Add support for @Command-annotated methods to codegen tools (was:ManPageGenerator: Can't find annotated method)

[msgilligan]

I'm using picocli 4.6.3 with Gradle.

I had a class method annotated with @Command that worked properly, but when I tried to generate a man page for it, I got the following error:

picocli.codegen.docgen.manpage.ManPageGenerator org.consensusj.ledgerexport.tool.WalletAccountingExport --outdir=/Users/sean/git/WalletLedgerExport/ledger-export-tool/build/generated-picocli-docs -v
Successfully started process 'command '/Users/sean/.sdkman/candidates/java/17.0.4.1-tem/bin/java''
picocli.CommandLine$InitializationException: class org.consensusj.ledgerexport.tool.WalletAccountingExport is not a command: it has no @Command, @Option, @Parameters or @Unmatched annotations
        at picocli.CommandLine$Model$CommandReflection.validateCommandSpec(CommandLine.java:11680)
        at picocli.CommandLine$Model$CommandReflection.extractCommandSpec(CommandLine.java:11510)
        at picocli.CommandLine$Model$CommandSpec.forAnnotatedObject(CommandLine.java:6236)
        at picocli.CommandLine.<init>(CommandLine.java:227)
        at picocli.CommandLine.<init>(CommandLine.java:221)
        at picocli.codegen.util.Util.getCommandSpecs(Util.java:22)
        at picocli.codegen.docgen.manpage.ManPageGenerator$App.call(ManPageGenerator.java:214)
        at picocli.codegen.docgen.manpage.ManPageGenerator$App.call(ManPageGenerator.java:166)
        at picocli.CommandLine.executeUserObject(CommandLine.java:1953)
        at picocli.CommandLine.access$1300(CommandLine.java:145)
        at picocli.CommandLine$RunLast.executeUserObjectOfLastSubcommandWithSameParent(CommandLine.java:2358)
        at picocli.CommandLine$RunLast.handle(CommandLine.java:2352)
        at picocli.CommandLine$RunLast.handle(CommandLine.java:2314)
        at picocli.CommandLine$AbstractParseResultHandler.execute(CommandLine.java:2179)
        at picocli.CommandLine$RunLast.execute(CommandLine.java:2316)
        at picocli.CommandLine.execute(CommandLine.java:2078)
        at picocli.codegen.docgen.manpage.ManPageGenerator.main(ManPageGenerator.java:239)
:ledger-export-tool:generateManpageAsciiDoc (Thread[Execution worker Thread 7,5,main]) completed. Took 0.159 secs.

The workaround was to move the annotation to the class itself (and supporting changes), but I actually preferred annotating a method and passing it @Mixin with all the options.

The fix (I believe) would be to add a way of specifying an annotated method to ManPageGenerator.

PS: You can see the changes I made to workaround here: ConsensusJ/WalletLedgerExport@22f4ba0#diff-f423761483c976760e2804c688f91600118acc272816cce90c6fe568ede763cd

[remkop]

I see, interesting! I only anticipated @Command-annotated methods that were subcommands of a @Command-annotated class, I did not anticipate your use case. 😅

Note that this is not limited to just ManPageGenerator, I think none of the tools currently support this use case where the class itself is not a command, but it has a @Command-annotated method that is invoked from the main method.

I won't have time to work on this, but if anyone offers to provide a pull request that implement this with some tests, I would be happy to review it.