Disallow empty command submission

Fixes #592

ledger/ledger-api-common/src/main/scala/com/digitalasset/ledger/api/validation/CommandsValidator.scala

@@ -41,7 +41,8 @@ final class CommandsValidator(ledgerId: LedgerId) {
       let <- requirePresence(commands.ledgerEffectiveTime, "ledger_effective_time")
       ledgerEffectiveTime = TimestampConversion.toInstant(let)
       mrt <- requirePresence(commands.maximumRecordTime, "maximum_record_time")
-      validatedCommands <- validateInnerCommands(commands.commands, submitter)
+      commandz <- requireNonEmpty(commands.commands, "commands")
+      validatedCommands <- validateInnerCommands(commandz, submitter)
       ledgerEffectiveTimestamp <- Time.Timestamp
         .fromInstant(ledgerEffectiveTime)
         .left

ledger/ledger-api-test-tool/src/main/scala/com/daml/ledger/api/testtool/tests/CommandService.scala

@@ -248,6 +248,20 @@ final class CommandService(session: LedgerSession) extends LedgerTestSuite(sessi
       assertGrpcError(failure, Status.Code.NOT_FOUND, s"Ledger ID '$invalidLedgerId' not found.")
   }
 
+  private[this] val disallowEmptyCommandSubmission = LedgerTest(
+    "CSDisallowEmptyTransactionsSubmission",
+    "The submission of an empty command should be rejected with INVALID_ARGUMENT"
+  ) { context =>
+    for {
+      ledger <- context.participant()
+      party <- ledger.allocateParty()
+      emptyRequest <- ledger.submitRequest(party)
+      failure <- ledger.submit(emptyRequest).failed
+    } yield {
+      assertGrpcError(failure, Status.Code.INVALID_ARGUMENT, "Missing field: commands")
+    }
+  }
+
   override val tests: Vector[LedgerTest] = Vector(
     submitAndWaitTest,
     submitAndWaitForTransactionTest,
@@ -260,6 +274,7 @@ final class CommandService(session: LedgerSession) extends LedgerTestSuite(sessi
     submitAndWaitWithInvalidLedgerIdTest,
     submitAndWaitForTransactionIdWithInvalidLedgerIdTest,
     submitAndWaitForTransactionWithInvalidLedgerIdTest,
-    submitAndWaitForTransactionTreeWithInvalidLedgerIdTest
+    submitAndWaitForTransactionTreeWithInvalidLedgerIdTest,
+    disallowEmptyCommandSubmission
   )
 }

unreleased.rst

@@ -10,3 +10,9 @@ HEAD — ongoing
 --------------
 
 - [DAML Compiler] Reduce the memory footprint of the IDE and the command line tools (ca. 18% in our experiments).
+- [DAML Triggers] The trigger runner now supports triggers using the high-level API directly. These no longer need to be converted to low-level Triggers using ``runTrigger``. Triggers using the low-level API are still supported.
+- [DAML Compiler] The package database is now be cleaned automatically on initialization.
+  This means that you should no longer have to run ``daml clean`` on SDK upgrades
+  if you use DAR dependencies (e.g. with DAML triggers).
+- [Sandbox] Improve performance of looking up contracts from postgres. See `issue #2330 <https://github.com/digital-asset/daml/issues/2330>`__.
+- [Ledger API] Disallow empty commands. See `issue #592 <https://github.com/digital-asset/daml/issues/592>`__.