• Validate engineVersion parameter accepts only 0, 1, or 2
• Reject invalid engineVersion == 2 && trackEmittedStreams combination
• Throw IllegalArgumentException locally instead of server-side error
• Improve error messages for invalid projection configurations

Add engineVersion parameter validation

• Added validation in engineVersion() method to reject values outside 0, 1, 2 range
• Throws IllegalArgumentException with descriptive message for invalid values
• Updated JavaDoc to document the exception behavior

src/main/java/io/kurrent/dbclient/CreateProjectionOptions.java

Validate V2 engine and trackEmittedStreams incompatibility

• Added validation in execute() method to reject engineVersion == 2 && trackEmittedStreams
 combination
• Throws IllegalArgumentException before sending request to server
• Prevents invalid V2 engine configuration from reaching the server

src/main/java/io/kurrent/dbclient/CreateProjection.java

Description

CreateProjection.execute() throws IllegalArgumentException before returning a CompletableFuture when
engineVersion==2 and trackEmittedStreams==true, so KurrentDBProjectionManagementClient.create(...)
can fail synchronously instead of completing the future exceptionally. This breaks common usage
patterns that handle failures via future completion (e.g., catching ExecutionException from .get()).

Code

src/main/java/io/kurrent/dbclient/CreateProjection.java[R32-35]

+        if (engineVersion == 2 && trackEmittedStreams) {
+            throw new IllegalArgumentException(
+                    "trackEmittedStreams is not supported when engineVersion is 2 (V2)");
+        }

Evidence

The new precondition throws before any CompletableFuture is created/returned, and the public
projection management client simply returns execute() directly—so the exception escapes
synchronously at the call site. Existing sample usage patterns show callers generally expecting
failures to surface through the future (ExecutionException on .get()).

src/main/java/io/kurrent/dbclient/CreateProjection.java[30-36]
src/main/java/io/kurrent/dbclient/KurrentDBProjectionManagementClient.java[74-79]
src/test/java/io/kurrent/dbclient/samples/projection_management/ProjectionManagement.java[59-66]
src/test/java/io/kurrent/dbclient/samples/projection_management/ProjectionManagement.java[155-176]
README.md[19-20]

Agent prompt

The issue below was found during a code review. Follow the provided context and guidance below and implement a solution

### Issue description
`CreateProjection.execute()` throws `IllegalArgumentException` synchronously for the invalid combination `engineVersion == 2 && trackEmittedStreams == true`. Since the public API returns `CompletableFuture`, callers commonly expect failures to arrive via exceptional completion rather than a synchronous throw.

### Issue Context
The project supports Java 8+, so prefer a Java-8-compatible way to create a failed future (i.e., `new CompletableFuture<>()` + `completeExceptionally(...)`).

### Fix Focus Areas
- src/main/java/io/kurrent/dbclient/CreateProjection.java[30-36]

### Suggested fix
Replace the synchronous `throw` with returning an exceptionally-completed `CompletableFuture` (or move the validation into the options setters while still ensuring the public `create(...)` method does not throw unexpectedly). For Java 8 compatibility:
- Create `CompletableFuture<Projectionmanagement.CreateResp>` (or raw `CompletableFuture` consistent with the current signature)
- `completeExceptionally(new IllegalArgumentException(...))`
- `return failed;`

Optionally, document this behavior in the public client/create Javadocs if you decide to keep synchronous throws.

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