feat: adding start() method to common client sdk package by joker23 · Pull Request #1244 · launchdarkly/js-core

joker23 · 2026-04-03T23:29:12Z

This PR will consolidate the start() method into the shared client sdk package.

To do this we also:

introduce an internal option called requiresStart which should be true for new SDKs (and only RN has it default false)
requiresStart is, effectively, a feature flag for whether the SDK is using the new create + start initialization pattern
consolidated the unit tests for the start method into client common
moved start method out of browser and electron sdks

Note

Medium Risk
Touches core initialization/identify behavior across multiple SDKs and changes when bootstrap parsing and goal tracking occur, which could affect startup sequencing and existing integrations if edge cases regress.

Overview
Moves the start() implementation (including bootstrap flag preloading and init promise caching/timeout behavior) from the Browser and Electron SDKs into the shared packages/shared/sdk-client LDClientImpl.

Introduces LDStartOptions in the shared API and adds internal options requiresStart and initialContext so platform SDKs can enforce the new create+start() initialization pattern; identifyResult() now blocks pre-start() calls when requiresStart is enabled and updates the logged error message.

Updates Browser/Electron wrappers and tests accordingly (Browser/Electron remove their custom start() logic, Browser ensures goal tracking only starts after start()), and adds a consolidated LDClientImpl.start() test suite in the shared package.

^{Reviewed by Cursor Bugbot for commit 5c9e61f. Bugbot is set up for automated code reviews on this repo. Configure here.}

github-actions · 2026-04-03T23:30:38Z

@launchdarkly/js-sdk-common size report
This is the brotli compressed size of the ESM build.
Compressed size: 25623 bytes
Compressed size limit: 29000
Uncompressed size: 125843 bytes

github-actions · 2026-04-03T23:31:00Z

@launchdarkly/browser size report
This is the brotli compressed size of the ESM build.
Compressed size: 179425 bytes
Compressed size limit: 200000
Uncompressed size: 830289 bytes

github-actions · 2026-04-03T23:38:50Z

@launchdarkly/js-client-sdk size report
This is the brotli compressed size of the ESM build.
Compressed size: 31731 bytes
Compressed size limit: 34000
Uncompressed size: 113100 bytes

github-actions · 2026-04-03T23:38:52Z

@launchdarkly/js-client-sdk-common size report
This is the brotli compressed size of the ESM build.
Compressed size: 37607 bytes
Compressed size limit: 38000
Uncompressed size: 207149 bytes

joker23 · 2026-04-03T23:44:35Z

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joker23 · 2026-04-06T19:27:52Z

+   * When true, the SDK requires `start()` to be called before `identify()`.
+   * Set this value to `true` to use the new initialization pattern.
+   */
+  requiresStart?: boolean;


added this to compat react native... this was the only way I found that would leave RN alone

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kinyoklion · 2026-04-13T15:58:40Z

-    const bootstrapModule = await import('@launchdarkly/js-client-sdk-common');
-    const readFlagsFromBootstrapSpy = jest.spyOn(bootstrapModule, 'readFlagsFromBootstrap');
-
+  it('parses bootstrap data when start is called with bootstrap', async () => {


This makes me assume it parses it more than once? Which actually I think was already true? Once synchronously and again during the identify process? But what behavior change is this test change for?

This test should have been moved to the shared instance. I think the reason the test changed in this way is that there is no longer a way to test that behavior on this level.

kinyoklion · 2026-04-13T17:41:31Z

+    }
+
+    let effectiveOptions = identifyOptions;
+    if (this._requiresStart && identifyOptions?.sheddable === undefined) {


I don't know that I like coupling of the default shedding behavior to the _requiresStart behavior.

okay - yea I got a little too ambitious with trying to change the common default option to be sheddable.

so for this one, I decided to revert to the old defaults (sheddable is false) and have the browser and electron override that (which is what they did before)

kinyoklion · 2026-04-13T17:43:18Z

+   * Sets the initial context for the client. This must be called before `start()`.
+   * @param context The initial context.
+   */
+  setInitialContext(context: LDContext): void {


Needs to be protected. React directly exposes the inheritance.

This may present somewhat of a problem to the approach. So maybe we can figure out another approach.

for this, I decided to get rid of this function altogether and introduced a new internal option that is initialContext

