Add SelectItem to flow single selector api

- This change makes single/multi same on an api level
  where single selector used key/value map and multi
  selector used list of SelectItem's.
- We still keep use of map on a single select but those
  essentially go directly via SelectItem's.
- Fixes #946

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022 the original author or authors.
+ * Copyright 2022-2023 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.
@@ -17,11 +17,11 @@ package org.springframework.shell.component.flow;
 
 import java.util.ArrayList;
 import java.util.Comparator;
-import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.function.Consumer;
 import java.util.function.Function;
+import java.util.stream.Collectors;
 
 import org.jline.utils.AttributedString;
 
@@ -40,7 +40,7 @@ public abstract class BaseSingleItemSelector extends BaseInput<SingleItemSelecto
 	private String name;
 	private String resultValue;
 	private ResultMode resultMode;
-	private Map<String, String> selectItems = new HashMap<>();
+	private List<SelectItem> selectItems = new ArrayList<>();
 	private String defaultSelect;
 	private Comparator<SelectorItem<String>> comparator;
 	private Function<SingleItemSelectorContext<String, SelectorItem<String>>, List<AttributedString>> renderer;
@@ -75,13 +75,22 @@ public abstract class BaseSingleItemSelector extends BaseInput<SingleItemSelecto
 
 	@Override
 	public SingleItemSelectorSpec selectItem(String name, String item) {
-		this.selectItems.put(name, item);
+		selectItems.add(SelectItem.of(name, item));
 		return this;
 	}
 
 	@Override
 	public SingleItemSelectorSpec selectItems(Map<String, String> selectItems) {
-		this.selectItems.putAll(selectItems);
+		List<SelectItem> items = selectItems.entrySet().stream()
+			.map(e -> SelectItem.of(e.getKey(), e.getValue()))
+			.collect(Collectors.toList());
+		selectItems(items);
+		return this;
+	}
+
+	@Override
+	public SingleItemSelectorSpec selectItems(List<SelectItem> selectItems) {
+		this.selectItems.addAll(selectItems);
 		return this;
 	}
 
@@ -163,7 +172,7 @@ public abstract class BaseSingleItemSelector extends BaseInput<SingleItemSelecto
 		return resultMode;
 	}
 
-	public Map<String, String> getSelectItems() {
+	public List<SelectItem> getSelectItems() {
 		return selectItems;
 	}
 
@@ -202,4 +211,4 @@ public abstract class BaseSingleItemSelector extends BaseInput<SingleItemSelecto
 	public Function<SingleItemSelectorContext<String, SelectorItem<String>>, String> getNext() {
 		return next;
 	}
-}
+}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022 the original author or authors.
+ * Copyright 2022-2023 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.
@@ -565,9 +565,9 @@ public interface ComponentFlow {
 
 		private Stream<OrderedInputOperation> singleItemSelectorsStream() {
 			return singleInputs.stream().map(input -> {
-				List<SelectorItem<String>> selectorItems = input.getSelectItems().entrySet().stream()
-					.map(e -> SelectorItem.of(e.getKey(), e.getValue()))
-					.collect(Collectors.toList());
+				List<SelectorItem<String>> selectorItems = input.getSelectItems().stream()
+						.map(si -> SelectorItem.of(si.name(), si.item()))
+						.collect(Collectors.toList());
 
 				// setup possible item for initial expose
 				String defaultSelect = input.getDefaultSelect();

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022 the original author or authors.
+ * Copyright 2022-2023 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.
@@ -65,6 +65,7 @@ public interface SingleItemSelectorSpec extends BaseInputSpec<SingleItemSelector
 	 * @param name the name
 	 * @param item the item
 	 * @return a builder
+	 * @see #selectItems(List)
 	 */
 	SingleItemSelectorSpec selectItem(String name, String item);
 
