Conditional function execution using the Common Expression Language

.golangci.yml

@@ -38,7 +38,7 @@ linters-settings:
       - default
       - prefix(github.com/crossplane/crossplane-runtime)
       - prefix(github.com/crossplane/function-sdk-go)
-      - prefix(github.com/crossplane-contrib/function-patch-and-transform)
+      - prefix(github.com/stevendborrelli/function-conditional-patch-and-transform)
       - blank
       - dot
 

Makefile

@@ -0,0 +1,13 @@
+
+DOCKER := docker
+GO := go
+
+GOLANGCI_VERSION := 1.55.2
+
+test:
+	$(GO) test ./...
+
+lint:
+	$(DOCKER) run --rm -v $(CURDIR):/app -v ~/.cache/golangci-lint/v$(GOLANGCI_VERSION):/root/.cache -w /app golangci/golangci-lint:v$(GOLANGCI_VERSION) golangci-lint run --fix
+
+reviewable: test lint

README.md

@@ -1,5 +1,9 @@
-# function-patch-and-transform
-[![CI](https://github.com/crossplane-contrib/function-patch-and-transform/actions/workflows/ci.yml/badge.svg)](https://github.com/crossplane-contrib/function-patch-and-transform/actions/workflows/ci.yml) ![GitHub release (latest SemVer)](https://img.shields.io/github/release/crossplane-contrib/function-patch-and-transform)
+# function-conditional-patch-and-transform
+[![CI](https://github.com/stevendborrelli/function-conditional-patch-and-transform/actions/workflows/ci.yml/badge.svg)](https://github.com/stevendborrelli/function-conditional-patch-and-transform/actions/workflows/ci.yml) ![GitHub release (latest SemVer)](https://img.shields.io/github/release/crossplane-contrib/function-conditional-patch-and-transform)
+
+This composition function is a fork of the upstream [function-patch-and-transform](https://github.com/crossplane-contrib/function-patch-and-transform)
+that adds support for Conditional invocation of the function and the rendering
+of individual resources.
 
 This [composition function][docs-functions] does everything Crossplane's
 built-in [patch & transform][docs-pandt] (P&T) composition does. Instead of
@@ -18,7 +22,7 @@ spec:
   pipeline:
   - step: patch-and-transform
     functionRef:
-      name: function-patch-and-transform
+      name: function-conditional-patch-and-transform
     input:
       apiVersion: pt.fn.crossplane.io/v1beta1
       kind: Resources
@@ -152,7 +156,7 @@ $ crossplane xpkg build -f package --embed-runtime-image=runtime
 [docs-composition]: https://docs.crossplane.io/v1.14/getting-started/provider-aws-part-2/#create-a-deployment-template
 [docs-functions]: https://docs.crossplane.io/v1.14/concepts/composition-functions/
 [docs-pandt]: https://docs.crossplane.io/v1.14/concepts/patch-and-transform/
-[fn-go-templating]: https://github.com/crossplane-contrib/function-go-templating
+[fn-go-templating]: https://github.com/stevendborrelli/function-go-templating
 [#4617]: https://github.com/crossplane/crossplane/issues/4617
 [#4746]: https://github.com/crossplane/crossplane/issues/4746
 [go]: https://go.dev

condition.go

@@ -0,0 +1,84 @@
+package main
+
+import (
+	"reflect"
+
+	"github.com/google/cel-go/cel"
+
+	"github.com/crossplane/crossplane-runtime/pkg/errors"
+
+	fnv1beta1 "github.com/crossplane/function-sdk-go/proto/v1beta1"
+
+	"github.com/stevendborrelli/function-conditional-patch-and-transform/input/v1beta1"
+)
+
+// NewCELEnvironment sets up the CEL Environment
+func NewCELEnvironment() (*cel.Env, error) {
+	return cel.NewEnv(
+		cel.Types(&fnv1beta1.State{}),
+		cel.Variable("observed", cel.ObjectType("apiextensions.fn.proto.v1beta1.State")),
+		cel.Variable("desired", cel.ObjectType("apiextensions.fn.proto.v1beta1.State")),
+	)
+}
+
+// ToCELVars formats a RunFunctionRequest for CEL evaluation
+func ToCELVars(req *fnv1beta1.RunFunctionRequest) map[string]any {
+	vars := make(map[string]any)
+	vars["desired"] = req.GetDesired()
+	vars["observed"] = req.GetObserved()
+	return vars
+}
+
+// EvaluateCondition will evaluate a CEL expression
+func EvaluateCondition(cs v1beta1.ConditionSpec, req *fnv1beta1.RunFunctionRequest) (bool, error) {
+	if cs.Expression == "" {
+		return false, nil
+	}
+
+	env, err := NewCELEnvironment()
+	if err != nil {
+		return false, errors.Wrap(err, "CEL Env error")
+	}
+
+	ast, iss := env.Parse(cs.Expression)
+	if iss.Err() != nil {
+		return false, errors.Wrap(iss.Err(), "CEL Parse error")
+	}
+
+	// Type-check the expression for correctness.
+	checked, iss := env.Check(ast)
+	// Report semantic errors, if present.
+	if iss.Err() != nil {
+		return false, errors.Wrap(iss.Err(), "CEL TypeCheck error")
+	}
+
+	// Ensure the output type is a bool.
+	if !reflect.DeepEqual(checked.OutputType(), cel.BoolType) {
+		return false, errors.Errorf(
+			"CEL Type error: expression '%s' must return a boolean, got %v instead",
+			cs.Expression,
+			checked.OutputType())
+	}
+
+	// Plan the program.
+	program, err := env.Program(checked)
+	if err != nil {
+		return false, errors.Wrap(err, "CEL program plan")
+	}
+
+	// Convert our Function Request into map[string]any for CEL evaluation
+	vars := ToCELVars(req)
+
+	// Evaluate the program without any additional arguments.
+	result, _, err := program.Eval(vars)
+	if err != nil {
+		return false, errors.Wrap(err, "CEL program Evaluation")
+	}
+
+	ret, ok := result.Value().(bool)
+	if !ok {
+		return false, errors.Wrap(err, "CEL program did not return a bool")
+	}
+
+	return ret, nil
+}