Allow exact version number "ranges"?

[garyb]

I'm finally looking at migrating my work stuff to Spago, but one of the things we have to do for compliance reasons is use exact version numbers for our dependencies. I could define them as like >=1.0.0 <1.0.1, but that kinda sucks. Any objection to me adding support for exact versions to Range?

[thomashoneyman]

The relevant discussion would be in purescript/registry-dev#43. cc: @f-f.

I think that allowing either >=X.Y.Z <X.Y.Z or =X.Y.Z in a config file would be fine, but it's not necessary for that to be implemented in the registry itself. Spago already accepts more than the registry syntax (it allows * for unbounded ranges), and it could also support exact version numbers.

On the registry side we would only need to update the Spago manifest conversion here:
https://github.com/purescript/registry-dev/blob/fc203a9e2a0b96a90ace20dc6958c157cbbca16b/app/src/App/Manifest/SpagoYaml.purs#L154-L159

[f-f]

Agreed, this should be implemented in Spago, I'll transfer the issue there

[f-f]

For reference, the implementation entrypoint is around here:

spago/core/src/Config.purs

Lines 322 to 332 in 4381814

	spagoRangeCodec :: CJ.Codec Range
	spagoRangeCodec = CJ.prismaticCodec "SpagoRange" rangeParse printSpagoRange CJ.string
	where
	rangeParse str =
	if str == "*" then Just widestRange
	else hush $ Range.parse str
	printSpagoRange :: Range -> String
	printSpagoRange range =
	if range == widestRange then "*"
	else Range.print range

I think we'll still want to output a Range in here, but we'd try to parse a Version as well, and call Range.exactVersion on it, where that function doesn't exist yet, but should be added to Registry.Range and look similar to the caret implementation:

caret :: Version -> Range
caret v = Range { lhs: v, rhs: Version.bumpHighest v }

exactVersion :: Version -> Range
exactVersion v = Range { lhs: v, rhs: Version.bumpPatch v }