From c068bc184c3c78b7bc9a1c5d43cc78c92bc41999 Mon Sep 17 00:00:00 2001
From: Jacob Kaplan-Moss <jacob@jacobian.org>
Date: Fri, 29 Aug 2008 19:28:03 +0000
Subject: [PATCH] Merge branch 'url-tag-asvar'

git-svn-id: http://code.djangoproject.com/svn/django/trunk@8716 bcc190cf-cafb-0310-a4f2-bffc1f526a37
---
 django/template/defaulttags.py           | 51 ++++++++++++++++++------
 docs/ref/templates/builtins.txt          | 23 +++++++++++
 tests/regressiontests/templates/tests.py |  5 +++
 3 files changed, 67 insertions(+), 12 deletions(-)

diff --git a/django/template/defaulttags.py b/django/template/defaulttags.py
index 489faa243e..8182cd4d8c 100644
--- a/django/template/defaulttags.py
+++ b/django/template/defaulttags.py
@@ -351,22 +351,40 @@ class TemplateTagNode(Node):
         return self.mapping.get(self.tagtype, '')
 
 class URLNode(Node):
-    def __init__(self, view_name, args, kwargs):
+    def __init__(self, view_name, args, kwargs, asvar):
         self.view_name = view_name
         self.args = args
         self.kwargs = kwargs
+        self.asvar = asvar
 
     def render(self, context):
         from django.core.urlresolvers import reverse, NoReverseMatch
         args = [arg.resolve(context) for arg in self.args]
         kwargs = dict([(smart_str(k,'ascii'), v.resolve(context))
                        for k, v in self.kwargs.items()])
+        
+        
+        # Try to look up the URL twice: once given the view name, and again
+        # relative to what we guess is the "main" app. If they both fail, 
+        # re-raise the NoReverseMatch unless we're using the 
+        # {% url ... as var %} construct in which cause return nothing.
+        url = ''
         try:
-            return reverse(self.view_name, args=args, kwargs=kwargs)
+            url = reverse(self.view_name, args=args, kwargs=kwargs)
         except NoReverseMatch:
             project_name = settings.SETTINGS_MODULE.split('.')[0]
-            return reverse(project_name + '.' + self.view_name,
-                           args=args, kwargs=kwargs)
+            try:
+                url = reverse(project_name + '.' + self.view_name,
+                              args=args, kwargs=kwargs)
+            except NoReverseMatch:
+                if self.asvar is None:
+                    raise
+                    
+        if self.asvar:
+            context[self.asvar] = url
+            return ''
+        else:
+            return url
 
 class WidthRatioNode(Node):
     def __init__(self, val_expr, max_expr, max_width):
@@ -1041,21 +1059,30 @@ def url(parser, token):
 
     The URL will look like ``/clients/client/123/``.
     """
-    bits = token.contents.split(' ', 2)
+    bits = token.contents.split(' ')
     if len(bits) < 2:
         raise TemplateSyntaxError("'%s' takes at least one argument"
                                   " (path to a view)" % bits[0])
+    viewname = bits[1]
     args = []
     kwargs = {}
+    asvar = None
+        
     if len(bits) > 2:
-        for arg in bits[2].split(','):
-            if '=' in arg:
-                k, v = arg.split('=', 1)
-                k = k.strip()
-                kwargs[k] = parser.compile_filter(v)
+        bits = iter(bits[2:])
+        for bit in bits:
+            if bit == 'as':
+                asvar = bits.next()
+                break
             else:
-                args.append(parser.compile_filter(arg))
-    return URLNode(bits[1], args, kwargs)
+                for arg in bit.split(","):
+                    if '=' in arg:
+                        k, v = arg.split('=', 1)
+                        k = k.strip()
+                        kwargs[k] = parser.compile_filter(v)
+                    elif arg:
+                        args.append(parser.compile_filter(arg))
+    return URLNode(viewname, args, kwargs, asvar)
 url = register.tag(url)
 
 #@register.tag
diff --git a/docs/ref/templates/builtins.txt b/docs/ref/templates/builtins.txt
index d3c8355241..2e143a3967 100644
--- a/docs/ref/templates/builtins.txt
+++ b/docs/ref/templates/builtins.txt
@@ -675,6 +675,29 @@ The template tag will output the string ``/clients/client/123/``.
 <naming-url-patterns>`, you can refer to the name of the pattern in the ``url``
 tag instead of using the path to the view.
 
+Note that if the URL you're reversing doesn't exist, you'll get an
+:exc:`NoReverseMatch` exception raised, which will cause your site to display an
+error page.
+
+**New in development verson:** If you'd like to retrieve a URL without displaying it,
+you can use a slightly different call:
+
+.. code-block:: html+django
+
+    {% url path.to.view arg, arg2 as the_url %}
+    
+    <a href="{{ the_url }}">I'm linking to {{ the_url }}</a>
+    
+This ``{% url ... as var %}`` syntax will *not* cause an error if the view is
+missing. In practice you'll use this to link to views that are optional:
+
+.. code-block:: html+django
+
+    {% url path.to.view as the_url %}
+    {% if the_url %}
+      <a href="{{ the_url }}">Link to optional stuff</a>
+    {% endif %}
+
 .. templatetag:: widthratio
 
 widthratio
diff --git a/tests/regressiontests/templates/tests.py b/tests/regressiontests/templates/tests.py
index 0eb5a2a586..f04bf0c33d 100644
--- a/tests/regressiontests/templates/tests.py
+++ b/tests/regressiontests/templates/tests.py
@@ -896,6 +896,11 @@ class Templates(unittest.TestCase):
             'url-fail02': ('{% url no_such_view %}', {}, urlresolvers.NoReverseMatch),
             'url-fail03': ('{% url regressiontests.templates.views.client %}', {}, urlresolvers.NoReverseMatch),
 
+            # {% url ... as var %}
+            'url-asvar01': ('{% url regressiontests.templates.views.index as url %}', {}, ''),
+            'url-asvar02': ('{% url regressiontests.templates.views.index as url %}{{ url }}', {}, '/url_tag/'),
+            'url-asvar03': ('{% url no_such_view as url %}{{ url }}', {}, ''),
+
             ### CACHE TAG ######################################################
             'cache01': ('{% load cache %}{% cache -1 test %}cache01{% endcache %}', {}, 'cache01'),
             'cache02': ('{% load cache %}{% cache -1 test %}cache02{% endcache %}', {}, 'cache02'),