Django JSONField Error: Invalid JSON Input Syntax

by Lucia Rojas 50 views

Hey everyone! Ever stumbled upon a cryptic error message that just leaves you scratching your head? Well, I recently ran into one while working with Django, Postgres, and the django-silk profiling tool, and I thought I'd share the journey of figuring it out. Let's dive into this DataError and how I managed to squash it.

The Mystery: A DataError in Django Admin

So, here's the scenario: I was happily saving records in the Django admin panel, working with a model that included a JSON type field. Everything seemed fine and dandy until I upgraded Silk from version 5.3.2 to 5.4.1. Suddenly, bam! I was greeted with this ominous DataError:

DataError at /admin/app/testmodel/2/change/
invalid input syntax for type json
`LINE 1: ... UPDATE "app_testmodel" SET "extended_data" = '''{}''', ...`
`                                                         ^`
DETAIL:  Token "'" is invalid.
CONTEXT:  JSON data, line 1: '...

This error popped up whenever I tried to save a record in the admin panel for a model with a JSON field. The traceback pointed towards an issue with the JSON input syntax, specifically the presence of an invalid token (a single quote in this case). It seemed like Postgres was having trouble parsing the JSON data being sent to it.

Digging Deeper: The Code Snippets

To give you a clearer picture, here are the relevant code snippets from my models.py and admin.py:

//models.py
class TestModel(models.Model):
    extended_data = models.JSONField(default=dict, blank=True, encoder=DjangoJSONEncoder)
    note = models.CharField(max_length=255, blank=True, null=True)

// admin.py
@admin.register(TestModel)
class TestModelAdmin(admin.ModelAdmin):
    pass

As you can see, the TestModel includes a JSONField named extended_data, which is configured with a default value of an empty dictionary and allows blank values. The DjangoJSONEncoder is used for encoding the JSON data. The TestModelAdmin simply registers the model with the admin interface, using the default settings.

The Plot Thickens: Environment Details

To add another layer to the puzzle, here are the details of my environment:

  • DB: Postgres (>14.1)
  • Django: 4.2
  • Silk: 5.3.2 (no errors) -> 5.4.1 (error)

This information highlighted that the issue seemed to be triggered by the upgrade to Silk 5.4.1, suggesting a potential incompatibility or bug in the newer version.

Unraveling the Mystery: Understanding the Root Cause

Okay, so we've got the error, the code, and the environment details. Now comes the fun part: figuring out what's actually going on. The error message itself provides a crucial clue: "invalid input syntax for type json". This strongly suggests that the JSON data being passed to Postgres is not in the correct format.

The presence of the single quote (') in the error message's DETAIL section is another key indicator. JSON data should use double quotes (`