fix(config-cat): Forward default value to underlying client (#1214)

Signed-off-by: Adam Simon <[email protected]>
Co-authored-by: Adam Simon <[email protected]>
Co-authored-by: Michael Beemer <[email protected]>

Author: 3 people

libs/providers/config-cat-web/src/lib/config-cat-web-provider.spec.ts

@@ -172,8 +172,9 @@ describe('ConfigCatWebProvider', () => {
       expect(() => provider.resolveObjectEvaluation('jsonInvalid', {}, { targetingKey })).toThrow(ParseError);
     });
 
-    it('should throw TypeMismatchError if string is only a JSON primitive', () => {
-      expect(() => provider.resolveObjectEvaluation('jsonPrimitive', {}, { targetingKey })).toThrow(TypeMismatchError);
+    it('should return right value if key exists and value is only a JSON primitive', () => {
+      const value = provider.resolveObjectEvaluation('jsonPrimitive', {}, { targetingKey });
+      expect(value).toHaveProperty('value', JSON.parse(values.jsonPrimitive));
     });
   });
 });

libs/providers/config-cat-web/src/lib/config-cat-web-provider.ts

@@ -1,6 +1,5 @@
 import {
   EvaluationContext,
-  FlagNotFoundError,
   JsonValue,
   OpenFeatureEventEmitter,
   Paradigm,
@@ -13,12 +12,20 @@ import {
 } from '@openfeature/web-sdk';
 import {
   isType,
+  parseError,
   PrimitiveType,
   PrimitiveTypeName,
   toResolutionDetails,
   transformContext,
 } from '@openfeature/config-cat-core';
-import { getClient, IConfig, IConfigCatClient, OptionsForPollingMode, PollingMode } from 'configcat-js-ssr';
+import {
+  getClient,
+  IConfig,
+  IConfigCatClient,
+  OptionsForPollingMode,
+  PollingMode,
+  SettingValue,
+} from 'configcat-js-ssr';
 
 export class ConfigCatWebProvider implements Provider {
   public readonly events = new OpenFeatureEventEmitter();
@@ -84,71 +91,81 @@ export class ConfigCatWebProvider implements Provider {
     defaultValue: boolean,
     context: EvaluationContext,
   ): ResolutionDetails<boolean> {
-    return this.evaluate(flagKey, 'boolean', context);
+    return this.evaluate(flagKey, 'boolean', defaultValue, context);
   }
 
   public resolveStringEvaluation(
     flagKey: string,
     defaultValue: string,
     context: EvaluationContext,
   ): ResolutionDetails<string> {
-    return this.evaluate(flagKey, 'string', context);
+    return this.evaluate(flagKey, 'string', defaultValue, context);
   }
 
   public resolveNumberEvaluation(
     flagKey: string,
     defaultValue: number,
     context: EvaluationContext,
   ): ResolutionDetails<number> {
-    return this.evaluate(flagKey, 'number', context);
+    return this.evaluate(flagKey, 'number', defaultValue, context);
   }
 
   public resolveObjectEvaluation<U extends JsonValue>(
     flagKey: string,
     defaultValue: U,
     context: EvaluationContext,
   ): ResolutionDetails<U> {
-    const objectValue = this.evaluate(flagKey, 'object', context);
+    const objectValue = this.evaluate(flagKey, 'object', defaultValue, context);
     return objectValue as ResolutionDetails<U>;
   }
 
   protected evaluate<T extends PrimitiveTypeName>(
     flagKey: string,
     flagType: T,
+    defaultValue: PrimitiveType<T>,
     context: EvaluationContext,
   ): ResolutionDetails<PrimitiveType<T>> {
     if (!this._client) {
       throw new ProviderNotReadyError('Provider is not initialized');
     }
 
+    // Make sure that the user-provided `defaultValue` is compatible with `flagType` as there is
+    // no guarantee that it actually is. (User may bypass type checking or may not use TypeScript at all.)
+    if (!isType(flagType, defaultValue)) {
+      throw new TypeMismatchError();
+    }
+
+    const configCatDefaultValue = flagType !== 'object' ? (defaultValue as SettingValue) : JSON.stringify(defaultValue);
+
     const { value, ...evaluationData } = this._client
       .snapshot()
-      .getValueDetails(flagKey, undefined, transformContext(context));
+      .getValueDetails(flagKey, configCatDefaultValue, transformContext(context));
 
     if (this._hasError && !evaluationData.errorMessage && !evaluationData.errorException) {
       this._hasError = false;
       this.events.emit(ProviderEvents.Ready);
     }
 
