Dev tools¶

iommi ships with several integrated tools to increase your development speed. They are shown on iommi pages when settings.DEBUG is True. Some are always active and some are optional and needs to be added to your project.

On iommi pages you get a debug panel to quickly access the debug tools:

▼ Hide result

Code (jump to your code)¶

Click this button to jump to the code of the current view in your IDE. By default it is configured to jump into PyCharm, but you can configure it for your use case by defining settings.IOMMI_DEBUG_URL_BUILDER. This is a callable that takes filename and lineno arguments and returns a string.

On your staging server you can use this to point to your source code too, which can be very handy.

For VSCode: IOMMI_DEBUG_URL_BUILDER = lambda filename, lineno: 'vscode://file/%s:' % (filename,)+ ('' if lineno is None else "%d" % (lineno,))

Tree¶

This tool shows you the full tree of the current page with the names, full iommi paths, types (with links to documentation), and the included state of all the nodes in the tree.

Pick¶

If you want to configure some part of a page, pick is your friend. Start the pick tool and then click on the item and you’ll get the iommi path to that part with the type shown (with a link to the documentation). You will also get the paths and types of all the parent components up the tree.

Edit¶

Edit the code of your view directly in your browser. It re-renders as-you-type and when the syntax is correct and execution succeeded it will save the code back to disk. This works not just for iommi views, but for any function based view.

Note

This feature isn’t enabled by default because it requires you to add 'iommi.live_edit.Middleware' to settings.MIDDLEWARE. Note that you need to add this at the very top of the middleware list!

This tool is full arbitrary remote execution so it will be very bad if you run this in production! It will only work when DEBUG is true.

Edit style¶

A special version of the live edit feature, but specific for editing a Style. This is most useful for implementing support for a new CSS framework.

Profile¶

Press this tool to get a cProfile output for the current page. By default it will do sorting on the cumulative time, but you can do ?_iommi_prof=tottime to get the total time.

If you have gprof2dot installed you can also do ?_iommi_prof=graph to get a graph output.
If you have snakeviz installed you can also do ?iommi_prof=snake to get snakeviz output.

Note

This feature isn’t enabled by default because it requires you to add 'iommi.profiling.Middleware' to settings.MIDDLEWARE. Note that you need to put this below django.contrib.auth.middleware.AuthenticationMiddleware if you want to use this in production. Only staff users are allowed to profile in production, but all users can profile in debug mode.

Profile POST¶

If you want to profile the POST of a form, click this button first and then click the normal submit button on the form.

SQL trace¶

This tool gives you a list of all SQL statements issued by the page, with timing for each, and a timeline at the top for each statement. There is also a grouped time graph so if you have many similar database hits you will see those easily.

Note

This feature isn’t enabled by default because it requires you to add 'iommi.sql_trace.Middleware' to settings.MIDDLEWARE. Note that you need to put this below django.contrib.auth.middleware.AuthenticationMiddleware if you want to use this in production. Only staff users are allowed to trace sql in production, but all users can trace sql in debug mode.

In DEBUG the SQL trace middleware will automatically warn you if you have views appear to have N+1 type errors. By default iommi will will print stack traces and example SQL statements for the worst offenders for your view to the console:

------ 5 times: -------
From source:
  File "/Users/boxed/Projects/iommi/examples/examples/table_examples.py", line 146, in root => return Page(
With Stack:
  File "iommi/table.py", line 308, in default_cell__value => return getattr_path(row, evaluate_strict(column.attr, row=row, column=column, **kwargs))
  File "iommi/evaluate.py", line 60, in evaluate => return func_or_value(**kwargs)
  File "iommi/evaluate.py", line 76, in evaluate_strict => return evaluate(func_or_value, __signature=None, __strict=True, __match_empty=__match_empty, **kwargs)
  File "iommi/table.py", line 933, in __init__ => self.tag = evaluate_strict(self.tag, **self._evaluate_parameters)
  File "iommi/table.py", line 887, in __iter__ => yield Cell(cells=self, column=column)
SELECT "examples_tfoo"."id", "examples_tfoo"."name", "examples_tfoo"."a" FROM "examples_tfoo" WHERE "examples_tfoo"."id" = 1
SELECT "examples_tfoo"."id", "examples_tfoo"."name", "examples_tfoo"."a" FROM "examples_tfoo" WHERE "examples_tfoo"."id" = 2
SELECT "examples_tfoo"."id", "examples_tfoo"."name", "examples_tfoo"."a" FROM "examples_tfoo" WHERE "examples_tfoo"."id" = 3
SELECT "examples_tfoo"."id", "examples_tfoo"."name", "examples_tfoo"."a" FROM "examples_tfoo" WHERE "examples_tfoo"."id" = 4
... and 1 more unique statements

If you want more detailed information in your console to debug a problem you can set settings.SQL_DEBUG to 'all' (which prints all SQL statements), 'stacks' (all SQL statements with tracebacks). You can also set it to None to turn it off.

You can use this middleware on non-iommi views too. Just add ?_iommi_sql_trace to your url.