Scholar plugin auto-creates page record and shows 404 when disabled

- OnInit ensures a research page exists in the pages table with
  default title, slug, nav settings. Users can customize these
  via the admin page editor.
- Migrates ScholarID from legacy page field to plugin settings
  for backward compatibility with existing installs.
- When the scholar plugin is disabled, visiting the research page
  shows a "Page Not Available" 404 instead of an empty content page.
- Added HasPageType to registry to distinguish "plugin disabled" from
  "no plugin for this page type".

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: compscidr

blog/blog.go

@@ -486,10 +486,11 @@ func (b *Blog) DynamicPage(c *gin.Context, page *Page) {
 	default:
 		// Check if a plugin handles this page type
 		if reg, exists := c.Get("plugin_registry"); exists {
-			type pageRenderer interface {
+			type pluginPageHandler interface {
 				RenderPluginPage(c *gin.Context, pageType string) (string, gin.H, bool)
+				HasPageType(pageType string) bool
 			}
-			if r, ok := reg.(pageRenderer); ok {
+			if r, ok := reg.(pluginPageHandler); ok {
 				tmpl, pluginData, handled := r.RenderPluginPage(c, page.PageType)
 				if handled {
 					data := gin.H{
@@ -503,13 +504,26 @@ func (b *Blog) DynamicPage(c *gin.Context, page *Page) {
 						"settings":   b.GetSettings(),
 						"nav_pages":  navPages,
 					}
-					// Merge plugin data into template data
 					for k, v := range pluginData {
 						data[k] = v
 					}
 					b.Render(c, http.StatusOK, tmpl, data)
 					return
 				}
+				// Plugin owns this page type but is disabled — show 404
+				if r.HasPageType(page.PageType) {
+					b.Render(c, http.StatusNotFound, "error.html", gin.H{
+						"error":       "Page Not Available",
+						"description": "This page is currently disabled.",
+						"version":     b.Version,
+						"title":       "Not Available",
+						"recent":      b.GetLatest(),
+						"admin_page":  false,
+						"settings":    b.GetSettings(),
+						"nav_pages":   navPages,
+					})
+					return
+				}
 			}
 		}
 		// Fallback: render as custom content page

plugin/registry.go

@@ -237,6 +237,20 @@ func (r *Registry) GetNavItems() []PageDefinition {
 	return items
 }
 
+// HasPageType returns true if any registered plugin (enabled or not) defines the given page type.
+func (r *Registry) HasPageType(pageType string) bool {
+	r.mu.RLock()
+	defer r.mu.RUnlock()
+	for _, p := range r.plugins {
+		for _, page := range p.Pages() {
+			if page.PageType == pageType {
+				return true
+			}
+		}
+	}
+	return false
+}
+
 // UpdateSetting saves a single plugin setting.
 func (r *Registry) UpdateSetting(pluginName, key, value string) {
 	r.db.Where("plugin_name = ? AND key = ?", pluginName, key).

plugins/scholar/scholar.go

@@ -5,6 +5,7 @@ package scholar
 
 import (
 	"fmt"
+	"goblog/blog"
 	"log"
 	"sort"
 	"time"
@@ -42,8 +43,35 @@ func (p *ScholarPlugin) Settings() []gplugin.SettingDefinition {
 }
 
 func (p *ScholarPlugin) OnInit(db *gorm.DB) error {
-	// Scholar library will be initialized lazily on first page render
-	// since we need the settings to know which cache files to use
+	// Ensure a research page exists in the pages table.
+	// The user can customize title, slug, hero, nav order via admin.
+	var page blog.Page
+	result := db.Where("page_type = ?", "research").First(&page)
+	if result.Error != nil {
+		// No research page exists — create the default
+		page = blog.Page{
+			Title:    "Research",
+			Slug:     "research",
+			PageType: "research",
+			ShowInNav: true,
+			NavOrder: 20,
+			Enabled:  true,
+		}
+		db.Create(&page)
+		log.Println("Scholar plugin: created research page")
+	}
+
+	// Migrate ScholarID from page record to plugin settings (backward compat)
+	if page.ScholarID != "" {
+		var existing gplugin.PluginSetting
+		if err := db.Where("plugin_name = ? AND key = ?", "scholar", "scholar_id").First(&existing).Error; err != nil || existing.Value == "" {
+			db.Where("plugin_name = ? AND key = ?", "scholar", "scholar_id").
+				Assign(gplugin.PluginSetting{Value: page.ScholarID}).
+				FirstOrCreate(&gplugin.PluginSetting{PluginName: "scholar", Key: "scholar_id", Value: page.ScholarID})
+			log.Printf("Scholar plugin: migrated scholar_id %s from page to plugin settings", page.ScholarID)
+		}
+	}
+
 	return nil
 }