feat!: Context Values support, `getEvaluationResult` #184

khvn26 · 2025-09-16T19:25:28Z

Contributes to #179.

In this PR, we:

Add EvaluationResult getEvaluationResult(EvaluationContext context) and remove all of the old engine APIs.
Add support for JSONPath-enabled context values.
Add EngineMappers class for engine-API data interop.
Breaking change: EnvironmentModel class, used by IOfflineHandler, is no longer part of com.flagsmith.flagengine package. Methods carrying the engine business logic and sub-models/fields not relevant to the SDK are removed.
Breaking change: drop Java 8 support.

Copilot

Pull Request Overview

This PR introduces support for context values and adds a new getEvaluationResult API while removing legacy engine APIs. The changes involve a breaking refactor from Java 8 to Java 11 and introduces JSONPath-enabled context value evaluation.

Key changes:

Introduces EvaluationResult getEvaluationResult(EvaluationContext context) API replacing old model-based APIs
Adds JSONPath support for context value evaluation and removes model-based segment evaluation
Drops Java 8 support in favor of Java 11 minimum requirement

Reviewed Changes

Copilot reviewed 58 out of 58 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
pom.xml	Updates Java version from 8 to 11, adds JsonPath dependency and code generation plugin
src/main/java/com/flagsmith/flagengine/Engine.java	Replaces model-based feature evaluation with context-based evaluation using new API
src/main/java/com/flagsmith/flagengine/segments/SegmentEvaluator.java	Refactors from model-based to context-based segment evaluation with JSONPath support
src/main/java/com/flagsmith/mappers/EngineMappers.java	New mapper utility for converting JSON documents to engine contexts
src/main/java/com/flagsmith/interfaces/IOfflineHandler.java	Breaking change: replaces EnvironmentModel with EvaluationContext
src/test/java/com/flagsmith/flagengine/unit/segments/SegmentModelTest.java	Updates test to use new context-based evaluation instead of model-based

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src/main/java/com/flagsmith/flagengine/segments/SegmentEvaluator.java

src/main/java/com/flagsmith/mappers/EngineMappers.java

src/test/java/com/flagsmith/flagengine/unit/segments/SegmentModelTest.java

src/main/java/com/flagsmith/flagengine/segments/SegmentEvaluator.java

src/main/java/com/flagsmith/mappers/EngineMappers.java

src/test/java/com/flagsmith/FlagsmithTestHelper.java

src/main/java/com/flagsmith/flagengine/Engine.java

src/main/java/com/flagsmith/mappers/EngineMappers.java

src/main/java/com/flagsmith/flagengine/segments/SegmentEvaluator.java

khvn26 · 2025-10-15T23:42:28Z

src/test/java/com/flagsmith/flagengine/unit/segments/SegmentEvaluatorTest.java

-
-  @ParameterizedTest
-  @MethodSource("identitiesInSegmentsPercentageSplit")
-  public void testIdentityInSegmentPercentageSplitUsesDjangoId(Integer djangoId, String identifier,


See Flagsmith/flagsmith#2186 (comment).

emyller

Non blocking comments, since engine tests pass. These comments may or may not require attention.

P.S. Reviewing this on the iPad was frustratingly difficult, as is reading this Java codebase sometimes. I’m sorry for the somewhat poor review compared to my standards.

emyller · 2025-10-17T03:37:01Z

src/main/java/com/flagsmith/flagengine/segments/SegmentEvaluator.java

+              .filter(String.class::isInstance)
+              .map(Object::toString)


Is .map here for typing? It looks redundant given the .filter above.

emyller · 2025-10-17T04:07:56Z

src/main/java/com/flagsmith/flagengine/segments/SegmentEvaluator.java

+        if (!(contextValue instanceof Boolean) && contextValue != null) {
+          contextValue = String.valueOf(contextValue);
+        }


I don't understand why booleans are left out of the party here. 😞 Will .contains below compare "true" == true / "false" == false? Sorry I don't follow. Our whole boolean thing is already a bit of a party pooper.

emyller · 2025-10-17T04:35:51Z

src/main/java/com/flagsmith/flagengine/segments/SegmentEvaluator.java

+            Double divisor = Double.parseDouble(parts[0]);
+            Double remainder = Double.parseDouble(parts[1]);


Do we need to worry divisor and remainder could be non-numeric strings?

emyller · 2025-10-17T04:47:16Z

src/main/java/com/flagsmith/flagengine/utils/types/TypeCasting.java

-        || Boolean.FALSE.toString().equalsIgnoreCase(((String) str));
+        || Boolean.TRUE.toString().equalsIgnoreCase((String.valueOf(str)))
+        || Boolean.FALSE.toString().equalsIgnoreCase((String.valueOf(str)))
+        || "1".equals(String.valueOf(str));


This final proposition here looks like cheating some specific test to pass. 😆
I admit I'm even more confused now. Sorry this may be correct as is and I just don't follow the "true" and "false" strings on steroids above.

