Add queryFilter to triggers (#13769)

* Add queryFilter to triggers

changelog_begin

- [Daml Triggers] Add `queryFilter` matching Daml Script’s
  `queryFilter` which queries contracts of a given template and filters
  them down to those where the predicate holds.

changelog_end

fixes #13746

* Update triggers/daml/Daml/Trigger.daml

triggers/daml/Daml/Trigger.daml

@@ -5,6 +5,7 @@
 
 module Daml.Trigger
  ( query
+ , queryFilter
  , queryContractId
  , queryContractKey
  , ActionTriggerAny
@@ -88,6 +89,11 @@ getContractById id (ACS tpls pending) = do
 query : forall a m. (Template a, ActionTriggerAny m) => m [(ContractId a, a)]
 query = implQuery
 
+-- | Extract the contracts of a given template from the ACS and filter
+-- to those that match the predicate.
+queryFilter : forall a m. (Functor m, Template a, ActionTriggerAny m) => (a -> Bool) -> m [(ContractId a, a)]
+queryFilter pred = filter (\(_, c) -> pred c) <$> implQuery
+
 -- | Find the contract with the given `key` in the ACS, if present.
 queryContractKey : forall a k m. (Template a, HasKey a k, Eq k, ActionTriggerAny m, Functor m)
     => k -> m (Optional (ContractId a, a))

triggers/tests/BUILD.bazel

@@ -42,6 +42,7 @@ DAML_LF_VERSIONS = [
       cp -L $(location :daml/Heartbeat.daml) $$TMP_DIR/daml
       cp -L $(location :daml/ReadAs.daml) $$TMP_DIR/daml
       cp -L $(location :daml/ActAs.daml) $$TMP_DIR/daml
+      cp -L $(location :daml/QueryFilter.daml) $$TMP_DIR/daml
       cp -L $(location //templates:copy-trigger/src/CopyTrigger.daml) $$TMP_DIR/daml
       cp -L $(location //triggers/daml:daml-trigger{suffix}.dar) $$TMP_DIR/daml-trigger.dar
       cp -L $(location //daml-script/daml:daml-script{suffix}.dar) $$TMP_DIR/daml-script.dar

triggers/tests/daml/QueryFilter.daml

@@ -0,0 +1,31 @@
+-- Copyright (c) 2022 Digital Asset (Switzerland) GmbH and/or its affiliates. All rights reserved.
+-- SPDX-License-Identifier: Apache-2.0
+
+
+module QueryFilter where
+
+import Daml.Trigger
+
+trigger : Trigger (Int, Int, Bool)
+trigger = Trigger
+  { initialize = pure (0, 0, False)
+  , updateState = const (pure ())
+  , rule = \p -> do
+      (_, _, started) <- get
+      if not started
+        then
+          emitCommands [createCmd (T p 1), createCmd (T p 2), createCmd (T p 2)] [] >> put (0, 0, True)
+        else do
+          xs <- queryFilter @T (\t -> t.i == 1)
+          ys <- queryFilter @T (\t -> t.i == 2)
+          put (length xs, length ys, started)
+  , registeredTemplates = AllInDar
+  , heartbeat = None
+  }
+
+template T
+  with
+    p : Party
+    i : Int
+  where
+    signatory p

triggers/tests/src/test/scala/com/digitalasset/daml/lf/engine/trigger/test/AbstractFuncTests.scala

@@ -584,5 +584,30 @@ abstract class AbstractFuncTests
         }
       }
     }
+
+    "queryFilter" should {
+      "return contracts matching predicates" in {
+        for {
+          client <- ledgerClient()
+          party <- allocateParty(client)
+          runner = getRunner(
+            client,
+            QualifiedName.assertFromString("QueryFilter:trigger"),
+            party,
+          )
+          (acs, offset) <- runner.queryACS()
+          // 1 for the completion & 1 for the transaction.
+          result <- runner.runWithACS(acs, offset, msgFlow = Flow[TriggerMsg].take(2))._2
+        } yield {
+          inside(toHighLevelResult(result).state) { case SRecord(_, _, values) =>
+            values.asScala shouldBe Seq[SValue](
+              SInt64(1),
+              SInt64(2),
+              SBool(true),
+            )
+          }
+        }
+      }
+    }
   }
 }