Add filters to package cataloger (#1021)

* Add filters to package cataloger

This PR adds filters so a package without name or version doesn't go in
the list of all discovered packages.

Integration and cli tests were added to validate the feature.

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* add nolint:funlen to cataloger/catalog.go

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* don't require package version

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* add package filtering to generic and python cataloger

also removes cli tests in favor of integration and unit tests

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* drop nolint:funlen

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* check for no-removal operation

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* remove unused fixtures

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* rename no-version file to hide semantic version

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* drop integration tests and add pkg func for validation

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* python cataloger use global pkg validation

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* check for valid packages on deb/go/rpm catalogers

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* update rpm cataloger after rebase

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* nit with pointers

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* simpler use of package validation

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* remmove double pkg validations

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* rename func param to artifactsToExclude

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* add test for relationships and bug fix

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

* feedback changes

Signed-off-by: Jonas Xavier <jonasx@anchore.com>

syft/pkg/package.go

@@ -68,3 +68,14 @@ func (p *Package) merge(other Package) error {
 	}
 	return nil
 }
+
+// IsValid checks whether a package has the minimum necessary info
+// which is a non-empty name.
+// The nil-check was added as a helper as often, in this code base, packages
+// move between callers as pointers.
+// CycloneDX and SPDX define Name as the minimum required info for a valid package:
+// * https://spdx.github.io/spdx-spec/package-information/#73-package-version-field
+// * https://cyclonedx.org/docs/1.4/json/#components_items_name
+func IsValid(p *Package) bool {
+	return p != nil && p.Name != ""
+}