(I don't mean to insult your code, or the previous author's)

(maybe lowkey I do but I don't mean any disrespect)

emyller · 2025-10-19T16:34:59Z

src/main/java/com/flagsmith/FlagsmithClient.java


      return segment;
-    }).collect(Collectors.toList());
+    }).filter(Objects::nonNull).collect(Collectors.toList());


Is this to support typing?

emyller · 2025-10-20T00:27:11Z

src/main/java/com/flagsmith/flagengine/IdentityContext.java

+  }
+
+  @Override
+  public int hashCode() {


Same as https://github.com/Flagsmith/flagsmith-java-client/pull/184/files#r2443390234

emyller · 2025-10-20T00:27:31Z

src/main/java/com/flagsmith/flagengine/IdentityContext.java

+  }
+
+  @Override
+  public boolean equals(Object other) {


Same as https://github.com/Flagsmith/flagsmith-java-client/pull/184/files#r2443390234

emyller · 2025-10-20T00:34:53Z

src/main/java/com/flagsmith/mappers/EngineMappers.java

+    metadata = MapperFactory.getMapper()
+        .convertValue(flagResult.getMetadata(), FeatureMetadata.class);
+
+    if (metadata == null || metadata.getFlagsmithId() == null) {


Do we expect metadata not to exist in a FlagResult?

I second that, as it's used internally and we seem to have an agreement on using them, I could see it required.

emyller · 2025-10-20T00:39:15Z

src/main/java/com/flagsmith/mappers/EngineMappers.java

+    if (traits != null && !traits.isEmpty()) {
+      for (Map.Entry<String, Object> entry : traits.entrySet()) {
+        Object traitValue = entry.getValue();
+        // Handle TraitConfig-like objects (maps with "value" key)


Just wondering: do we cover this in engine test data?

emyller · 2025-10-20T00:41:52Z

src/main/java/com/flagsmith/mappers/EngineMappers.java

+   * @param environmentModel the environment model
+   * @return the evaluation context
+   */
+  public static EvaluationContext mapEnvironmentToContext(


Why is this a separate function?

Zaimwa9

Looks good to me overall. I share Evandro's confusion surrounding boolean management - some clarification could help, also to have other implementations ISO.
I added a comment on the modulo evaluator

Zaimwa9 · 2025-10-20T09:36:47Z

src/main/java/com/flagsmith/flagengine/segments/SegmentEvaluator.java

+        return false;
+
+      case MODULO:
+        if (contextValue instanceof Number && conditionValue instanceof String) {


Don't we want to try parsing context value in case it's a numerical string ?

khvn26 added 17 commits September 15, 2025 10:53

wip

14bf7cc

mapper wip

da5b62b

mapper fixes

f989a8c

wip + offline handlers

05abbe9

wip + working build

9f25722

wip + fix build errors for tests

8be5116

test fixes

59583be

wip + fix null contextValue

c55c339

use correct module

f72f1ff

wip + fix segment tests

e697b61

fix assertEquals

4dcdaed

wip + fix django_id

7be7e3d

fix engine and evaluator tests

c4750b4

build success

15155e6

drop Java 8 support

bf4dddf

maybe use git url

9d4b0d8

bump submodule

afdaec0

khvn26 requested a review from Copilot September 16, 2025 20:58

Copilot AI reviewed Sep 16, 2025

View reviewed changes

khvn26 added 5 commits September 16, 2025 22:22

delete more code

6a7e1c3

minimise formatting changes

c742ec3

minimise formatting changes pt. 2

89f420a

minimise formatting changes pt. 3

d4e5b1e

improve formatting, comment

d99e9d1

emyller reviewed Sep 16, 2025

View reviewed changes

src/test/java/com/flagsmith/FlagsmithTestHelper.java Outdated Show resolved Hide resolved

khvn26 added 2 commits September 16, 2025 23:17

minimise formatting changes pt. 4

b861a72

remove debugging code

4730f9a

Zaimwa9 reviewed Sep 18, 2025

View reviewed changes

src/main/java/com/flagsmith/flagengine/Engine.java Show resolved Hide resolved

Zaimwa9 reviewed Sep 18, 2025

View reviewed changes

src/main/java/com/flagsmith/mappers/EngineMappers.java Outdated Show resolved Hide resolved

Zaimwa9 reviewed Sep 22, 2025

View reviewed changes

src/main/java/com/flagsmith/flagengine/segments/SegmentEvaluator.java Show resolved Hide resolved

refactor getEvaluationResult, add priority constants

db248dd

khvn26 requested a review from a team as a code owner October 10, 2025 10:33

khvn26 requested review from gagantrivedi and removed request for a team October 10, 2025 10:33

khvn26 added 12 commits October 10, 2025 12:57

improve docs

c4d35e2

improve readability

0e827fc

Support segment metadata

3819cd9

improve naming

de0362b

support variant priority

b8ae5ab

prevent illegal state

7764097

clarify context value getter behaviour

7303aeb

fix type casting

c37164b

fix boolean coercion

50b4bec

add test names

b4ee7ff

use latest test data

540832f

cleanup

60d5d9e

khvn26 requested review from Zaimwa9 and emyller October 15, 2025 16:04

khvn26 added 4 commits October 15, 2025 18:02

bump maven-surefire-plugin

e7cfad5

bring models back

c5821d9

...but they don't belong to the engine anymore

711ff13

restore IOfflineHandler

27b4b8e

khvn26 commented Oct 15, 2025

View reviewed changes

khvn26 added 5 commits October 16, 2025 01:04

cleanup to improve diff

000e96c

support feature metadata, unset segments in context

211c5bd

remove extra FeatureStateModel

8389a90

support setting Flag.featureId via metadata

69f00a4

fix

b5889e8

emyller reviewed Oct 20, 2025

View reviewed changes

Zaimwa9 reviewed Oct 20, 2025

View reviewed changes

		Double divisor = Double.parseDouble(parts[0]);
		Double remainder = Double.parseDouble(parts[1]);

feat!: Context Values support, getEvaluationResult #184

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feat!: Context Values support, `getEvaluationResult` #184

feat!: Context Values support, `getEvaluationResult` #184

khvn26 commented Sep 16, 2025 •

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