fix: preserve registry on OpenShift redeploy

cmd/deploy.go

@@ -291,9 +291,7 @@ func runDeploy(cmd *cobra.Command, newClient ClientFactory) (err error) {
 	// also update the registry because there is a registry per namespace,
 	// and their name includes the namespace.
 	// This saves needing a manual flag ``--registry={destination namespace registry}``
-	if changingNamespace(f) && k8s.IsOpenShift() {
-		// TODO(lkingland): this appears to force use of the openshift
-		// internal registry.
+	if changingNamespace(f) && k8s.IsOpenShift() && k8s.IsOpenShiftInternalRegistry(f.Registry) {
 		f.Registry = "image-registry.openshift-image-registry.svc:5000/" + f.Namespace
 		if cfg.Verbose {
 			fmt.Fprintf(cmd.OutOrStdout(), "Info: Overriding openshift registry to %s\n", f.Registry)

pkg/config/config.go

@@ -154,7 +154,15 @@ func (c Global) Configure(f fn.Function) fn.Function {
 		f.Deploy.Namespace = c.Namespace
 	}
 	if c.Registry != "" {
-		f.Registry = c.Registry
+		// Apply the config registry unless it's an auto-detected OpenShift
+		// internal registry that would overwrite a user-configured external
+		// registry. This prevents OpenShift auto-detection (via RegistryDefault)
+		// from silently overriding a previously stored registry on redeploy.
+		// Explicit sources (--registry flag, FUNC_REGISTRY env, global config)
+		// set non-OpenShift values and are always applied.
+		if f.Registry == "" || !k8s.IsOpenShiftInternalRegistry(c.Registry) {
+			f.Registry = c.Registry
+		}
 	}
 	return f
 }

pkg/config/config_test.go

@@ -269,6 +269,31 @@ func TestConfigure(t *testing.T) {
 		t.Error("empty cfg.Registry should not mutate f")
 	}
 
+	// An auto-detected OpenShift internal registry should not overwrite
+	// a function's stored external registry. This is the key guard for
+	// https://github.com/knative/func/issues/2172
+	f = fn.Function{Registry: "docker.io/user"}
+	cfg = config.Global{Registry: "image-registry.openshift-image-registry.svc:5000/ns"}
+	f = cfg.Configure(f)
+	if f.Registry != "docker.io/user" {
+		t.Errorf("auto-detected OpenShift registry should not overwrite stored external registry, got %q", f.Registry)
+	}
+
+	// But when the function has no registry yet, the OpenShift default should apply.
+	f = fn.Function{}
+	f = cfg.Configure(f)
+	if f.Registry != "image-registry.openshift-image-registry.svc:5000/ns" {
+		t.Errorf("OpenShift registry should be applied when function has no registry, got %q", f.Registry)
+	}
+
+	// An explicit (non-OpenShift) registry in config should always apply,
+	// even when the function already has a registry.
+	f = fn.Function{Registry: "docker.io/user"}
+	cfg = config.Global{Registry: "quay.io/org"}
+	f = cfg.Configure(f)
+	if f.Registry != "quay.io/org" {
+		t.Errorf("explicit config registry should override function registry, got %q", f.Registry)
+	}
 }
 
 // TestGet_Invalid ensures that attempting to get the value of a nonexistent

pkg/k8s/openshift.go

@@ -5,6 +5,7 @@ import (
 	"crypto/x509"
 	"encoding/pem"
 	"errors"
+	"strings"
 	"sync"
 	"time"
 
@@ -93,6 +94,12 @@ func GetDefaultOpenShiftRegistry() string {
 	return openShiftRegistryHostPort + "/" + ns
 }
 
+// IsOpenShiftInternalRegistry returns true if the given registry string
+// refers to the OpenShift internal image registry.
+func IsOpenShiftInternalRegistry(registry string) bool {
+	return strings.HasPrefix(registry, openShiftRegistryHost)
+}
+
 func GetOpenShiftDockerCredentialLoaders() []creds.CredentialsCallback {
 	conf := GetClientConfig()
 

pkg/k8s/openshift_unit_test.go

@@ -0,0 +1,26 @@
+package k8s
+
+import "testing"
+
+func TestIsOpenShiftInternalRegistry(t *testing.T) {
+	tests := []struct {
+		name     string
+		registry string
+		want     bool
+	}{
+		{"internal with port and namespace", "image-registry.openshift-image-registry.svc:5000/mynamespace", true},
+		{"internal without port", "image-registry.openshift-image-registry.svc/mynamespace", true},
+		{"internal host only", "image-registry.openshift-image-registry.svc", true},
+		{"docker.io", "docker.io/user", false},
+		{"ghcr.io", "ghcr.io/user", false},
+		{"quay.io", "quay.io/user", false},
+		{"empty string", "", false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := IsOpenShiftInternalRegistry(tt.registry); got != tt.want {
+				t.Errorf("IsOpenShiftInternalRegistry(%q) = %v, want %v", tt.registry, got, tt.want)
+			}
+		})
+	}
+}