fix(openfeature-web): reject blank numeric flag variants

.changeset/olive-showers-make.md

@@ -0,0 +1,5 @@
+---
+'@posthog/openfeature-web-provider': patch
+---
+
+Reject blank numeric flag variants so OpenFeature returns the caller's default.

packages/openfeature-web-provider/src/__tests__/provider.spec.ts

@@ -141,6 +141,18 @@ describe('PostHogWebProvider', () => {
         (p) => p.resolveNumberEvaluation('flag', 0),
         ErrorCode.TYPE_MISMATCH,
       ],
+      [
+        'number from an empty variant',
+        { key: 'flag', enabled: true, variant: '' },
+        (p) => p.resolveNumberEvaluation('flag', 42),
+        ErrorCode.TYPE_MISMATCH,
+      ],
+      [
+        'number from a whitespace-only variant',
+        { key: 'flag', enabled: true, variant: '   ' },
+        (p) => p.resolveNumberEvaluation('flag', 42),
+        ErrorCode.TYPE_MISMATCH,
+      ],
       [
         'object from an enabled flag with no payload',
         { key: 'flag', enabled: true, variant: 'x' },
@@ -285,5 +297,25 @@ describe('PostHogWebProvider', () => {
       expect(details.errorCode).toBe(ErrorCode.TYPE_MISMATCH)
       expect(details.reason).toBe(StandardResolutionReasons.ERROR)
     })
+
+    it.each(['', '   ', '\t\n'])('returns the numeric default for a blank variant %j', async (variant) => {
+      const { client } = makeClient({ key: 'flag', enabled: Boolean(variant), variant })
+      await OpenFeature.setProviderAndWait(new PostHogWebProvider(client))
+
+      const details = OpenFeature.getClient().getNumberDetails('flag', 42)
+      expect(details.value).toBe(42)
+      expect(details.errorCode).toBe(ErrorCode.TYPE_MISMATCH)
+      expect(details.reason).toBe(StandardResolutionReasons.ERROR)
+    })
+
+    it.each(['0', '7'])('preserves a numeric variant %j', async (variant) => {
+      const { client } = makeClient({ key: 'flag', enabled: true, variant })
+      await OpenFeature.setProviderAndWait(new PostHogWebProvider(client))
+
+      const details = OpenFeature.getClient().getNumberDetails('flag', 42)
+      expect(details.value).toBe(Number(variant))
+      expect(details.errorCode).toBeUndefined()
+      expect(details.reason).toBe(StandardResolutionReasons.TARGETING_MATCH)
+    })
   })
 })

packages/openfeature-web-provider/src/mapping.ts

@@ -141,7 +141,7 @@ export function resolveNumberDetails(
     throw new TypeMismatchError(`Flag '${flagKey}' has no variant to parse as a number.`)
   }
   const value = Number(resolved.variant)
-  if (!Number.isFinite(value)) {
+  if (resolved.variant.trim() === '' || !Number.isFinite(value)) {
     throw new TypeMismatchError(`Flag '${flagKey}' variant '${resolved.variant}' is not a valid number.`)
   }
   return { value, variant: resolved.variant, reason: reasonFor(resolved) }