Keep each model's parent out of its JSON (closes #177)

Every reference from a model to the record it belongs to is now
json:"-", so the webhook and target models (and the other parent and
child pairs in internal/database) can no longer marshal each other in
a loop. Preloading maps associations without reading json tags, so it
still fills these references. One test preloads a webhook with its
targets and entrypoints and a target with its webhook, checks the
references are filled, and checks the JSON leaves them out; another
builds each other model with its parent set and checks the parent's
id is absent from its JSON.

Model: opus-5-5

internal/database/model_apikey.go

@@ -15,6 +15,7 @@ type APIKey struct {
 	Description string     `json:"description"`
 	LastUsedAt  *time.Time `json:"lastUsedAt,omitempty"`
 
-	// Relations
-	User User `json:"user,omitzero"`
+	// Relations. No model marshals the record it belongs to:
+	// User.APIKeys leads back here, and the JSON could loop.
+	User User `json:"-"`
 }

internal/database/model_delivery.go

@@ -56,8 +56,10 @@ type Delivery struct {
 	// the index.
 	FinishedAt *time.Time `gorm:"index:idx_deliveries_status,priority:3" json:"finishedAt,omitempty"`
 
-	// Relations
-	Event           Event            `json:"event,omitzero"`
-	Target          Target           `json:"target,omitzero"`
+	// Relations. No model marshals the record it belongs to:
+	// Event.Deliveries and Target.Deliveries lead back here, and the
+	// JSON could loop.
+	Event           Event            `json:"-"`
+	Target          Target           `json:"-"`
 	DeliveryResults []DeliveryResult `json:"deliveryResults,omitempty"`
 }

internal/database/model_delivery_result.go

@@ -23,6 +23,7 @@ type DeliveryResult struct {
 	Error        string `json:"error,omitempty"`
 	Duration     int64  `json:"durationMs"` // Duration in milliseconds
 
-	// Relations
-	Delivery Delivery `json:"delivery,omitzero"`
+	// Relations. No model marshals the record it belongs to:
+	// Delivery.DeliveryResults leads back here, and the JSON could loop.
+	Delivery Delivery `json:"-"`
 }

internal/database/model_entrypoint.go

@@ -15,6 +15,7 @@ type Entrypoint struct {
 	Description string `json:"description"`
 	Active      bool   `gorm:"default:true" json:"active"`
 
-	// Relations
-	Webhook Webhook `json:"webhook,omitzero"`
+	// Relations. No model marshals the record it belongs to:
+	// Webhook.Entrypoints leads back here, and the JSON could loop.
+	Webhook Webhook `json:"-"`
 }

internal/database/model_event.go

@@ -44,8 +44,9 @@ type Event struct {
 	// kept as the record of where the copy came from either way.
 	ResubmittedFromID *string `gorm:"type:uuid;index" json:"resubmittedFromId,omitempty"`
 
-	// Relations
-	Webhook    Webhook    `json:"webhook,omitzero"`
-	Entrypoint Entrypoint `json:"entrypoint,omitzero"`
+	// Relations. No model marshals the record it belongs to, so
+	// Webhook and Entrypoint are left out of the JSON.
+	Webhook    Webhook    `json:"-"`
+	Entrypoint Entrypoint `json:"-"`
 	Deliveries []Delivery `json:"deliveries,omitempty"`
 }

