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sameeranksameerank
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FFL-2664 Extract rules evaluator into core (#332)
* FFL-2664 Extract rules evaluator into core * Fix evaluator formatting
1 parent 01d5c87 commit df6377a

18 files changed

Lines changed: 567 additions & 557 deletions

‎packages/core/src/evaluation/errors.ts‎

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export class TargetingKeyMissingError extends Error {
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constructor() {
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super('Targeting key is required for split evaluation')
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this.name = 'TargetingKeyMissingError'
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}
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}

‎packages/core/src/evaluation/evaluateForSubject.ts‎

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import type { TimeStamp } from '@datadog/js-core/time'
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import { timeStampNow } from '@datadog/js-core/time'
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import type { ErrorCode, EvaluationContext, FlagValueType, Logger, ResolutionDetails } from '@openfeature/core'
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import type { FlagTypeToValue, PrecomputedFlagMetadata } from '../configuration'
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import { TargetingKeyMissingError } from './errors'
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import { createEvaluationTimestampMetadata } from './evaluationMetadata'
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import { matchesShard } from './matchesShard'
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import { matchesRule, type Rule } from './rules'
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import { type Flag, type Split, type VariantType, variantTypeToFlagValueType } from './ufc-v1'
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export function evaluateForSubject<T extends FlagValueType>(
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flag: Flag,
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type: T,
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subjectKey: string | null | undefined,
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subjectAttributes: EvaluationContext,
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defaultValue: FlagTypeToValue<T>,
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logger: Logger,
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evaluationTimestampMs: TimeStamp = timeStampNow()
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): ResolutionDetails<FlagTypeToValue<T>> {
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if (!flag.enabled) {
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logger.debug(`returning default assignment because flag is disabled`, {
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flagKey: flag.key,
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subjectKey,
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})
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return {
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value: defaultValue,
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reason: 'DISABLED',
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flagMetadata: createEvaluationTimestampMetadata(evaluationTimestampMs),
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}
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}
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const isValid = validateTypeMatch(type, flag.variationType)
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if (!isValid) {
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logger.debug(`variant value type mismatch, returning default value`, {
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flagKey: flag.key,
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subjectKey,
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expectedType: type,
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variantType: flag.variationType,
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})
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return {
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value: defaultValue,
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reason: 'ERROR',
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errorCode: 'TYPE_MISMATCH' as ErrorCode,
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flagMetadata: createEvaluationTimestampMetadata(evaluationTimestampMs),
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}
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}
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const now = new Date(evaluationTimestampMs)
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for (const allocation of flag.allocations) {
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if (allocation.startAt && now < new Date(allocation.startAt)) {
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logger.debug(`allocation before start date`, {
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flagKey: flag.key,
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subjectKey,
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allocationKey: allocation.key,
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startAt: allocation.startAt,
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})
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continue
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}
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if (allocation.endAt && now >= new Date(allocation.endAt)) {
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logger.debug(`allocation after end date`, {
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flagKey: flag.key,
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subjectKey,
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allocationKey: allocation.key,
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endAt: allocation.endAt,
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})
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continue
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}
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const matched = containsMatchingRule(allocation.rules, subjectAttributes, logger)
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if (!matched) {
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continue
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}
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const selectedSplit = selectSplitUsingSharding(allocation.splits, subjectKey, flag.key, logger)
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if (selectedSplit) {
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const variant = flag.variations[selectedSplit.variationKey]
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if (variant) {
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logger.debug(`evaluated a flag`, {
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flagKey: flag.key,
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subjectKey,
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assignment: variant.value,
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})
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return {
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value: variant.value as FlagTypeToValue<T>,
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reason: 'TARGETING_MATCH',
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variant: variant.key,
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flagMetadata: {
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...createEvaluationTimestampMetadata(evaluationTimestampMs),
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// Keys for dd-trace-js
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__dd_allocation_key: allocation.key,
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__dd_do_log: !!allocation.doLog,
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__dd_split_serial_id: selectedSplit.serialId,
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// Legacy keys (internal) - to be removed from server-side
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allocationKey: allocation.key,
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variationType: variantTypeToFlagValueType(flag.variationType),
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doLog: !!allocation.doLog,
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} as PrecomputedFlagMetadata,
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}
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}
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} else {
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logger.debug(`no matching split found for subject`, {
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flagKey: flag.key,
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subjectKey,
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allocationKey: allocation.key,
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})
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}
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}
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// This shouldn't happen since a default allocation is generated by the server
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logger.debug(`returning default assignment because no allocation matched`, {
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flagKey: flag.key,
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subjectKey,
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})
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return {
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value: defaultValue,
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reason: 'DEFAULT',
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flagMetadata: createEvaluationTimestampMetadata(evaluationTimestampMs),
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}
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}
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function validateTypeMatch(expectedType: FlagValueType, variantType: VariantType): boolean {
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if (expectedType === 'boolean') {
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return variantType === 'BOOLEAN'
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}
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if (expectedType === 'string') {
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return variantType === 'STRING'
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}
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if (expectedType === 'number') {
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return variantType === 'INTEGER' || variantType === 'NUMERIC'
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}
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if (expectedType === 'object') {
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return variantType === 'JSON'
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}
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throw new Error(`Invalid expected type: ${expectedType}`)
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}
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export function containsMatchingRule(
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rules: Rule[] | undefined,
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subjectAttributes: EvaluationContext,
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logger: Logger
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): boolean {
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if (!rules?.length) {
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return true
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}
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logger.debug(`evaluating rules`, {
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rules: JSON.stringify(rules),
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subjectAttributes,
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})
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return rules.some((rule) => matchesRule(rule, subjectAttributes))
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}
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function selectSplitUsingSharding(
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splits: Split[],
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subjectKey: string | null | undefined,
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flagKey: string,
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logger: Logger
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): Split | null {
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if (!splits || splits.length === 0) {
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return null
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}
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for (const split of splits) {
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logger.debug(`evaluating split sharding`, {
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flagKey,
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subjectKey,
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variationKey: split.variationKey,
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shards: split.shards,
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})
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const matches = split.shards.every((shard) => {
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if (subjectKey == null) {
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throw new TargetingKeyMissingError()
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}
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const shardMatches = matchesShard(shard, subjectKey)
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logger.debug(`shard match result`, {
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flagKey,
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subjectKey,
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variationKey: split.variationKey,
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shard: shard,
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matches: shardMatches,
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})
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return shardMatches
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})
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if (matches) {
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logger.debug(`subject matches split`, {
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flagKey,
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subjectKey,
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variationKey: split.variationKey,
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})
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return split
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}
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}
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logger.debug(`subject matches no splits`, {
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flagKey,
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subjectKey,
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})
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return null
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}

