feat: lenient local date parser

in java.time parsing a LocalDate is stricter than in joda
we want to guaranteebackwards compatibility

BEC-254

json/json-core/src/main/scala/io/sphere/json/FromJSON.scala

@@ -403,6 +403,21 @@ object FromJSON extends FromJSONInstances {
       .parseDefaulting(time.temporal.ChronoField.OFFSET_SECONDS, 0L)
       .toFormatter()
 
+  private val lenientLocalDateParser =
+    new time.format.DateTimeFormatterBuilder()
+      .appendValue(time.temporal.ChronoField.YEAR, 1, 9, java.time.format.SignStyle.NORMAL)
+      .optionalStart()
+      .appendLiteral('-')
+      .appendValue(time.temporal.ChronoField.MONTH_OF_YEAR, 1, 2, java.time.format.SignStyle.NORMAL)
+      .optionalStart()
+      .appendLiteral('-')
+      .appendValue(time.temporal.ChronoField.DAY_OF_MONTH, 1, 2, java.time.format.SignStyle.NORMAL)
+      .optionalEnd()
+      .optionalEnd()
+      .parseDefaulting(time.temporal.ChronoField.MONTH_OF_YEAR, 1L)
+      .parseDefaulting(time.temporal.ChronoField.DAY_OF_MONTH, 1L)
+      .toFormatter()
+
   implicit val javaInstantReader: FromJSON[time.Instant] =
     jsonStringReader("Failed to parse date/time: %s")(s =>
       time.Instant.from(lenientInstantParser.parse(s)))
@@ -412,8 +427,8 @@ object FromJSON extends FromJSONInstances {
       time.LocalTime.parse(_, time.format.DateTimeFormatter.ISO_LOCAL_TIME))
 
   implicit val javaLocalDateReader: FromJSON[time.LocalDate] =
-    jsonStringReader("Failed to parse date: %s")(
-      time.LocalDate.parse(_, time.format.DateTimeFormatter.ISO_LOCAL_DATE))
+    jsonStringReader("Failed to parse date: %s")(s =>
+      time.LocalDate.from(lenientLocalDateParser.parse(s)))
 
   implicit val javaYearMonthReader: FromJSON[time.YearMonth] =
     jsonStringReader("Failed to parse year/month: %s")(

json/json-core/src/test/scala/io/sphere/json/JodaJavaLocalDateCompatSpec.scala

@@ -0,0 +1,48 @@
+package io.sphere.json
+
+import org.json4s.JString
+import org.scalatest.matchers.should.Matchers
+import org.scalatest.wordspec.AnyWordSpec
+import java.time.Instant
+import cats.data.Validated.Valid
+
+class JodaJavaLocalDateCompatSpec extends AnyWordSpec with Matchers {
+
+  val jodaReader = FromJSON.dateReader
+  val javaReader = FromJSON.javaLocalDateReader
+  def jsonDateStringWith(
+      year: String = "2035",
+      dayOfTheMonth: String = "23",
+      monthOfTheYear: String = "11"): JString = JString(s"$year-$monthOfTheYear-${dayOfTheMonth}")
+
+  private def test(value: JString) =
+    (jodaReader.read(value), javaReader.read(value)) match {
+      case (Valid(jodaDate), Valid(javaDate)) =>
+        jodaDate.getYear shouldBe javaDate.getYear
+        jodaDate.getMonthOfYear shouldBe javaDate.getMonthValue
+        jodaDate.getDayOfMonth shouldBe javaDate.getDayOfMonth
+      case (jodaDate, javaDate) =>
+        fail(s"invalid date. joda: $jodaDate, java: $javaDate")
+    }
+
+  "parsing a LocalDate" should {
+    "accept two digit years" in {
+      test(jsonDateStringWith(year = "50"))
+    }
+    "accept year zero" in {
+      test(JString("0-10-31"))
+    }
+    "accept no day set" in {
+      test(JString("2024-09"))
+    }
+    "accept up to nine digit years" in {
+      (1 to 9).foreach { l =>
+        val year = List.fill(l)("1").mkString("")
+        test(jsonDateStringWith(year = year))
+      }
+    }
+    "accept a year with leading zero" in {
+      test(jsonDateStringWith(year = "02020"))
+    }
+  }
+}