What is a “Feature”?

The set of features that compose your application must be defined before they can be used in assignments. The features of an application decompose its overall function into discrete, coherent units. This gem defines a “feature” as follows:

A feature is an internal component of the system that performs a well defined and relatively isolated set of responsibilities.

It’s also helpful to understand what articulating the features of a system does:

• Allows useful conversations about the operation of a given function of the system (e.g., authentication, payment processing)
• Allows folks without deep, firsthand knowledge of the details of a given set of source files, to understand the value that they provide as a whole
• Allows for extension, refactoring, or other planning activities to consider specific, but holistic units of the system without delving into individual files
• In systems where files are organized by type (e.g., models, controllers, views, service classes), allows for source files to be grouped by function without clumsy in-code namespacing

Here are a few examples of poorly-constructed features

In short, a feature is well-defined if it can be used to reason about a distinct part of a system at a level more abstract that a few source files.

Where are features defined?

All features are defined within a single CSV file located at .feature_map/feature_definitions.csv. That file may optionally begin with one or more # denoted, sequential comments that describe the file and the strategy used to manage the feature list. Then it must have a single header row with following headings – followed by corresponding values. Only the Name must be populated with a value for each row.

• Name: Canonical name of the feature. May include spaces or other punctuation.
• Description: A text description of the feature for reference.
• Documentation Link: A URL that points to more comprehensive, external documentation if available.

Here’s an example of what that file might look like

# Comment explaining the purpose of this file and how it should be managed.
# Perhaps directly modifying this file in the repository, or exporting it from elsewhere.

Name,Description,
Onboarding,"Lorem ipsum dolor sit amet, consectetur adipiscing elit.",https://www.notion.so/onboarding-feature-abcd1234
User Management,"Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation",