feature

feature

Package feature implements a simple abstraction for feature flags with arbitrary values.

Examples

Registering a flag

A flag is registered on a FlagSet.

Flags are created using a specific method based on the type of the value of the flag, named after the type.

Currently, the supported methods are

• FlagSet.Bool for boolean flags,
• FlagSet.Float for float flags,
• FlagSet.Int for int flags and
• FlagSet.String for string flags.
• FlagSet.Uint for uint flags.

Each method will return a callback that takes a context.Context and returns a value of the specific type.

Additionally, each method can take an arbitrary number of options for adding metadata to the flag.

For example:

package main

import (
	"context"

	"github.com/nussjustin/feature"
)

func main() {
	var set feature.FlagSet

	myFeature := set.Bool("my-feature", false, "some new feature")

	if myFeature(context.Background()) {
		println("my-feature enabled") // never runs, see next section
	}
}

Context-specific values

By default, the values returned for each flag will be the default value specified when creating the flag.

The FlagSet.Context method can be used to set custom values for feature flags on a per-context basis.

Example:

package main

import (
	"context"

	"github.com/nussjustin/feature"
)

func main() {
	var set feature.FlagSet

	myFeature := set.Bool("my-feature", false, "some new feature")

	// Enable the feature for our context
	ctx := set.Context(context.Background(),
		feature.BoolValue("my-feature", true))
	
	if myFeature(ctx) {
		println("my-feature enabled")
	}
}

Contributing

Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.

Please make sure to update tests as appropriate.

License

MIT