Keep what was typed when a target or webhook edit is refused (closes #381)

A refused save on the target edit page answered with a bare text page, losing the form and everything typed, and the webhook edit page came back with the stored values instead of the submitted ones. A refused target edit now shows the edit form again with the reason above it and every value submitted, with the same status codes as before; a refused webhook edit keeps the submitted name, description and retention. Target edits use the same validation as new targets, with no second copy; an encoding or database failure stays a logged 500. The browser test covers a refused save on both pages, and its main function is now a plain list of checks.

Model: opus-5-5

internal/handlers/source_management.go

@@ -616,13 +616,13 @@ func (h *Handlers) renderSourceDetail(
 		// Targets are projected to a display-safe view: a
 		// target's stored config blob holds a credential, and it
 		// must never reach a template.
-		"Entrypoints": entrypointViews,
-		"Targets":     h.targetRows(&webhook, targets),
-		"Events":      events,
-		"BaseURL":     baseURL,
-		"Stats":       h.loadWebhookStats(webhook.ID, entrypoints, targets),
-		"TargetForm":  targetForm,
-		"TargetError": targetErr,
+		"Entrypoints":     entrypointViews,
+		"Targets":         h.targetRows(&webhook, targets),
+		"Events":          events,
+		"BaseURL":         baseURL,
+		"Stats":           h.loadWebhookStats(webhook.ID, entrypoints, targets),
+		tmplKeyTargetForm: targetForm,
+		"TargetError":     targetErr,
 	}
 
 	status := http.StatusOK
@@ -658,12 +658,12 @@ func (h *Handlers) HandleSourceEdit() http.HandlerFunc {
 			return
 		}
 
-		data := map[string]any{
-			tmplKeyWebhook: &webhook,
-			tmplKeyError:   "",
-		}
-
-		h.renderTemplate(w, r, "source_edit.html", data)
+		h.renderWebhookEdit(
+			w, r, &webhook,
+			webhook.Name, webhook.Description,
+			strconv.Itoa(webhook.RetentionDays),
+			"", http.StatusOK,
+		)
 	}
 }
 
@@ -709,7 +709,8 @@ func (h *Handlers) HandleSourceEditSubmit() http.HandlerFunc {
 	}
 }
 
-// applyWebhookEdit validates and saves webhook edits.
+// applyWebhookEdit validates and saves webhook edits. A refused save
+// shows the edit form again with the values submitted and the reason.
 func (h *Handlers) applyWebhookEdit(
 	w http.ResponseWriter,
 	r *http.Request,
@@ -718,52 +719,52 @@ func (h *Handlers) applyWebhookEdit(
 	// The body size cap is enforced by the MaxBodySize middleware,
 	// which runs before CSRF parses the form.
 	name := r.PostFormValue("name")
-	if name == "" {
-		data := map[string]any{
-			tmplKeyWebhook: webhook,
-			tmplKeyError:   "Name is required",
-		}
+	description := r.PostFormValue("description")
+	retention := r.PostFormValue("retention_days")
 
-		h.renderTemplateStatus(w, r, "source_edit.html", data, http.StatusBadRequest)
+	if name == "" {
+		h.renderWebhookEdit(
+			w, r, webhook, name, description, retention,
+			"Name is required", http.StatusBadRequest,
+		)
 
 		return
 	}
 
-	oldName := webhook.Name
-	webhook.Name = name
-	webhook.Description = r.PostFormValue("description")
-
 	// An empty field falls back to the stored value, so submitting the
 	// form without touching retention leaves the policy alone.
 	retentionDays, errMsg := parseRetentionDays(
-		r.PostFormValue("retention_days"), webhook.RetentionDays,
+		retention, webhook.RetentionDays,
 	)
 	if errMsg != "" {
-		data := map[string]any{
-			tmplKeyWebhook: webhook,
-			tmplKeyError:   errMsg,
-		}
-
-		h.renderTemplateStatus(w, r, "source_edit.html", data, http.StatusBadRequest)
+		h.renderWebhookEdit(
+			w, r, webhook, name, description, retention,
+			errMsg, http.StatusBadRequest,
+		)
 
 		return
 	}
 
-	webhook.RetentionDays = retentionDays
+	// edited is the webhook as the submission leaves it; webhook stays
+	// as stored, for the page shown again when the save is refused.
+	edited := *webhook
+	edited.Name = name
+	edited.Description = description
+	edited.RetentionDays = retentionDays
 
 	// A new name renames the archive files before it is saved (see
 	// delivery.Engine.Rename). If either step fails, the same targets'
 	// archives go back to the name that is still stored, without
 	// reading the main database again.
 	targets, err := h.renameWebhookArchives(
-		webhook.ID, oldName, webhook.Name,
+		webhook.ID, webhook.Name, edited.Name,
 	)
 	if err == nil {
-		err = h.db.DB().Save(webhook).Error
+		err = h.db.DB().Save(&edited).Error
 	}
 
 	if err != nil {
-		restoreErr := h.renameArchives(targets, oldName)
+		restoreErr := h.renameArchives(targets, webhook.Name)
 		if restoreErr != nil {
 			h.log.Error(
 				"failed to rename archives back",
@@ -773,15 +774,14 @@ func (h *Handlers) applyWebhookEdit(
 		}
 
 		if errors.Is(err, delivery.ErrArchiveNameTaken) {
-			data := map[string]any{
-				tmplKeyWebhook: webhook,
-				tmplKeyError: "Not saved: " + err.Error() +
-					". Move that archive out of the data directory, " +
-					"its .db together with any -wal and -shm beside " +
+			h.renderWebhookEdit(
+				w, r, webhook, name, description, retention,
+				"Not saved: "+err.Error()+
+					". Move that archive out of the data directory, "+
+					"its .db together with any -wal and -shm beside "+
 					"it, then save again.",
-			}
-
-			h.renderTemplateStatus(w, r, "source_edit.html", data, http.StatusConflict)
+				http.StatusConflict,
+			)
 
 			return
 		}
@@ -797,6 +797,27 @@ func (h *Handlers) applyWebhookEdit(
 	)
 }
 
+// renderWebhookEdit renders the webhook edit page for the webhook as
+// stored, its form showing name, description and retentionDays, with
+// an optional error message above it.
+func (h *Handlers) renderWebhookEdit(
+	w http.ResponseWriter,
+	r *http.Request,
+	webhook *database.Webhook,
+	name, description, retentionDays, errMsg string,
+	status int,
+) {
+	data := map[string]any{
+		tmplKeyWebhook:  webhook,
+		tmplKeyError:    errMsg,
+		"Name":          name,
+		"Description":   description,
+		"RetentionDays": retentionDays,
+	}
+
+	h.renderTemplateStatus(w, r, "source_edit.html", data, status)
+}
+
 // HandleSourceDelete handles webhook deletion.
 func (h *Handlers) HandleSourceDelete() http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
@@ -1668,49 +1689,57 @@ func (h *Handlers) newTarget(
 	webhookID string,
 	in targetFormInput,
 ) (*database.Target, string, error) {
-	if in.Name == "" {
-		return nil, "Name is required", nil
+	target := &database.Target{
+		WebhookID: webhookID,
+		Type:      in.Type,
+		Active:    true,
 	}
 
-	if !isValidTargetType(in.Type) {
-		return nil, "Invalid target type", nil
-	}
-
-	configJSON, errMsg, err := h.buildTargetConfig(ctx, in.Type, in)
+	errMsg, err := h.setTargetFromForm(ctx, target, in)
 	if err != nil || errMsg != "" {
 		return nil, errMsg, err
 	}
 
-	// A new target has no stored retry count, so an absent field
-	// takes the fire-and-forget default. A field the operator filled
-	// in with something invalid is refused rather than becoming
-	// that default.
-	maxRetries, err := parseMaxRetries(in.MaxRetries, 0)
-	if err != nil {
-		return nil, "Invalid max retries: " + retriesErrorMessage(err), nil
-	}
-
-	return &database.Target{
-		WebhookID:  webhookID,
-		Name:       in.Name,
-		Type:       in.Type,
-		Active:     true,
-		Config:     configJSON,
-		MaxRetries: maxRetries,
-	}, "", nil
+	return target, "", nil
 }
 
-// isValidTargetType checks whether the target type is supported.
-func isValidTargetType(tt database.TargetType) bool {
-	switch tt {
-	case database.TargetTypeHTTP,
-		database.TargetTypeDatabase,
-		database.TargetTypeLog,
-		database.TargetTypeSlack:
-		return true
-	default:
-		return false
+// setTargetFromForm validates a target form against the target's type
+// and, when it accepts it, sets the target's name, configuration and
+// retry count from it. It returns the message the form shows for
+// anything it refuses, an unknown type among them, and then leaves the
+// target unchanged; an error is the server's fault, as for newTarget.
+// The add target form and the target edit form both go through here,
+// so the two cannot come to disagree about what a target may be.
+func (h *Handlers) setTargetFromForm(
+	ctx context.Context,
+	target *database.Target,
+	in targetFormInput,
+) (string, error) {
+	if in.Name == "" {
+		return "Name is required", nil
 	}
+
+	configJSON, errMsg, err := h.buildTargetConfig(ctx, target.Type, in)
+	if err != nil || errMsg != "" {
+		return errMsg, err
+	}
+
+	// An empty max_retries keeps the target's count: the
+	// fire-and-forget default of 0 for a new target, and the stored
+	// count for an edited one, since the forms for target types that
+	// do not retry have no such field. A value that is filled in but
+	// invalid is refused rather than becoming that count, so a typo
+	// cannot destroy the count a target is delivering with.
+	maxRetries, err := parseMaxRetries(in.MaxRetries, target.MaxRetries)
+	if err != nil {
+		return "Invalid max retries: " + retriesErrorMessage(err), nil
+	}
+
+	target.Name = in.Name
+	target.Config = configJSON
+	target.MaxRetries = maxRetries
+
+	return "", nil
 }
 
 // pageOrFirst parses a paginated page number, answering 1 for
@@ -1732,9 +1761,10 @@ func pageOrFirst(s string) int {
 }
 
 // targetFormInput carries the raw values of a target form. Both the
-// create and the edit path fill one and hand it to buildTargetConfig,
-// so neither can come to validate a destination differently from the
-// other. A refused add target form is shown again from it.
+// create and the edit path fill one and hand it to setTargetFromForm,
+// so neither can come to validate a target differently from the
+// other. Both forms are filled from one: the edit form with the
+// stored values, and a refused form with the values submitted.
 type targetFormInput struct {
 	// Name is the target's name.
 	Name string