validator

README

Validator Hook

The validator hook taps into the After lifecycle event to validate the result of flag evaluations. If the result is invalid, the default value and an error are returned.

The hook defines a validator interface with function

IsValid(flagEvaluationDetails of.EvaluationDetails) error

to allow application authors to supply their own validators.

There are, however, ready to be used validators that conform to the interface.

Setup

Import the OpenFeature SDK and the validator.

Create an instance of the validator hook struct (using the hex validator as an example):

package main

import (
	"fmt"
	"github.com/open-feature/go-sdk-contrib/hooks/validator/pkg/regex"
	"github.com/open-feature/go-sdk-contrib/hooks/validator/pkg/validator"
	"github.com/open-feature/go-sdk/openfeature"
	"log"
)

func main() {
	hexValidator, err := regex.Hex()
	if err != nil {
		log.Fatal(err)
	}
	v := validator.Hook{Validator: hexValidator}
}

Use the validator hook (on invocation as an example):

client := openfeature.NewClient("foo")
value, err := client.
    StringValueDetails("blue", "#0000FF", openfeature.EvaluationContext{}, openfeature.WithHooks(v))
if err != nil {
    fmt.Println("err:", err)
}

Example

Following setup, use the NoopProvider, this simply returns the given default value on flag evaluation. Give a false hex color as the default value call and check that the flag evaluation returns an error.

package main

import (
	"fmt"
	"github.com/open-feature/go-sdk-contrib/hooks/validator/pkg/regex"
	"github.com/open-feature/go-sdk-contrib/hooks/validator/pkg/validator"
	"github.com/open-feature/go-sdk/openfeature"
	"log"
)

func main() {
	openfeature.SetProvider(openfeature.NoopProvider{})
	hexValidator, err := regex.Hex()
	if err != nil {
		log.Fatal(err)
	}
	v := validator.Hook{Validator: hexValidator}
	client := openfeature.NewClient("foo")

	result, err := client.
		StringValueDetails("blue", "invalidhex", openfeature.EvaluationContext{}, openfeature.WithHooks(v))
	if err != nil {
		fmt.Println("err:", err)
	}

	fmt.Println("result:", result)
}

go run main.go
err: execute after hook: regex doesn't match on flag value
result: {blue 1 {invalidhex   }}

Note that despite getting an error we still get a result.

Validators

• Regex validates the result matches the given regex
• Hex validates the result is a valid hex color (e.g. #FFFFFF)

License

Apache 2.0 - See LICENSE for more information.