CODEWITHSUNDEEP
javapicocli
user7610
user7610

Reputation: 28889

How do I get picocli to parse `"--item --item foo"` as `[null, "foo"]` `:List<String>`

I have a parameter named --msg-content-list-item

public class CliProtonJ2Sender implements Callable<Integer> {

    @CommandLine.Option(
        names = {"--msg-content-list-item"},
        arity = "0..1",
        defaultValue = CommandLine.Option.NULL_VALUE)
    private List<String> msgContentListItem;


    // ...
}

I wish for the following test to pass

    @Test
    void test_msgContentListItem() {
        CliProtonJ2Sender a = new CliProtonJ2Sender();
        CommandLine b = new CommandLine(a);
        CommandLine.ParseResult r = b.parseArgs("--msg-content-list-item", "--msg-content-list-item", "pepa");

        // https://github.com/powermock/powermock/wiki/Bypass-Encapsulation
        List<String> v = Whitebox.getInternalState(a, "msgContentListItem", a.getClass());
        assertThat(v).containsExactly(null, "pepa");
    }

But it doesn't and I get

missing (1): null
---
expected   : [null, pepa]
but was    : [pepa]

How do I define @CommandLine.Option to behave the way I want?

Upvotes: 0

Views: 220

Answers (2)

user7610
user7610

Reputation: 28889

There was a bug which is now fixed.

Prior to version 4.7.2, use the workaround in my other answer.

As of picocli 4.7.2, use the fallbackValue like this

@Option(names = {"--list"}, arity = "0..1", fallbackValue = CommandLine.Option.NULL_VALUE)
List<String> list;

from https://github.com/remkop/picocli/blob/2944addb8ba34d2ee6f97564bd43128bb62ec382/src/test/java/picocli/FallbackTest.java#L192-L193

Upvotes: 0

user7610
user7610

Reputation: 28889

I suspect this is a bug/inconvenience. In method consumeArguments, at https://github.com/remkop/picocli/blob/main/src/main/java/picocli/CommandLine.java

            // now process the varargs if any
            String fallback = consumed == 0 && argSpec.isOption() && !OptionSpec.DEFAULT_FALLBACK_VALUE.equals(((OptionSpec) argSpec).fallbackValue())
                    ? ((OptionSpec) argSpec).fallbackValue()
                    : null;
            if (fallback != null && (args.isEmpty() || !varargCanConsumeNextValue(argSpec, args.peek()))) {
                args.push(fallback);
            }

Because ((OptionSpec) argSpec).fallbackValue() returns null, it is understood as if there was no fallbackValue, and therefore the if (fallback != null does not push the fallback value to args.

Workaround

Define your own fallbackValue magic string and a converter that later converts it to null. The convertor runs after consumeArguments completes (with the failbackValue).

public static final String MY_NULL_VALUE = "MY_" + CommandLine.Option.NULL_VALUE;

public class MyNullValueConvertor implements CommandLine.ITypeConverter<String> {
    @Override
    public String convert(String value) throws Exception {
        if (value.equals(MY_NULL_VALUE)) {
            return null;
        }
        return value;
    }
}

    @CommandLine.Option(
        names = {"--msg-content-list-item"},
        arity = "0..1", fallbackValue = MY_NULL_VALUE,
        converter = MyNullValueConvertor.class)
    private List<String> msgContentListItem;

Upvotes: 0

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