Add auto-config for ComponentFlow

- ComponentFlowAutoConfiguration which creates a builder bean
  and configures ComponentFlowCustomizer to set needed
  defaults for terminal, resource loader and template executor.
- Fixes #387

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

@@ -0,0 +1,84 @@
+/*
+ * 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.springframework.beans.factory.ObjectProvider;
+import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Scope;
+import org.springframework.core.annotation.Order;
+import org.springframework.core.io.ResourceLoader;
+import org.springframework.shell.component.flow.ComponentFlow;
+import org.springframework.shell.component.flow.ComponentFlow.Builder;
+import org.springframework.shell.style.TemplateExecutor;
+
+/**
+ * {@link EnableAutoConfiguration Auto-configuration} for {@link ComponentFlow}.
+ *
+ * @author Janne Valkealahti
+ */
+@Configuration(proxyBeanMethods = false)
+@ConditionalOnClass(ComponentFlow.class)
+public class ComponentFlowAutoConfiguration {
+
+	@Bean
+	@Scope("prototype")
+	@ConditionalOnMissingBean
+	public ComponentFlow.Builder componentFlowBuilder(ObjectProvider<ComponentFlowCustomizer> customizerProvider) {
+		ComponentFlow.Builder builder = ComponentFlow.builder();
+		customizerProvider.orderedStream().forEach((customizer) -> customizer.customize(builder));
+		return builder;
+	}
+
+	@Configuration(proxyBeanMethods = false)
+	protected static class ComponentFlowConfiguration {
+
+		@Bean
+		@ConditionalOnMissingBean
+		@Order(0)
+		public ComponentFlowCustomizer exchangeStrategiesCustomizer(ObjectProvider<Terminal> terminal,
+				ObjectProvider<ResourceLoader> resourceLoader, ObjectProvider<TemplateExecutor> templateExecutor) {
+			return new CommonComponentFlowCustomizer(terminal, resourceLoader, templateExecutor);
+		}
+
+	}
+
+	private static class CommonComponentFlowCustomizer implements ComponentFlowCustomizer {
+
+		private final ObjectProvider<Terminal> terminal;
+		private final ObjectProvider<ResourceLoader> resourceLoader;
+		private final ObjectProvider<TemplateExecutor> templateExecutor;
+
+		CommonComponentFlowCustomizer(ObjectProvider<Terminal> terminal, ObjectProvider<ResourceLoader> resourceLoader,
+				ObjectProvider<TemplateExecutor> templateExecutor) {
+			this.terminal = terminal;
+			this.resourceLoader = resourceLoader;
+			this.templateExecutor = templateExecutor;
+		}
+
+		@Override
+		public void customize(Builder componentFlowBuilder) {
+			terminal.ifAvailable(dep -> componentFlowBuilder.terminal(dep));
+			resourceLoader.ifAvailable(dep -> componentFlowBuilder.resourceLoader(dep));
+			templateExecutor.ifAvailable(dep -> componentFlowBuilder.templateExecutor(dep));
+		}
+	}
+}

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

@@ -0,0 +1,33 @@
+/*
+ * 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.springframework.shell.component.flow.ComponentFlow;
+
+/**
+ * Callback interface that can be used to customize a {@link ComponentFlow.Builder}.
+ *
+ * @author Janne Valkealahti
+ */
+@FunctionalInterface
+public interface ComponentFlowCustomizer {
+
+	/**
+	 * Callback to customize a {@link ComponentFlow.Builder} instance.
+	 * @param componentFlowBuilder the component flow builder to customize
+	 */
+	void customize(ComponentFlow.Builder componentFlowBuilder);
+}

spring-shell-autoconfigure/src/main/resources/META-INF/spring.factories

@@ -12,4 +12,5 @@ org.springframework.shell.boot.JCommanderParameterResolverAutoConfiguration,\
 org.springframework.shell.boot.ParameterResolverAutoConfiguration,\
 org.springframework.shell.boot.StandardAPIAutoConfiguration,\
 org.springframework.shell.boot.ThemingAutoConfiguration,\
-org.springframework.shell.boot.StandardCommandsAutoConfiguration
+org.springframework.shell.boot.StandardCommandsAutoConfiguration,\
+org.springframework.shell.boot.ComponentFlowAutoConfiguration

spring-shell-core/src/main/java/org/springframework/shell/component/flow/ComponentFlow.java

