feat: adding mandatory flag to string input

spring-shell-core/src/main/java/org/springframework/shell/core/tui/component/StringInput.java

@@ -49,20 +49,28 @@ public class StringInput extends AbstractTextComponent<String, StringInputContex
 
 	private @Nullable Character maskCharacter;
 
+	private boolean required;
+
 	public StringInput(Terminal terminal) {
-		this(terminal, null, null, null);
+		this(terminal, null, null, null, false);
 	}
 
 	public StringInput(Terminal terminal, @Nullable String name, @Nullable String defaultValue) {
-		this(terminal, name, defaultValue, null);
+		this(terminal, name, defaultValue, null, false);
 	}
 
 	public StringInput(Terminal terminal, @Nullable String name, @Nullable String defaultValue,
 			@Nullable Function<StringInputContext, List<AttributedString>> renderer) {
+		this(terminal, name, defaultValue, renderer, false);
+	}
+
+	public StringInput(Terminal terminal, @Nullable String name, @Nullable String defaultValue,
+      @Nullable Function<StringInputContext, List<AttributedString>> renderer, boolean required) {
 		super(terminal, name, null);
 		setRenderer(renderer != null ? renderer : new DefaultRenderer());
 		setTemplateLocation("classpath:org/springframework/shell/component/string-input-default.stg");
 		this.defaultValue = defaultValue;
+		this.required = required;
 	}
 
 	/**
@@ -73,12 +81,21 @@ public void setMaskCharacter(@Nullable Character maskCharacter) {
 		this.maskCharacter = maskCharacter;
 	}
 
+	/**
+	 * Sets a required flag to check that the result is not empty
+	 *
+	 * @param required if input is required
+	 */
+	public void setRequired(boolean required) {
+		this.required = required;
+	}
+
 	@Override
 	public StringInputContext getThisContext(@Nullable ComponentContext<?> context) {
 		if (context != null && currentContext == context) {
 			return currentContext;
 		}
-		currentContext = StringInputContext.of(defaultValue, maskCharacter);
+		currentContext = StringInputContext.of(defaultValue, maskCharacter, required);
 		currentContext.setName(getName());
 		if (context != null) {
 			context.stream().forEach(e -> {
@@ -124,6 +141,9 @@ protected boolean read(BindingReader bindingReader, KeyMap<String> keyMap, Strin
 				}
 				else if (context.getDefaultValue() != null) {
 					context.setResultValue(context.getDefaultValue());
+				} else if (required) {
+					context.setMessage("This field is mandatory", TextComponentContext.MessageLevel.ERROR);
+					break;
 				}
 				return true;
 			default:
@@ -176,20 +196,43 @@ public interface StringInputContext extends TextComponentContext<String, StringI
 		 */
 		@Nullable Character getMaskCharacter();
 
+		/**
+		 * Sets flag for mandatory input.
+		 *
+		 * @param required true if input is required
+		 */
+		void setRequired(boolean required);
+
+		/**
+		 * Returns flag if input is required.
+		 *
+		 * @return true if input is required, false otherwise
+		 */
+		boolean isRequired();
+
 		/**
 		 * Gets an empty {@link StringInputContext}.
 		 * @return empty path input context
 		 */
 		public static StringInputContext empty() {
-			return of(null, null);
+			return of(null, null, false);
 		}
 
 		/**
 		 * Gets an {@link StringInputContext}.
 		 * @return path input context
 		 */
 		public static StringInputContext of(@Nullable String defaultValue, @Nullable Character maskCharacter) {
-			return new DefaultStringInputContext(defaultValue, maskCharacter);
+			return of(defaultValue, maskCharacter, false);
+		}
+
+		/**
+		 * Gets an {@link StringInputContext}.
+		 *
+		 * @return path input context
+		 */
+		public static StringInputContext of(@Nullable String defaultValue, @Nullable Character maskCharacter, boolean required) {
+			return new DefaultStringInputContext(defaultValue, maskCharacter, required);
 		}
 
 	}
@@ -201,9 +244,12 @@ private static class DefaultStringInputContext extends BaseTextComponentContext<
 
 		private @Nullable Character maskCharacter;
 
-		public DefaultStringInputContext(@Nullable String defaultValue, @Nullable Character maskCharacter) {
+		private boolean required;
+
+		public DefaultStringInputContext(@Nullable String defaultValue, @Nullable Character maskCharacter, boolean required) {
 			this.defaultValue = defaultValue;
 			this.maskCharacter = maskCharacter;
+			this.required = required;
 		}
 
 		@Override
@@ -221,6 +267,11 @@ public void setMaskCharacter(Character maskCharacter) {
 			this.maskCharacter = maskCharacter;
 		}
 