‎packages/core/src/evaluation/evaluation.ts‎

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import { timeStampNow } from '@datadog/js-core/time'
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import type { ErrorCode, EvaluationContext, FlagValueType, Logger, ResolutionDetails } from '@openfeature/core'
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import type { FlagTypeToValue } from '../configuration'
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import { TargetingKeyMissingError } from './errors'
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import { evaluateForSubject } from './evaluateForSubject'
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import { createEvaluationTimestampMetadata } from './evaluationMetadata'
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import type { UniversalFlagConfigurationV1 } from './ufc-v1'
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export function evaluateRulesBasedConfiguration<T extends FlagValueType>(
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config: UniversalFlagConfigurationV1 | undefined,
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type: T,
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flagKey: string,
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defaultValue: FlagTypeToValue<T>,
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context: EvaluationContext,
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logger: Logger
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): ResolutionDetails<FlagTypeToValue<T>> {
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const evaluationTimestampMs = timeStampNow()
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if (!config) {
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return {
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value: defaultValue,
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reason: 'ERROR',
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errorCode: 'PROVIDER_NOT_READY' as ErrorCode,
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flagMetadata: createEvaluationTimestampMetadata(evaluationTimestampMs),
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}
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}
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const { targetingKey: subjectKey, ...remainingContext } = context
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// Include the subjectKey as an "id" attribute for rule matching only when present
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const subjectAttributes = {
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...(subjectKey != null ? { id: subjectKey } : {}),
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...remainingContext,
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}
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const flag = config.flags[flagKey]
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if (!flag) {
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logger.debug('returning default value because flag is not found', { flagKey, subjectKey })
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return {
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value: defaultValue,
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reason: 'ERROR',
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errorCode: 'FLAG_NOT_FOUND' as ErrorCode,
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flagMetadata: createEvaluationTimestampMetadata(evaluationTimestampMs),
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}
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}
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try {
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return evaluateForSubject(flag, type, subjectKey, subjectAttributes, defaultValue, logger, evaluationTimestampMs)
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} catch (error) {
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if (error instanceof TargetingKeyMissingError) {
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return {
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value: defaultValue,
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reason: 'ERROR',
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errorCode: 'TARGETING_KEY_MISSING' as ErrorCode,
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flagMetadata: createEvaluationTimestampMetadata(evaluationTimestampMs),
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}
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}
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logger.error('Error evaluating flag', { error })
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return {
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value: defaultValue,
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reason: 'ERROR',
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errorCode: 'GENERAL' as ErrorCode,
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flagMetadata: createEvaluationTimestampMetadata(evaluationTimestampMs),
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}
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}
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}

‎packages/core/src/evaluation/evaluationMetadata.ts‎

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import type { TimeStamp } from '@datadog/js-core/time'
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import type { PrecomputedFlagMetadata } from '../configuration'
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export function createEvaluationTimestampMetadata(evaluationTimestampMs: TimeStamp): PrecomputedFlagMetadata {
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return { __dd_eval_timestamp_ms: evaluationTimestampMs } as PrecomputedFlagMetadata
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}

‎packages/core/src/evaluation/index.ts‎

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export * from './errors'
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export * from './evaluateForSubject'
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export * from './evaluation'
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export * from './evaluationMetadata'
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export * from './matchesShard'
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export * from './rules'
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export * from './sharders'
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export * from './ufc-v1'

‎packages/core/src/evaluation/matchesShard.ts‎

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import { MD5Sharder, type Sharder } from './sharders'
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import type { Shard, ShardRange } from './ufc-v1'
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export function matchesShard(shard: Shard, subjectKey: string, customSharder?: Sharder): boolean {
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const sharder = customSharder ?? new MD5Sharder()
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const assignedShard = sharder.getShard(hashKey(shard.salt, subjectKey), shard.totalShards)
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return shard.ranges.some((range) => isInShardRange(assignedShard, range))
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}
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function isInShardRange(shard: number, range: ShardRange): boolean {
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return range.start <= shard && shard < range.end
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}
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function hashKey(salt: string, subjectKey: string): string {
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return `${salt}-${subjectKey}`
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}

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