[Transform] geo_bounds aggregation failed with NPE error

[wwang500]

After #71696 was merged, one of our transform:geo_bounds test failed with this error: Cannot invoke "org.elasticsearch.geometry.Geometry.visit(org.elasticsearch.geometry.GeometryVisitor)" because "geometry" is null]

The better error handling is expected because the real failure was caused by non-existent geo.location field.

Build:
Latest 8.0.0 and 7.13.0 build on Apr 19

8.0.0 build hash:

"build" : {
    "hash" : "6dbad503d931d96acbc0c4bf1d2cfe08855265f1",
    "date" : "2021-04-19T14:47:16.966879383Z"
  },

Step to reproduce in dev console

PUT /_transform/test-nonexist-geo-field
{
  "source": {
    "index": [
      "airplane"
    ],
    "query": {
      "match_all": {}
    }
  },
  "dest": {
    "index": "test-nonexist-geo-field"
  },
  "pivot": {
    "group_by": {
      "aircrafttype": {
        "terms": {
          "field": "aircrafttype"
        }
      }
    },
    "aggregations": {
      "bounds": {
        "geo_bounds": {
          "field": "geo.location",
          "wrap_longitude": true
        }
      }
    }
  }
}
POST _transform/test-nonexist-geo-field/_start
GET _transform/test-nonexist-geo-field/_stats

Error:

"id" : "test-nonexist-geo-field",
      "state" : "failed",
      "reason" : """Failed to index documents into destination index due to permanent error: [org.elasticsearch.xpack.transform.transforms.BulkIndexingException: Bulk index experienced [185] failures and at least 1 irrecoverable [org.elasticsearch.xpack.transform.transforms.TransformException: Destination index mappings are incompatible with the transform configuration.; org.elasticsearch.index.mapper.MapperParsingException: failed to parse; java.lang.NullPointerException: Cannot invoke "org.elasticsearch.geometry.Geometry.visit(org.elasticsearch.geometry.GeometryVisitor)" because "geometry" is null]. Other failures:; org.elasticsearch.xpack.transform.transforms.TransformException: Destination index mappings are incompatible with the transform configuration.; org.elasticsearch.index.mapper.MapperParsingException: failed to parse; java.lang.NullPointerException: Cannot invoke "org.elasticsearch.geometry.Geometry.visit(org.elasticsearch.geometry.GeometryVisitor)" because "geometry" is null]""",

Expected:
Better error handling about the non-existent field: geo.location.

[elasticmachine]

Pinging @elastic/es-analytics-geo (Team:Analytics)

[elasticmachine]

Pinging @elastic/ml-core (Team:ML)

[hendrikmuhs]

I debugged this, it fails in the indexing step

Repro:

POST test-nonexist-geo-field/_doc
{
  "aircrafttype":"A319",
  "bounds": null
}

fails for fields of type "geo_shape"