+		@Override
+		public void setRequired(boolean required) {
+			this.required = required;
+		}
+
 		@Override
 		public @Nullable String getMaskedInput() {
 			return maybeMask(getInput());
@@ -241,6 +292,11 @@ public boolean hasMaskCharacter() {
 			return maskCharacter;
 		}
 
+		@Override
+		public boolean isRequired() {
+			return required;
+		}
+
 		@Override
 		public Map<String, @Nullable Object> toTemplateModel() {
 			Map<String, @Nullable Object> attributes = super.toTemplateModel();
@@ -249,6 +305,7 @@ public boolean hasMaskCharacter() {
 			attributes.put("maskedResultValue", getMaskedResultValue());
 			attributes.put("maskCharacter", getMaskCharacter());
 			attributes.put("hasMaskCharacter", hasMaskCharacter());
+			attributes.put("required", isRequired());
 			Map<String, Object> model = new HashMap<>();
 			model.put("model", attributes);
 			return model;

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

@@ -45,6 +45,8 @@ public abstract class BaseStringInput extends BaseInput<StringInputSpec> impleme
 
 	private @Nullable Character maskCharacter;
 
+	private boolean required = false;
+
 	private @Nullable Function<StringInputContext, List<AttributedString>> renderer;
 
 	private List<Consumer<StringInputContext>> preHandlers = new ArrayList<>();
@@ -91,6 +93,12 @@ public StringInputSpec maskCharacter(Character maskCharacter) {
 		return this;
 	}
 
+	@Override
+	public StringInputSpec required() {
+		this.required = true;
+		return this;
+	}
+
 	@Override
 	public StringInputSpec renderer(Function<StringInputContext, List<AttributedString>> renderer) {
 		this.renderer = renderer;
@@ -158,6 +166,10 @@ public StringInputSpec getThis() {
 		return maskCharacter;
 	}
 
+	public boolean isRequired() {
+		return required;
+	}
+
 	public @Nullable Function<StringInputContext, List<AttributedString>> getRenderer() {
 		return renderer;
 	}

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

@@ -468,7 +468,7 @@ else if (n.isPresent()) {
 
 		private Stream<OrderedInputOperation> stringInputsStream() {
 			return stringInputs.stream().map(input -> {
-				StringInput selector = new StringInput(terminal, input.getName(), input.getDefaultValue());
+				StringInput selector = new StringInput(terminal, input.getName(), input.getDefaultValue(), null, input.isRequired());
 				Function<ComponentContext<?>, ComponentContext<?>> operation = (context) -> {
 					if (input.getResultMode() == ResultMode.ACCEPT && input.isStoreResult()
 							&& StringUtils.hasText(input.getResultValue())) {
@@ -492,6 +492,7 @@ private Stream<OrderedInputOperation> stringInputsStream() {
 						if (input.getResultMode() == ResultMode.VERIFY && StringUtils.hasText(input.getResultValue())) {
 							selector.addPreRunHandler(c -> {
 								c.setDefaultValue(input.getResultValue());
+								c.setRequired(input.isRequired());
 							});
 						}
 						selector.addPostRunHandler(c -> {

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

@@ -67,6 +67,13 @@ public interface StringInputSpec extends BaseInputSpec<StringInputSpec> {
 	 */
 	StringInputSpec maskCharacter(Character maskCharacter);
 
+	/**
+	 * Sets input to required
+	 *
+	 * @return a builder
+	 */
+	StringInputSpec required();
+
 	/**
 	 * Sets a renderer function.
 	 * @param renderer the renderer

spring-shell-core/src/test/java/org/springframework/shell/core/tui/component/StringInputTests.java

@@ -162,6 +162,39 @@ void testResultUserInput() {
 		});
 	}
 
+	@Test
+	void testResultMandatoryInput() {
+		ComponentContext<?> empty = ComponentContext.empty();
+		StringInput component1 = new StringInput(getTerminal());
+		component1.setResourceLoader(new DefaultResourceLoader());
+		component1.setTemplateExecutor(getTemplateExecutor());
+		component1.setRequired(true);
+
+		service.execute(() -> {
+			StringInputContext run1Context = component1.run(empty);
+			result1.set(run1Context);
+		});
+
+		TestBuffer testBuffer = new TestBuffer().cr();
+		write(testBuffer.getBytes());
+
+		await().atMost(Duration.ofSeconds(2)).untilAsserted(() -> {
+			StringInputContext run1Context = result1.get();
+			assertThat(consoleOut()).contains("This field is mandatory");
+			assertThat(run1Context).isNull();
+		});
+
+		testBuffer.append("test").cr();
+		write(testBuffer.getBytes());
+
+		await().atMost(Duration.ofSeconds(2)).untilAsserted(() -> {
+			StringInputContext run1Context = result1.get();
+
+			assertThat(run1Context).isNotNull();
+			assertThat(run1Context.getResultValue()).isEqualTo("test");
+		});
+	}
+
 	@Test
 	void testResultUserInputUnicode() {
 		ComponentContext<?> empty = ComponentContext.empty();

