Fix t8n encoding issue

ethereum/evmtool/build.gradle

@@ -62,6 +62,7 @@ dependencies {
   testImplementation 'org.assertj:assertj-core'
   testImplementation 'org.junit.jupiter:junit-jupiter'
   testImplementation 'org.mockito:mockito-core'
+  testImplementation 'org.mockito:mockito-junit-jupiter'
 
   testRuntimeOnly 'org.junit.vintage:junit-vintage-engine'
 

ethereum/evmtool/src/main/java/org/hyperledger/besu/evmtool/T8nServerSubCommand.java

@@ -178,7 +178,7 @@ public void disposeTracer(final OperationTracer tracer) {
       t.printStackTrace(ps);
       ObjectNode json = objectMapper.createObjectNode();
       json.put("error", t.getMessage());
-      json.put("stacktrace", baos.toString(StandardCharsets.UTF_8));
+      json.put("stacktrace", baos.toString(StandardCharsets.UTF_8).replaceAll("\\s", " "));
 
       t.printStackTrace(System.out);
 

ethereum/evmtool/src/test/java/org/hyperledger/besu/evmtool/T8nServerSubCommandTest.java

@@ -0,0 +1,46 @@
+package org.hyperledger.besu.evmtool;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import io.vertx.core.http.HttpServerRequest;
+import io.vertx.core.http.HttpServerResponse;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.Answers;
+import org.mockito.ArgumentCaptor;
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+@ExtendWith(MockitoExtension.class)
+class T8nServerSubCommandTest {
+
+  @Mock HttpServerRequest httpServerRequest;
+
+  @Mock(answer = Answers.RETURNS_SELF)
+  HttpServerResponse httpServerResponse;
+
+  @Test
+  void exceptionEncodedProperlyInJSON() {
+    T8nServerSubCommand subject = new T8nServerSubCommand();
+    ObjectMapper objectMapper = new ObjectMapper();
+
+    when(httpServerRequest.response()).thenReturn(httpServerResponse);
+
+    // Should trigger a NPE within the try block.
+    subject.handleT8nRequest(httpServerRequest, objectMapper, null, null);
+
+    ArgumentCaptor<Integer> responseCodeCaptor = ArgumentCaptor.forClass(Integer.class);
+    ArgumentCaptor<String> responseStringCaptor = ArgumentCaptor.forClass(String.class);
+
+    verify(httpServerResponse).setStatusCode(responseCodeCaptor.capture());
+    verify(httpServerResponse).end(responseStringCaptor.capture());
+
+    System.out.println(responseCodeCaptor.getValue());
+    System.out.println(responseStringCaptor.getValue());
+    assertThat(responseCodeCaptor.getValue()).isEqualTo(500);
+    assertThat(responseStringCaptor.getValue()).doesNotContain("\\t");
+  }
+}