From b8084080cb86e3aa9c6eb2285a7d20ae6913748e Mon Sep 17 00:00:00 2001
From: Jakub Zych <jakub@keios.eu>
Date: Thu, 1 Oct 2026 21:05:33 +0200
Subject: [PATCH] fix(09): WR-04 apply a form field's required flag only in the
 contexts that can supply it

---
 modules/cabana/crud.go      |  9 ++++++---
 modules/cabana/crud_test.go | 29 +++++++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/modules/cabana/crud.go b/modules/cabana/crud.go
index d89bb84..c64f926 100644
--- a/modules/cabana/crud.go
+++ b/modules/cabana/crud.go
@@ -335,7 +335,7 @@ func (s CRUDService) save(ctx context.Context, cc *CompiledController, id any, i
 				return &CapabilityError{ControllerID: controllerID(cc)}
 			}
 		}
-		rules := mergedRules(cc, target)
+		rules := mergedRules(cc, target, op)
 		msgs, err := lagoon.Validate(ctx, tx, target, rules, valuesForRules(target, rules), nil)
 		if err != nil {
 			return &CapabilityError{ControllerID: controllerID(cc)}
@@ -689,7 +689,10 @@ func fillAllowed(cc *CompiledController, model any, op string) []string {
 	return out
 }
 
-func mergedRules(cc *CompiledController, model any) map[string]string {
+// mergedRules combines the model's rules with the form's `required` flags. A
+// field whose `context` hides it on op cannot be supplied there, so its form
+// level `required` does not apply to that operation.
+func mergedRules(cc *CompiledController, model any, op string) map[string]string {
 	out := map[string]string{}
 	if rules, ok := model.(hasRules); ok && rules != nil {
 		for key, rule := range rules.Rules() {
@@ -702,7 +705,7 @@ func mergedRules(cc *CompiledController, model any) map[string]string {
 	for _, field := range cc.Form.Fields {
 		// Relation fields are not writable columns. required stays on the
 		// schema for the client, but it cannot be checked by Fill.
-		if field.Required && scalarFormField(field.Type) {
+		if field.Required && scalarFormField(field.Type) && contextAllows(cc, field.Name, op) {
 			out[field.Name] = mergeRequired(out[field.Name])
 		}
 	}
diff --git a/modules/cabana/crud_test.go b/modules/cabana/crud_test.go
index fa7d2a0..80faca2 100644
--- a/modules/cabana/crud_test.go
+++ b/modules/cabana/crud_test.go
@@ -608,3 +608,32 @@ func TestIsJSONScalar(t *testing.T) {
 type scalarAsArray string
 
 func (s scalarAsArray) MarshalJSON() ([]byte, error) { return json.Marshal([]string{string(s)}) }
+
+// TestCRUDRequiredFollowsContext pins WR-04: a form field that is `required`
+// but limited to the update context cannot be supplied on create, so it must
+// not make every create fail; it still binds on update.
+func TestCRUDRequiredFollowsContext(t *testing.T) {
+	svc, cc, db := crudFixture(t)
+	for i := range cc.Form.Fields {
+		if cc.Form.Fields[i].Name == "note" {
+			cc.Form.Fields[i].Required = true
+			cc.Form.Fields[i].Context = &fieldContext{values: []string{"update"}}
+		}
+	}
+	created, err := svc.CreateRecord(context.Background(), cc, RecordInput{Body: crudBody(t, `{"name":"Ada"}`)})
+	if err != nil {
+		t.Fatalf("create with an update-only required field: %v", err)
+	}
+	id := created.Data["id"]
+	if _, err := svc.UpdateRecord(context.Background(), cc, id, RecordInput{Body: crudBody(t, `{"name":"Bea"}`)}); err == nil {
+		t.Fatal("update without the required update-context field succeeded")
+	} else {
+		assertValidation(t, err, "note", "The note field is required.")
+	}
+	if _, err := svc.UpdateRecord(context.Background(), cc, id, RecordInput{Body: crudBody(t, `{"name":"Bea","note":"n"}`)}); err != nil {
+		t.Fatalf("update with the field: %v", err)
+	}
+	if row := loadCrud(t, db, "Bea"); row.Note != "n" {
+		t.Fatalf("row=%+v", row)
+	}
+}