internal/database/model_parent_test.go

@@ -0,0 +1,120 @@
+package database_test
+
+import (
+	"testing"
+
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"sneak.berlin/go/webhooker/internal/database"
+)
+
+// TestPreloadedModelsMarshalWithoutTheirParent pins that a child's
+// reference to the record it belongs to is left out of the JSON, so a
+// webhook and its targets cannot marshal each other in a loop, and that
+// GORM still preloads that reference, since it ignores json tags.
+func TestPreloadedModelsMarshalWithoutTheirParent(t *testing.T) {
+	t.Parallel()
+
+	db := startedTestDB(t)
+
+	stored := database.Webhook{
+		UserID:      uuid.New().String(),
+		Name:        testWebhookName,
+		Entrypoints: []database.Entrypoint{{Path: uuid.New().String()}},
+		Targets: []database.Target{{
+			Name: "log",
+			Type: database.TargetTypeLog,
+		}},
+	}
+	require.NoError(t, db.Create(&stored).Error)
+
+	entrypointID := stored.Entrypoints[0].ID
+	targetID := stored.Targets[0].ID
+
+	var webhook database.Webhook
+
+	require.NoError(t, db.
+		Preload("Entrypoints.Webhook").
+		Preload("Targets.Webhook").
+		First(&webhook, "id = ?", stored.ID).Error)
+
+	require.Len(t, webhook.Entrypoints, 1)
+	require.Len(t, webhook.Targets, 1)
+	assert.Equal(t, stored.ID, webhook.Entrypoints[0].Webhook.ID)
+	assert.Equal(t, stored.ID, webhook.Targets[0].Webhook.ID)
+
+	encoded := marshalModel(t, webhook)
+
+	assert.Contains(t, encoded, entrypointID)
+	assert.Contains(t, encoded, targetID)
+	assert.NotContains(t, encoded, `"webhook":`)
+
+	var target database.Target
+
+	require.NoError(t, db.
+		Preload("Webhook").
+		First(&target, "id = ?", targetID).Error)
+
+	assert.Equal(t, stored.ID, target.Webhook.ID)
+
+	encoded = marshalModel(t, target)
+
+	assert.Contains(t, encoded, stored.ID)
+	assert.NotContains(t, encoded, `"webhook":`)
+}
+
+// TestModelsMarshalWithoutTheirParent covers the other references to a
+// parent: each model is built with its parent set, and the parent's id
+// must not appear in the JSON.
+func TestModelsMarshalWithoutTheirParent(t *testing.T) {
+	t.Parallel()
+
+	parent := database.BaseModel{ID: uuid.New().String()}
+
+	cases := []struct {
+		name  string
+		model any
+	}{
+		{
+			name:  "Webhook.User",
+			model: database.Webhook{User: database.User{BaseModel: parent}},
+		},
+		{
+			name:  "APIKey.User",
+			model: database.APIKey{User: database.User{BaseModel: parent}},
+		},
+		{
+			name:  "Delivery.Event",
+			model: database.Delivery{Event: database.Event{BaseModel: parent}},
+		},
+		{
+			name:  "Delivery.Target",
+			model: database.Delivery{Target: database.Target{BaseModel: parent}},
+		},
+		{
+			name: "DeliveryResult.Delivery",
+			model: database.DeliveryResult{
+				Delivery: database.Delivery{BaseModel: parent},
+			},
+		},
+		{
+			name:  "Event.Webhook",
+			model: database.Event{Webhook: database.Webhook{BaseModel: parent}},
+		},
+		{
+			name: "Event.Entrypoint",
+			model: database.Event{
+				Entrypoint: database.Entrypoint{BaseModel: parent},
+			},
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			assert.NotContains(t, marshalModel(t, tc.model), parent.ID)
+		})
+	}
+}

internal/database/model_target.go

@@ -34,7 +34,8 @@ type Target struct {
 	MaxRetries   int `json:"maxRetries,omitempty"`
 	MaxQueueSize int `json:"maxQueueSize,omitempty"`
 
-	// Relations
-	Webhook    Webhook    `json:"webhook,omitzero"`
+	// Relations. No model marshals the record it belongs to:
+	// Webhook.Targets leads back here, and the JSON could loop.
+	Webhook    Webhook    `json:"-"`
 	Deliveries []Delivery `json:"deliveries,omitempty"`
 }

internal/database/model_webhook.go

@@ -66,8 +66,9 @@ type Webhook struct {
 	// must equal DefaultRetentionDays.
 	RetentionDays int `gorm:"default:30" json:"retentionDays"`
 
-	// Relations
-	User        User         `json:"user,omitzero"`
+	// Relations. No model marshals the record it belongs to:
+	// User.Webhooks leads back here, and the JSON could loop.
+	User        User         `json:"-"`
 	Entrypoints []Entrypoint `json:"entrypoints,omitempty"`
 	Targets     []Target     `json:"targets,omitempty"`
 }