NoReverseMatch error message is unclear, view does exist

[Diederik van der Boor]

As Django newcomer, the NoReverseMatch error appears confusing to me.
It took me about 1 hour to figure out my problem because the error message was unclear.
This might not be technically a bug but I believe this is a "user experience" bug.

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This is the error message:

Caught NoReverseMatch while rendering: Reverse for 'webgtd-contexts-index' with arguments '()' and keyword arguments '{}' not found.

The line in error was:

<a accesskey="c" href="{% url webgtd-contexts-index %}">

The URLConf has the following entry:

    url(r'^contexts/(?P<id>\d*)$', 'todo.by_context', name='webgtd-contexts-index'),

The todo view looked like like:

def by_context(request, id=0):
    return index(request)

In my reasoning this parameter would be optional, but I was wrong.
The function signature looked fine to me, which made the error message confusing.

I've rewritten the regex now as: '^contexts/(?P<id>\d+)?$'.

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Could you please improve the error message, so that it either:

• ...mentions the view function does not exist at all.
• ...mentions the view function does exist, but requires more parameters
• ...mentions the URLconf regex pattern requires more parameters

[Aymeric Augustin]

Change UI/UX from NULL to False.

[Aymeric Augustin]

Change Easy pickings from NULL to False.

[Aymeric Augustin]

#19091 was a duplicate.

[Aymeric Augustin]

#18373 is related.

[Wilfred]

#17076 is related.

[Bas Peschier]

I am going to close this on the basis that the NoReverseMatch now contains the tried pattern(s):

django.core.urlresolvers.NoReverseMatch: Reverse for 'webgtd-contexts-index' with arguments '()' and keyword arguments '{}' not found. 1 pattern(s) tried: ['contexts/(?P<id>\\d*)$']

This means the NoReverseMatch is no longer a complete dead end: it now provides a bit of information where to look. Since there are a lot of reasons the pattern could not match (especially now we support lookarounds), it is going to be very difficult to provide more information.