allowing on cluster build for go runtime

docs/building-functions/on_cluster_build.md

@@ -34,12 +34,16 @@ git remote add origin git@github.com:my-repo/my-function.git
 ```
 4. Update the Function configuration in `func.yaml` to enable on cluster builds for the Git repository:
 ```yaml
-build: git                                          # required, specify `git` build type
-git:
-  url: https://github.com/my-repo/my-function.git   # required, git repository with the function source code
-  revision: main                                    # optional, git revision to be used (branch, tag, commit)
-  # contextDir: myfunction                          # optional, needed only if the function is not located
-                                                    # in the repository root folder
+build:
+  git:
+    url: https://github.com/my-repo/my-function.git   # required, git repository with the function source code
+    revision: main                                    # optional, git revision to be used (branch, tag, commit)
+    # contextDir: myfunction                          # optional, needed only if the function is not located in the repository root folder
+  # builderImages:                                    # optional, needed only if the runtime is golang
+  #   pack: ghcr.io/boson-project/go-function-builder:tip
+  buildpacks: []
+  builder: ""
+  buildEnvs: []
 ```
 5. Implement the business logic of your Function, then commit and push changes
 ```bash

pkg/pipelines/tekton/pipelines_pac_provider.go

@@ -30,9 +30,14 @@ func (pp *PipelinesProvider) ConfigurePAC(ctx context.Context, f fn.Function, me
 		return fmt.Errorf("incorrect type of pipelines metadata: %T", metadata)
 	}
 
-	if err := validatePipeline(f); err != nil {
+	var warningMsg string
+	var err error
+	if warningMsg, err = validatePipeline(f); err != nil {
 		return err
 	}
+	if warningMsg != "" {
+		pp.progressListener.Increment(warningMsg)
+	}
 
 	if data.ConfigureLocalResources {
 		if err := pp.createLocalPACResources(ctx, f); err != nil {

pkg/pipelines/tekton/pipelines_provider.go

@@ -118,10 +118,14 @@ func NewPipelinesProvider(opts ...Opt) *PipelinesProvider {
 // After the PipelineRun is being initialized, the progress of the PipelineRun is being watched and printed to the output.
 func (pp *PipelinesProvider) Run(ctx context.Context, f fn.Function) error {
 	pp.progressListener.Increment("Creating Pipeline resources")
-
-	if err := validatePipeline(f); err != nil {
+	var warningMsg string
+	var err error
+	if warningMsg, err = validatePipeline(f); err != nil {
 		return err
 	}
+	if warningMsg != "" {
+		pp.progressListener.Increment(warningMsg)
+	}
 
 	client, namespace, err := NewTektonClientAndResolvedNamespace(pp.namespace)
 	if err != nil {

pkg/pipelines/tekton/validate.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 
 	"knative.dev/func/pkg/builders"
+	"knative.dev/func/pkg/builders/buildpacks"
 	"knative.dev/func/pkg/builders/s2i"
 	fn "knative.dev/func/pkg/functions"
 )
@@ -21,28 +22,36 @@ type ErrRuntimeNotSupported struct {
 }
 
 func (e ErrRuntimeNotSupported) Error() string {
-	return fmt.Sprintf("runtime %q is not supported for on cluster build", e.Runtime)
+	return fmt.Sprintf("runtime %q is not supported for on cluster build with default builders", e.Runtime)
 }
 
-func validatePipeline(f fn.Function) error {
+func validatePipeline(f fn.Function) (string, error) {
+	var warningMsg string
 	if f.Build.Builder == builders.Pack {
 		if f.Runtime == "" {
-			return ErrRuntimeRequired
+			return "", ErrRuntimeRequired
 		}
 
 		if f.Runtime == "go" || f.Runtime == "rust" {
-			return ErrRuntimeNotSupported{f.Runtime}
+			builder := f.Build.BuilderImages[builders.Pack]
+			defaultBuilder := buildpacks.DefaultBuilderImages[f.Runtime]
+			if builder != "" && builder != defaultBuilder {
+				warningMsg = fmt.Sprintf("runtime %q is not supported for on cluster build with default builders, "+
+					"continuing with the custom builder provided", f.Runtime)
+			} else {
+				return "", ErrRuntimeNotSupported{f.Runtime}
+			}
 		}
 
 		if len(f.Build.Buildpacks) > 0 {
-			return ErrBuilpacksNotSupported
+			return "", ErrBuilpacksNotSupported
 		}
 	} else if f.Build.Builder == builders.S2I {
 		_, err := s2i.BuilderImage(f, builders.S2I)
-		return err
+		return "", err
 	} else {
-		return builders.ErrUnknownBuilder{Name: f.Build.Builder}
+		return "", builders.ErrUnknownBuilder{Name: f.Build.Builder}
 	}
 
-	return nil
+	return warningMsg, nil
 }

pkg/pipelines/tekton/validate_test.go

@@ -108,7 +108,7 @@ func Test_validatePipeline(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			err := validatePipeline(tt.function)
+			_, err := validatePipeline(tt.function)
 			if (err != nil) != tt.wantErr {
 				t.Errorf("validatePipeline() error = %v, wantErr %v", err, tt.wantErr)
 				return