Marketplace - Search - Milestone 5

In this assignment, you will expand your classified ads web site to add search and tags functionality equivalent to:

https://market.dj4e.com/m5

You can log into this site using an account: facebook and a password of Marketnn! where "nn" is the two-digit number of Dr. Chuck's race car or the numeric value for asterisk in the ASCII character set.

Important: The number of lines you need to add to your code is relatively small. Take your time read the sample code carefully - only make changes that you understand. Wholesale cutting and pasting sample code will make it almost impossible to complete this assignment.

This is somewhat like the kind of real work you do when you have a working application and want to add a feature to the application. First - don't break what you have working.

Taking a Snapshot of Your Previous Assignment using git

We want to take a snapshot of your previous assignment code using the git version management tool before we start making schanges to your code. Only do this once and only once after you have fully completed the previous assignment before you start editing your files for this assignment.

You should already have your github identity set up. The following should print your name

git config --global user.name 

If you do not see your name, following the instructions to configure git at dj4e-samples/README.md

Once your git account is configured, run these commands:

Then run these commands:

cd ~/django_projects/market
git tag             # Make sure you don't already have a mkt4 tag (only do this once!)

git add .
git commit -a -m mkt4
git tag -a mkt4 -m mkt4
git tag             # Make sure you do have a mkt4 tag

The whole ~/django_projects/market folder is a git repository so you can use git for many cool things. But for now we are just making sure you have a "re-spawn" point if AI breaks your code badly.

The instructions to "revert" to the saved tag are at the bottom of this document. Hopefully you won't need to use them.

Adding Search

The well sample application contains code you can adapt to implement the code to search the title and text:

https://samples.dj4e.com/well/

To avoid getting too much broken at one time - it is probably a good idea to make search work and then further evolve your code to support tags.

Adding Support for Tags

The tagme application adds a tags field to the model and adds support for tags to the user interface and search code. Make sure the tags field has blank=True in the models.py (take a look at the sample code) so that the field can be left blank while creating or updating an Ad.

https://samples.dj4e.com/tagme/

You should also review the documentation for the django-taggit library at:

https://django-taggit.readthedocs.io/en/latest/

You might find the easiest path is to use the taggit documentation to make your changes, looking at the tagme code to verify what you are doing.

There is a bit of an extra wrinkle when adapting the approach in tagme because we are using a ModelForm in order to process uploaded pictures. The key is that you have to save the tags after the form has been copied to the model and the model has been saved because the tags are stored using a many-to-many data model.

https://django-taggit.readthedocs.io/en/latest/forms.html#commit-false

In your forms.py code you will need to (a) add 'tags' to the field list and (b) update the code in the commit to look like:

    if commit:
        instance.save()
        self.save_m2m()    # Add this

In your views.py, we have our own code to pull data from the form to the model and then save the model. This code is in both the insert and edit views:

    # Adjust the model owner before saving
    inst = form.save(commit=False)
    inst.owner = self.request.user
    inst.save()

    # https://django-taggit.readthedocs.io/en/latest/forms.html#commit-false
    form.save_m2m()    # Add this

You need to add the save_m2m() call after the instance was saved.

Finally, the detail template for the tagme application contains code that can be adapted to display the tags in your application.

Note About using AI with this Assignment

By this point in the course, you should already have the earlier assignments working correctly. While it’s fine to use AI to help diagnose specific errors, one of the worst approaches is to take a file you’ve been developing for weeks, hand it to an AI, and paste back a completely rewritten version without reviewing it carefully.

AI-generated solutions often “work” in the sense that they run without crashing, but they may remove or alter details the autograder expects. This can cause confusing autograder failures that are very hard to untangle.

There are many ways to solve these assignments that are roughly equivalent, but the autograder is not checking for just any equivalent solution. It's verifying that you’ve adapted the provided sample code in the expected ways.

If AI produces a solution that is only “approximately” like the samples, it probably won’t pass. And if AI overwrites working code you already built and have working perfectly, you may find yourself needing to start over from the beginning.

Manual Testing

It is always a good idea to manually test your application before submitting it for grading. Here are a set of manual test steps:

• Log in to your application and create several ads add a tag to one of the ads. Make sure that you put unique words that are only in the title, text, and tag so you can verify that you can search for a word in any of the three places.

• Go into the detail page for an ad and verify that it shows you the title, text, and tag(s) that you entered

• Make sure to edit an ad and verify that you are able to change the title, text, and tags.

• Search for some text that is only in a title and verify that the correct ads come back.

• Search for some text that is only in a body and verify that the correct ads come back.

• Search for some text that is only in a tag and verify that the correct ads come back.

• Note the "?search=" in the location bar in your browser while you are doing searches

• Clear the search and see all of the results and verify there is no "?search=" get parameter

Resetting Your Database

If python manage.py check is working and python manage.py makemigrations is working, you may have made a series of changes to models.py and ended up with a mis-match between your migration files and database have become confused causing makemigrations to fail.

We have provided a Python script that completely resets your Django project's database and removes all migration files, allowing you to start fresh with a clean database schema. This is particularly useful when migration files have become corrupted or when you need to restructure your models significantly.

First we update the samples code so you have the latest helper scripts.

cd ~/dj4e-samples/
git checkout django52
git pull origin django52

Then follow the instructions at README_DB.md

The reset script will:

• Drop all tables in your database
• Delete all migration files (except __init__.py)
• Allow you to start fresh with makemigrations and migrate

Discarding Code Changes and Going back to a previous version of your code

If you make a mistake (or if AI makes a mistake) and you paste it into your code and break everything (i.e. not migrations and models.py) you can decide to reset your code base to the tag your created above (if you created a tag). Follow these instructions - move slowly and if things blow up - get help.

If python manage.py check is working and python manage.py makemigrations is not working, you may not need to throw your code away and might want to try a database reset first.

First we update the samples code so you have the latest helper scripts.

cd ~/dj4e-samples/
git checkout django52
git pull origin django52

Then follow the instructions at README_GIT.md

If you go back, and have discarded your code changes - you probably need to reset your database as well as shown in the previous section.