalled with the error `read`
+	// operation `notImplemented`. Custom read function allows the
+	// reconciler's progression.
+	ReadOperation *ReadOperationsConfig `json:"find_operation,omitempty"`
 	// Reconcile describes options for controlling the reconciliation
 	// logic for a particular resource.
 	Reconcile *ReconcileConfig `json:"reconcile,omitempty"`
@@ -326,6 +338,15 @@ type UpdateOperationConfig struct {
 	OmitUnchangedFields bool `json:"omit_unchanged_fields"`
 }
 
+// ReadOperationsConfig contains instructions for the code generator to handle
+// custom read operations for service APIs that have resources that have
+// difficult-to-standardize read operations.
+type ReadOperationsConfig struct {
+	// CustomMethodName is a string for the method name to replace the
+	// sdkFind() method implementation for this resource
+	CustomMethodName string `json:"custom_method_name"`
+}
+
 // AdditionalColumnConfig can be used to specify additional printer columns to be included
 // in a Resource's output from kubectl.
 type AdditionalColumnConfig struct {
@@ -651,6 +672,19 @@ func (c *Config) GetCustomUpdateMethodName(resourceName string) string {
 	return ""
 }
 
+func (c *Config) GetCustomFindMethodName(resourceName string) string {
+	if c == nil {
+		return ""
+	}
+	rConfig, found := c.Resources[resourceName]
+	if found {
+		if rConfig.ReadOperation != nil {
+			return rConfig.ReadOperation.CustomMethodName
+		}
+	}
+	return ""
+}
+
 // GetAllRenames returns all of the CRD's field renames observed in the generator config
 // for a given map of operations.
 func (c *Config) GetAllRenames(

pkg/generate/ack/controller.go

@@ -46,6 +46,7 @@ var (
 	controllerIncludePaths = []string{
 		"boilerplate.go.tpl",
 		"pkg/resource/references_read_referenced_resource.go.tpl",
+		"pkg/resource/sdk_find_custom.go.tpl",
 		"pkg/resource/sdk_find_read_one.go.tpl",
 		"pkg/resource/sdk_find_get_attributes.go.tpl",
 		"pkg/resource/sdk_find_read_many.go.tpl",

pkg/generate/code/set_resource.go

@@ -962,6 +962,8 @@ func SetResourceIdentifiers(
 		case r.Ops.ReadMany != nil:
 			// If single lookups can only be done using ReadMany
 			op = r.Ops.ReadMany
+		default:
+			return ""
 		}
 	}
 	inputShape := op.InputRef.Shape

pkg/model/crd.go

@@ -720,6 +720,10 @@ func (r *CRD) CustomUpdateMethodName() string {
 	return r.cfg.GetCustomUpdateMethodName(r.Names.Original)
 }
 
+func (r *CRD) CustomFindMethodName() string {
+	return r.cfg.GetCustomFindMethodName(r.Names.Original)
+}
+
 // ListOpMatchFieldNames returns a slice of strings representing the field
 // names in the List operation's Output shape's element Shape that we should
 // check a corresponding value in the target Spec exists.

templates/pkg/resource/sdk.go.tpl

@@ -39,7 +39,9 @@ var (
 )
 
 // sdkFind returns SDK-specific information about a supplied resource
-{{ if .CRD.Ops.ReadOne }}
+{{ if .CRD.CustomFindMethodName }}
+	{{- template "sdk_find_custom" . }}
+{{- else if .CRD.Ops.ReadOne }}
 	{{- template "sdk_find_read_one" . }}
 {{- else if .CRD.Ops.GetAttributes }}
 	{{- template "sdk_find_get_attributes" . }}

templates/pkg/resource/sdk_find_custom.go.tpl

@@ -0,0 +1,8 @@
+{{- define "sdk_find_custom" -}}
+func (rm *resourceManager) sdkFind(
+	ctx context.Context,
+	r *resource,
+) (*resource, error) {
+	return rm.{{ .CRD.CustomFindMethodName }}(ctx, r)
+}
+{{- end -}}