Refactor validation

[armintaenzertng]

We want a refactored validation using the new data model (available on https://github.com/spdx/tools-python/tree/refactor-python-tools). The main goal is to keep it completely separated from the parsing/writing layers.

Validation error messages could be instances of a class that tracks their context like this:

class ErrorMessage:
    element_type: SpdxElementType # an enum with values document, package, file, snippet, relationship, annotation, ...
    id: Optional[str] # not every type has an id or it might be missing
    validation_messages: List[str]

Validation can be performed by calling validation methods that return List[ErrorMessage]. Keeping them in separate classes allows for better unit testing by using mocks. The spdx version will be passed to validators that differ for different versions.

class DocumentValidator:
    spdx_version: str
    creation_info_validator = CreationInfoValidator()
    package_validator = PackageValidator(spdx_version)
    file_validator = FileValidator(spdx_version)
    ...

    def validate_document(self, document: Document) -> List[ErrorMessage]:
        error_messages = []
        error_messages.extend(creation_info_validator.validate_creation_info(document))
        error_messages.extend(package_validator.validate_packages(document.packages))
        ...
        return error_messages

class CreationInfoValidator()
    def validate_creation_info(self, document: Document) -> List[ErrorMessage]:
        error_messages = []
        spdx_id: Optional[str]

        ... # check and set the spdx_id
        
        if document.namespace is None:
            error_messages.append(ErrorMessage(SpdxElementType.Document, spdx_id, 'Missing required field "namespace."'))

[armintaenzertng]

Completion overview:

• actor
• annotation
• checksum
• external document ref
• extracted licensing info
• file
• license: Implement license expression validation #374
• package: Finish package validation #386
• package download location
• external package ref: Implement External Package Reference validation #373
• relationship
• snippet
• URI/URL: More tests for URI/URL/download location validation #377
• document tests: Add document validation tests #375
• spdx ids: Test spdx_id_validators #376
• duplicate spdx ids: Check for duplicated SPDX ids #378
• SPDX2.2 validation: Implement SPDX2.2 specific validation #463

[armintaenzertng]

This has been implemented in 0.8.0