mirror of https://github.com/grpc/grpc-java.git
acbbf869a1
Fixes https://github.com/grpc/grpc-java/issues/12444 This PR addresses a bug in the `NameResolver.Listener` to `NameResolver.Listener2` bridge affecting custom NameResolver implementations using Listener. The bridge in `NameResolver.start(Listener)` at https://github.com/grpc/grpc-java/blob/master/api/src/main/java/io/grpc/NameResolver.java#L100 unconditionally calls `getValue()` on the `StatusOr`, throwing `java.lang.IllegalStateException: No value present.` when the result contains an error. This was identified when upgrading from gRPC `v1.63.3` to `v1.75.0`. The bug occurs due to `DnsNameResolver`'s error handling changes between versions: - `v1.63.3`: Errors reported via `Listener.onError()` (https://github.com/grpc/grpc-java/blob/v1.63.x/core/src/main/java/io/grpc/internal/DnsNameResolver.java#L319) - `v1.75.0`: Errors passed via `Listener2.onResult2()` with a ResolutionResult containing either addresses OR an error (https://github.com/grpc/grpc-java/blob/master/core/src/main/java/io/grpc/internal/DnsNameResolver.java#L322) This PR updates the bridge to check whether `ResolutionResult` contains addresses or an error. It passes the error via `onError` and addresses via `onAddresses`. **Reproducing the Issue** The `startOnOldListener_resolverReportsError` test reproduces a similar issue. It creates a custom `NameResolver` that reports errors through the `ResolutionResult` like the `DNSNameResolver` in `v1.75.0`, passes an old Listener to `resolver.start`, which triggers the bridge code path. Without the fix, the bridge calls `getValue()` on the error containing `StatusOr`, throwing `IllegalStateException: No value present`. With the fix, the bridge checks `hasValue()` first and correctly routes to `listener.onError()` when appropriate. This ensures backward compatibility for `Listener` implementations when resolvers report errors via `ResolutionResult`. |
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