-    if (typeof value === 'undefined') {
-      throw new FlagNotFoundError();
+    if (evaluationData.isDefaultValue) {
+      throw parseError(evaluationData.errorMessage);
     }
 
     if (flagType !== 'object') {
-      return toResolutionDetails(flagType, value, evaluationData);
-    }
-
-    if (!isType('string', value)) {
-      throw new TypeMismatchError();
+      // When `flagType` (more precisely, `configCatDefaultValue`) is boolean, string or number,
+      // ConfigCat SDK guarantees that the returned `value` is compatible with `PrimitiveType<T>`.
+      // See also: https://configcat.com/docs/sdk-reference/js-ssr/#setting-type-mapping
+      return toResolutionDetails(value as PrimitiveType<T>, evaluationData);
     }
 
     let json: JsonValue;
     try {
-      json = JSON.parse(value);
+      // In this case we can be sure that `value` is string since `configCatDefaultValue` is string,
+      // which means that ConfigCat SDK is guaranteed to return a string value.
+      json = JSON.parse(value as string);
     } catch (e) {
       throw new ParseError(`Unable to parse "${value}" as JSON`);
     }
 
-    return toResolutionDetails(flagType, json, evaluationData);
+    return toResolutionDetails(json as PrimitiveType<T>, evaluationData);
   }
 }

libs/providers/config-cat/src/lib/config-cat-provider.spec.ts

@@ -183,10 +183,9 @@ describe('ConfigCatProvider', () => {
       await expect(provider.resolveObjectEvaluation('jsonInvalid', {}, { targetingKey })).rejects.toThrow(ParseError);
     });
 
-    it('should throw TypeMismatchError if string is only a JSON primitive', async () => {
-      await expect(provider.resolveObjectEvaluation('jsonPrimitive', {}, { targetingKey })).rejects.toThrow(
-        TypeMismatchError,
-      );
+    it('should return right value if key exists and value is only a JSON primitive', async () => {
+      const value = await provider.resolveObjectEvaluation('jsonPrimitive', {}, { targetingKey });
+      expect(value).toHaveProperty('value', JSON.parse(values.jsonPrimitive));
     });
   });
 });

libs/providers/config-cat/src/lib/config-cat-provider.ts

@@ -8,17 +8,17 @@ import {
   Paradigm,
   ProviderNotReadyError,
   TypeMismatchError,
-  FlagNotFoundError,
   ParseError,
 } from '@openfeature/server-sdk';
 import {
   isType,
+  parseError,
   PrimitiveType,
   PrimitiveTypeName,
   toResolutionDetails,
   transformContext,
 } from '@openfeature/config-cat-core';
-import { PollingMode } from 'configcat-common';
+import { PollingMode, SettingValue } from 'configcat-common';
 import { IConfigCatClient, getClient, IConfig, OptionsForPollingMode } from 'configcat-node';
 
 export class ConfigCatProvider implements Provider {
@@ -88,46 +88,55 @@ export class ConfigCatProvider implements Provider {
     defaultValue: boolean,
     context: EvaluationContext,
   ): Promise<ResolutionDetails<boolean>> {
-    return this.evaluate(flagKey, 'boolean', context);
+    return this.evaluate(flagKey, 'boolean', defaultValue, context);
   }
 
   public async resolveStringEvaluation(
     flagKey: string,
     defaultValue: string,
     context: EvaluationContext,
   ): Promise<ResolutionDetails<string>> {
-    return this.evaluate(flagKey, 'string', context);
+    return this.evaluate(flagKey, 'string', defaultValue, context);
   }
 
   public async resolveNumberEvaluation(
     flagKey: string,
     defaultValue: number,
     context: EvaluationContext,
   ): Promise<ResolutionDetails<number>> {
-    return this.evaluate(flagKey, 'number', context);
+    return this.evaluate(flagKey, 'number', defaultValue, context);
   }
 
   public async resolveObjectEvaluation<U extends JsonValue>(
     flagKey: string,
     defaultValue: U,
     context: EvaluationContext,
   ): Promise<ResolutionDetails<U>> {
-    const objectValue = await this.evaluate(flagKey, 'object', context);
+    const objectValue = await this.evaluate(flagKey, 'object', defaultValue, context);
     return objectValue as ResolutionDetails<U>;
   }
 
   protected async evaluate<T extends PrimitiveTypeName>(
     flagKey: string,
     flagType: T,
+    defaultValue: PrimitiveType<T>,
     context: EvaluationContext,
   ): Promise<ResolutionDetails<PrimitiveType<T>>> {
     if (!this._client) {
       throw new ProviderNotReadyError('Provider is not initialized');
     }
 
+    // Make sure that the user-provided `defaultValue` is compatible with `flagType` as there is
+    // no guarantee that it actually is. (User may bypass type checking or may not use TypeScript at all.)
+    if (!isType(flagType, defaultValue)) {
+      throw new TypeMismatchError();
+    }
+
+    const configCatDefaultValue = flagType !== 'object' ? (defaultValue as SettingValue) : JSON.stringify(defaultValue);
+
     const { value, ...evaluationData } = await this._client.getValueDetailsAsync(
       flagKey,
-      undefined,
+      configCatDefaultValue,
       transformContext(context),
     );
 