Co-authored-by: Ryan Lamb <4955475+kinyoklion@users.noreply.github.com>

🤖 I have created a release *beep* *boop* --- <details><summary>browser: 0.1.15</summary> ## [0.1.15](browser-v0.1.14...browser-v0.1.15) (2026-04-17) ### Dependencies * The following workspace dependencies were updated * dependencies * @launchdarkly/js-client-sdk bumped from 4.5.0 to 4.6.0 </details> <details><summary>browser-telemetry: 1.0.31</summary> ## [1.0.31](browser-telemetry-v1.0.30...browser-telemetry-v1.0.31) (2026-04-17) ### Dependencies * The following workspace dependencies were updated * devDependencies * @launchdarkly/js-client-sdk bumped from 4.5.0 to 4.6.0 </details> <details><summary>cloudflare-server-sdk: 2.7.19</summary> ## [2.7.19](cloudflare-server-sdk-v2.7.18...cloudflare-server-sdk-v2.7.19) (2026-04-17) ### Bug Fixes * remove `rollup-plugin-dts` dependency ([#1288](#1288)) ([ea64b82](ea64b82)) </details> <details><summary>jest: 1.0.10</summary> ## [1.0.10](jest-v1.0.9...jest-v1.0.10) (2026-04-17) ### Dependencies * The following workspace dependencies were updated * dependencies * @launchdarkly/react-native-client-sdk bumped from ~10.15.2 to ~10.16.0 </details> <details><summary>js-client-sdk: 4.6.0</summary> ## [4.6.0](js-client-sdk-v4.5.0...js-client-sdk-v4.6.0) (2026-04-17) ### Features * adding start() method to common client sdk package ([#1244](#1244)) ([7f5f468](7f5f468)) ### Dependencies * The following workspace dependencies were updated * dependencies * @launchdarkly/js-client-sdk-common bumped from 1.24.0 to 1.25.0 </details> <details><summary>js-client-sdk-common: 1.25.0</summary> ## [1.25.0](js-client-sdk-common-v1.24.0...js-client-sdk-common-v1.25.0) (2026-04-17) ### Features * Add experimental FDv2 support for React Native. ([#1243](#1243)) ([7ed2c08](7ed2c08)) * adding start() method to common client sdk package ([#1244](#1244)) ([7f5f468](7f5f468)) ### Bug Fixes * FDv2 -- cache initializer returns transfer-none on cache miss ([#1275](#1275)) ([7bf3c31](7bf3c31)) </details> <details><summary>react-native-client-sdk: 10.16.0</summary> ## [10.16.0](react-native-client-sdk-v10.15.2...react-native-client-sdk-v10.16.0) (2026-04-17) ### Features * Add experimental FDv2 support for React Native. ([#1243](#1243)) ([7ed2c08](7ed2c08)) ### Dependencies * The following workspace dependencies were updated * dependencies * @launchdarkly/js-client-sdk-common bumped from 1.24.0 to 1.25.0 </details> <details><summary>react-sdk: 0.2.1</summary> ## [0.2.1](react-sdk-v0.2.0...react-sdk-v0.2.1) (2026-04-17) ### Dependencies * The following workspace dependencies were updated * dependencies * @launchdarkly/js-client-sdk bumped from ^4.5.0 to ^4.6.0 </details> --- This PR was generated with [Release Please](https://github.com/googleapis/release-please). See [documentation](https://github.com/googleapis/release-please#release-please).  --- > [!NOTE] > **Medium Risk** > Mostly mechanical version/changelog updates, but it publishes new SDK versions (including new/experimental client capabilities) which could affect downstream consumers if the release contents are incorrect. > > **Overview** > Updates release metadata for a multi-package publish, bumping versions across the Browser, React Native, React, Cloudflare, combined-browser, browser-telemetry, and jest packages and updating their changelogs and example app dependencies accordingly. > > Also updates embedded `x-release-please-version` strings (for SDK/wrapper reporting) to match the new package versions. > > <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit d56c92d. Bugbot is set up for automated code reviews on this repo. Configure [here](https://www.cursor.com/dashboard/bugbot).</sup>  Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

joker23 force-pushed the skz/sdk-1759/client-start branch from 1a440b9 to d249ad8 Compare April 3, 2026 23:36

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joker23 force-pushed the skz/sdk-1759/client-start branch from d249ad8 to 8f1e564 Compare April 6, 2026 18:54

joker23 marked this pull request as ready for review April 6, 2026 19:25

joker23 requested a review from a team as a code owner April 6, 2026 19:25

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Comment thread packages/shared/sdk-client/__tests__/LDClientImpl.start.test.ts

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joker23 force-pushed the skz/sdk-1759/client-start branch from 8f1e564 to 111c7e2 Compare April 7, 2026 15:26

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Comment thread packages/sdk/browser/__tests__/BrowserClient.test.ts

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Comment thread packages/shared/sdk-client/src/LDClientImpl.ts Outdated

joker23 force-pushed the skz/sdk-1759/client-start branch from 66673ed to 8b2405c Compare April 10, 2026 17:48

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joker23 force-pushed the skz/sdk-1759/client-start branch 2 times, most recently from ad291be to 0af525e Compare April 10, 2026 20:38

joker23 requested a review from kinyoklion April 10, 2026 20:42

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joker23 requested a review from kinyoklion April 13, 2026 20:26

joker23 force-pushed the skz/sdk-1759/client-start branch 2 times, most recently from 51c47b1 to 1284889 Compare April 14, 2026 16:37

joker23 force-pushed the skz/sdk-1759/client-start branch from 1284889 to 8289496 Compare April 14, 2026 16:54

joker23 and others added 6 commits April 15, 2026 12:09

feat: adding start() method to common client sdk package

5703bc8

chore: bot comment

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Update packages/shared/sdk-client/src/LDClientImpl.ts

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Co-authored-by: Ryan Lamb <4955475+kinyoklion@users.noreply.github.com>

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chore: removing setInitialContext

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joker23 force-pushed the skz/sdk-1759/client-start branch from 8289496 to 5cf93ab Compare April 15, 2026 17:09

chore: reverting sheddable defaults

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joker23 force-pushed the skz/sdk-1759/client-start branch from 5cf93ab to e3c5cc7 Compare April 15, 2026 20:41

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joker23 force-pushed the skz/sdk-1759/client-start branch from 39e0210 to 289e6fa Compare April 16, 2026 17:37

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chore: remove em dash

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joker23 merged commit 7f5f468 into main Apr 16, 2026
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joker23 deleted the skz/sdk-1759/client-start branch April 16, 2026 21:59

github-actions Bot mentioned this pull request Apr 16, 2026

chore: release main #1276

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