@@ -73,9 +74,18 @@ public interface SingleItemSelectorSpec extends BaseInputSpec<SingleItemSelector
 	 *
 	 * @param selectItems the select items
 	 * @return a builder
+	 * @see #selectItems(List)
 	 */
 	SingleItemSelectorSpec selectItems(Map<String, String> selectItems);
 
+	/**
+	 * Adds a list of select items.
+	 *
+	 * @param selectItems the select items
+	 * @return a builder
+	 */
+	SingleItemSelectorSpec selectItems(List<SelectItem> selectItems);
+
 	/**
 	 * Automatically selects and exposes a given item.
 	 *
@@ -156,4 +166,4 @@ public interface SingleItemSelectorSpec extends BaseInputSpec<SingleItemSelector
 	 * @return the parent builder
 	 */
 	Builder and();
-}
+}

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022 the original author or authors.
+ * Copyright 2022-2023 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.
@@ -28,7 +28,9 @@ import java.util.concurrent.atomic.AtomicReference;
 
 import org.junit.jupiter.api.Test;
 
+import org.springframework.shell.component.flow.ComponentFlow.Builder;
 import org.springframework.shell.component.flow.ComponentFlow.ComponentFlowResult;
+import org.springframework.test.util.ReflectionTestUtils;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
@@ -339,4 +341,34 @@ public class ComponentFlowTests extends AbstractShellTests {
 		String single1 = inputWizardResult.getContext().get("single1");
 		assertThat(single1).isEqualTo("value2");
 	}
+
+	@Test
+	@SuppressWarnings("unchecked")
+	public void testBuilderSingleTypes() {
+		List<SelectItem> selectItems1 = Arrays.asList(SelectItem.of("key1", "value1"), SelectItem.of("key2", "value2"));
+		Map<String, String> selectItems2 = new HashMap<>();
+		selectItems2.put("key2", "value2");
+		selectItems2.put("key3", "value3");
+
+		Builder builder1 = ComponentFlow.builder()
+			.withSingleItemSelector("field1")
+				.selectItems(selectItems1)
+				.and();
+		Builder builder2 = ComponentFlow.builder()
+			.withSingleItemSelector("field2")
+				.selectItems(selectItems2)
+				.and();
+
+		List<BaseSingleItemSelector> field1 = (List<BaseSingleItemSelector>) ReflectionTestUtils.getField(builder1,
+				"singleItemSelectors");
+		List<BaseSingleItemSelector> field2 = (List<BaseSingleItemSelector>) ReflectionTestUtils.getField(builder2,
+				"singleItemSelectors");
+		assertThat(field1).hasSize(1);
+		assertThat(field2).hasSize(1);
+
+		List<SelectItem> selectItems11 = (List<SelectItem>) ReflectionTestUtils.getField(field1.get(0), "selectItems");
+		List<SelectItem> selectItems21 = (List<SelectItem>) ReflectionTestUtils.getField(field2.get(0), "selectItems");
+		assertThat(selectItems11).hasSize(2);
+		assertThat(selectItems21).hasSize(2);
+	}
 }

spring-shell-docs/src/test/java/org/springframework/shell/docs/FlowComponentSnippets.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2022 the original author or authors.
+ * Copyright 2022-2023 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.
@@ -33,9 +33,8 @@ public class FlowComponentSnippets {
 		private ComponentFlow.Builder componentFlowBuilder;
 
 		public void runFlow() {
-			Map<String, String> single1SelectItems = new HashMap<>();
-			single1SelectItems.put("key1", "value1");
-			single1SelectItems.put("key2", "value2");
+			List<SelectItem> single1SelectItems = Arrays.asList(SelectItem.of("key1", "value1"),
+					SelectItem.of("key2", "value2"));
 			List<SelectItem> multi1SelectItems = Arrays.asList(SelectItem.of("key1", "value1"),
 					SelectItem.of("key2", "value2"), SelectItem.of("key3", "value3"));
 			ComponentFlow flow = componentFlowBuilder.clone().reset()