fix: support DATETIME field that has a space between date and time and has only date (#2176)

* fix: support DATETIME field that has a space between date and time
and has only date.

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

---------

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: agrawal-siddharth

google-cloud-bigquerystorage/src/main/java/com/google/cloud/bigquery/storage/v1/JsonToProtoMessage.java

@@ -100,6 +100,25 @@ public class JsonToProtoMessage implements ToProtoConverter<Object> {
           .toFormatter()
           .withZone(ZoneOffset.UTC);
 
+  private static final DateTimeFormatter DATETIME_FORMATTER =
+      new DateTimeFormatterBuilder()
+          .parseLenient()
+          .append(DateTimeFormatter.ISO_LOCAL_DATE)
+          .optionalStart()
+          .optionalStart()
+          .parseCaseInsensitive()
+          .appendLiteral('T')
+          .optionalEnd()
+          .optionalStart()
+          .appendLiteral(' ')
+          .optionalEnd()
+          .append(DateTimeFormatter.ISO_LOCAL_TIME)
+          .optionalEnd()
+          .parseDefaulting(ChronoField.HOUR_OF_DAY, 0)
+          .parseDefaulting(ChronoField.MINUTE_OF_HOUR, 0)
+          .parseDefaulting(ChronoField.SECOND_OF_MINUTE, 0)
+          .toFormatter();
+
   /** You can use {@link #INSTANCE} instead */
   public JsonToProtoMessage() {}
 
@@ -402,7 +421,8 @@ private void fillField(
             if (val instanceof String) {
               protoMsg.setField(
                   fieldDescriptor,
-                  CivilTimeEncoder.encodePacked64DatetimeMicros(LocalDateTime.parse((String) val)));
+                  CivilTimeEncoder.encodePacked64DatetimeMicros(
+                      LocalDateTime.parse((String) val, DATETIME_FORMATTER)));
               return;
             } else if (val instanceof Long) {
               protoMsg.setField(fieldDescriptor, val);
@@ -663,7 +683,8 @@ private void fillRepeatedField(
             if (val instanceof String) {
               protoMsg.addRepeatedField(
                   fieldDescriptor,
-                  CivilTimeEncoder.encodePacked64DatetimeMicros(LocalDateTime.parse((String) val)));
+                  CivilTimeEncoder.encodePacked64DatetimeMicros(
+                      LocalDateTime.parse((String) val, DATETIME_FORMATTER)));
             } else if (val instanceof Long) {
               protoMsg.addRepeatedField(fieldDescriptor, val);
             } else {

google-cloud-bigquerystorage/src/test/java/com/google/cloud/bigquery/storage/v1/JsonToProtoMessageTest.java

@@ -608,7 +608,7 @@ public void testDateTimeMismatch() throws Exception {
         TableFieldSchema.newBuilder()
             .setName("datetime")
             .setType(TableFieldSchema.Type.DATETIME)
-            .setMode(TableFieldSchema.Mode.REPEATED)
+            .setMode(TableFieldSchema.Mode.NULLABLE)
             .build();
     TableSchema tableSchema = TableSchema.newBuilder().addFields(field).build();
     JSONObject json = new JSONObject();
@@ -623,6 +623,34 @@ public void testDateTimeMismatch() throws Exception {
     }
   }
 
+  private void dateTimeMatch_Internal(String jsonVal, Long expectedVal) throws Exception {
+    TableFieldSchema field =
+        TableFieldSchema.newBuilder()
+            .setName("datetime")
+            .setType(TableFieldSchema.Type.DATETIME)
+            .setMode(TableFieldSchema.Mode.NULLABLE)
+            .build();
+    TableSchema tableSchema = TableSchema.newBuilder().addFields(field).build();
+    TestDatetime expectedProto = TestDatetime.newBuilder().setDatetime(expectedVal).build();
+    JSONObject json = new JSONObject();
+    json.put("datetime", jsonVal);
+    DynamicMessage protoMsg =
+        JsonToProtoMessage.INSTANCE.convertToProtoMessage(
+            TestDatetime.getDescriptor(), tableSchema, json);
+    assertEquals(expectedProto, protoMsg);
+  }
+
+  @Test
+  public void testDateTimeMatch() throws Exception {
+    dateTimeMatch_Internal("2021-09-27T20:51:10.752", 142258614586538368L);
+    dateTimeMatch_Internal("2021-09-27t20:51:10.752", 142258614586538368L);
+    dateTimeMatch_Internal("2021-09-27 20:51:10.752", 142258614586538368L);
+    dateTimeMatch_Internal("2021-9-27T20:51:10.752", 142258614586538368L);
+    dateTimeMatch_Internal("2021-09-27T00:00:00", 142258525253402624L);
+    dateTimeMatch_Internal("2021-09-27T00:0:00", 142258525253402624L);
+    dateTimeMatch_Internal("2021-09-27", 142258525253402624L);
+  }
+
   @Test
   public void testTimeMismatch() throws Exception {
     TableFieldSchema field =
@@ -952,6 +980,9 @@ public void testStructComplex() throws Exception {
             .setTestDate(1)
             .setTestDatetime(1)
             .addTestDatetimeStr(142258614586538368L)
+            .addTestDatetimeStr(142258614586538368L)
+            .addTestDatetimeStr(142258614586538368L)
+            .addTestDatetimeStr(142258525253402624L)
             .addTestDatetimeStr(142258525253402624L)
             .setComplexLvl1(
                 ComplexLvl1.newBuilder()
@@ -1020,7 +1051,14 @@ public void testStructComplex() throws Exception {
     json.put("test_datetime", 1);
     json.put(
         "test_datetime_str",
-        new JSONArray(new String[] {"2021-09-27T20:51:10.752", "2021-09-27T00:00:00"}));
+        new JSONArray(
+            new String[] {
+              "2021-09-27T20:51:10.752",
+              "2021-09-27t20:51:10.752",
+              "2021-09-27 20:51:10.752",
+              "2021-09-27T00:00:00",
+              "2021-09-27"
+            }));
     json.put("complex_lvl1", complex_lvl1);
     json.put("complex_lvl2", complex_lvl2);
     json.put(