[#360] [stbx-core] patch root tx decoder for missing 'previous' field

Author: epost

Diff for: stbx-core/src/Statebox/Core/Transaction/Codec.purs

@@ -8,16 +8,16 @@ import Data.Argonaut.Encode.Class (encodeJson)
 import Data.Argonaut.Decode (decodeJson, (.:), (.:?))
 import Data.Argonaut.Decode.Class (decodeJArray)
 import Data.Lens (over)
+import Data.Maybe (fromMaybe, maybe)
 import Data.Profunctor.Choice (left)
 import Data.Either (Either(..))
 import Data.Either.Nested (type (\/))
-import Data.Maybe (maybe)
 import Data.NonEmpty (singleton)
 import Data.Traversable (traverse)
 import Foreign.Object (Object, lookup)
 
 import Statebox.Core.Lenses (_wiring')
-import Statebox.Core.Transaction (Tx, InitialTx, WiringTx, FiringTx, TxSum(..), mapTx, evalTxSum)
+import Statebox.Core.Transaction (Tx, InitialTx, WiringTx, FiringTx, TxSum(..), mapTx, evalTxSum, uberRootHash)
 import Statebox.Core.Types (Net, Wiring, Firing)
 import Statebox.Core.Wiring as Wiring
 import Statebox.Core.Wiring (WiringRaw)
@@ -46,8 +46,15 @@ decodeTxFiringTx = decodeTxWith decodeFiringTx <=< decodeJson
 
 --------------------------------------------------------------------------------
 
+-- | A handcrafted decoder that ensures a field "previous": "z" is present in the result, even if "previous" is missing
+-- | from the JSON input. The "z" value is the `uberRootHash`.
 decodeInitialTx :: Json -> String \/ InitialTx
-decodeInitialTx = decodeJson
+decodeInitialTx = decodeJson >=> \x -> do
+  root          <- x .: "root"
+  previousMaybe <- x .:? "previous"
+  -- if we encounter JSON without a "previous" field in the root's "decoded" payload, insert it artificially
+  let previous   = fromMaybe uberRootHash previousMaybe
+  pure { root, previous }
 
 decodeWiringTx :: Json -> String \/ WiringTx
 decodeWiringTx = decodeJson >=> \x -> do

Diff for: stbx-core/test/Statebox/Core.purs

@@ -18,6 +18,10 @@ foreign import requireStbxJs_HACK :: String
 suite :: Spec Unit
 suite = do
   describe "Stbx" do
+    it "should decode a root transaction from hex correctly" do
+      let eitherDecodedString = Stbx.decodeToJsonString "0a0022200a1e47756172616e746565642d456e7472616e63652d546f6b656e2e74657374"
+      eitherDecodedString `shouldEqual` Right "{\"root\":{\"message\":\"47756172616e746565642d456e7472616e63652d546f6b656e2e74657374\"}}"
+
     it "should decode a wiring transaction from hex correctly" do
       let eitherDecodedString = Stbx.decodeToJsonString "0a04deadbeef1a2c0a150a01611000100110001001100010001a01781a0179120f0a017a10011801180222017322017418001800"
       eitherDecodedString `shouldEqual` Right """{"wiring":{"nets":[{"name":"a","partition":[0,1,0,1,0,0],"names":["x","y"]}],"diagrams":[{"name":"z","width":1,"pixels":[1,2],"names":["s","t"]}],"labels":[0,0]},"previous":"z6h8cQN"}"""

Diff for: stbx-rest-integration/test/Main.purs

@@ -70,8 +70,7 @@ postExampleTransactionsSpec =
 getExampleTransactionsSpec :: Spec Unit
 getExampleTransactionsSpec =
   describe "Statebox transaction API HTTP service" do
-    pending "TODO: GETting root transaction fails"
-    -- requestTransactionSpec "root"                 "zFsGM27VMNWZne1SSkWnDQTzr6TdjmsKpbxGkJKKaEC8e"
+    requestTransactionSpec "root"                 "zFsGM27VMNWZne1SSkWnDQTzr6TdjmsKpbxGkJKKaEC8e"
     requestTransactionSpec "wiring"               "zFsGM27o59f9Lu8bWjNHBG7Wbq5iftQA6uDt14zRdjCrH"
     requestTransactionSpec "firing 0 (execution)" "zFsGM26E6xAuYMXox2zMGUChk3HmbEAMGXBiWG3UL7KF5"
     requestTransactionSpec "firing 1"             "zFsGM28DqZKjjGbfCEsjsXTj8xJAqWaBXpDSc1CqR6ihi"