@@ -70,11 +70,10 @@ public interface ComponentFlow {
 	/**
 	 * Gets a new instance of an input wizard builder.
 	 *
-	 * @param terminal the terminal
 	 * @return the input wizard builder
 	 */
-	public static Builder builder(Terminal terminal) {
-		return new DefaultBuilder(terminal);
+	public static Builder builder() {
+		return new DefaultBuilder();
 	}
 
 	/**
@@ -135,6 +134,14 @@ public interface ComponentFlow {
 		 */
 		MultiItemSelectorSpec withMultiItemSelector(String id);
 
+		/**
+		 * Sets a {@link Terminal}.
+		 *
+		 * @param terminal the terminal
+		 * @return a builder
+		 */
+		Builder terminal(Terminal terminal);
+
 		/**
 		 * Sets a {@link ResourceLoader}.
 		 *
@@ -151,6 +158,20 @@ public interface ComponentFlow {
 		 */
 		Builder templateExecutor(TemplateExecutor templateExecutor);
 
+		/**
+		 * Clones existing builder.
+		 *
+		 * @return a builder
+		 */
+		Builder clone();
+
+		/**
+		 * Resets existing builder.
+		 *
+		 * @return a builder
+		 */
+		Builder reset();
+
 		/**
 		 * Builds instance of input wizard.
 		 *
@@ -161,7 +182,6 @@ public interface ComponentFlow {
 
 	static abstract class BaseBuilder implements Builder {
 
-		private Terminal terminal;
 		private final List<BaseStringInput> stringInputs = new ArrayList<>();
 		private final List<BasePathInput> pathInputs = new ArrayList<>();
 		private final List<BaseConfirmationInput> confirmationInputs = new ArrayList<>();
@@ -169,11 +189,11 @@ public interface ComponentFlow {
 		private final List<BaseMultiItemSelector> multiItemSelectors = new ArrayList<>();
 		private final AtomicInteger order = new AtomicInteger();
 		private final HashSet<String> uniqueIds = new HashSet<>();
+		private Terminal terminal;
 		private ResourceLoader resourceLoader;
 		private TemplateExecutor templateExecutor;
 
-		BaseBuilder(Terminal terminal) {
-			this.terminal = terminal;
+		BaseBuilder() {
 		}
 
 		@Override
@@ -207,6 +227,12 @@ public interface ComponentFlow {
 			return new DefaultMultiInputSpec(this, id);
 		}
 
+		@Override
+		public Builder terminal(Terminal terminal) {
+			this.terminal = terminal;
+			return this;
+		}
+
 		@Override
 		public Builder resourceLoader(ResourceLoader resourceLoader) {
 			this.resourceLoader = resourceLoader;
@@ -219,6 +245,23 @@ public interface ComponentFlow {
 			return this;
 		}
 
+		@Override
+		public Builder clone() {
+			return new DefaultBuilder(this);
+		}
+
+		@Override
+		public Builder reset() {
+			stringInputs.clear();
+			pathInputs.clear();
+			confirmationInputs.clear();
+			singleItemSelectors.clear();
+			multiItemSelectors.clear();
+			order.set(0);
+			uniqueIds.clear();
+			return this;
+		}
+
 		void addStringInput(BaseStringInput input) {
 			checkUniqueId(input.getId());
 			input.setOrder(order.getAndIncrement());
@@ -249,6 +292,10 @@ public interface ComponentFlow {
 			multiItemSelectors.add(input);
 		}
 
