Summary

Add support for light-weight feature checks.

Review Request #8031 — Created March 4, 2016 and submitted June 14, 2016, 5 p.m.

Information

Owner

chipx86

Repository

Djblets

Branch

release-0.10.x

Bugs

Depends On

Reviewers

Groups

djblets

People

Description

Feature checks (aka feature switches/toggles) are a way to allow new
features to be built and tested in a codebase without exposing them to
every user.

This introduces support for light-weight feature checks. There are three
parts: Features, Feature Checkers, and the Feature Registry.

The Feature class is used to define a feature. It just requires a
feature ID and an optional name, summary, and stability level. It may
also contain functions for handling initialization and shutdown (for
when the feature is registered and unregistered, respectively). Once
instantiated, the feature is registered and ready to check.

Feature checkers determine whether a feature should be enabled, based on
the severity level and any other custom criteria. When an application
checks if a feature should be enabled, it can pass any criteria it
wants (user, request, etc.), and if the checker understands it, it can
consider it. This gives applications a lot of control of how features
and their checkers are to be used, without imposing major requirements
on them like other frameworks.

The feature registry contains all the features that have been
instantiated, and can be used to look up or list features dynamically.

There are template tags available as well for limiting bits of a
template based on whether a feature is enabled.

Documentation is provided covering how features work, and how to write
both features and feature checkers.

Testing Done

Unit tests pass.

Checked the docs for errors and bad code references.

Issues

Description	From	Last Updated
'FeatureNotFoundError' imported but unused	reviewbot	March 4, 2016, 8:17 p.m.
redefinition of unused 'test_is_enabled_with_unavailable' from line 91	reviewbot	March 4, 2016, 8:17 p.m.
'settings' imported but unused	reviewbot	March 4, 2016, 8:17 p.m.
'Site' imported but unused	reviewbot	March 4, 2016, 8:18 p.m.
'ImproperlyConfigured' imported but unused	reviewbot	March 4, 2016, 8:18 p.m.
'set_feature_checker' imported but unused	reviewbot	March 4, 2016, 8:18 p.m.
'SiteConfigFeatureChecker' imported but unused	reviewbot	March 4, 2016, 8:18 p.m.
'SettingsFeatureChecker' imported but unused	reviewbot	March 4, 2016, 8:18 p.m.
'BaseFeatureChecker' imported but unused	reviewbot	March 4, 2016, 8:18 p.m.
'get_feature_checker' imported but unused	reviewbot	March 4, 2016, 8:18 p.m.
'FeatureNotFoundError' imported but unused	reviewbot	March 4, 2016, 8:18 p.m.
'SiteConfiguration' imported but unused	reviewbot	March 4, 2016, 8:18 p.m.
local variable 't' is assigned to but never used	reviewbot	March 4, 2016, 8:19 p.m.
local variable 't' is assigned to but never used	reviewbot	March 4, 2016, 8:19 p.m.
local variable 'feature' is assigned to but never used	reviewbot	March 4, 2016, 8:19 p.m.
local variable 'feature' is assigned to but never used	reviewbot	March 4, 2016, 8:19 p.m.
local variable 'feature' is assigned to but never used	reviewbot	March 4, 2016, 8:19 p.m.
local variable 'feature' is assigned to but never used	reviewbot	March 4, 2016, 8:19 p.m.
local variable 't' is assigned to but never used	reviewbot	March 4, 2016, 8:19 p.m.
local variable 't' is assigned to but never used	reviewbot	March 4, 2016, 8:19 p.m.
local variable 'feature' is assigned to but never used	reviewbot	March 4, 2016, 8:19 p.m.
local variable 'feature' is assigned to but never used	reviewbot	March 4, 2016, 8:20 p.m.
local variable 'feature' is assigned to but never used	reviewbot	March 4, 2016, 8:20 p.m.
local variable 'feature' is assigned to but never used	reviewbot	March 4, 2016, 8:20 p.m.
'cache' imported but unused	reviewbot	March 4, 2016, 8:20 p.m.
Can we log the original exception?	david	May 18, 2016, 3:48 p.m.
Missing closing paren.	brennie	May 18, 2016, 6:07 p.m.
I think we should initialize the feature before registering it.	david	May 18, 2016, 4:37 p.m.
This should be djblets.features.feature.Feature	brennie	May 18, 2016, 6:08 p.m.
Docstrings in this file?	david	May 18, 2016, 4:37 p.m.
'Site' imported but unused	reviewbot	March 4, 2016, 8:21 p.m.
Too many blank lines.	david	May 18, 2016, 4:37 p.m.
Too many blank lines.	david	May 18, 2016, 4:37 p.m.
typo: "registerd"	david	May 18, 2016, 4:38 p.m.
I don't suppose it's possible to extract the docs for these from the code?	david	May 18, 2016, 4:47 p.m.
Can you add a period here?	david	May 18, 2016, 4:38 p.m.
Can you add a period here?	david	May 18, 2016, 4:38 p.m.
undefined name 'feature_id'	reviewbot	May 18, 2016, 6:30 p.m.
'set_feature_checker' imported but unused	reviewbot	May 18, 2016, 6:30 p.m.
'get_feature_checker' imported but unused	reviewbot	May 18, 2016, 6:30 p.m.

