IDefaultValueProvider for Map options with multiple values without using split regexp

[usmansaleem]

I have following declaration for key/value pairs to be captured:

  @Option(
      names = "--aws-kms-tag,
      mapFallbackValue = "",
      description =
          "Optional key-value pair to filter KMS keys based on tags. Format: --aws-kms-tag <tag-name>=<tag-value>. Can be repeated.",
      paramLabel = "<TAG_NAME>=<TAG_VALUE>")
  private Map<String, String> tags = new LinkedHashMap<>();

I can specify it on command line as follows and it works fine:

java myApp --aws-kms-tag tagNameA=tagValueA --aws-kms-tag tagNameB=tagValueB

However, my application is also using IDefaultValueProvider to capture values from configuration file and environment variables. The defaultValue method returns a String.

    public interface IDefaultValueProvider {
        String defaultValue(Model.ArgSpec var1) throws Exception;
    }

If the option is not using a split RegExp, how can I assign multiple key=value pairs for defaultValue?

i.e. yaml configuration file would look like:

aws-kms-tag:
  tagNameA: tagValueA
  tagNameB: tagValueB

If above is not possible, I think I have to introduce split regexp approach that I use with Collection classes with setting arity to 0..1.

Reference of current Yaml based default provider:

• https://github.com/ConsenSys/web3signer/blob/d43c899a79584d119514633e56d00e0566626afe/commandline/src/main/java/tech/pegasys/web3signer/commandline/valueprovider/YamlConfigFileDefaultProvider.java#L44

• https://github.com/ConsenSys/web3signer/blob/ababf2651a219248fbd47b90a21c868d12fd3118/commandline/src/main/java/tech/pegasys/web3signer/commandline/valueprovider/EnvironmentVariableDefaultProvider.java#L24

[remkop]

Hi, I think your request is a duplicate of #1595, #879 and #877.

These are on the roadmap for picocli 4.8, but I am finding it very difficult to find time to work on picocli.
The likelihood of this feature being released depends on whether someone is willing to do the implementation, automated tests and documentation work.
Would you be willing to work on this?

[remkop]

To summarize the analysis from #1595, #879 and #877, the proposed new APIs would be:

Add new "defaultValues" and "fallbackValues" elements in the Option and Parameters annotations:

@Option(defaultValues = {"1", "2"}, fallbackValues = {"3", "4"})
@Parameters(defaultValues = {"1", "2"}, fallbackValues = {"3", "4"})

Add new IDefaultValuesProvider (notice the "s" in "Values") interface that returns multiple values:

public interface IDefaultValuesProvider {
    String[] defaultValue(ArgSpec argSpec) throws Exception; // or List<String>?
}

Add new "defaultValuesProvider" (notice the "s" in "Values") elements in the Command annotation:

@Command(defaultValuesProvider = pkg.MyMultiValueDefaultProvider.class)

(See also #1743, which is about @Command-annotated methods, which should perhaps be one of the test cases.)

[usmansaleem]

I'll try to checkout the code over the weekend.