feat: add transaction propagation (open-feature#212)

Signed-off-by: Michael Beemer <[email protected]>
Co-authored-by: Todd Baert <[email protected]>

.eslintrc.json

@@ -26,7 +26,10 @@
 		 ],
 		 "quotes":[
 				"error",
-				"single"
+				"single",
+				{
+					"avoidEscape": true
+				}
 		 ],
 		 "semi":[
 				"error",

src/client.ts

@@ -194,6 +194,7 @@ export class OpenFeatureClient implements Client {
     // merge global and client contexts
     const mergedContext = {
       ...OpenFeature.getContext(),
+      ...OpenFeature.getTransactionContext(),
       ...this._context,
       ...invocationContext,
     };

src/no-op-transaction-context-propagator.ts

@@ -0,0 +1,13 @@
+import { EvaluationContext, TransactionContextPropagator } from './types';
+
+class NoopTransactionContextPropagator implements TransactionContextPropagator {
+  getTransactionContext(): EvaluationContext {
+    return {};
+  }
+
+  setTransactionContext(_: EvaluationContext, callback: () => void): void {
+    callback();
+  }
+}
+
+export const NOOP_TRANSACTION_CONTEXT_PROPAGATOR = new NoopTransactionContextPropagator();

src/open-feature.ts

@@ -1,7 +1,19 @@
 import { OpenFeatureClient } from './client';
 import { DefaultLogger, SafeLogger } from './logger';
 import { NOOP_PROVIDER } from './no-op-provider';
-import { Client, EvaluationContext, FlagValue, GlobalApi, Hook, Logger, Provider, ProviderMetadata } from './types';
+import { NOOP_TRANSACTION_CONTEXT_PROPAGATOR } from './no-op-transaction-context-propagator';
+import {
+  Client,
+  EvaluationContext,
+  FlagValue,
+  GlobalApi,
+  Hook,
+  Logger,
+  Provider,
+  ProviderMetadata,
+  TransactionContext,
+  TransactionContextPropagator,
+} from './types';
 
 // use a symbol as a key for the global singleton
 const GLOBAL_OPENFEATURE_API_KEY = Symbol.for('@openfeature/js.api');
@@ -13,6 +25,7 @@ const _globalThis = globalThis as OpenFeatureGlobal;
 
 class OpenFeatureAPI implements GlobalApi {
   private _provider: Provider = NOOP_PROVIDER;
+  private _transactionContextPropagator: TransactionContextPropagator = NOOP_TRANSACTION_CONTEXT_PROPAGATOR;
   private _context: EvaluationContext = {};
   private _hooks: Hook[] = [];
   private _logger: Logger = new DefaultLogger();
@@ -78,6 +91,37 @@ class OpenFeatureAPI implements GlobalApi {
   getContext(): EvaluationContext {
     return this._context;
   }
+
+  setTransactionContextPropagator(transactionContextPropagator: TransactionContextPropagator): OpenFeatureAPI {
+    const baseMessage = 'Invalid TransactionContextPropagator, will not be set: ';
+    if (typeof transactionContextPropagator?.getTransactionContext !== 'function') {
+      this._logger.error(`${baseMessage}: getTransactionContext is not a function.`);
+    } else if (typeof transactionContextPropagator?.setTransactionContext !== 'function') {
+      this._logger.error(`${baseMessage}: setTransactionContext is not a function.`);
+    } else {
+      this._transactionContextPropagator = transactionContextPropagator;
+    }
+    return this;
+  }
+
+  setTransactionContext<R>(
+    transactionContext: TransactionContext,
+    callback: (...args: unknown[]) => R,
+    ...args: unknown[]
+  ): void {
+    this._transactionContextPropagator.setTransactionContext(transactionContext, callback, ...args);
+  }
+
+  getTransactionContext(): TransactionContext {
+    try {
+      return this._transactionContextPropagator.getTransactionContext();
+    } catch (err: unknown) {
+      const error = err as Error | undefined;
+      this._logger.error(`Error getting transaction context: ${error?.message}, returning empty context.`);
+      this._logger.error(error?.stack);
+      return {};
+    }
+  }
 }
 
 export const OpenFeature = OpenFeatureAPI.getInstance();

src/types.ts

@@ -1,4 +1,4 @@
-type PrimitiveValue = null | boolean | string | number ;
+type PrimitiveValue = null | boolean | string | number;
 
 export type JsonObject = { [key: string]: JsonValue };
 
@@ -12,7 +12,11 @@ export type JsonValue = PrimitiveValue | JsonObject | JsonArray;
 /**
  * Represents a JSON node value, or Date.
  */
-export type EvaluationContextValue = PrimitiveValue | Date | { [key: string]: EvaluationContextValue } | EvaluationContextValue[];
+export type EvaluationContextValue =
+  | PrimitiveValue
+  | Date
+  | { [key: string]: EvaluationContextValue }
+  | EvaluationContextValue[];
 