Tool: PEP8 Style Checker
Processed Files:
    djblets/features/tests/test_feature.py
    djblets/features/tests/test_checkers.py
    djblets/features/feature.py
    djblets/features/errors.py
    djblets/registries/registry.py
    djblets/features/tests/test_template_tags.py
    djblets/features/tests/test_registry.py
    djblets/features/templatetags/features.py
    djblets/features/registry.py
    djblets/siteconfig/models.py
    djblets/features/__init__.py
    djblets/features/level.py
    djblets/features/checkers.py

Ignored Files:
    docs/djblets/guides/features/intro.rst
    docs/djblets/guides/features/index.rst
    docs/djblets/guides/index.rst
    docs/djblets/guides/features/writing-feature-checkers.rst
    docs/djblets/guides/features/writing-features.rst
    docs/djblets/coderef/index.rst
    djblets/features/templatetags/__init__.py
    djblets/features/tests/__init__.py



Tool: Pyflakes
Processed Files:
    djblets/features/tests/test_feature.py
    djblets/features/tests/test_checkers.py
    djblets/features/feature.py
    djblets/features/errors.py
    djblets/registries/registry.py
    djblets/features/tests/test_template_tags.py
    djblets/features/tests/test_registry.py
    djblets/features/templatetags/features.py
    djblets/features/registry.py
    djblets/siteconfig/models.py
    djblets/features/__init__.py
    djblets/features/level.py
    djblets/features/checkers.py

Ignored Files:
    docs/djblets/guides/features/intro.rst
    docs/djblets/guides/features/index.rst
    docs/djblets/guides/index.rst
    docs/djblets/guides/features/writing-feature-checkers.rst
    docs/djblets/guides/features/writing-features.rst
    docs/djblets/coderef/index.rst
    djblets/features/templatetags/__init__.py
    djblets/features/tests/__init__.py

djblets/features/templatetags/features.py (Diff revision 1)
The issue has been resolved. Show all issues
```
 'FeatureNotFoundError' imported but unused
```
djblets/features/tests/test_feature.py (Diff revision 1)
The issue has been resolved. Show all issues
```
 redefinition of unused 'test_is_enabled_with_unavailable' from line 91
```
djblets/features/tests/test_registry.py (Diff revision 1)
The issue has been resolved. Show all issues
```
 'settings' imported but unused
```
djblets/features/tests/test_registry.py (Diff revision 1)
The issue has been resolved. Show all issues
```
 'Site' imported but unused
```
djblets/features/tests/test_registry.py (Diff revision 1)
The issue has been resolved. Show all issues
```
 'ImproperlyConfigured' imported but unused
```
djblets/features/tests/test_registry.py (Diff revision 1)
The issue has been resolved. Show all issues
```
 'set_feature_checker' imported but unused
```
djblets/features/tests/test_registry.py (Diff revision 1)
The issue has been resolved. Show all issues
```
 'SiteConfigFeatureChecker' imported but unused
```
djblets/features/tests/test_registry.py (Diff revision 1)
The issue has been resolved. Show all issues
```
 'SettingsFeatureChecker' imported but unused
```
djblets/features/tests/test_registry.py (Diff revision 1)
The issue has been resolved. Show all issues
```
 'BaseFeatureChecker' imported but unused
```
djblets/features/tests/test_registry.py (Diff revision 1)
The issue has been resolved. Show all issues
```
 'get_feature_checker' imported but unused
```
djblets/features/tests/test_registry.py (Diff revision 1)
The issue has been resolved. Show all issues
```
 'FeatureNotFoundError' imported but unused
```
djblets/features/tests/test_registry.py (Diff revision 1)
The issue has been resolved. Show all issues
```
 'SiteConfiguration' imported but unused
```
djblets/features/tests/test_template_tags.py (Diff revision 1)
The issue has been resolved. Show all issues
```
 local variable 't' is assigned to but never used
```
djblets/features/tests/test_template_tags.py (Diff revision 1)
The issue has been resolved. Show all issues
```
 local variable 't' is assigned to but never used
```
djblets/features/tests/test_template_tags.py (Diff revision 1)
The issue has been resolved. Show all issues
```
 local variable 'feature' is assigned to but never used
```
djblets/features/tests/test_template_tags.py (Diff revision 1)
The issue has been resolved. Show all issues
```
 local variable 'feature' is assigned to but never used
```
djblets/features/tests/test_template_tags.py (Diff revision 1)
The issue has been resolved. Show all issues
```
 local variable 'feature' is assigned to but never used
```
djblets/features/tests/test_template_tags.py (Diff revision 1)
The issue has been resolved. Show all issues
```
 local variable 'feature' is assigned to but never used
```
djblets/features/tests/test_template_tags.py (Diff revision 1)
The issue has been resolved. Show all issues
```
 local variable 't' is assigned to but never used
```
djblets/features/tests/test_template_tags.py (Diff revision 1)
The issue has been resolved. Show all issues
```
 local variable 't' is assigned to but never used
```
djblets/features/tests/test_template_tags.py (Diff revision 1)
The issue has been resolved. Show all issues
```
 local variable 'feature' is assigned to but never used
```
djblets/features/tests/test_template_tags.py (Diff revision 1)
The issue has been resolved. Show all issues
```
 local variable 'feature' is assigned to but never used
```
djblets/features/tests/test_template_tags.py (Diff revision 1)
The issue has been resolved. Show all issues
```
 local variable 'feature' is assigned to but never used
```
djblets/features/tests/test_template_tags.py (Diff revision 1)
The issue has been resolved. Show all issues
```
 local variable 'feature' is assigned to but never used
```
djblets/siteconfig/models.py (Diff revision 1)
The issue has been resolved. Show all issues
```
 'cache' imported but unused
```

Change Summary:

Fixed warnings.

Diff:

Revision 2 (+1829 -8)

Show changes

	djblets/features/__init__.py
	djblets/features/checkers.py
	djblets/features/errors.py
	djblets/features/feature.py
	djblets/features/level.py
	djblets/features/registry.py
	djblets/features/templatetags/__init__.py
	djblets/features/templatetags/features.py
	13 more

Tool: Pyflakes
Processed Files:
    djblets/features/tests/test_feature.py
    djblets/features/tests/test_checkers.py
    djblets/features/feature.py
    djblets/features/errors.py
    djblets/registries/registry.py
    djblets/features/tests/test_template_tags.py
    djblets/features/tests/test_registry.py
    djblets/features/templatetags/features.py
    djblets/features/registry.py
    djblets/siteconfig/models.py
    djblets/features/__init__.py
    djblets/features/level.py
    djblets/features/checkers.py

Ignored Files:
    docs/djblets/guides/features/intro.rst
    docs/djblets/guides/features/index.rst
    docs/djblets/guides/index.rst
    docs/djblets/guides/features/writing-feature-checkers.rst
    docs/djblets/guides/features/writing-features.rst
    docs/djblets/coderef/index.rst
    djblets/features/templatetags/__init__.py
    djblets/features/tests/__init__.py



Tool: PEP8 Style Checker
Processed Files:
    djblets/features/tests/test_feature.py
    djblets/features/tests/test_checkers.py
    djblets/features/feature.py
    djblets/features/errors.py
    djblets/registries/registry.py
    djblets/features/tests/test_template_tags.py
    djblets/features/tests/test_registry.py
    djblets/features/templatetags/features.py
    djblets/features/registry.py
    djblets/siteconfig/models.py
    djblets/features/__init__.py
    djblets/features/level.py
    djblets/features/checkers.py