@@ -136,25 +145,26 @@ export class ConfigCatProvider implements Provider {
       this.events.emit(ProviderEvents.Ready);
     }
 
-    if (typeof value === 'undefined') {
-      throw new FlagNotFoundError();
+    if (evaluationData.isDefaultValue) {
+      throw parseError(evaluationData.errorMessage);
     }
 
     if (flagType !== 'object') {
-      return toResolutionDetails(flagType, value, evaluationData);
-    }
-
-    if (!isType('string', value)) {
-      throw new TypeMismatchError();
+      // When `flagType` (more precisely, `configCatDefaultValue`) is boolean, string or number,
+      // ConfigCat SDK guarantees that the returned `value` is compatible with `PrimitiveType<T>`.
+      // See also: https://configcat.com/docs/sdk-reference/node/#setting-type-mapping
+      return toResolutionDetails(value as PrimitiveType<T>, evaluationData);
     }
 
     let json: JsonValue;
     try {
-      json = JSON.parse(value);
+      // In this case we can be sure that `value` is string since `configCatDefaultValue` is string,
+      // which means that ConfigCat SDK is guaranteed to return a string value.
+      json = JSON.parse(value as string);
     } catch (e) {
       throw new ParseError(`Unable to parse "${value}" as JSON`);
     }
 
-    return toResolutionDetails(flagType, json, evaluationData);
+    return toResolutionDetails(json as PrimitiveType<T>, evaluationData);
   }
 }

libs/shared/config-cat-core/src/lib/result-mapping.ts

@@ -1,16 +1,22 @@
 import { IEvaluationDetails } from 'configcat-js-ssr';
-import { ResolutionDetails, ResolutionReason, TypeMismatchError, StandardResolutionReasons } from '@openfeature/core';
+import {
+  ResolutionDetails,
+  ResolutionReason,
+  TypeMismatchError,
+  StandardResolutionReasons,
+  JsonValue,
+  OpenFeatureError,
+  ParseError,
+  TargetingKeyMissingError,
+  GeneralError,
+  FlagNotFoundError,
+} from '@openfeature/core';
 
-export function toResolutionDetails<T extends PrimitiveTypeName>(
-  type: T,
-  value: unknown,
+export function toResolutionDetails<T>(
+  value: T,
   data: Omit<IEvaluationDetails, 'value'>,
   reason?: ResolutionReason,
-): ResolutionDetails<PrimitiveType<T>> {
-  if (!isType(type, value)) {
-    throw new TypeMismatchError(`Requested ${type} flag but the actual value is ${typeof value}`);
-  }
-
+): ResolutionDetails<T> {
   const matchedTargeting = data.matchedTargetingRule;
   const matchedPercentage = data.matchedPercentageOption;
 
@@ -25,19 +31,55 @@ export function toResolutionDetails<T extends PrimitiveTypeName>(
   };
 }
 
-export type PrimitiveTypeName = 'string' | 'boolean' | 'number' | 'object' | 'undefined';
+export function parseError(errorMessage: string | undefined): OpenFeatureError {
+  // Detecting the error type by checking the error message is awkward and fragile,
+  // but ConfigCat SDK doesn't allow a better way at the moment.
+  // However, there are plans to improve this situation, so let's revise this
+  // as soon as ConfigCat SDK implements returning error codes.
+
+  if (errorMessage) {
+    if (errorMessage.includes('Config JSON is not present')) {
+      return new ParseError();
+    }
+    if (errorMessage.includes('the key was not found in config JSON')) {
+      return new FlagNotFoundError();
+    }
+    if (
+      errorMessage.includes('The type of a setting must match the type of the specified default value') ||
+      /Setting value (?:is null|is undefined|'.*' is of an unsupported type)/.test(errorMessage)
+    ) {
+      return new TypeMismatchError();
+    }
+  }
+  return new GeneralError();
+}
+
+export type PrimitiveTypeName = 'string' | 'boolean' | 'number' | 'object';
 export type PrimitiveType<T> = T extends 'string'
   ? string
   : T extends 'boolean'
     ? boolean
     : T extends 'number'
       ? number
       : T extends 'object'
-        ? object
-        : T extends 'undefined'
-          ? undefined
-          : unknown;
+        ? JsonValue
+        : never;
 
 export function isType<T extends PrimitiveTypeName>(type: T, value: unknown): value is PrimitiveType<T> {
-  return typeof value !== 'undefined' && typeof value === type;
+  switch (type) {
+    case 'string':
+    case 'boolean':
+    case 'number':
+      return typeof value === type;
+    case 'object':
+      return (
+        value === null ||
+        typeof value === 'string' ||
+        typeof value === 'boolean' ||
+        typeof value === 'number' ||
+        Array.isArray(value) ||
+        typeof value === 'object'
+      );
+  }
+  return false;
 }