feat: precomputed assignment methods for supported types (#135)

* Add methods for boolean, integer, numeric, and json types

* Add tests for typed assignments

* Remove eslint warnings

Author: sameerank

src/client/eppo-precomputed-client.spec.ts

@@ -22,14 +22,46 @@ describe('EppoPrecomputedClient E2E test', () => {
       name: 'Test',
     },
     flags: {
-      'new-user-onboarding': {
+      'string-flag': {
         allocationKey: 'allocation-123',
         variationKey: 'variation-123',
         variationType: 'STRING',
         variationValue: 'red',
         extraLogging: {},
         doLog: true,
       },
+      'boolean-flag': {
+        allocationKey: 'allocation-124',
+        variationKey: 'variation-124',
+        variationType: 'BOOLEAN',
+        variationValue: true,
+        extraLogging: {},
+        doLog: true,
+      },
+      'integer-flag': {
+        allocationKey: 'allocation-125',
+        variationKey: 'variation-125',
+        variationType: 'INTEGER',
+        variationValue: 42,
+        extraLogging: {},
+        doLog: true,
+      },
+      'numeric-flag': {
+        allocationKey: 'allocation-126',
+        variationKey: 'variation-126',
+        variationType: 'NUMERIC',
+        variationValue: 3.14,
+        extraLogging: {},
+        doLog: true,
+      },
+      'json-flag': {
+        allocationKey: 'allocation-127',
+        variationKey: 'variation-127',
+        variationType: 'JSON',
+        variationValue: '{"key": "value", "number": 123}',
+        extraLogging: {},
+        doLog: true,
+      },
     },
   }; // TODO: readMockPrecomputedFlagsResponse(MOCK_PRECOMPUTED_FLAGS_RESPONSE_FILE);
 
@@ -337,7 +369,7 @@ describe('EppoPrecomputedClient E2E test', () => {
     let precomputedFlagStore: IConfigurationStore<PrecomputedFlag>;
     let requestParameters: PrecomputedFlagsRequestParameters;
 
-    const precomputedFlagKey = 'new-user-onboarding';
+    const precomputedFlagKey = 'string-flag';
     const red = 'red';
 
     const maxRetryDelay = DEFAULT_POLL_INTERVAL_MS * POLL_JITTER_PCT;
@@ -467,6 +499,50 @@ describe('EppoPrecomputedClient E2E test', () => {
       expect(variation).toBe('default');
     });
 
+    describe('Gets typed assignments', () => {
+      let client: EppoPrecomputedClient;
+
+      beforeEach(async () => {
+        client = new EppoPrecomputedClient(storage, requestParameters);
+        await client.fetchPrecomputedFlags();
+      });
+
+      it('returns string assignment', () => {
+        expect(client.getStringAssignment('string-flag', 'default')).toBe('red');
+        expect(client.getStringAssignment('non-existent', 'default')).toBe('default');
+      });
+
+      it('returns boolean assignment', () => {
+        expect(client.getBooleanAssignment('boolean-flag', false)).toBe(true);
+        expect(client.getBooleanAssignment('non-existent', false)).toBe(false);
+      });
+
+      it('returns integer assignment', () => {
+        expect(client.getIntegerAssignment('integer-flag', 0)).toBe(42);
+        expect(client.getIntegerAssignment('non-existent', 0)).toBe(0);
+      });
+
+      it('returns numeric assignment', () => {
+        expect(client.getNumericAssignment('numeric-flag', 0)).toBe(3.14);
+        expect(client.getNumericAssignment('non-existent', 0)).toBe(0);
+      });
+
+      it('returns JSON assignment', () => {
+        expect(client.getJSONAssignment('json-flag', {})).toEqual({
+          key: 'value',
+          number: 123,
+        });
+        expect(client.getJSONAssignment('non-existent', {})).toEqual({});
+      });
+
+      it('returns default value when type mismatches', () => {
+        // Try to get a string value from a boolean flag
+        expect(client.getStringAssignment('boolean-flag', 'default')).toBe('default');
+        // Try to get a boolean value from a string flag
+        expect(client.getBooleanAssignment('string-flag', false)).toBe(false);
+      });
+    });
+
     it.each([
       { pollAfterSuccessfulInitialization: false },
       { pollAfterSuccessfulInitialization: true },

src/client/eppo-precomputed-client.ts

@@ -17,7 +17,7 @@ import {
 import { decodePrecomputedFlag } from '../decoding';
 import { FlagEvaluationWithoutDetails } from '../evaluator';
 import FetchHttpClient from '../http-client';
-import { FormatEnum, PrecomputedFlag } from '../interfaces';
+import { PrecomputedFlag, VariationType } from '../interfaces';
 import { getMD5Hash } from '../obfuscation';
 import initPoller, { IPoller } from '../poller';
 import PrecomputedRequestor from '../precomputed-requestor';
@@ -130,16 +130,12 @@ export default class EppoPrecomputedClient {
     }
   }
 
