Fix availability feature

- Bring back some missing functionality which got missing
  during the rework to new command model.
- Polish some classes.
- Restore origin sample.
- Add availability things into help templates and its
  representation model.
- Fixes #423

spring-shell-core/src/main/java/org/springframework/shell/CommandNotCurrentlyAvailable.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2017 the original author or authors.
+ * Copyright 2017-2022 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.
@@ -13,7 +13,6 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-
 package org.springframework.shell;
 
 /**
@@ -23,20 +22,21 @@ package org.springframework.shell;
  */
 public class CommandNotCurrentlyAvailable extends RuntimeException {
 
-    private final String command;
-    private final Availability availability;
+	private final String command;
+	private final Availability availability;
 
-    public CommandNotCurrentlyAvailable(String command, Availability availability) {
-        super(String.format("Command '%s' exists but is not currently available because %s", command, availability.getReason()));
-        this.command = command;
-        this.availability = availability;
-    }
+	public CommandNotCurrentlyAvailable(String command, Availability availability) {
+		super(String.format("Command '%s' exists but is not currently available because %s", command,
+				availability.getReason()));
+		this.command = command;
+		this.availability = availability;
+	}
 
-    public String getCommand() {
-        return command;
-    }
+	public String getCommand() {
+		return command;
+	}
 
-    public Availability getAvailability() {
-        return availability;
-    }
+	public Availability getAvailability() {
+		return availability;
+	}
 }

spring-shell-core/src/main/java/org/springframework/shell/command/CommandExecution.java

@@ -29,6 +29,8 @@ import org.springframework.core.convert.ConversionService;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.handler.invocation.HandlerMethodArgumentResolver;
 import org.springframework.messaging.support.MessageBuilder;
+import org.springframework.shell.Availability;
+import org.springframework.shell.CommandNotCurrentlyAvailable;
 import org.springframework.shell.command.CommandParser.CommandParserException;
 import org.springframework.shell.command.CommandParser.CommandParserResults;
 import org.springframework.shell.command.CommandRegistration.TargetInfo;
@@ -95,6 +97,11 @@ public interface CommandExecution {
 		}
 
 		public Object evaluate(CommandRegistration registration, String[] args) {
+			// fast fail with availability before doing anything else
+			Availability availability = registration.getAvailability();
+			if (availability != null && !availability.isAvailable()) {
+				return new CommandNotCurrentlyAvailable(registration.getCommand(), availability);
+			}
 
 			List<CommandOption> options = registration.getOptions();
 			CommandParser parser = CommandParser.of(conversionService);

spring-shell-core/src/test/java/org/springframework/shell/command/CommandExecutionTests.java

@@ -26,6 +26,8 @@ import org.junit.jupiter.params.provider.ValueSource;
 import org.springframework.core.convert.ConversionService;
 import org.springframework.core.convert.support.DefaultConversionService;
 import org.springframework.messaging.handler.invocation.HandlerMethodArgumentResolver;
+import org.springframework.shell.Availability;
+import org.springframework.shell.CommandNotCurrentlyAvailable;
 import org.springframework.shell.command.CommandExecution.CommandParserExceptionsException;
 import org.springframework.shell.command.CommandRegistration.OptionArity;
 
@@ -459,4 +461,22 @@ public class CommandExecutionTests extends AbstractCommandTests {
 			execution.evaluate(r1, new String[]{});
 		}).isInstanceOf(CommandParserExceptionsException.class);
 	}
+
+	@Test
+	public void testCommandNotAvailable() {
+		CommandRegistration r1 = CommandRegistration.builder()
+			.command("command1")
+			.description("help")
+			.withOption()
+				.longNames("arg1")
+				.description("some arg1")
+				.and()
+			.availability(() -> Availability.unavailable("fake reason"))
+			.withTarget()
+				.function(function1)
+				.and()
+			.build();
+		Object result = execution.evaluate(r1, new String[]{"--arg1", "myarg1value"});
+		assertThat(result).isInstanceOf(CommandNotCurrentlyAvailable.class);
+	}
 }

spring-shell-core/src/test/java/org/springframework/shell/command/CommandRegistrationTests.java

