Make Terminal configurable

- Add TerminalCustomizer which can be used to customise
  TerminalBuilder before instance from it is build.
- Fixes #516

Author: jvalkeal

spring-shell-autoconfigure/src/main/java/org/springframework/shell/boot/JLineShellAutoConfiguration.java

@@ -25,6 +25,7 @@
 import org.jline.utils.AttributedStyle;
 
 import org.springframework.beans.factory.BeanCreationException;
+import org.springframework.beans.factory.ObjectProvider;
 import org.springframework.boot.autoconfigure.AutoConfiguration;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.context.annotation.Bean;
@@ -41,12 +42,14 @@
 public class JLineShellAutoConfiguration {
 
 	@Bean(destroyMethod = "close")
-	public Terminal terminal() {
+	public Terminal terminal(ObjectProvider<TerminalCustomizer> customizers) {
 		try {
-			return TerminalBuilder.builder().build();
+			TerminalBuilder builder = TerminalBuilder.builder();
+			customizers.orderedStream().forEach(customizer -> customizer.customize(builder));
+			return builder.build();
 		}
 		catch (IOException e) {
-			throw new BeanCreationException("Could not create Terminal: " + e.getMessage());
+			throw new BeanCreationException("Could not create Terminal", e);
 		}
 	}
 

spring-shell-autoconfigure/src/main/java/org/springframework/shell/boot/TerminalCustomizer.java

@@ -0,0 +1,36 @@
+/*
+ * Copyright 2022 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.shell.boot;
+
+import org.jline.terminal.Terminal;
+import org.jline.terminal.TerminalBuilder;
+
+/**
+ * Callback interface that can be used to customize a {@link Terminal} via its
+ * {@link TerminalBuilder}.
+ *
+ * @author Janne Valkealahti
+ */
+@FunctionalInterface
+public interface TerminalCustomizer {
+
+	/**
+	 * Callback to customize a {@link TerminalBuilder} instance.
+	 *
+	 * @param builder the terminal builder
+	 */
+	void customize(TerminalBuilder builder);
+}

spring-shell-autoconfigure/src/test/java/org/springframework/shell/boot/JLineShellAutoConfigurationTests.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2022 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.shell.boot;
+
+import org.jline.terminal.Terminal;
+import org.jline.terminal.TerminalBuilder;
+import org.junit.jupiter.api.Test;
+
+import org.springframework.boot.autoconfigure.AutoConfigurations;
+import org.springframework.boot.test.context.runner.ApplicationContextRunner;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.verify;
+
+class JLineShellAutoConfigurationTests {
+
+	private final ApplicationContextRunner contextRunner = new ApplicationContextRunner()
+			.withConfiguration(AutoConfigurations.of(JLineShellAutoConfiguration.class));
+
+	@Test
+	void canCreatePlainTerminal() {
+		contextRunner.run(context -> {
+			assertThat(context).hasSingleBean(Terminal.class);
+		});
+	}
+
+	@Test
+	void canCustomizeTerminalBuilder() {
+		TerminalCustomizer customizer = mock(TerminalCustomizer.class);
+		contextRunner.withBean(TerminalCustomizer.class, () -> customizer)
+				.run(context -> {
+					verify(customizer).customize(any(TerminalBuilder.class));
+				});
+	}
+}