feat: graceful fallback to code default when no default variant resolved by leakonvalinka · Pull Request #1707 · open-feature/java-sdk-contrib

leakonvalinka · 2026-03-04T14:28:28Z

This PR

when a flag resolves to the default variant, but no default variant exists, the code default value is returned (as opposed to throwing a FlagNotFoundError, which was the behaviour until now)

Related Issues

#1704

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gemini-code-assist · 2026-03-04T14:32:46Z

Summary of Changes

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This pull request enhances the flag evaluation process by introducing a more robust handling of default values. It ensures that if a flag evaluation results in a default variant but no specific default is configured, the system will now gracefully fall back to the code-provided default value instead of throwing an error. This change improves the resilience and predictability of flag evaluations, preventing unexpected failures in scenarios where flag configurations might be incomplete or misconfigured. Additionally, it includes an upgrade to the gRPC evaluation API to version 2, reflecting updates in the underlying flagd specification.

Highlights

Default Variant Resolution: Modified flag resolution logic to return the provided code default value when a flag resolves to the default variant but no explicit default variant is defined in the flag configuration. Previously, this scenario would result in a FlagNotFoundError.
gRPC API Version Update: Updated gRPC evaluation service imports and configurations from v1 to v2 across various components, aligning with the latest flagd specification.
Resolver Interface and Implementation Updates: Adjusted the Evaluator interface and its implementations (InProcessResolver, RpcResolver, FlagdCore, MockEvaluator) to accept and utilize a defaultValue parameter in all flag resolution methods.

Changelog

providers/flagd/spec
- Updated the subproject commit to reflect the latest flagd specification.
providers/flagd/src/main/java/dev/openfeature/contrib/providers/flagd/resolver/common/ChannelBuilder.java
- Added flagd.evaluation.v2.Service to the gRPC service configuration for channel building.
providers/flagd/src/main/java/dev/openfeature/contrib/providers/flagd/resolver/process/InProcessResolver.java
- Modified all resolve*Evaluation methods to pass the defaultValue parameter to the underlying evaluator.
providers/flagd/src/main/java/dev/openfeature/contrib/providers/flagd/resolver/rpc/RpcResolver.java
- Updated gRPC evaluation imports from dev.openfeature.flagd.grpc.evaluation to dev.openfeature.flagd.grpc.evaluation.v2.
- Modified the private resolve method to accept a defaultValue parameter.
- Adjusted the resolve method logic to return the defaultValue when the evaluation reason is 'DEFAULT' and the variant is empty.
- Relocated the getBlockingStub method for better code organization.
- Applied minor formatting adjustments in the observeEventStream method.
providers/flagd/src/test/java/dev/openfeature/contrib/providers/flagd/FlagdProviderTest.java
- Updated gRPC evaluation imports to use version 2.
providers/flagd/src/test/java/dev/openfeature/contrib/providers/flagd/FlagdTestUtils.java
- Updated gRPC service import to use version 2.
providers/flagd/src/test/java/dev/openfeature/contrib/providers/flagd/e2e/RunFileTest.java
- Excluded tests tagged as 'deprecated' from execution.
providers/flagd/src/test/java/dev/openfeature/contrib/providers/flagd/e2e/RunInProcessTest.java
- Excluded tests tagged as 'deprecated' from execution.
providers/flagd/src/test/java/dev/openfeature/contrib/providers/flagd/e2e/RunRpcTest.java
- Excluded tests tagged as 'deprecated' from execution.
providers/flagd/src/test/java/dev/openfeature/contrib/providers/flagd/resolver/process/MockEvaluator.java
- Modified all resolve*Value methods to accept a defaultValue parameter.
- Updated the private resolve method signature to include defaultValue.
- Changed the error handling for flags without a default variant to return the defaultValue with a 'DEFAULT' reason, instead of throwing a FlagNotFoundError.
providers/flagd/src/test/java/dev/openfeature/contrib/providers/flagd/resolver/rpc/RpcResolverTest.java
- Updated gRPC evaluation imports to use version 2.
providers/flagd/test-harness
- Updated the subproject commit for the test harness.
tools/flagd-api/src/main/java/dev/openfeature/contrib/tools/flagd/api/Evaluator.java
- Modified all resolve*Value methods in the Evaluator interface to include a defaultValue parameter.
tools/flagd-core/schemas
- Updated the subproject commit for flagd core schemas.
tools/flagd-core/src/main/java/dev/openfeature/contrib/tools/flagd/core/FlagdCore.java
- Modified all resolve*Value methods to accept a defaultValue parameter.
- Updated the private resolve method signature to include defaultValue.
- Changed the error handling for flags without a default variant to return the defaultValue with a 'DEFAULT' reason, instead of throwing a FlagNotFoundError.

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Code Review

This pull request correctly implements the feature to return the code's default value when a flag resolves to a default variant that doesn't exist, instead of throwing an error. The changes are consistently applied across both RPC and in-process resolvers, including updates to the gRPC v2 API. I've included a couple of suggestions to enhance code readability and follow modern Java best practices.

gemini-code-assist · 2026-03-04T14:36:13Z

...gd/src/main/java/dev/openfeature/contrib/providers/flagd/resolver/common/ChannelBuilder.java

+                                        new HashMap() {
+                                            {
+                                                put("service", "flagd.evaluation.v2.Service");
+                                            }


While this follows the existing pattern in the file, using double-brace initialization is generally considered an anti-pattern in modern Java. It creates an anonymous inner class for each instance, which can have performance overhead and may lead to memory leaks if not used carefully. A better alternative is to use java.util.Collections.singletonMap().

java.util.Collections.singletonMap("service", "flagd.evaluation.v2.Service")

should we apply this? if so, i'd apply this to all the other maps too, ofc

If it is really better, I would do it

...rs/flagd/src/main/java/dev/openfeature/contrib/providers/flagd/resolver/rpc/RpcResolver.java

Signed-off-by: Konvalinka <lea.konvalinka@dynatrace.com> Signed-off-by: Todd Baert <todd.baert@dynatrace.com>

github-actions bot assigned beeme1mr, Kavindu-Dodan, thisthat and toddbaert Mar 4, 2026

github-actions bot requested review from Kavindu-Dodan, beeme1mr, thisthat and toddbaert March 4, 2026 14:28

gemini-code-assist bot reviewed Mar 4, 2026

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leakonvalinka force-pushed the feat/optional-default-variant branch from 8c4ff54 to 23128f6 Compare March 4, 2026 14:36

leakonvalinka changed the title ~~feat: return code default when no default variant~~ feat: graceful fallback to code default when no default variant resolved Mar 5, 2026

leakonvalinka force-pushed the feat/optional-default-variant branch from 300c0a9 to cf05eaf Compare March 5, 2026 09:04

leakonvalinka marked this pull request as ready for review March 5, 2026 09:12

leakonvalinka requested a review from a team as a code owner March 5, 2026 09:12

toddbaert force-pushed the feat/optional-default-variant branch 3 times, most recently from 3617e68 to 84eebf6 Compare March 5, 2026 10:10

feat: return code default when no default variant

9c47de0

Signed-off-by: Konvalinka <lea.konvalinka@dynatrace.com> Signed-off-by: Todd Baert <todd.baert@dynatrace.com>

toddbaert force-pushed the feat/optional-default-variant branch from 84eebf6 to 9c47de0 Compare March 5, 2026 10:14

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feat: graceful fallback to code default when no default variant resolved#1707

feat: graceful fallback to code default when no default variant resolved#1707
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leakonvalinka commented Mar 4, 2026 •

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leakonvalinka commented Mar 4, 2026 •

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