[question] Hardlocked options and diamonds

[Minimonium]

Related to #3524, #5530

It's explicitly allowed to hardcode dependencies' options in the documentation.

Alternatively, it's encouraged to use default_options. But it becomes a problem comically fast as this test shows:
https://github.com/conan-io/conan/blob/develop/conans/test/unittests/model/transitive_reqs_test.py#L1063

@Morwenn has provided us in the Slack with a great minimal example of a conflict of hardlocked options in subgraphs:

from conans import ConanFile

class LibFirstConan(ConanFile):
    name = "zero"
    version = "1.0.0"
    description = "Zero library"

from conans import ConanFile

class LibFirstConan(ConanFile):
    name = "first"
    version = "1.0.0"
    description = "First library"

    options = {"with_zero": [True, False]}
    default_options = {"with_zero": True}

    def requirements(self):
        if self.options.with_zero:
            self.requires("zero/1.0.0@")

from conans import ConanFile

class LibSecondConan(ConanFile):
    name = "second"
    version = "1.0.0"
    description = "Second library"

    options = {"with_first": [True, False]}
    default_options = {"with_first": False}

    def configure(self):
        if self.options.with_first:
            self.options["first"].with_zero = False

    def requirements(self):
        if self.options.with_first:
            self.requires("first/1.0.0@")

from conans import ConanFile

class LibThirdConan(ConanFile):
    name = "third"
    version = "1.0.0"
    description = "Third library"

    def configure(self):
        self.options["second"].with_first = True

    def requirements(self):
        self.requires("first/1.0.0@")
        self.requires("second/1.0.0@")

conan export zero
conan export first
conan export second
conan create third

Depending on the order of requirements in the third/1.0.0@ we get the diamond error, although in the whole graph we do have only one set of hardlocked options, which in this case was unexpected for the user.

It highlights issues with the runtime graph construction and in-recipe external configuration modifications and preferences (not only settings but external options too). It's practically impossible to dynamically alter other subgraphs from a parallel subgraph and in a sequential solution, we'd have an unreliable build.

The question is - what should we do with recommendations for that in the documentation?

[memsharded]

Sorry this was not responded back then @Minimonium

I am closing this as outdated, Conan 2 already changed how options are managed, including new important! options definitions, not conflicting by default, etc.

Please open new tickets if necessary, thanks for the feedback!