Handle fetchByKey callback correctly in scenario runner (#10980)

fixes #10977

Turns out assertions are good unless they’re wrong …

This only affects scenarios, the engine never looks at the callback.

changelog_begin
changelog_end

compiler/damlc/tests/daml-test-files/ConsumedContractKey.daml

@@ -0,0 +1,36 @@
+-- @ERROR range=23:1-23:32; no contract with that key was found
+-- @ERROR range=33:1-33:29; consumed in same transaction
+module ConsumedContractKey where
+
+template Foo
+  with
+    signer: Party
+  where
+    signatory signer
+    key signer : Party
+    maintainer key
+    controller signer can
+      FetchKey : Foo
+        do
+          snd <$> fetchByKey @Foo signer
+      LookupKey : ()
+        do
+          None <- lookupByKey @Foo signer
+          pure ()
+      Fetch : Foo
+        do fetch self
+
+testFetchKeyFromConsumingChoice = do
+  alice <- getParty "Alice"
+  fooId <- alice `submit` create Foo with signer = alice
+  alice `submit` exercise fooId FetchKey
+
+testLookupKeyFromConsumingChoice = do
+  alice <- getParty "Alice"
+  fooId <- alice `submit` create Foo with signer = alice
+  alice `submit` exercise fooId LookupKey
+
+testFetchFromConsumingChoice = do
+  alice <- getParty "Alice"
+  fooId <- alice `submit` create Foo with signer = alice
+  alice `submit` exercise fooId Fetch

daml-lf/scenario-interpreter/BUILD.bazel

@@ -32,6 +32,7 @@ da_scala_library(
         "//daml-lf/language",
         "//daml-lf/transaction",
         "//libs-scala/nameof",
+        "//libs-scala/scala-utils",
     ],
 )
 

daml-lf/scenario-interpreter/src/main/scala/com/digitalasset/daml/lf/ScenarioRunner.scala

@@ -15,6 +15,7 @@ import com.daml.lf.speedy.SResult._
 import com.daml.lf.transaction.IncompleteTransaction
 import com.daml.lf.value.Value
 import com.daml.nameof.NameOf
+import com.daml.scalautil.Statement.discard
 
 import scala.annotation.tailrec
 import scala.util.{Failure, Success, Try}
@@ -328,9 +329,12 @@ object ScenarioRunner {
           ) match {
             case ScenarioLedger.LookupOk(_, _, stakeholders) =>
               if (!readers.intersect(stakeholders).isEmpty)
-                // We should always be able to continue with a SKeyLookupResult.Found.
-                // Run to get side effects and assert result.
-                assert(callback(Some(acoid)))
+                // Note that even with a successful global lookup
+                // the callback can return false. This happens for a fetch-by-key
+                // if the contract got archived in the meantime.
+                // We discard the result here and rely on fetch-by-key
+                // setting up the state such that continuing interpretation fails.
+                discard(callback(Some(acoid)))
               else
                 throw Error.ContractKeyNotVisible(acoid, gk, actAs, readAs, stakeholders)
             case ScenarioLedger.LookupContractNotFound(coid) =>