picocli.AutoComplete should return non-zero return code on error

[bobtiernay-okta]

Currently this will not fail a build if the command is run via Maven, Gradle etc.

For example, the following Maven configuration (might be useful for docs):

            <plugin>
                <groupId>org.codehaus.mojo</groupId>
                <artifactId>exec-maven-plugin</artifactId>
                <version>${exec-maven-plugin.version}</version>
                <executions>
                    <execution>
                        <id>generate-autocompletion-script</id>
                        <phase>package</phase>
                        <goals>
                            <goal>java</goal>
                        </goals>
                        <configuration>
                            <!-- See https://picocli.info/autocomplete.html#_generate_completion_script -->
                            <mainClass>picocli.AutoComplete</mainClass>
                            <arguments>
                                <argument>-f</argument>
                                <argument>-n</argument>
                                <argument>sage</argument>
                                <argument>-o</argument>
                                <argument>${project.build.directory}/completion.sh</argument>
                                <argument>app.Commands</argument>
                            </arguments>
                        </configuration>
                    </execution>
                    <execution>
                        <id>default-cli</id>
                        <configuration>
                            <executable>echo</executable>
                            <commandlineArgs>
                                alias sage-dev='"'java -classpath %classpath -noverify -XX:TieredStopAtLevel=1 -XX:CICompilerCount=1 -XX:+UseSerialGC -XX:-UsePerfData -Xmx128m ${mainClass}'"'
                            </commandlineArgs>
                        </configuration>
                    </execution>
                </executions>
            </plugin>

produces

picocli.CommandLine$InitializationException: Cannot instantiate subcommand app.AppCommand: the class has no constructor
	at picocli.CommandLine$Model$CommandReflection.initSubcommands(CommandLine.java:5969)
	at picocli.CommandLine$Model$CommandReflection.updateCommandAttributes(CommandLine.java:5956)
	at picocli.CommandLine$Model$CommandReflection.updateCommandAttributes(CommandLine.java:5940)
	at picocli.CommandLine$Model$CommandReflection.extractCommandSpec(CommandLine.java:5910)
	at picocli.CommandLine$Model$CommandSpec.forAnnotatedObject(CommandLine.java:3594)
	at picocli.CommandLine.<init>(CommandLine.java:185)
	at picocli.CommandLine.<init>(CommandLine.java:164)
	at picocli.AutoComplete$App.run(AutoComplete.java:92)
	at picocli.CommandLine.execute(CommandLine.java:1048)
	at picocli.CommandLine.access$900(CommandLine.java:142)
	at picocli.CommandLine$RunLast.handle(CommandLine.java:1255)
	at picocli.CommandLine$RunLast.handle(CommandLine.java:1223)
	at picocli.CommandLine$AbstractParseResultHandler.handleParseResult(CommandLine.java:1131)
	at picocli.CommandLine.parseWithHandlers(CommandLine.java:1414)
	at picocli.CommandLine.run(CommandLine.java:1878)
	at picocli.CommandLine.run(CommandLine.java:1824)
	at picocli.AutoComplete.main(AutoComplete.java:53)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.codehaus.mojo.exec.ExecJavaMojo$1.run(ExecJavaMojo.java:282)
	at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NoSuchMethodException: app.AppCommand.<init>()
	at java.lang.Class.getConstructor0(Class.java:3082)
	at java.lang.Class.getDeclaredConstructor(Class.java:2178)
	at picocli.CommandLine$DefaultFactory.create(CommandLine.java:3260)
	at picocli.CommandLine$Model$CommandReflection.initSubcommands(CommandLine.java:5963)
	... 22 more
Usage: picocli.AutoComplete [-fhw] [-n=<commandName>] [-o=<autoCompleteScript>]
                            <commandLineFQCN>
Generates a bash completion script for the specified command class.
      <commandLineFQCN>      Fully qualified class name of the annotated @Command
                               class to generate a completion script for.
  -n, --name=<commandName>   Name of the command to create a completion script for.
                               When omitted, the annotated class @Command 'name'
                               attribute is used. If no @Command 'name' attribute
                               exists, '<CLASS-SIMPLE-NAME>' (in lower-case) is used.
  -o, --completionScript=<autoCompleteScript>
                             Path of the completion script file to generate. When
                               omitted, a file named '<commandName>_completion' is
                               generated in the current directory.
  -w, --writeCommandScript   Write a '<commandName>' sample command script to the
                               same directory as the completion script.
  -f, --force                Overwrite existing script files.
  -h, --help                 Display this help message and quit.

[remkop]

Thank you for pointing this out.
I pushed a fix for this to master, please verify.

[remkop]

I added an example Maven snippet based on your example to the autocompletion docs (#584).
Can you take a look?

It's a bit more minimal than your example:

• omitted the -n option, so the command name is taken from the @Command(name = "mycommand") value in the annotations
• omitted the default-cli execution snippet (I wasn't sure why this was needed)

Any feedback or suggestions for improvement welcome.

[bobtiernay-okta]

Regarding default-cli, you're right that's not strictly needed. However, it's quite useful for development with Maven so that you don't have setup a classpath or rebuild a jar. If your IDE has automatic build you can simply save and go to the command line and execute.