Simplify template inheritance

cruds_adminlte/template_loader.py

@@ -0,0 +1,138 @@
+"""The Template Loader.
+
+Using the standard django template inheritance and extension mechanism,
+it would happen that you would end up with lots of template overrides.
+
+That is, you cannot, by default, override a block defined in an included
+template (like the sidebar, or the headbar) thus, in order to define the
+sidebar you would need to override that template. And if you want different
+sidebars for different things... you get the point.
+
+The Template Loader those a simple trick: it "compiles" a template by embedding
+into its contents the contents of the included templates. So that at the eyes
+of Django Template System when you extend from such compiled template, all is one
+single template the block of which can be extended.
+
+Note that we can only handle embedding of calls to include which do not have a 'with'.
+Also, we do not currently support embedding a template that uses 'extends' itself.
+
+THIS IS EXPERIMENTAL FEATURE.
+Our solution is heavily based in the code by github's @uw-it-aca/django-template-preprocess
+which is in turn based of django-compressor.
+Also borrowing some code of django's builtin cached template loader.
+"""
+from importlib import import_module
+from django.template import engines
+from django.template import loader
+from django.utils.encoding import smart_text
+import hashlib
+
+from django.template import TemplateDoesNotExist
+from django.template.backends.django import copy_exception
+
+from django.template.loaders.base import Loader as BaseLoader
+from fnmatch import fnmatch
+import codecs
+import re
+import os
+
+
+class Loader(BaseLoader):
+    # List of templates on which rendering we intervene.
+    templates = ['adminlte/base.html', 
+                 r'^adminlte/lib/.*',
+                 r'^cruds/.*',
+                 ]
+
+    def __init__(self, engine, templates=None):
+        if templates:
+            self.templates = templates
+        self.engine = engine
+        #self.loaders = engine.get_template_loaders(loaders)
+        super().__init__(engine)
+
+    def check_intervene(self, template_name):
+        for m in self.templates:
+            if m == template_name or re.match(m, template_name):
+                return True
+        return False
+
+    def get_template_sources(self, template_name):
+        if self.check_intervene(template_name):
+            for loader in self.loaders:
+                if isinstance(loader, self.__class__):
+                    continue
+                for t in loader.get_template_sources(template_name):
+                    t.wrapped_loader = t.loader
+                    t.loader = self
+                    yield t
+
+    def get_contents(self, origin):
+        loader = origin.wrapped_loader
+        content = loader.get_contents(origin)
+        content = process_template_content(content)
+        return content
+
+    _loaders = None
+
+    @property
+    def loaders(self):
+        if self._loaders:
+            return self._loaders
+        template_source_loaders = self.engine.loaders[:]
+        template_source_loaders = self.engine.get_template_loaders(template_source_loaders)
+        loaders = []
+        # Unwrap the loaders inside the CachedTemplateLoader if applicable.
+        for loader in template_source_loaders:
+            if isinstance(loader, self.__class__):
+                continue
+            if hasattr(loader, 'loaders'):
+                loaders.extend(loader.loaders)
+            else:
+                loaders.append(loader)
+        self._loaders = loaders
+        return loaders
+
+    def get_template(self, template_name, skip=None):
+        template = super().get_template(template_name, skip)
+        return template
+
+
+def handle_includes(content, seen_templates, template_processor):
+    def insert_template(match):
+        name = match.group(1)
+
+        if name in seen_templates:
+            raise Exception("Recursive template includes")
+
+        seen_templates[name] = True
+
+        content = template_processor(name, seen_templates)
+        return content
+
+    # FIXME: Make sure we do not process an include with 'with'
+    content = re.sub(r"""{%\s*include\s*['"]([^"']+?)["']\s*%}""",
+                     insert_template,
+                     content, flags=re.UNICODE)
+
+    return content
+
+
+def process_sub_template(name, seen_templates):
+    content = loader.get_template(name).template.source
+    return process_template_content(content,
+                                    seen_templates,
+                                    subcall=True)
+
+
+def process_template_content(content,
+                             seen_templates=None,
+                             subcall=False):
+    if seen_templates is None:
+        seen_templates = {}
+    content = handle_includes(content,
+                        seen_templates=seen_templates,
+                        template_processor=process_sub_template,
+                        )
+    return content
+

tests/demo_project/demo/settings.py

@@ -56,16 +56,21 @@
         'BACKEND': 'django.template.backends.django.DjangoTemplates',
         'DIRS': [
             str(DEMO_ROOT / 'demo' / 'templates'),
+            str(DEMO_ROOT / 'project_templates'),
         ],
-        'APP_DIRS': True,
         'OPTIONS': {
             'context_processors': [
                 'django.template.context_processors.debug',
                 'django.template.context_processors.request',
                 'django.contrib.auth.context_processors.auth',
                 'django.contrib.messages.context_processors.messages',
             ],
-        },
+            'loaders': [
+                'cruds_adminlte.template_loader.Loader',
+                'django.template.loaders.filesystem.Loader',
+                'django.template.loaders.app_directories.Loader',
+            ]
+        }
     },
 ]
 

