feat:scaffolding-go

Author: gauron99

pkg/builders/buildpacks/builder.go

@@ -23,20 +23,25 @@ import (
 	"knative.dev/func/pkg/builders"
 	"knative.dev/func/pkg/docker"
 	fn "knative.dev/func/pkg/functions"
+	"knative.dev/func/pkg/scaffolding"
 )
 
 // DefaultName when no WithName option is provided to NewBuilder
 const DefaultName = builders.Pack
 
 var DefaultBaseBuilder = "ghcr.io/knative/builder-jammy-base:latest"
+
+// var DefaultGoBaseBuilder = "paketobuildpacks/builder-jammy-base:latest"
+
 var DefaultTinyBuilder = "ghcr.io/knative/builder-jammy-tiny:latest"
+var DefaultGoTinyBuilder = "paketobuildpacks/builder-jammy-tiny:latest"
 
 var (
 	DefaultBuilderImages = map[string]string{
 		"node":       DefaultBaseBuilder,
 		"nodejs":     DefaultBaseBuilder,
 		"typescript": DefaultBaseBuilder,
-		"go":         DefaultTinyBuilder,
+		"go":         DefaultGoTinyBuilder,
 		"python":     DefaultBaseBuilder,
 		"quarkus":    DefaultTinyBuilder,
 		"rust":       DefaultBaseBuilder,
@@ -134,7 +139,6 @@ func (b *Builder) Build(ctx context.Context, f fn.Function, platforms []fn.Platf
 	if len(buildpacks) == 0 {
 		buildpacks = defaultBuildpacks[f.Runtime]
 	}
-
 	// Reading .funcignore file
 	var excludes []string
 	filePath := filepath.Join(f.Root, ".funcignore")
@@ -171,6 +175,16 @@ func (b *Builder) Build(ctx context.Context, f fn.Function, platforms []fn.Platf
 			Volumes []string
 		}{Network: "", Volumes: nil},
 	}
+
+	// NOTE: gauron99 - this might be even created into a Client function and
+	// ran before the client.Build() all together (in the CLI). There are gonna
+	// be commonalitites across the builders for scaffolding with some nuances
+	// which could be handled by each "scaffolder" - similarly to builders.
+	// scaffold
+	if err = scaffold(f); err != nil {
+		return
+	}
+
 	if b.withTimestamp {
 		now := time.Now()
 		opts.CreationTime = &now
@@ -186,6 +200,12 @@ func (b *Builder) Build(ctx context.Context, f fn.Function, platforms []fn.Platf
 		opts.Env["BPE_DEFAULT_LISTEN_ADDRESS"] = "[::]:8080"
 	}
 
+	if f.Runtime == "go" {
+		if _, ok := opts.Env["BP_GO_WORKDIR"]; !ok {
+			opts.Env["BP_GO_WORKDIR"] = ".func/builds/last"
+		}
+	}
+
 	var bindings = make([]string, 0, len(f.Build.Mounts))
 	for _, m := range f.Build.Mounts {
 		bindings = append(bindings, fmt.Sprintf("%s:%s", m.Source, m.Destination))
@@ -312,3 +332,34 @@ type ErrRuntimeNotSupported struct {
 func (e ErrRuntimeNotSupported) Error() string {
 	return fmt.Sprintf("Pack builder has no default builder image for the '%v' language runtime.  Please provide one.", e.Runtime)
 }
+
+// TODO: gauron99 - unify this with other builders; temporary for the go pack
+// to work for release.
+//
+// scaffold the project
+// Returns a config with settings suitable for building runtimes which
+// support scaffolding.
+func scaffold(f fn.Function) error {
+	// Scafffolding is currently only supported by the Go and Python runtimes
+	if f.Runtime != "go" && f.Runtime != "python" {
+		return nil
+	}
+
+	contextDir := filepath.Join(".func", "builds", "last")
+	appRoot := filepath.Join(f.Root, contextDir)
+	_ = os.RemoveAll(appRoot)
+
+	// The enbedded repository contains the scaffolding code itself which glues
+	// together the middleware and a function via main
+	embeddedRepo, err := fn.NewRepository("", "") // default is the embedded fs
+	if err != nil {
+		return fmt.Errorf("unable to load the embedded scaffolding. %w", err)
+	}
+
+	// Write scaffolding to .func/builds/last
+	err = scaffolding.Write(appRoot, f.Root, f.Runtime, f.Invoke, embeddedRepo.FS())
+	if err != nil {
+		return fmt.Errorf("unable to build due to a scaffold error. %w", err)
+	}
+	return nil
+}

pkg/builders/buildpacks/builder_test.go

@@ -86,11 +86,11 @@ func TestBuild_BuildpacksDefault(t *testing.T) {
 	var (
 		i = &mockImpl{}
 		b = NewBuilder(WithImpl(i))
-		f = fn.Function{Runtime: "go"}
+		f = fn.Function{Runtime: "node"}
 	)
 
 	i.BuildFn = func(ctx context.Context, opts pack.BuildOptions) error {
-		expected := defaultBuildpacks["go"]
+		expected := defaultBuildpacks["node"]
 		if !reflect.DeepEqual(expected, opts.Buildpacks) {
 			t.Fatalf("expected buildpacks '%v', got '%v'", expected, opts.Buildpacks)
 		}
@@ -141,7 +141,7 @@ func TestBuild_BuilderImageExclude(t *testing.T) {
 		b = NewBuilder( // Func Builder logic
 			WithName(builders.Pack), WithImpl(i))
 		f = fn.Function{
-			Runtime: "go",
+			Runtime: "node",
 		}
 	)
 	funcIgnoreContent := []byte(`#testing comments

pkg/creds/auth.json

@@ -0,0 +1,3 @@
+{
+    "credsStore": ""
+}

pkg/functions/testdata/default_home/.config/go/telemetry/local/asm@go1.24.0-go1.24.0-linux-amd64-2025-10-05.v1.count

@@ -0,0 +1 @@
+6

pkg/functions/testdata/default_home/.config/go/telemetry/local/compile@go1.24.0-go1.24.0-linux-amd64-2025-10-05.v1.count

@@ -0,0 +1 @@
+/var/example/absolute/link