Ignored Files:
    docs/djblets/guides/features/intro.rst
    docs/djblets/guides/features/index.rst
    docs/djblets/guides/index.rst
    docs/djblets/guides/features/writing-feature-checkers.rst
    docs/djblets/guides/features/writing-features.rst
    docs/djblets/coderef/index.rst
    djblets/features/templatetags/__init__.py
    djblets/features/tests/__init__.py

djblets/features/tests/test_registry.py (Diff revision 2)
The issue has been resolved. Show all issues
```
 'Site' imported but unused
```

Would you mind adding some utilities (either a method decorator or a context manager) to make it possible to set whether or not a feature is enabled when unit testing?

chipx86 May 18, 2016, 4:58 p.m.
```
Good idea. Will do!
```

djblets/features/checkers.py (Diff revision 2)
The issue has been resolved. Show all issues
```
Can we log the original exception?
```
djblets/features/registry.py (Diff revision 2)
The issue has been resolved. Show all issues
```
I think we should initialize the feature before registering it.
```
djblets/features/templatetags/features.py (Diff revision 2)
The issue has been resolved. Show all issues
```
Docstrings in this file?
```
djblets/features/tests/test_checkers.py (Diff revision 2)
```
:)
```
docs/djblets/guides/features/intro.rst (Diff revision 2)
The issue has been resolved. Show all issues
```
Too many blank lines.
```
docs/djblets/guides/features/intro.rst (Diff revision 2)
The issue has been resolved. Show all issues
```
Too many blank lines.
```
docs/djblets/guides/features/writing-features.rst (Diff revision 2)
The issue has been resolved. Show all issues
```
typo: "registerd"
```

docs/djblets/guides/features/writing-features.rst (Diff revision 2)

The issue has been dropped. Show all issues

I don't suppose it's possible to extract the docs for these from the code?

chipx86 May 18, 2016, 4:58 p.m.

Kind of is, but the presentation isn't quite right for this guide, and ends up not linking to the right place anymore (wants to link to itself).

docs/djblets/guides/features/writing-features.rst (Diff revision 2)
The issue has been resolved. Show all issues
```
Can you add a period here?
```
docs/djblets/guides/features/writing-features.rst (Diff revision 2)
The issue has been resolved. Show all issues
```
Can you add a period here?
```

djblets/features/registry.py (Diff revision 2)
The issue has been resolved. Show all issues
```
Missing closing paren.
```
djblets/features/registry.py (Diff revision 2)
The issue has been resolved. Show all issues
```
This should be djblets.features.feature.Feature
```

Change Summary:


Added unit test helpers for overriding feature enabled states.
Features are now registered after being initialized.
Exceptions are logged if failing to construct a feature checker.
Improved the documentation throughout, including fixes to guides and addition of docstrings.
Added a new guide on testing features in unit tests.

Diff:

Revision 3 (+2184 -8)

Show changes

	djblets/features/__init__.py
	djblets/features/checkers.py
	djblets/features/errors.py
	djblets/features/feature.py
	djblets/features/level.py
	djblets/features/registry.py
	djblets/features/testing.py
	djblets/features/templatetags/__init__.py
	16 more

Tool: PEP8 Style Checker
Processed Files:
    djblets/features/tests/test_feature.py
    djblets/features/tests/test_checkers.py
    djblets/features/feature.py
    djblets/features/errors.py
    djblets/registries/registry.py
    djblets/features/tests/test_template_tags.py
    djblets/features/tests/test_registry.py
    djblets/features/templatetags/features.py
    djblets/features/registry.py
    djblets/siteconfig/models.py
    djblets/features/__init__.py
    djblets/features/tests/test_testing.py
    djblets/features/level.py
    djblets/features/checkers.py
    djblets/features/testing.py

Ignored Files:
    docs/djblets/guides/features/intro.rst
    docs/djblets/guides/features/index.rst
    docs/djblets/guides/index.rst
    docs/djblets/guides/features/testing.rst
    docs/djblets/guides/features/writing-feature-checkers.rst
    docs/djblets/guides/features/writing-features.rst
    docs/djblets/coderef/index.rst
    djblets/features/templatetags/__init__.py
    djblets/features/tests/__init__.py



