release notes

40

Upgrade instructions:

Version 40 introduces no language changes at all beyond an updated model dependency. It does include a breaking change to the 'network' stdlib that needs to be manually resolved. ./alan upgrade runs the transformation from 39 (upgrade/39) on every connector system; it does not cover the 'network' change. The build reports each entry that a processor creates in a 'key value list' and each lookup by key in one.

In 'network', the type 'key value list' is no longer an indexed collection as its usages have no concept of key uniqueness. This was a long standing bug. To obtain a value by key from a 'key value list', either use the provided 'network'::'key value find' — which returns a list of all values, possibly empty — or 'network'::'key value shared' — which returns a single value if, and only if, there are 1..N entries with identical values.

// 39
'headers' = create [ "content-type" ] "application/json"
'content type' = $'response'.'headers'[ "content-type" ] || "application/octet-stream"

// 40
'headers' = create (
	'name' = "content-type"
	'value' = "application/json"
)
'content type' = call 'network'::'key value shared' (
	$'response'.'headers'
	$'key' = "content-type"
) || "application/octet-stream"

Neither function is a drop-in replacement for the 39 lookup X[ "name" ], so choose per lookup:

All three compare the name with case folding. A response can carry a header more than once (Set-Cookie, for one); there 'key value shared' with || <value>, as in the example above, gives the fallback where the 39 lookup gave a value.