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Fix NPE in addRoot/removeRoot when roots listChanged is unset #1179

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Merged
Kehrlann merged 1 commit into from
Oct 13, 2026
+48 −2
Merged

Fix NPE in addRoot/removeRoot when roots listChanged is unset #1179

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4 changes: 2 additions & 2 deletions mcp-core/src/main/java/io/modelcontextprotocol/client/McpAsyncClient.java
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Original file line number Diff line number Diff line change
Expand Up @@ -511,7 +511,7 @@ public Mono<Void> addRoot(Root root) {

logger.debug("Added root: {}", root);

if (this.clientCapabilities.roots().listChanged()) {
if (Boolean.TRUE.equals(this.clientCapabilities.roots().listChanged())) {
if (this.isInitialized()) {
return this.rootsListChangedNotification();
}
Expand Down Expand Up @@ -539,7 +539,7 @@ public Mono<Void> removeRoot(String rootUri) {

if (removed != null) {
logger.debug("Removed Root: {}", rootUri);
if (this.clientCapabilities.roots().listChanged()) {
if (Boolean.TRUE.equals(this.clientCapabilities.roots().listChanged())) {
if (this.isInitialized()) {
return this.rootsListChangedNotification();
}
Expand Down
26 changes: 26 additions & 0 deletions mcp-core/src/test/java/io/modelcontextprotocol/client/McpAsyncClientTest.java
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Expand Up @@ -12,11 +12,15 @@
import org.junit.jupiter.api.Nested;
import org.junit.jupiter.api.Test;
import reactor.core.publisher.Mono;
import reactor.test.StepVerifier;

import static org.assertj.core.api.Assertions.assertThat;
import static org.assertj.core.api.Assertions.assertThatCode;
import static org.assertj.core.api.Assertions.assertThatThrownBy;
import static org.mockito.ArgumentMatchers.any;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.never;
import static org.mockito.Mockito.verify;
import static org.mockito.Mockito.when;

/**
Expand Down Expand Up @@ -179,4 +183,26 @@ void noElicitationFromCapabilities() {

}

@Nested
class Roots {

@Test
void addAndRemoveRootWithUnsetListChanged() {
McpClientTransport transport = mock(McpClientTransport.class);
when(transport.protocolVersions()).thenReturn(List.of("2024-11-05"));
var client = McpClient.async(transport)
.capabilities(McpSchema.ClientCapabilities.builder().roots(null).build())
.jsonSchemaValidator(mock(JsonSchemaValidator.class))
.build();

assertThat(client.getClientCapabilities().roots().listChanged()).isNull();

StepVerifier.create(client.addRoot(new McpSchema.Root("file:///added", "added"))).verifyComplete();
StepVerifier.create(client.removeRoot("file:///added")).verifyComplete();

verify(transport, never()).sendMessage(any());
}

}

}
20 changes: 20 additions & 0 deletions mcp-core/src/test/java/io/modelcontextprotocol/client/McpSyncClientTest.java
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Expand Up @@ -13,6 +13,7 @@
import org.junit.jupiter.api.Test;

import static org.assertj.core.api.Assertions.assertThat;
import static org.assertj.core.api.Assertions.assertThatCode;
import static org.mockito.Mockito.mock;
import static org.mockito.Mockito.when;

Expand Down Expand Up @@ -91,4 +92,23 @@ void noElicitationFromCapabilities() {

}

@Nested
class Roots {

@Test
void addAndRemoveRootWithUnsetListChanged() {
McpClientTransport transport = mock(McpClientTransport.class);
when(transport.protocolVersions()).thenReturn(List.of("2024-11-05"));
var client = McpClient.sync(transport)
.capabilities(McpSchema.ClientCapabilities.builder().roots(null).build())
.jsonSchemaValidator(mock(JsonSchemaValidator.class))
.build();

assertThatCode(() -> client.addRoot(new McpSchema.Root("file:///added", "added")))
.doesNotThrowAnyException();
assertThatCode(() -> client.removeRoot("file:///added")).doesNotThrowAnyException();
}

}

}
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