 /**
  * A container for arbitrary contextual data that can be used as a basis for dynamic evaluation
@@ -43,7 +47,6 @@ export interface Logger {
 }
 
 export interface Features {
-
   /**
    * Performs a flag evaluation that returns a boolean.
    *
@@ -86,7 +89,7 @@ export interface Features {
    * @param {FlagEvaluationOptions} options Additional flag evaluation options
    * @returns {Promise<T>} Flag evaluation response
    */
-   getStringValue(
+  getStringValue(
     flagKey: string,
     defaultValue: string,
     context?: EvaluationContext,
@@ -155,7 +158,7 @@ export interface Features {
    * @param {FlagEvaluationOptions} options Additional flag evaluation options
    * @returns {Promise<EvaluationDetails<T>>} Flag evaluation details response
    */
-   getNumberDetails(
+  getNumberDetails(
     flagKey: string,
     defaultValue: number,
     context?: EvaluationContext,
@@ -277,7 +280,7 @@ export const StandardResolutionReasons = {
    * The resolved value was the result of a dynamic evaluation, such as a rule or specific user-targeting.
    */
   TARGETING_MATCH: 'TARGETING_MATCH',
-  
+
   /**
    * The resolved value was the result of pseudorandom assignment.
    */
@@ -301,7 +304,7 @@ export const StandardResolutionReasons = {
   /**
    * The resolved value was the result of an error.
    *
-   * Note: The `errorCode` and `errorMessage` fields may contain additional details of this error. 
+   * Note: The `errorCode` and `errorMessage` fields may contain additional details of this error.
    */
   ERROR: 'ERROR',
 } as const;
@@ -361,7 +364,11 @@ export interface Client extends EvaluationLifeCycle<Client>, Features, ManageCon
   readonly metadata: ClientMetadata;
 }
 
-export interface GlobalApi extends EvaluationLifeCycle<GlobalApi>, ManageContext<GlobalApi>, ManageLogger<GlobalApi> {
+export interface GlobalApi
+  extends EvaluationLifeCycle<GlobalApi>,
+    ManageContext<GlobalApi>,
+    ManageLogger<GlobalApi>,
+    ManageTransactionContextPropagator<GlobalApi> {
   readonly providerMetadata: ProviderMetadata;
   /**
    * A factory function for creating new OpenFeature clients. Clients can contain
@@ -374,15 +381,15 @@ export interface GlobalApi extends EvaluationLifeCycle<GlobalApi>, ManageContext
    * @returns {Client} OpenFeature Client
    */
   getClient(name?: string, version?: string, context?: EvaluationContext): Client;
-  
+
   /**
    * Sets the provider that OpenFeature will use for flag evaluations. Setting
    * a provider supersedes the current provider used in new and existing clients.
    *
    * @param {Provider} provider The provider responsible for flag evaluations.
    * @returns {GlobalApi} OpenFeature API
    */
-   setProvider(provider: Provider): GlobalApi
+  setProvider(provider: Provider): GlobalApi;
 }
 
 interface EvaluationLifeCycle<T> {
@@ -442,7 +449,7 @@ interface ManageLogger<T> {
    * unless overridden in a particular client.
    *
    * @template T The type of the receiver
-   * @param {Logger} logger The logger to to be used
+   * @param {Logger} logger The logger to be used
    * @returns {T} The receiver (this object)
    */
   setLogger(logger: Logger): T;
@@ -520,3 +527,56 @@ export interface Hook<T extends FlagValue = FlagValue> {
    */
   finally?(hookContext: Readonly<HookContext<T>>, hookHints?: HookHints): Promise<void> | void;
 }
+
+/**
+ * Transaction context is a mechanism for adding transaction specific context that
+ * is merged with evaluation context prior to flag evaluation. Examples of potential
+ * transaction specific context include: a user id, user agent, or request path.
+ */
+export type TransactionContext = EvaluationContext;
+
+interface ManageTransactionContextPropagator<T> extends TransactionContextPropagator {
+  /**
+   * EXPERIMENTAL: Transaction context propagation is experimental and subject to change.
+   * The OpenFeature Enhancement Proposal regarding transaction context can be found [here](https://github.com/open-feature/ofep/pull/32).
+   *
+   * Sets a transaction context propagator on this receiver. The transaction context
+   * propagator is responsible for persisting context for the duration of a single
+   * transaction.
+   *
+   * @template T The type of the receiver
+   * @param {TransactionContextPropagator} transactionContextPropagator The context propagator to be used
+   * @returns {T} The receiver (this object)
+   */
+  setTransactionContextPropagator(transactionContextPropagator: TransactionContextPropagator): T;
+}
+
+export interface TransactionContextPropagator {
+  /**
+   * EXPERIMENTAL: Transaction context propagation is experimental and subject to change.
+   * The OpenFeature Enhancement Proposal regarding transaction context can be found [here](https://github.com/open-feature/ofep/pull/32).
+   *
+   * Returns the currently defined transaction context using the registered transaction
+   * context propagator.
+   *
+   * @returns {TransactionContext} The current transaction context
+   */
+  getTransactionContext(): TransactionContext;
+
+  /**
+   * EXPERIMENTAL: Transaction context propagation is experimental and subject to change.
+   * The OpenFeature Enhancement Proposal regarding transaction context can be found [here](https://github.com/open-feature/ofep/pull/32).
+   *
+   * Sets the transaction context using the registered transaction context propagator.
+   *
+   * @template R The return value of the callback
+   * @param {TransactionContext} transactionContext The transaction specific context
+   * @param {(...args: unknown[]) => R} callback Callback function used to set the transaction context on the stack
+   * @param {...unknown[]} args Optional arguments that are passed to the callback function
+   */
+  setTransactionContext<R>(
+    transactionContext: TransactionContext,
+    callback: (...args: unknown[]) => R,
+    ...args: unknown[]
+  ): void;
+}