@@ -18,6 +18,7 @@ package org.springframework.shell.command;
 import org.junit.jupiter.api.Test;
 
 import org.springframework.core.ResolvableType;
+import org.springframework.shell.Availability;
 import org.springframework.shell.command.CommandRegistration.OptionArity;
 import org.springframework.shell.command.CommandRegistration.TargetInfo.TargetType;
 import org.springframework.shell.context.InteractionMode;
@@ -410,4 +411,27 @@ public class CommandRegistrationTests extends AbstractCommandTests {
 		assertThat(registration.getExitCode()).isNotNull();
 		assertThat(registration.getExitCode().getMappingFunctions()).hasSize(4);
 	}
+
+	@Test
+	public void testAvailability() {
+		CommandRegistration registration;
+		registration = CommandRegistration.builder()
+			.command("command1")
+			.withTarget()
+				.function(function1)
+				.and()
+			.build();
+		assertThat(registration.getAvailability()).isNotNull();
+		assertThat(registration.getAvailability().isAvailable()).isTrue();
+
+		registration = CommandRegistration.builder()
+			.command("command1")
+			.availability(() -> Availability.unavailable("fake"))
+			.withTarget()
+				.function(function1)
+				.and()
+			.build();
+		assertThat(registration.getAvailability()).isNotNull();
+		assertThat(registration.getAvailability().isAvailable()).isFalse();
+	}
 }

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2017-2021 the original author or authors.
+ * Copyright 2017-2022 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.
@@ -29,29 +29,37 @@ import org.springframework.shell.standard.ShellMethodAvailability;
 @ShellComponent
 public class DynamicCommands {
 
-    private boolean connected;
+	private boolean connected;
 
-    public Availability authenticateAvailability() {
-        return connected ? Availability.available() : Availability.unavailable("you are not connected");
-    }
+	private boolean authenticated;
 
-    @ShellMethod(value = "Authenticate with the system", group = "Dynamic Commands")
-    public void authenticate(String credentials) {
-    }
+	public Availability authenticateAvailability() {
+		return connected ? Availability.available() : Availability.unavailable("you are not connected");
+	}
 
-    @ShellMethod(value = "Connect to the system", group = "Dynamic Commands")
-    public void connect() {
-        connected = true;
-    }
+	@ShellMethod(value = "Authenticate with the system", group = "Dynamic Commands")
+	public void authenticate(String credentials) {
+		authenticated = "sesame".equals(credentials);
+	}
 
-    @ShellMethod(value = "Disconnect from the system", group = "Dynamic Commands")
-    public void disconnect() {
-        connected = false;
-    }
+	@ShellMethod(value = "Connect to the system", group = "Dynamic Commands")
+	public void connect() {
+		connected = true;
+	}
 
-    @ShellMethod(value = "Blow Everything up", group = "Dynamic Commands")
-    @ShellMethodAvailability("dangerousAvailability")
-    public String blowUp() {
-        return "Boom!";
-    }
+	@ShellMethod(value = "Disconnect from the system", group = "Dynamic Commands")
+	public void disconnect() {
+		connected = false;
+	}
+
+	@ShellMethod(value = "Blow Everything up", group = "Dynamic Commands")
+	@ShellMethodAvailability("dangerousAvailability")
+	public String blowUp() {
+		return "Boom!";
+	}
+
+	public Availability dangerousAvailability() {
+		return connected && authenticated ? Availability.available()
+				: Availability.unavailable("you failed to authenticate. Try 'sesame'.");
+	}
 }

spring-shell-standard-commands/src/main/java/org/springframework/shell/standard/commands/CommandAvailabilityInfoModel.java

@@ -0,0 +1,51 @@
+/*
+ * 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.standard.commands;
+
+/**
+ * Model encapsulating info about {@code command availability}.
+ *
+ * @author Janne Valkealahti
+ */
+class CommandAvailabilityInfoModel {
+
+	private boolean available;
+	private String reason;
+
+	CommandAvailabilityInfoModel(boolean available, String reason) {
+		this.available = available;
+		this.reason = reason;
+	}
+
+	/**
+	 * Builds {@link CommandAvailabilityInfoModel}.
+	 *
+	 * @param available the available flag
+	 * @param reason the reason
+	 * @return a command parameter availability model
+	 */
+	static CommandAvailabilityInfoModel of(boolean available, String reason) {
+		return new CommandAvailabilityInfoModel(available, reason);
+	}
+
+	public boolean getAvailable() {
+		return available;
+	}
+
+	public String getReason() {
+		return reason;
+	}
+}

spring-shell-standard-commands/src/main/java/org/springframework/shell/standard/commands/CommandInfoModel.java

@@ -19,6 +19,7 @@ import java.util.List;
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
+import org.springframework.shell.Availability;
 import org.springframework.shell.command.CommandOption;
 import org.springframework.shell.command.CommandRegistration;
 import org.springframework.util.ClassUtils;
@@ -34,11 +35,14 @@ class CommandInfoModel {
 	private String name;
 	private String description;
 	private List<CommandParameterInfoModel> parameters;
+	private CommandAvailabilityInfoModel availability;
 
