Added default templates in Grav itself

CHANGELOG.md

@@ -1,6 +1,9 @@
 # v1.7.0-rc.17
 ## mm/dd/2020
 
+1. [](#improved)
+    * Fall back through various templates scenarios if they don't exist in theme to avoid unhelpful error.
+    * Added default templates for `external.html.twig`, `default.html.twig`, and `modular.html.twig`
 1. [](#bugfix)
     * Fixed `Security::sanitizeSVG()` creating an empty file if SVG file cannot be parsed
     * Fixed infinite loop in blueprints with `extend@` to a parent stream

system/src/Grav/Common/Twig/Twig.php

@@ -445,14 +445,31 @@ class Twig
         $twig_extension = $extension ? '.'. $extension .TWIG_EXT : TEMPLATE_EXT;
         $template_file = $this->template($page->template() . $twig_extension);
 
+        $page_template = null;
+
         $loader = $this->twig->getLoader();
-        if ($loader instanceof ExistsLoaderInterface && $loader->exists($template_file)) {
-            return $template_file;
+        if ($loader instanceof ExistsLoaderInterface ) {
+
+            if ($loader->exists($template_file)) {
+                $page_template = $template_file;
+            } else {
+                // Try with template + html.twig
+                if ($twig_extension !== TEMPLATE_EXT && $loader->exists($template . TEMPLATE_EXT)) {
+                    $page_template = $template . TEMPLATE_EXT;
+                // Try with default and original extension
+                } elseif ($loader->exists('default' . $twig_extension)) {
+                    $page_template = 'default' . $twig_extension;
+                // Else try default + default extension
+                } elseif (!$page->modular() && $loader->exists('default' . TEMPLATE_EXT)) {
+                    $page_template = 'default' . TEMPLATE_EXT;
+                } else {
+                    $page_template = 'modular/default' . TEMPLATE_EXT;
+                }
+            }
         }
 
-        // Default to HTML
-        $page->templateFormat('html');
-        return $template . TEMPLATE_EXT;
+        return $page_template;
+
     }
 
     /**

system/templates/default.html.twig

@@ -0,0 +1,4 @@
+{# Default output if no theme #}
+<h3 style="color:red">ERROR: <code>{{ page.template() ~'.'~ page.templateFormat() ~".twig" }}</code> template not found for page: <code>{{ page.route() }}</code></h3>
+<h1>{{ page.title() }}</h1>
+{{ page.content()|raw }}

system/templates/external.html.twig

@@ -0,0 +1 @@
+{# Default external template #}

system/templates/modular/default.html.twig

@@ -0,0 +1,4 @@
+{# Default output if no theme #}
+<h3 style="color:red">ERROR: <code>{{ page.template() ~'.'~ page.templateFormat() ~".twig" }}</code> template not found for page: <code>{{ page.route() }}</code></h3>
+<h1>{{ page.title() }}</h1>
+{{ page.content()|raw }}