Add field starting with digit test

modules/loaders-common/src/test/resources/iglu-client-embedded/schemas/myvendor/digit/jsonschema/1-0-0

@@ -0,0 +1,14 @@
+{
+  "$schema": "http://iglucentral.com/schemas/com.snowplowanalytics.self-desc/schema/jsonschema/1-0-0#",
+  "self": {
+    "vendor": "myvendor",
+    "name": "digit",
+    "format": "jsonschema",
+    "version": "1-0-0"
+  },
+  "type": "object",
+  "properties": {
+    "1col_a": {"type": "string"}
+  },
+  "required": ["1col_a"]
+}

modules/loaders-common/src/test/scala/com.snowplowanalytics.snowplow.loaders/transform/NonAtomicFieldsSpec.scala

@@ -28,6 +28,7 @@ class NonAtomicFieldsSpec extends Specification with CatsEffect {
       return a merged schema if the batch uses all schemas in a series $ue3
       return nothing for the Iglu Central ad_break_end_event schema $ue4
       return a JSON field for the Iglu Central anything-a schema $ue5
+      return a field prefixed with underscore if field starts with a digit $ueDigit
 
     when resolving for known schemas in contexts should
       return an un-merged schema if the batch uses the first schema in a series $c1
@@ -197,6 +198,37 @@ class NonAtomicFieldsSpec extends Specification with CatsEffect {
 
   }
 
+  def ueDigit = {
+    val tabledEntity = TabledEntity(TabledEntity.UnstructEvent, "myvendor", "digit", 1)
+
+    val input = Map(
+      tabledEntity -> Set((0, 0))
+    )
+
+    val expected = {
+      val expectedStruct = Type.Struct(
+        NonEmptyVector.of(
+          Field("_1col_a", Type.String, Required).copy(accessors = Set("1col_a"))
+        )
+      )
+
+      val expectedField = Field("unstruct_event_myvendor_digit_1", expectedStruct, Nullable, Set.empty)
+
+      TypedTabledEntity(
+        tabledEntity,
+        expectedField,
+        Set((0, 0)),
+        Nil
+      )
+    }
+
+    NonAtomicFields.resolveTypes(embeddedResolver, input, List.empty).map { case NonAtomicFields.Result(fields, failures) =>
+      (failures must beEmpty) and
+        (fields must haveSize(1)) and
+        (fields.head must beEqualTo(expected))
+    }
+  }
+
   def c1 = {
 
     val tabledEntity = TabledEntity(TabledEntity.Context, "myvendor", "myschema", 7)