Fix entity handler validation for state-level handlers

Entity handler validation now checks per-state rather than only at
entity level. States can contain their own handlers, so the old check
that errored when an entity had states but no entity-level handlers
was incorrect. New behavior:
- Each state without handlers errors individually (unless entity has
  entity-level handlers that cover it)
- Entities with no states and no handlers but other content get a
  guidance error suggesting adding a handler or a state with a handler
- Pending institutional-commerce tests until that repo adds handlers

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: reid-spencer

passes/input/check/saga/saga.check

@@ -10,6 +10,9 @@ passes/input/check/saga/saga.riddl(12:5->16):
 passes/input/check/saga/saga.riddl(12:5->16):
  Metadata in Entity 'blah' should not be empty:
      entity blah is {
+passes/input/check/saga/saga.riddl(12:5->16):
+ Entity 'blah' has no handlers and no states with handlers. Add a handler to the entity or add a state with a handler.:
+     entity blah is {
 passes/input/check/saga/saga.riddl(13:26->34):
  Inlet 'in' is not connected:
        sink trashCan is { inlet in is command Something }

passes/jvm-native/src/test/scala/com/ossuminc/riddl/passes/validate/EntityValidatorTest.scala

@@ -92,7 +92,7 @@ class EntityValidatorTest extends AbstractValidatingTest {
             assertValidationMessage(
               msgs,
               Error,
-              "Entity 'Hamburger' has 1 state but no handlers."
+              "State 'foo' in Entity 'Hamburger' has no handlers."
             )
             assertValidationMessage(
               msgs,

passes/jvm-native/src/test/scala/com/ossuminc/riddl/passes/validate/FunctionValidatorTest.scala

@@ -22,6 +22,7 @@ class FunctionValidatorTest extends AbstractValidatingTest with Inside {
          |    returns {r: Integer }
          |    ???
          |  }
+         |  handler x is { ??? }
          |}
          |""".stripMargin) { (e, rpi, msgs) =>
         inside(e.functions.head) { (f: Function) =>

passes/jvm-native/src/test/scala/com/ossuminc/riddl/passes/validate/InvariantValidator.scala

@@ -19,6 +19,7 @@ class InvariantValidator extends AbstractValidatingTest {
         """
           |entity user is {
           | invariant small is ??? with { described as { "self explanatory!" } }
+          | handler x is { ??? }
           |}
           |""".stripMargin
       ) { (_, _, msgs) =>
@@ -44,6 +45,7 @@ class InvariantValidator extends AbstractValidatingTest {
         """
           |entity user is {
           | invariant large is "x must be greater or equal to 10"
+          | handler x is { ??? }
           |}
           |""".stripMargin
       ) { (_, _, msgs) =>
@@ -58,6 +60,7 @@ class InvariantValidator extends AbstractValidatingTest {
       parseAndValidateInContext[AST.Entity]("""
                                               |entity user is {
                                               | invariant large is "true"
+                                              | handler x is { ??? }
                                               |}
                                               |""".stripMargin) { (_, _, msgs) =>
         assertValidationMessage(

passes/shared/src/main/scala/com/ossuminc/riddl/passes/validate/ValidationPass.scala

@@ -728,14 +728,25 @@ case class ValidationPass(
           s"${entity.identify} is declared as a finite-state-machine but its handlers contain no morph or become statements"
         )
     }
-    if entity.states.nonEmpty && entity.handlers.isEmpty then {
+    if entity.states.nonEmpty then {
+      val statesWithoutHandlers = entity.states.filter { state =>
+        state.handlers.isEmpty && entity.handlers.isEmpty
+      }
+      for state <- statesWithoutHandlers do
+        messages.add(
+          Message(
+            state.errorLoc,
+            s"${state.identify} in ${entity.identify} has no handlers.",
+            Messages.Error
+          )
+        )
+      end for
+    } else if entity.handlers.isEmpty && !entity.isEmpty then {
       messages.add(
         Message(
           entity.errorLoc,
-          s"${entity.identify} has ${entity.states.size} state${
-              if entity.states.size != 1 then "s"
-              else ""
-            } but no handlers.",
+          s"${entity.identify} has no handlers and no states with handlers. " +
+            "Add a handler to the entity or add a state with a handler.",
           Messages.Error
         )
       )

passes/shared/src/test/scala/com/ossuminc/riddl/passes/validate/SharedAdaptorTest.scala

@@ -69,6 +69,7 @@ trait SharedAdaptorTest(using PlatformContext) extends AbstractValidatingTest {
           |
           |  entity MyEntity is {
           |    sink phum is { inlet commands is command LetsDoIt }
+          |    handler x is { ??? }
           |  }
           |  connector only is {
           |    from outlet Foo.PaymentAdapter.foo.forMyEntity

riddlc/jvm/src/test/scala/com/ossuminc/riddl/RunRiddlcOnRemoteTest.scala

@@ -58,6 +58,7 @@ class RunRiddlcOnRemoteTest extends RunCommandSpecBase {
 
   "riddlc" should {
     "validate on ossuminc/institutional-commerce" in {
+      pending // entities in institutional-commerce need handlers or states with handlers
       runOnGitHubProject(
         "ossuminc",
         "institutional-commerce",

riddlc/shared/src/test/scala/com/ossuminc/riddl/ReportedIssuesTest.scala

@@ -64,11 +64,12 @@ class ReportedIssuesTest extends JVMAbstractValidatingTest {
           // info(messages.format)
           val errors = messages.justErrors
           info(errors.format)
-          errors.length must be(3)
+          errors.length must be(4)
           val f = errors.map(_.format)
           f contains "Path 'FooExamplexxx.garbage' was not resolved,"
           f contains "Path 'FooExamplexxxx.garbage' was not resolved"
           f contains "Path 'Examplexxxx.Foo' was not resolved,"
+          f contains "Entity 'OtherEntity' has no handlers and no states with handlers."
           val usage = messages.justUsage
           usage.length must be(0)
           val u = usage.map(_.format)

riddlc/shared/src/test/scala/com/ossuminc/riddl/RunRiddlcOnLocalTest.scala

@@ -46,6 +46,7 @@ class RunRiddlcOnLocalTest extends RunCommandSpecBase {
       runOnLocalProject(cwd, config, "validate")
     }
     "validate on ossuminc/institutional-commerce" in {
+      pending // entities in institutional-commerce need handlers or states with handlers
       val cwd = "/Users/reid/Code/ossuminc/institutional-commerce"
       val config = "src/main/riddl/ImprovingApp.conf"
       runOnLocalProject(cwd, config, "validate")