JVM BUILD file symbol help text isn't shown in `help`/`help-all`

[huonw]

Describe the bug

There's a few "JVM shading rules" (and similar types) that set help as instructed by their ABC:

pants/src/python/pants/jvm/target_types.py

Lines 602 to 614 in ec86d19

	class JvmShadingRule(ABC):
	"""Base class for defining JAR shading rules as valid aliases in BUILD files.
	Subclasses need to provide with an `alias` and a `help` message. The `alias` represents
	the name that will be used in BUILD files to instantiate the given subclass.
	Set the `help` class property with a description, which will be used in `./pants help`. For the
	best rendering, use soft wrapping (e.g. implicit string concatenation) within paragraphs, but
	hard wrapping (`\n`) to separate distinct paragraphs and/or lists.
	"""
	alias: ClassVar[str]
	help: ClassVar[str | Callable[[], str]]

However, it seems like this isn't hooked up right: these rules are BUILD file symbols and the help isn't obeyed: for instance, for

pants/src/python/pants/jvm/target_types.py

Lines 693 to 695 in ec86d19

	class JvmShadingZapRule(JvmShadingRule):
	alias = "shading_zap"
	help = "Removes from the final artifact the occurrences of the `pattern`."

PANTS_VERSION=2.22.0.dev3 pants --backend-packages=pants.backend.experimental.java help shading_zap

`shading_zap` BUILD file symbol
-------------------------------

Signature: shading_zap(pattern: 'str') -> None

JvmShadingZapRule(pattern: 'str')

The default JvmShadingZapRule(...) text appears to just be reiterating the dataclass definition.

I think these BUILD file symbols use the doc string, not help, so potentially the example above should be formatted as something like this:

class JvmShadingZapRule(JvmShadingRule): 
    "Removes from the final artifact the occurrences of the `pattern`." 

    alias = "shading_zap" 

This appears to affect:

• shading_keep
• shading_relocate
• shading_rename
• shading_zap
• duplicate_rule
• jvm_exclude
• scala_exclude

(The last three aren't JvmShadingRule subclasses but follow a similar pattern.)

Pants version

2.22.0.dev3

OS
both

Additional info

• Will appear in online docs too after Add reference docs for BUILD file symbols pantsbuild.org#216
• Relevant issues:
  • BUILD file symbols #18117
  • Modernizing objects and context_aware_object_factories (including so it shows up in docsite) #14832