Fix special IDs for right-side 2.2 Relationships

In SPDX 2.2, the right-hand side of Relationships are not limited
to SPDX IDs; they can also include the special values NONE and
NOASSERTION.

To handle these, since Golang doesn't (to my knowledge) have a
concept of union types, and since I don't want to use interface{},
this commit instead adds a new SpecialID field to DocElementID.
When SpecialID is non-empty, it should be treated as being a
"special" ID value, and DocumentRefID / ElementRefID should be
ignored.

(Unfortunately, we can't just use ElementRefID == "NONE", etc.
for this purpose, because in theory an SPDX document could define
the identifier SPDXRef-NONE to mean something. Even though they
really, really shouldn't do that.)

This commit updates tvloader and tvsaver to appropriately handle
the possibility of NONE and NOASSERTION for this field.

Signed-off-by: Steve Winslow <steve@swinslow.net>

1 files changed, 18 insertions, 1 deletions

diff --git a/spdx/identifier.go b/spdx/identifier.go
index 496aeb3..baf44c1 100644
--- a/spdx/identifier.go
+++ b/spdx/identifier.go
@@ -18,9 +18,14 @@ type ElementID string
 // present document.
 // DocElementIDs should NOT contain the mandatory 'DocumentRef-' or
 // 'SPDXRef-' portions.
+// SpecialID is used ONLY if the DocElementID matches a defined set of
+// permitted special values for a particular field, e.g. "NONE" or
+// "NOASSERTION" for the right-hand side of Relationships. If SpecialID
+// is set, DocumentRefID and ElementRefID should be empty (and vice versa).
 type DocElementID struct {
 	DocumentRefID string
 	ElementRefID  ElementID
+	SpecialID     string
 }
 
 // TODO: add equivalents for LicenseRef- identifiers
@@ -36,6 +41,14 @@ func MakeDocElementID(docRef string, eltRef string) DocElementID {
 	}
 }
 
+// MakeDocElementSpecial takes a "special" string (e.g. "NONE" or
+// "NOASSERTION" for the right side of a Relationship), nd returns
+// a DocElementID with it in the SpecialID field. Other fields will
+// be empty.
+func MakeDocElementSpecial(specialID string) DocElementID {
+	return DocElementID{SpecialID: specialID}
+}
+
 // RenderElementID takes an ElementID and returns the string equivalent,
 // with the SPDXRef- prefix reinserted.
 func RenderElementID(eID ElementID) string {
@@ -44,8 +57,12 @@ func RenderElementID(eID ElementID) string {
 
 // RenderDocElementID takes a DocElementID and returns the string equivalent,
 // with the SPDXRef- prefix (and, if applicable, the DocumentRef- prefix)
-// reinserted.
+// reinserted. If a SpecialID is present, it will be rendered verbatim and
+// DocumentRefID and ElementRefID will be ignored.
 func RenderDocElementID(deID DocElementID) string {
+	if deID.SpecialID != "" {
+		return deID.SpecialID
+	}
 	prefix := ""
 	if deID.DocumentRefID != "" {
 		prefix = "DocumentRef-" + deID.DocumentRefID + ":"