Merge branch 'sexy-search' into 'master'

Sexy search

The goal of this MR is to solve the search issue #96. Let's assume we have a user with firstname `Jean-François`, lastname `Du Pont` and nickname `Ai'gnan`. Here is a list of search that did not include him previously but now includes him (was and still is case-insensitive):

* `jean françois` (missing -) ;
* `jean-francois` (missing ç) ;
* `jean francois` (both) ;
* `dupont` (space) ;
* `françois` (not the start of his name) ;
* `aignan` (missing ').

You get it, there are a lot of mistakes that humans can do. It also sorts results by `User.last_update` to avoid putting old accounts at the top of common requests (such as firstname-only or lastname-only requests).

### How it works

For those who don't know, the search is handled by Xapian (the search backend) through the haystack library which provides a Django-friendly interface to multiple search backends. Xapian maintains kind of a duplicate of the database (only for models against which we want to search something) which is optimised for search operations. Its "models" are called "indexes" (see `core.search_indexes.UserIndex` for the user model).

Every time a user is created or modified, it is indexed (through a signal handler) so that Xapian knows about it. For the user search, what is indexed is the string outputted by the `core/templates/search/indexes/core/user_auto.txt` template. For our example from above, it looks like this:

```
jean francois
du pont
aignan
jeanfrancois
dupont

jeanfrancoisdupont
```

As you can see, unicode is removed. There also are kind-of duplicates with different spacing as we are using an autocomplete algorithm: it searches from the beginning of words.

The one I am not sure about is the last one. Its goal is to allow searching without putting a space between the firstname and lastname. Is this useful?

The prod will have to do a `./manage.py update_index`, not sure it does it in the upgrade script.

See merge request ae/Sith!269

core/search_indexes.py

@@ -34,6 +34,7 @@ from forum.models import ForumMessage, ForumMessageMeta
 class UserIndex(indexes.SearchIndex, indexes.Indexable):
     text = indexes.CharField(document=True, use_template=True)
     auto = indexes.EdgeNgramField(use_template=True)
+    last_update = indexes.DateTimeField(model_attr="last_update")
 
     def get_model(self):
         return User
@@ -45,6 +46,9 @@ class UserIndex(indexes.SearchIndex, indexes.Indexable):
     def get_updated_field(self):
         return "last_update"
 
+    def prepare_auto(self, obj):
+        return self.prepared_data["auto"].strip()[:245]
+
 
 class IndexSignalProcessor(signals.BaseSignalProcessor):
     def setup(self):

core/templates/search/indexes/core/user_auto.txt

@@ -1,3 +1,13 @@
-{{ object.first_name }}
-{{ object.last_name }}
-{{ object.nick_name }}
+{% load search_helpers %}
+
+{% with first=object.first_name|safe|slugify last=object.last_name|safe|slugify nick=object.nick_name|default_if_none:""|safe|slugify %}
+
+{{ first|replace:"|-| " }}
+{{ last|replace:"|-| " }}
+{{ nick|replace:"|-| " }}
+{% if first|count:"-" != 0 %}{{ first|cut:"-" }}{% endif %}
+{% if last|count:"-" != 0 %}{{ last|cut:"-" }}{% endif %}
+{% if nick|count:"-" != 0 %}{{ nick|cut:"-" }}{% endif %}
+{{ first|cut:"-" }}{{ last|cut:"-" }}
+
+{% endwith %}

core/templatetags/search_helpers.py

@@ -0,0 +1,27 @@
+from django.template.exceptions import TemplateSyntaxError
+from django import template
+from django.template.defaultfilters import stringfilter
+
+register = template.Library()
+
+
+# arg should be of the form "|foo|bar" where the first character is the
+# separator between old and new in value.replace(old, new)
+@register.filter
+@stringfilter
+def replace(value, arg):
+    # s.replace('', '') == s so len(arg) == 2 is fine
+    if len(arg) < 2:
+        raise TemplateSyntaxError("badly formatted argument")
+
+    arg = arg.split(arg[0])
+
+    if len(arg) != 3:
+        raise TemplateSyntaxError("badly formatted argument")
+
+    return value.replace(arg[1], arg[2])
+
+
+@register.filter
+def count(value, arg):
+    return value.count(arg)

core/views/site.py

@@ -30,6 +30,7 @@ from django.contrib.auth.decorators import login_required
 from django.utils import html
 from django.views.generic import ListView, TemplateView
 from django.conf import settings
+from django.utils.text import slugify
 
 import json
 
@@ -73,7 +74,18 @@ def notification(request, notif_id):
 
 def search_user(query, as_json=False):
     try:
-        res = SearchQuerySet().models(User).autocomplete(auto=html.escape(query))[:20]
+        # slugify turns everything into ascii and every whitespace into -
+        # it ends by removing duplicate - (so ' - ' will turn into '-')
+        # replace('-', ' ') because search is whitespace based
+        query = slugify(query).replace("-", " ")
+        # TODO: is this necessary?
+        query = html.escape(query)
+        res = (
+            SearchQuerySet()
+            .models(User)
+            .autocomplete(auto=query)
+            .order_by("-last_update")[:20]
+        )
         return [r.object for r in res]
     except TypeError:
         return []