schema/ExactlyOneOf: Fix handling of unknowns in complex types

[radeksimko]

Fixes #280

---

I also added some more tests to check that the same bug doesn't affect ConflictsWith or AtLeastOneOf - it doesn't, but it's IMO useful to have the test there to ensure it stays that way.

---

The reason ConflictsWith isn't affected is because it runs after we check for unknowns:

terraform-plugin-sdk/helper/schema/schema.go

Lines 1417 to 1433 in 6184b31

	// If the value is unknown then we can't validate it yet.
	// In particular, this avoids spurious type errors where downstream
	// validation code sees UnknownVariableValue as being just a string.
	// The SDK has to allow the unknown value through initially, so that
	// Required fields set via an interpolated value are accepted.
	if !isWhollyKnown(raw) {
	if schema.Deprecated != "" {
	return []string{fmt.Sprintf("%q: [DEPRECATED] %s", k, schema.Deprecated)}, nil
	}
	return nil, nil
	}
	err = validateConflictingAttributes(k, schema, c)
	if err != nil {
	return nil, []error{err}
	}

I decided not to move things around in the main validate() as there is a risk of introducing some more unknown edge cases when folks combine ConflictsWith, AtLeastOneOf and ExactlyOneOf.

Perhaps that code deserves some cleanup, but I think it's safer to leave it for later, bigger refactoring and/or for when we introduce cty here.

---

I guess the reason IsComputed() wasn't used in the initial implementation is for its confusing name.

It does not to have anything to do with Computed in the schema, but "computed" here just means "unknown". Cty already uses that clearer naming convention of "(un)knowns", so we can adopt it here too when we switch to it from the old type system.

IsComputed() seems to be more or less equivalent of cty's IsWhollyKnown() as it leverages reflectwalk's ability to walk through the complex types and find nested unknowns there:

terraform-plugin-sdk/terraform/resource.go

Lines 393 to 397 in 6184b31

	// Test if the value contains an unknown value
	var w unknownCheckWalker
	if err := reflectwalk.Walk(v, &w); err != nil {
	panic(err)
	}

[appilon]

Great Work Radek!

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you have found a problem that seems similar to this, please open a new issue and complete the issue template so we can capture all the details necessary to investigate further.