Datadog OpenFeature Core Library

Configuration parsing entry points

The default @datadog/flagging-core entry point parses precomputed configuration without loading the protobuf decoder. To parse both precomputed and rules-based configuration, opt into the full parser:

import { configurationFromString, configurationToString } from '@datadog/flagging-core/rules-based'

The /rules-based entry point is available through both the package's exports map and a physical rules-based/package.json for resolvers that do not support package exports:

• Modern resolvers use the existing modular CommonJS/ESM implementations.
• Legacy resolvers use self-contained CommonJS/ESM compatibility bundles generated from the same source during yarn build / package preparation. These include the required protobuf code, so consumers do not have to resolve its /wire or /codegenv2 subpaths.
• Both paths expose the same API and reuse the same TypeScript declarations. The default entry point stays modular and does not import the compatibility bundles or protobuf decoder.

The compatibility bundles increase the npm package size, but only applications using the legacy rules-based entry point include them in their application bundle. They retain dependency copyright/license notices and source maps, and are left unminified for the application bundler to optimize.

The packed-package smoke test covers Android and iOS bundles with Metro package exports both enabled and disabled, including legacy CommonJS and ESM resolution. It executes those bundles in Node without BigInt, TextEncoder, or TextDecoder; this checks fallback behavior but does not replace execution tests on an actual Hermes or JavaScriptCore runtime.

Preparing activation timestamps

Rules configurations are snapshots. The protobuf decoder prepares randomization activation timestamps once, and the Node provider prepares JSON configurations in setConfiguration. Invalid activation marks only the affected flag as a parse error, regardless of opt-out mode. Evaluation compares the prepared seconds and fractional seconds without reparsing the timestamp; using a JavaScript Date here would lose the nanosecond precision needed at the opt-out cutoff.

Direct JSON core consumers can call prepareUniversalFlagConfiguration(configuration) when receiving configuration. Existing low-level evaluation calls still accept raw configurations and prepare each flag once on first use. Replace changed flags instead of mutating prepared flags in place. Preparation does not change the serialized configuration.

Adding a public entry point

packages/core/package.json exports is the single source of truth for public paths. To add @datadog/flagging-core/foo:

1. Create src/foo.ts with the intended exports. Keep any required initialization in this source entry point, rather than adding it to a bundler-specific list.

2. Add its modern mapping to exports:

   {
     "./foo": {
       "types": "./cjs/foo.d.ts",
       "import": "./esm/foo.js",
       "require": "./cjs/foo.js",
       "default": "./esm/foo.js"
     }
   }
   

3. Run yarn workspace @datadog/flagging-core build and commit the generated metadata with the source change. Add the feature's behavior tests as usual.

The build generates the physical fallback manifests, publish-file list, legacy declaration mappings, and compatibility-bundle side-effect entries. It discovers and builds a CJS/ESM compatibility bundle for every public JavaScript subpath automatically. Do not edit those fallback manifests or register new paths in the Webpack configuration or smoke fixtures.

Concrete nested subpaths are supported; wildcard exports and mismatched CJS/ESM/type targets fail with an actionable error. Removing a path from exports and rebuilding removes its owned fallback manifest and derived metadata without deleting unrelated files.

yarn check:entrypoints checks generated metadata without changing files. CI runs it before building, and prepack checks it before packing so a stale publish-file list cannot silently omit a new entry point. The packed-package tests discover every declared path and generate static imports for the full Metro matrix. The default entry point remains separate and light.

End-user license agreement

https://www.datadoghq.com/legal/eula