-	CommandInfoModel(String name, String description, List<CommandParameterInfoModel> parameters) {
+	CommandInfoModel(String name, String description, List<CommandParameterInfoModel> parameters,
+			CommandAvailabilityInfoModel availability) {
 		this.name = name;
 		this.description = description;
 		this.parameters = parameters;
+		this.availability = availability;
 	}
 
 	/**
@@ -65,7 +69,15 @@ class CommandInfoModel {
 			.collect(Collectors.toList());
 
 		String description = registration.getDescription();
-		return new CommandInfoModel(name, description, parameters);
+		boolean available = true;
+		String availReason = "";
+		if (registration.getAvailability() != null) {
+			Availability a = registration.getAvailability();
+			available = a.isAvailable();
+			availReason = a.getReason();
+		}
+		CommandAvailabilityInfoModel availModel = CommandAvailabilityInfoModel.of(available, availReason);
+		return new CommandInfoModel(name, description, parameters, availModel);
 	}
 
 	private static String commandOptionType(CommandOption o) {
@@ -88,4 +100,8 @@ class CommandInfoModel {
 	public List<CommandParameterInfoModel> getParameters() {
 		return parameters;
 	}
+
+	public CommandAvailabilityInfoModel getAvailability() {
+		return availability;
+	}
 }

spring-shell-standard-commands/src/main/java/org/springframework/shell/standard/commands/GroupsInfoModel.java

@@ -36,11 +36,14 @@ class GroupsInfoModel {
 	private boolean showGroups = true;
 	private final List<GroupCommandInfoModel> groups;
 	private final List<CommandInfoModel> commands;
+	private boolean hasUnavailableCommands = false;
 
-	GroupsInfoModel(boolean showGroups, List<GroupCommandInfoModel> groups, List<CommandInfoModel> commands) {
+	GroupsInfoModel(boolean showGroups, List<GroupCommandInfoModel> groups, List<CommandInfoModel> commands,
+			boolean hasUnavailableCommands) {
 		this.showGroups = showGroups;
 		this.groups = groups;
 		this.commands = commands;
+		this.hasUnavailableCommands = hasUnavailableCommands;
 	}
 
 	/**
@@ -71,7 +74,17 @@ class GroupsInfoModel {
 		List<CommandInfoModel> commands = gcims.stream()
 			.flatMap(gcim -> gcim.getCommands().stream())
 			.collect(Collectors.toList());
-		return new GroupsInfoModel(showGroups, gcims, commands);
+		boolean hasUnavailableCommands = commands.stream()
+			.map(c -> {
+				if (c.getAvailability() != null) {
+					return c.getAvailability().getAvailable();
+				}
+				return true;
+			})
+			.filter(a -> !a)
+			.findFirst()
+			.isPresent();
+		return new GroupsInfoModel(showGroups, gcims, commands, hasUnavailableCommands);
 	}
 
 	public boolean getShowGroups() {
@@ -85,4 +98,8 @@ class GroupsInfoModel {
 	public List<CommandInfoModel> getCommands() {
 		return commands;
 	}
+
+	public boolean getHasUnavailableCommands() {
+		return hasUnavailableCommands;
+	}
 }

spring-shell-standard-commands/src/main/resources/template/help-command-default.stg

@@ -57,6 +57,15 @@ options(options) ::= <<
        <options:{ o | <option(o)>}>
 >>
 
+// AVAILABILITY
+availability(availability) ::= <<
+<if(!availability.available)>
+
+<("CURRENTLY UNAVAILABLE"); format="style-highlight">
+       <availability.reason>
+<endif>
+>>
+
 // main
 main(model) ::= <<
 <name(model.name, model.description)>
@@ -64,4 +73,5 @@ main(model) ::= <<
 <synopsis(model.name, model.parameters)>
 
 <options(model.parameters)>
+<availability(model.availability)>
 >>

spring-shell-standard-commands/src/main/resources/template/help-commands-default.stg

@@ -3,8 +3,21 @@ name() ::= <<
 
 >>
 
+availability(availability) ::= <%
+<if(!availability.available)>
+<("* "); format="style-highlight">
+<endif>
+%>
+
+availabilityDesc(hasUnavailableCommands) ::= <<
+<if(hasUnavailableCommands)>
+<("Commands marked with (*) are currently unavailable.")>
+<("Type `help <command>` to learn more.")>
+<endif>
+>>
+
 command(command) ::= <<
-<(command.name); format="style-highlight"><(":"); format="style-highlight"> <command.description>
+<availability(command.availability)><(command.name); format="style-highlight"><(":"); format="style-highlight"> <command.description>
 
 >>
 
@@ -29,4 +42,5 @@ main(model) ::= <<
 <else>
 <flat(model.commands)>
 <endif>
+<availabilityDesc(model.hasUnavailableCommands)>
 >>