zencode when cast string dictionary to another encoding

internal cast in heap only available for string objects and tables:
when for instance a base64 is imported as a string, it can be
re-decoded internally (cast)

src/lua/zencode_when.lua

@@ -511,3 +511,23 @@ end)
 -- 	have(target)
 -- 	ACK[target] = deepmap(function(v) if trim(v) == '' then return nil end, ACK[target])
 -- end)
+
+When("create the '' cast of strings in ''", function(conv, source)
+	ZEN.assert(ZEN.CODEC[source], "Object has no codec: "..source)
+	ZEN.assert(ZEN.CODEC[source].encoding == 'string', "Object has no string encoding: "..source)
+	empty(conv)
+	local src = have(source)
+	local enc = input_encoding(conv)
+	if luatype(src) == 'table' then
+	   ACK[conv] = deepmap(function(v)
+		 local s = OCTET.to_string(v)
+		 ZEN.assert(enc.check(s), "Object value is not a "..conv..": "..source)
+		 return enc.fun( s )
+	   end, src)
+	else
+	   local s = OCTET.to_string(src)
+	   ZEN.assert(enc.check(s), "Object value is not a "..conv..": "..source)
+	   ACK[conv] = enc.fun(s)
+	end
+	new_codec(conv, {encoding = conv})
+end)

test/zencode_when/run.sh

@@ -29,14 +29,41 @@ cat <<EOF | save when stringnum.json
 {
 	"api": "http://3.68.108.18/api/v1/blocks/latest",
 	"path": "blocks/",
-	"height": 102
+	"latest": {
+		"result": {
+			"height": 102
+		}
+	}
+
+}
+EOF
+
+cat <<EOF | zexe append_number_try.zen -a stringnum.json
+Given I have a 'string dictionary' named 'latest'
+
+and I have a 'string' named 'path'
+
+When I pickup from path 'latest.result.height'
+and I append 'height' to 'path'
+
+Then print the 'path'
+EOF
+
+cat <<EOF | save when string-mpack.json
+{
+"newblock": {
+	"newblock-mpack": "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",
+	"txid": "dd445fed8ab124ab0c38720db060b730ddcf4c3fe71b3668eacf9505cd17da8f"
+	},
+	"version": "2.0",
+	"id": "20cfe258df01bf6c634b6b79329b20ef7f5bdf69e6c319b06adb44ac9a4b6c67"
 }
 EOF
 
-cat <<EOF | zexe append_number.zen -a stringnum.json
-Given I have a 'string' named 'api'
-and a 'string' named 'path'
-and a 'number' named 'height'
-When I append 'height' to 'path'
-Then print 'path'
+cat <<EOF | zexe base64-string-cast.zen -a string-mpack.json
+Given I have a 'string dictionary' named 'newblock'
+When I pickup from path 'newblock.newblock-mpack'
+When I create the 'base64' cast of strings in 'newblock-mpack'
+and I create the 'contents' decoded from mpack 'base64'
+Then print the 'contents' as 'string'
 EOF