licenseChoice streamlined

[jkowalleck]

fixes #204

proposal to streamline licenses: make JSON meat the existing XML spec

this does not change the actual SBOM structure in any way.
it only puts a constraint on the document to have exactly one expression in the list, if there is any expression.

[jkowalleck]

defined items as a list(tuple!) with only one item and set additionalItems to false.
this causes validators and other to see: this list must have exactly one item with the defined predicates.

[johan-boule]

What do we have to do when the tool raises a LicenseExpressionAlongWithOthersException ?
Is there anything wrong with https://github.com/conan-io/conan-center-index/blob/master/recipes/openjdk/all/conanfile.py ?
I don't understand at all what I'm doing but, if I keep only one licence element in that conanfile.py, this fixes the error.

[jkowalleck]

It is expected to be either an expression, or a list of licenses; not both.
In case an expression exists, the list of licenses should be ignored for the following reasons:
expression knows the concatenation type (AND, OR, WITHOUT/EXCEPT) of the licenses, and is therefore more verbose.

[johan-boule]

I don't understand at all what I'm doing but, if I keep only one licence element in that conanfile.py, this fixes the error.

[jkowalleck]

I don't understand at all what I'm doing but, if I keep only one licence element in that conanfile.py, this fixes the error.

This is the repository of CycloneDX specification - the international standard.
This is not the place to tell about possible bugs in some implementation. Please refer to the issue tracker in the respective repository of your domain.

[johan-boule]

OK, thanks, I will suggest on Conan's repository to combine the the 2 license expressions into one with and AND operator:

GPL-2.0-only WITH Classpath-exception-2.0 AND GPL-2.0-only WITH OpenJDK-assembly-exception-1.0

Perhaps multiple WITH clauses are allowed, but my guess is that would mean the same.