+		Terminal getTerminal() {
+			return terminal;
+		}
+
 		ResourceLoader getResourceLoader() {
 			return resourceLoader;
 		}
@@ -267,8 +314,14 @@ public interface ComponentFlow {
 
 	static class DefaultBuilder extends BaseBuilder {
 
-		DefaultBuilder(Terminal terminal) {
-			super(terminal);
+		DefaultBuilder() {
+			super();
+		}
+
+		DefaultBuilder(BaseBuilder other) {
+			terminal(other.getTerminal());
+			resourceLoader(other.getResourceLoader());
+			templateExecutor(other.getTemplateExecutor());
 		}
 	}
 

spring-shell-core/src/test/java/org/springframework/shell/component/flow/ComponentFlowTests.java

@@ -41,7 +41,8 @@ public class ComponentFlowTests extends AbstractShellTests {
 		single1SelectItems.put("key2", "value2");
 		List<SelectItem> multi1SelectItems = Arrays.asList(SelectItem.of("key1", "value1"),
 				SelectItem.of("key2", "value2"), SelectItem.of("key3", "value3"));
-		ComponentFlow wizard = ComponentFlow.builder(getTerminal())
+		ComponentFlow wizard = ComponentFlow.builder()
+				.terminal(getTerminal())
 				.resourceLoader(getResourceLoader())
 				.templateExecutor(getTemplateExecutor())
 				.withStringInput("field1")
@@ -107,7 +108,8 @@ public class ComponentFlowTests extends AbstractShellTests {
 
 	@Test
 	public void testSkipsGivenComponents() throws InterruptedException {
-		ComponentFlow wizard = ComponentFlow.builder(getTerminal())
+		ComponentFlow wizard = ComponentFlow.builder()
+			.terminal(getTerminal())
 			.withStringInput("id1")
 				.name("name")
 				.resultValue("value1")
@@ -154,7 +156,8 @@ public class ComponentFlowTests extends AbstractShellTests {
 
 		@Test
 		public void testChoosesDynamically() throws InterruptedException {
-			ComponentFlow wizard = ComponentFlow.builder(getTerminal())
+			ComponentFlow wizard = ComponentFlow.builder()
+				.terminal(getTerminal())
 				.resourceLoader(getResourceLoader())
 				.templateExecutor(getTemplateExecutor())
 				.withStringInput("id1")

spring-shell-samples/src/main/java/org/springframework/shell/samples/standard/ComponentFlowCommands.java

@@ -20,6 +20,7 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
+import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.shell.component.flow.ComponentFlow;
 import org.springframework.shell.component.flow.SelectItem;
 import org.springframework.shell.standard.AbstractShellComponent;
@@ -29,6 +30,9 @@ import org.springframework.shell.standard.ShellMethod;
 @ShellComponent
 public class ComponentFlowCommands extends AbstractShellComponent {
 
+	@Autowired
+	private ComponentFlow.Builder componentFlowBuilder;
+
 	@ShellMethod(key = "flow showcase", value = "Showcase", group = "Flow")
 	public void showcase() {
 		Map<String, String> single1SelectItems = new HashMap<>();
@@ -36,9 +40,7 @@ public class ComponentFlowCommands extends AbstractShellComponent {
 		single1SelectItems.put("key2", "value2");
 		List<SelectItem> multi1SelectItems = Arrays.asList(SelectItem.of("key1", "value1"),
 				SelectItem.of("key2", "value2"), SelectItem.of("key3", "value3"));
-		ComponentFlow flow = ComponentFlow.builder(getTerminal())
-				.resourceLoader(getResourceLoader())
-				.templateExecutor(getTemplateExecutor())
+		ComponentFlow flow = componentFlowBuilder.clone().reset()
 				.withStringInput("field1")
 					.name("Field1")
 					.defaultValue("defaultField1Value")
@@ -69,9 +71,7 @@ public class ComponentFlowCommands extends AbstractShellComponent {
 		Map<String, String> single1SelectItems = new HashMap<>();
 		single1SelectItems.put("Field1", "field1");
 		single1SelectItems.put("Field2", "field2");
-		ComponentFlow flow = ComponentFlow.builder(getTerminal())
-				.resourceLoader(getResourceLoader())
-				.templateExecutor(getTemplateExecutor())
+		ComponentFlow flow = componentFlowBuilder.clone().reset()
 				.withSingleItemSelector("single1")
 					.name("Single1")
 					.selectItems(single1SelectItems)