Add implements attribute in ConanFile to provide opt-in automatic management of some options and settings.

[czoido]

Changelog: Feature: Add implements attribute in ConanFile to provide automatic management of some options and settings.
Docs: conan-io/docs#3303

Closes: #14308

[memsharded]

Did some minor changes:

• Replaced getattr for normal access
• Changed GenConanFile specialized for generic with_class_attribute

Add options_auto_handle=True to the conan new template?

Probably not yet? The advantage of the current template is that it will work too as-is in latest Conan 1.X

[memsharded]

Don't love the name, but challenging to find a better one. Some ideas:

• auto_configuration = True
• manage_options = True
• auto_manage_library_type_configuration = True
• auto_manage_library_configuration = True
• auto_library_configuration = True
• library_type_defaults = True

Generic list of things?

• auto_manage = ["library_type_configuration", "app_type_configuration"]

• auto_manage = ["library_configuration", "app_configuration"]

• auto = ["library_configuration", "app_configuration"]

• policies = ["auto_shared_fpic", "auto_header_only", "auto_cmake"]

• auto_manage = ["shared_fpic", "header_only"]

• rules, auto, defaults, implicits, auto_behaviors, mods, builtins, mixin, recipe_auto, recipe_defaults, config_templates

• implements = ["auto_shared_fpic", "cmake_template"]

• applies = [

• sidecar = ["auto_shared_fpic", ]

• recipe_presets = [

• salt_and_pepper = ["auto_shared_fpic"

• pre-cooked = ["auto_shared_

build_policy = "missing", upload_policy = "skip"

The language case would be a different one most likely:

• languages = "C", "C++", "fortran"

Maybe "configuration" and "options" should be in the var name?

FINAL DECISION:

• implements = ["auto_shared_fpic", "auto_header_only"]

[franramirez688]

I agree. We should think of another shorter one if possible.

[danimtb]

I like the attribute name "activate_default_behavior" (without S at the end).

[memsharded]

Suggested change

	default_configure(conanfile)
	if ... => auto_shared_fpic_configure(conanfile)
	if ... => auto_header_only_configure(conanfile)

[memsharded]

Drop the public methods

[memsharded]

Should this if be part of the header_only automation? Maybe not, I guess the meaning of auto-shared_fpic is "you can remove these options if they are not necessary"

[danimtb]

I think is fine as is but would require a clear explanation in the docs

[danimtb]

I like it!

[uilianries]

Just like I asked before, a magic attribute 😝