Tool: Pyflakes
Processed Files:
    djblets/features/tests/test_feature.py
    djblets/features/tests/test_checkers.py
    djblets/features/feature.py
    djblets/features/errors.py
    djblets/registries/registry.py
    djblets/features/tests/test_template_tags.py
    djblets/features/tests/test_registry.py
    djblets/features/templatetags/features.py
    djblets/features/registry.py
    djblets/siteconfig/models.py
    djblets/features/__init__.py
    djblets/features/tests/test_testing.py
    djblets/features/level.py
    djblets/features/checkers.py
    djblets/features/testing.py

Ignored Files:
    docs/djblets/guides/features/intro.rst
    docs/djblets/guides/features/index.rst
    docs/djblets/guides/index.rst
    docs/djblets/guides/features/testing.rst
    docs/djblets/guides/features/writing-feature-checkers.rst
    docs/djblets/guides/features/writing-features.rst
    docs/djblets/coderef/index.rst
    djblets/features/templatetags/__init__.py
    djblets/features/tests/__init__.py

djblets/features/templatetags/features.py (Diff revision 3)
The issue has been resolved. Show all issues
```
 undefined name 'feature_id'
```
djblets/features/testing.py (Diff revision 3)
The issue has been resolved. Show all issues
```
 'set_feature_checker' imported but unused
```
djblets/features/testing.py (Diff revision 3)
The issue has been resolved. Show all issues
```
 'get_feature_checker' imported but unused
```

Change Summary:


Removed unused imports.
Fixed a bad variable reference in IfFeatureNode.__repr__.

Diff:

Revision 4 (+2182 -8)

Show changes

	djblets/features/__init__.py
	djblets/features/checkers.py
	djblets/features/errors.py
	djblets/features/feature.py
	djblets/features/level.py
	djblets/features/registry.py
	djblets/features/testing.py
	djblets/features/templatetags/__init__.py
	16 more

Tool: Pyflakes
Processed Files:
    djblets/features/tests/test_feature.py
    djblets/features/tests/test_checkers.py
    djblets/features/feature.py
    djblets/features/errors.py
    djblets/registries/registry.py
    djblets/features/tests/test_template_tags.py
    djblets/features/tests/test_registry.py
    djblets/features/templatetags/features.py
    djblets/features/registry.py
    djblets/siteconfig/models.py
    djblets/features/__init__.py
    djblets/features/tests/test_testing.py
    djblets/features/level.py
    djblets/features/checkers.py
    djblets/features/testing.py

Ignored Files:
    docs/djblets/guides/features/intro.rst
    docs/djblets/guides/features/index.rst
    docs/djblets/guides/index.rst
    docs/djblets/guides/features/testing.rst
    docs/djblets/guides/features/writing-feature-checkers.rst
    docs/djblets/guides/features/writing-features.rst
    docs/djblets/coderef/index.rst
    djblets/features/templatetags/__init__.py
    djblets/features/tests/__init__.py



Tool: PEP8 Style Checker
Processed Files:
    djblets/features/tests/test_feature.py
    djblets/features/tests/test_checkers.py
    djblets/features/feature.py
    djblets/features/errors.py
    djblets/registries/registry.py
    djblets/features/tests/test_template_tags.py
    djblets/features/tests/test_registry.py
    djblets/features/templatetags/features.py
    djblets/features/registry.py
    djblets/siteconfig/models.py
    djblets/features/__init__.py
    djblets/features/tests/test_testing.py
    djblets/features/level.py
    djblets/features/checkers.py
    djblets/features/testing.py

Ignored Files:
    docs/djblets/guides/features/intro.rst
    docs/djblets/guides/features/index.rst
    docs/djblets/guides/index.rst
    docs/djblets/guides/features/testing.rst
    docs/djblets/guides/features/writing-feature-checkers.rst
    docs/djblets/guides/features/writing-features.rst
    docs/djblets/coderef/index.rst
    djblets/features/templatetags/__init__.py
    djblets/features/tests/__init__.py

Ship it!

```
Ship It!
```

Status:: Completed
Change Summary:: Pushed to release-0.10.x (9e2737e)