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

@@ -54,6 +54,10 @@ void testSimpleFlow() {
 			.withStringInput("field2")
 			.name("Field2")
 			.and()
+			.withStringInput("field3")
+			.name("Field3")
+			.required()
+			.and()
 			.withPathInput("path1")
 			.name("Path1")
 			.and()
@@ -78,6 +82,9 @@ void testSimpleFlow() {
 		// field2
 		testBuffer = new TestBuffer().append("Field2Value").cr();
 		write(testBuffer.getBytes());
+		// field3
+		testBuffer = new TestBuffer().cr().append("Field3Value").cr();
+		write(testBuffer.getBytes());
 		// path1
 		testBuffer = new TestBuffer().append("fakedir").cr();
 		write(testBuffer.getBytes());
@@ -93,17 +100,18 @@ void testSimpleFlow() {
 			assertThat(inputWizardResult).isNotNull();
 			String field1 = inputWizardResult.getContext().get("field1");
 			String field2 = inputWizardResult.getContext().get("field2");
+			String field3 = inputWizardResult.getContext().get("field3");
 			Path path1 = inputWizardResult.getContext().get("path1");
 			String single1 = inputWizardResult.getContext().get("single1");
 			List<String> multi1 = inputWizardResult.getContext().get("multi1");
 			assertThat(field1).isEqualTo("defaultField1Value");
+			assertThat(field3).isEqualTo("Field3Value");
 			assertThat(field2).isEqualTo("Field2Value");
 			assertThat(path1.toString()).contains("fakedir");
 			assertThat(single1).isEqualTo("value1");
 			assertThat(multi1).containsExactlyInAnyOrder("value2");
 			assertThat(consoleOut()).contains("Field1 defaultField1Value");
 		});
-
 	}
 
 	@Test

spring-shell-core/src/test/resources/org/springframework/shell/component/string-input-default.stg

@@ -1,3 +1,14 @@
+// message
+message(model) ::= <%
+<if(model.message && model.hasMessageLevelError)>
+  <({<figures.error>}); format="style-level-error"> <model.message; format="style-level-error">
+<elseif(model.message && model.hasMessageLevelWarn)>
+  <({<figures.warning>}); format="style-level-warn"> <model.message; format="style-level-warn">
+<elseif(model.message && model.hasMessageLevelInfo)>
+  <({<figures.info>}); format="style-level-info"> <model.message; format="style-level-info">
+<endif>
+%>
+
 // info section after '? xxx'
 info(model) ::= <%
 <if(model.hasMaskCharacter)>
@@ -6,6 +17,8 @@ info(model) ::= <%
   <else>
     <if(model.defaultValue)>
       <("[Default "); format="style-value"><model.defaultValue; format="style-value"><("]"); format="style-value">
+    <elseif(model.required)>
+      <("[Required]"); format="style-value">
     <endif>
   <endif>
 <else>
@@ -14,6 +27,8 @@ info(model) ::= <%
   <else>
     <if(model.defaultValue)>
       <("[Default "); format="style-value"><model.defaultValue; format="style-value"><("]"); format="style-value">
+    <elseif(model.required)>
+      <("[Required]"); format="style-value">
     <endif>
   <endif>
 <endif>
@@ -32,6 +47,7 @@ result(model) ::= <<
 // component is running
 running(model) ::= <<
 <question_name(model)> <info(model)>
+<message(model)>
 >>
 
 // main

spring-shell-docs/modules/ROOT/pages/components/ui/stringinput.adoc

@@ -4,7 +4,8 @@
 ifndef::snippets[:snippets: ../../../../../src/test/java/org/springframework/shell/docs]
 
 The string input component asks a user for simple text input, optionally masking values
-if the content contains something sensitive. The following listing shows an example:
+if the content contains something sensitive. The input can also be required (at least 1 char). +
+The following listing shows an example:
 
 [source, java, indent=0]
 ----
@@ -40,6 +41,9 @@ The context object is `StringInputContext`. The following table lists its contex
 |`hasMaskCharacter`
 |`true` if a mask character is set. Otherwise, false.
 
+|`required`
+|`true` if the input is required. Otherwise, false.
+
 |`model`
 |The parent context variables (see xref:/components/ui/render.adoc#textcomponentcontext-template-variables[TextComponentContext Template Variables]).
 |===

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

@@ -61,6 +61,10 @@ public void showcase1() {
 			.withStringInput("field2")
 			.name("Field2")
 			.and()
+			.withStringInput("field3")
+			.name("Field3")
+			.mandatory()
+			.and()
 			.withConfirmationInput("confirmation1")
 			.name("Confirmation1")
 			.and()