Evaluation reasons and error codes

When you evaluate a flag using the binding's *Details methods or the OpenFeature SDK, the response includes a reason field that explains why a particular value was returned. If an error occurs, the response includes an errorCode field.

Evaluation reasons

Reason	Description
`TARGETING_MATCH`	A targeting rule's conditions matched the evaluation context, and the rule's variant was returned.
`SPLIT`	A targeting rule with a percentage rollout matched. The user fell within the rollout percentage and received the rule's variant.
`DEFAULT`	No targeting rule matched the evaluation context. The flag's default variant was returned.
`DISABLED`	The flag is disabled. The default variant was returned regardless of targeting rules.
`CACHED`	The SDK returned a cached evaluation result.
`ERROR`	Evaluation failed and the default value was returned.

Error codes

When an evaluation error occurs, the method returns the default value you provided. The *Details methods include additional metadata about the error.

Error code	Description
`TYPE_MISMATCH`	The flag's variant type does not match the requested type. For example, calling `getBooleanValue` on a flag whose variant is a string. The default value is returned.
`FLAG_NOT_FOUND`	The specified flag key does not exist in the app. The default value is returned.
`INVALID_CONTEXT`	The evaluation context contains unsupported values, such as objects or arrays in HTTP evaluation. The default value is returned.
`PARSE_ERROR`	The SDK received an invalid evaluation response. The default value is returned.
`GENERAL`	An unexpected error occurred during evaluation, such as a timeout or network failure. The default value is returned.

Example

The following example inspects evaluation details returned by getBooleanDetails:

const details = await env.FLAGS.getBooleanDetails("my-feature", false, {
	userId: "user-42",
});

switch (details.reason) {
	case "TARGETING_MATCH":
		console.log(`Matched targeting rule, variant: ${details.variant}`);
		break;
	case "SPLIT":
		console.log(`Included in rollout, variant: ${details.variant}`);
		break;
	case "DEFAULT":
		console.log("No rule matched, using default variant");
		break;
	case "DISABLED":
		console.log("Flag is disabled");
		break;
}

if (details.errorCode) {
	console.error(`Evaluation error: ${details.errorCode}`);
}

const details = await env.FLAGS.getBooleanDetails("my-feature", false, {
	userId: "user-42",
});

switch (details.reason) {
	case "TARGETING_MATCH":
		console.log(`Matched targeting rule, variant: ${details.variant}`);
		break;
	case "SPLIT":
		console.log(`Included in rollout, variant: ${details.variant}`);
		break;
	case "DEFAULT":
		console.log("No rule matched, using default variant");
		break;
	case "DISABLED":
		console.log("Flag is disabled");
		break;
}

if (details.errorCode) {
	console.error(`Evaluation error: ${details.errorCode}`);
}