Added EXPLAIN_TEMPLATE_LOADING to help people debug templates not being loaded.

docs/blueprints.rst

@@ -185,6 +185,24 @@ want to render the template ``'admin/index.html'`` and you have provided
 ``templates`` as a `template_folder` you will have to create a file like
 this: ``yourapplication/admin/templates/admin/index.html``.
 
+To further reiterate this: if you have a blueprint named ``admin`` and you
+want to render a template called ``index.html`` which is specific to this
+blueprint, the best idea is to lay out your templates like this::
+
+    yourpackage/
+        blueprints/
+            admin/
+                templates/
+                    admin/
+                        index.html
+                __init__.py
+
+And then when you want to render the template, use ``admin/index.html`` as
+the name to look up the template by.  If you encounter problems loading
+the correct templates enable the ``EXPLAIN_TEMPLATE_LOADING`` config
+variable which will instruct Flask to print out the steps it goes through
+to locate templates on every ``render_template`` call.
+
 Building URLs
 -------------
 

docs/config.rst

@@ -188,6 +188,13 @@ The following configuration values are used internally by Flask:
                                   be viable to disable this feature by setting
                                   this key to ``False``. This option does not
                                   affect debug mode.
+``EXPLAIN_TEMPLATE_LOADING``      If this is enabled then every attempt to
+                                  load a template will write an info
+                                  message to the logger explaining the
+                                  attempts to locate the template.  This
+                                  can be useful to figure out why
+                                  templates cannot be found or wrong
+                                  templates appear to be loaded.
 ================================= =========================================
 
 .. admonition:: More on ``SERVER_NAME``
@@ -234,10 +241,8 @@ The following configuration values are used internally by Flask:
    ``JSON_AS_ASCII``, ``JSON_SORT_KEYS``, ``JSONIFY_PRETTYPRINT_REGULAR``
 
 .. versionadded:: 1.0
-   ``SESSION_REFRESH_EACH_REQUEST``
-
-.. versionadded:: 1.0
-   ``TEMPLATES_AUTO_RELOAD``, ``LOGGER_HANDLER_POLICY``
+   ``SESSION_REFRESH_EACH_REQUEST``, ``TEMPLATES_AUTO_RELOAD``,
+   ``LOGGER_HANDLER_POLICY``, ``EXPLAIN_TEMPLATE_LOADING``
 
 Configuring from Files
 ----------------------