-  /**
-   * Maps a subject to a string variation for a given experiment.
-   *
-   * @param flagKey feature flag identifier
-   * @param defaultValue default value to return if the subject is not part of the experiment sample
-   * The subject attributes are used for evaluating any targeting rules tied to the experiment.
-   * @returns a variation value if a flag was precomputed for the subject, otherwise the default value
-   * @public
-   */
-  public getStringAssignment(flagKey: string, defaultValue: string): string {
+  private getPrecomputedAssignment<T>(
+    flagKey: string,
+    defaultValue: T,
+    expectedType: VariationType,
+    valueTransformer: (value: unknown) => T = (v) => v as T,
+  ): T {
     validateNotBlank(flagKey, 'Invalid argument: flagKey cannot be blank');
 
     const preComputedFlag = this.getPrecomputedFlag(flagKey);
@@ -149,6 +145,14 @@ export default class EppoPrecomputedClient {
       return defaultValue;
     }
 
+    // Check variation type
+    if (preComputedFlag.variationType !== expectedType) {
+      logger.error(
+        `[Eppo SDK] Type mismatch: expected ${expectedType} but flag ${flagKey} has type ${preComputedFlag.variationType}`,
+      );
+      return defaultValue;
+    }
+
     const result: FlagEvaluationWithoutDetails = {
       flagKey,
       format: this.precomputedFlagStore.getFormat() ?? '',
@@ -170,7 +174,77 @@ export default class EppoPrecomputedClient {
     } catch (error) {
       logger.error(`[Eppo SDK] Error logging assignment event: ${error}`);
     }
-    return (result.variation?.value as string) ?? defaultValue;
+
+    try {
+      return result.variation?.value !== undefined
+        ? valueTransformer(result.variation.value)
+        : defaultValue;
+    } catch (error) {
+      logger.error(`[Eppo SDK] Error transforming value: ${error}`);
+      return defaultValue;
+    }
+  }
+
+  /**
+   * Maps a subject to a string variation for a given experiment.
+   *
+   * @param flagKey feature flag identifier
+   * @param defaultValue default value to return if the subject is not part of the experiment sample
+   * @returns a variation value if a flag was precomputed for the subject, otherwise the default value
+   * @public
+   */
+  public getStringAssignment(flagKey: string, defaultValue: string): string {
+    return this.getPrecomputedAssignment(flagKey, defaultValue, VariationType.STRING);
+  }
+
+  /**
+   * Maps a subject to a boolean variation for a given experiment.
+   *
+   * @param flagKey feature flag identifier
+   * @param defaultValue default value to return if the subject is not part of the experiment sample
+   * @returns a variation value if a flag was precomputed for the subject, otherwise the default value
+   * @public
+   */
+  public getBooleanAssignment(flagKey: string, defaultValue: boolean): boolean {
+    return this.getPrecomputedAssignment(flagKey, defaultValue, VariationType.BOOLEAN);
+  }
+
+  /**
+   * Maps a subject to an integer variation for a given experiment.
+   *
+   * @param flagKey feature flag identifier
+   * @param defaultValue default value to return if the subject is not part of the experiment sample
+   * @returns a variation value if a flag was precomputed for the subject, otherwise the default value
+   * @public
+   */
+  public getIntegerAssignment(flagKey: string, defaultValue: number): number {
+    return this.getPrecomputedAssignment(flagKey, defaultValue, VariationType.INTEGER);
+  }
+
+  /**
+   * Maps a subject to a numeric (floating point) variation for a given experiment.
+   *
+   * @param flagKey feature flag identifier
+   * @param defaultValue default value to return if the subject is not part of the experiment sample
+   * @returns a variation value if a flag was precomputed for the subject, otherwise the default value
+   * @public
+   */
+  public getNumericAssignment(flagKey: string, defaultValue: number): number {
+    return this.getPrecomputedAssignment(flagKey, defaultValue, VariationType.NUMERIC);
+  }
+
+  /**
+   * Maps a subject to a JSON object variation for a given experiment.
+   *
+   * @param flagKey feature flag identifier
+   * @param defaultValue default value to return if the subject is not part of the experiment sample
+   * @returns a parsed JSON object if a flag was precomputed for the subject, otherwise the default value
+   * @public
+   */
+  public getJSONAssignment(flagKey: string, defaultValue: object): object {
+    return this.getPrecomputedAssignment(flagKey, defaultValue, VariationType.JSON, (value) =>
+      typeof value === 'string' ? JSON.parse(value) : defaultValue,
+    );
   }
 
   private getPrecomputedFlag(flagKey: string): PrecomputedFlag | null {