tests/demo_project/demo/templates/adminlte/base.html

@@ -0,0 +1,41 @@
+{% extends "adminlte/base.html" %}
+{% load i18n %}
+
+{% block nav_links %}
+<li>
+    <a href="{% url 'testapp_author_list' %}">
+        <i class="fa fa-pencil"></i> <span>{% trans "Authors" %}</span>
+    </a>
+</li>
+<li>
+    <a href="{% url 'testapp_addresses_list' %}">
+        <i class="fa fa-address-book-o"></i> <span>{% trans "Addresses" %}</span>
+    </a>
+</li>
+<li>
+    <a href="{% url 'testapp_customer_list' %}">
+        <i class="fa fa-users"></i> <span>{% trans "Customers" %}</span>
+    </a>
+</li>
+<li>
+    <a href="{% url 'testapp_invoice_list' %}">
+        <i class="fa fa-file-pdf-o"></i> <span>{% trans "Invoices" %}</span>
+    </a>
+</li>
+<li class="header">AUTH</li>
+<li>
+    <a href="{% url 'auth_user_list' %}">
+        <i class="fa fa-user"></i> <span>{% trans "Users" %}</span>
+    </a>
+</li>
+<li>
+    <a href="{% url 'auth_group_list' %}">
+        <i class="fa fa-users"></i> <span>{% trans "Groups" %}</span>
+    </a>
+</li>
+<li>
+    <a href="{% url 'auth_permission_list' %}">
+        <i class="fa fa-id-card-o"></i> <span>{% trans "Permissions" %}</span>
+    </a>
+</li>
+{% endblock nav_links %}

tests/demo_project/demo/templates/cruds/base.html

@@ -0,0 +1,44 @@
+{% extends "cruds/base.html" %}
+
+{% block title %}CRUDS Demo{% endblock %}
+
+{% load i18n %}
+
+{% block nav_links %}
+<li>
+    <a href="{% url 'testapp_author_list' %}">
+        <i class="fa fa-pencil"></i> <span>{% trans "Authors" %}</span>
+    </a>
+</li>
+<li>
+    <a href="{% url 'testapp_addresses_list' %}">
+        <i class="fa fa-address-book-o"></i> <span>{% trans "Addresses" %}</span>
+    </a>
+</li>
+<li>
+    <a href="{% url 'testapp_customer_list' %}">
+        <i class="fa fa-users"></i> <span>{% trans "Customers" %}</span>
+    </a>
+</li>
+<li>
+    <a href="{% url 'testapp_invoice_list' %}">
+        <i class="fa fa-file-pdf-o"></i> <span>{% trans "Invoices" %}</span>
+    </a>
+</li>
+<li class="header">AUTH</li>
+<li>
+    <a href="{% url 'auth_user_list' %}">
+        <i class="fa fa-user"></i> <span>{% trans "Users" %}</span>
+    </a>
+</li>
+<li>
+    <a href="{% url 'auth_group_list' %}">
+        <i class="fa fa-users"></i> <span>{% trans "Groups" %}</span>
+    </a>
+</li>
+<li>
+    <a href="{% url 'auth_permission_list' %}">
+        <i class="fa fa-id-card-o"></i> <span>{% trans "Permissions" %}</span>
+    </a>
+</li>
+{% endblock nav_links %}

tests/demo_project/project_templates/README.md

@@ -0,0 +1,12 @@
+Thought the right place to put the project templates would be
+the "project app" (that is, the app that holds the settings file)
+
+It is not uncommon for a non-app template directory to exist.
+Such directory gets picked up the filesystem.Loader instead of 
+the app_directories.Loader.
+
+In order to properly test template loading / rendering features,
+we need to supply our test project with such a directory.
+
+That is, this directory exists in order to be able to test against
+the filesystem.Loader

tests/demo_project/project_templates/project_homepage.html

@@ -0,0 +1,5 @@
+{% extends "adminlte/base.html" %}
+
+{% block body %}
+    Hi there, I am the project_homepage.html
+{% endblock %}

tests/test_template_loader.py

@@ -0,0 +1,46 @@
+# -*- coding: utf-8 -*-
+from cruds_adminlte.template_loader import Loader
+from django.template import loader
+from django.template import engines
+
+
+def test_template_loading():
+    """Make sure that both app_directories and filesystem Loaders work. """
+    tpl = loader.get_template('homepage.html')
+    assert "tests/demo_project/demo/templates/homepage.html" in tpl.origin.name
+    tpl_content = tpl.render()
+    assert "Hello." in tpl_content
+
+    tpl = loader.get_template('project_homepage.html')
+    assert "tests/demo_project/project_templates/project_homepage.html" in tpl.origin.name
+    tpl_content = tpl.render()
+    assert "Hi there, I am the project_homepage.html" in tpl_content
+
+    tpl = loader.get_template('adminlte/base.html')
+    assert "tests/demo_project/demo/templates/adminlte/base.html" in tpl.origin.name
+
+    tpl = loader.get_template('cruds/base.html')
+    assert "tests/demo_project/demo/templates/cruds/base.html" in tpl.origin.name
+
+
+def test_get_loaders():
+    tpl_index = loader.get_template('adminlte/index.html')
+    assert "block nav_links_ul" not in tpl_index.template.source
+
+    tpl_base = loader.get_template('adminlte/base.html')
+    assert "tests/demo_project/demo/templates/adminlte/base.html" in tpl_base.origin.name    
+    base_content = tpl_base.render()
+    assert "fa-address-book-o" in base_content
+
+    tpl_base2 = loader.get_template('cruds/base.html')
+    assert "templates/cruds/base.html" in tpl_base2.origin.name    
+    base_content = tpl_base2.render()
+    assert "fa-address-book-o" in base_content
+
+    # Now we ask for a template that is outside of the library,
+    # but extends the library
+    tpl = loader.get_template('homepage.html')
+    assert "templates/homepage.html" in tpl.origin.name
+    tpl_content = tpl.render()
+    assert "Hello." in tpl_content
+    assert "fa-address-book-o" in tpl_content