= Finding Similar Bugs =

The normal bug search requires all the specified keywords to be present
in the found bugs. This works quite well in general, but not when you
want to find bugs similar to a given bug summary when filing a new bug;
then the search is too restrictive.

To address this use case, IBugTask.findSimilar can be used, which uses
nl_phrase_search in order to construct a suitable search string.

It doesn't make much sense to find bugs similar to an empty string, so
no results will be returned.

    >>> from lp.bugs.interfaces.bugtask import IBugTaskSet
    >>> from lp.registry.interfaces.person import IPersonSet
    >>> from lp.registry.interfaces.product import IProductSet
    >>> firefox = getUtility(IProductSet).getByName('firefox')
    >>> sample_person = getUtility(IPersonSet).getByEmail(
    ...     'test@canonical.com')
    >>> similar_bugs = getUtility(IBugTaskSet).findSimilar(
    ...     sample_person, '', product=firefox)
    >>> similar_bugs.count()
    0

Also, of course, if the given summary isn't similar to any other bugs,
no results are returned.


    >>> similar_bugs = getUtility(IBugTaskSet).findSimilar(
    ...     sample_person, 'nosimilarbugs', product=firefox)
    >>> similar_bugs.count()
    0

Now, let's enter a real bug summary, which doesn't match any other
exactly. We can see that it still manages to find a bug.

    >>> similar_bugs = getUtility(IBugTaskSet).findSimilar(
    ...     sample_person, "Can't display SVG", product=firefox)
    >>> for bugtask in similar_bugs:
    ...     print bugtask.bug.title
    Firefox does not support SVG


Above we specified that only bugs against Firefox should be searched. If
we specify Evolution, no bugs will be returned, since no similar bugs
are found there.

    >>> evolution = getUtility(IProductSet).getByName('evolution')
    >>> similar_bugs = getUtility(IBugTaskSet).findSimilar(
    ...     sample_person, "Can't display SVG", product=evolution)
    >>> similar_bugs.count()
    0

We can also search for distribution bugs:


    >>> from lp.registry.interfaces.distribution import IDistributionSet
    >>> ubuntu = getUtility(IDistributionSet).getByName('ubuntu')
    >>> similar_bugs = getUtility(IBugTaskSet).findSimilar(
    ...     sample_person, "Thunderbird SVG",
    ...     distribution=ubuntu)
    >>> for bugtask in similar_bugs:
    ...     print bugtask.bug.title
    Firefox does not support SVG
    Thunderbird crashes

As well as limiting it to a specific source package:


    >>> ubuntu_thunderbird = ubuntu.getSourcePackage('thunderbird')
    >>> similar_bugs = getUtility(IBugTaskSet).findSimilar(
    ...     sample_person, "Can't display SVG",
    ...     distribution=ubuntu,
    ...     sourcepackagename=ubuntu_thunderbird.sourcepackagename)
    >>> similar_bugs.count()
    0


== Private bugs ==

Only bugs that the user has access to view will be searched. If we set
the Firefox bug to private, and repeat the search as a user who isn't
allowed to view it, only the Thunderbird bug will be returned this time.

    >>> from lp.bugs.interfaces.bug import IBugSet
    >>> login('test@canonical.com')
    >>> firefox_svg_bug = getUtility(IBugSet).get(1)
    >>> firefox_svg_bug.setPrivate(True, getUtility(ILaunchBag).user)
    True

    >>> from canonical.launchpad.webapp.authorization import check_permission
    >>> login('no-priv@canonical.com')
    >>> check_permission('launchpad.View', firefox_svg_bug)
    False
    >>> no_priv = getUtility(ILaunchBag).user
    >>> similar_bugs = getUtility(IBugTaskSet).findSimilar(
    ...     no_priv, "Thunderbird SVG",
    ...     distribution=ubuntu)
    >>> for bugtask in similar_bugs:
    ...     print bugtask.bug.title
    Thunderbird crashes

    >>> login('test@canonical.com')
    >>> firefox_svg_bug.setPrivate(False, getUtility(ILaunchBag).user)
    True


== Ordering of search results ==

Since the search uses OR to match bugs against the entered phrase, many
bugs will be returned by a search. Since we usually want to display on
a few number of bugs to the user, it's important that the results are
ordered in a way that the bugs matching the phrase best are first in the
list.

When searching for similar bugs, the results are ordered by ranking the
results of the fulltext search on the Bug table, so bugs that have a
summary or description that match the phrase will be displayed first.

Due to the sample data assuming a way-to-wide search facility, this test
has been narrowed - see bug 612384.

    >>> similar_bugs = getUtility(IBugTaskSet).findSimilar(
    ...     sample_person, "Another test bug for Thunderbird",
    ...     distribution=ubuntu)
    >>> for bugtask in similar_bugs:
    ...     print bugtask.bug.title
    another test bug
    >>> #Thunderbird crashes

    >>> similar_bugs = getUtility(IBugTaskSet).findSimilar(
    ...     sample_person, "Another Thunderbird crash",
    ...     distribution=ubuntu)
    >>> for bugtask in similar_bugs:
    ...     print bugtask.bug.title
    Thunderbird crashes
    >>> #another test bug

== Not returning the same bug ==

findSimilarBugs() does not include the bug of the bugtask upon which
it is invoked.

    >>> orig_bug = factory.makeBug(
    ...     title="So you walk into this restaurant",
    ...     owner=firefox.owner, product=firefox)

    >>> dupe_bug = factory.makeBug(
    ...     title="So you walk into this restaurant",
    ...     owner=firefox.owner, product=firefox)
    >>> dupe_bug.markAsDuplicate(orig_bug)

    >>> similar_bugs = orig_bug.default_bugtask.findSimilarBugs(firefox.owner)
    >>> orig_bug in similar_bugs
    False