Merge pull request #331 from DataDog/blake.thomas/fix-configurationToString

fix(core): serialize precomputed.response in configurationToString

Author: btthomas

packages/core/src/configuration/wire.test.ts

@@ -0,0 +1,57 @@
+import type { FlagsConfiguration } from './configuration'
+import { configurationFromString, configurationToString } from './wire'
+
+const configuration: FlagsConfiguration = {
+  precomputed: {
+    response: {
+      data: {
+        attributes: {
+          createdAt: '2026-07-06T23:01:56.822Z',
+          flags: {
+            'my-flag': {
+              allocationKey: 'alloc-1',
+              variationKey: 'true',
+              variationType: 'boolean',
+              variationValue: true,
+              reason: 'STATIC',
+              doLog: true,
+              extraLogging: {},
+            },
+          },
+        },
+      },
+    },
+    context: { targetingKey: 'user-1', country: 'US' },
+  },
+}
+
+describe('configuration wire', () => {
+  it('round-trips a precomputed configuration', () => {
+    const restored = configurationFromString(configurationToString(configuration))
+
+    expect(restored).toEqual(configuration)
+  })
+
+  it('keeps flags readable after a round-trip', () => {
+    const restored = configurationFromString(configurationToString(configuration))
+
+    expect(restored.precomputed?.response.data.attributes.flags['my-flag'].variationValue).toBe(true)
+  })
+
+  it('serializes precomputed.response as a stringified response object, not the whole precomputed', () => {
+    const wire = JSON.parse(configurationToString(configuration))
+
+    // `precomputed.response` on the wire must be the response only, so parsing it yields
+    // the response object (regression guard: it previously stringified the whole
+    // precomputed object, double-nesting the response and losing the flags).
+    expect(JSON.parse(wire.precomputed.response)).toEqual(configuration.precomputed?.response)
+  })
+
+  it('returns an empty configuration for an unknown version', () => {
+    expect(configurationFromString(JSON.stringify({ version: 2 }))).toEqual({})
+  })
+
+  it('returns an empty configuration for malformed input', () => {
+    expect(configurationFromString('not json')).toEqual({})
+  })
+})

packages/core/src/configuration/wire.ts

@@ -50,7 +50,7 @@ export function configurationToString(configuration: FlagsConfiguration): string
   if (configuration.precomputed) {
     wire.precomputed = {
       ...configuration.precomputed,
-      response: JSON.stringify(configuration.precomputed),
+      response: JSON.stringify(configuration.precomputed.response),
     }
   }