sort criteria on invalid field should report well-formed json error

[dnesting]

We've seen this a few times in production. It's not clear how I can reproduce it and it may be the result of someone playing with the API, but we should not generate internal errors as a result of bad user input.

Elasticsearch::Transport::Transport::Errors::BadRequest: [400] 
{"error":"SearchPhaseExecutionException[Failed to execute phase [query_fetch], all shards failed; shardFailures {[7WAeJDHBSg-crOH2AwOEMg][production-school-data][0]: SearchParseException[[production-school-data][0]: query[ConstantScore(*:*)],from[0],size[20]: Parse Failure [Failed to parse source [{\"from\":0,\"size\":20,\"query\":{\"match_all\":{}},\"_source\":{\"exclude\":[\"_*\"]},\"sort\":[{\"advantage\":{\"order\":\"desc\"}}]}]]]; nested: 
SearchParseException[[production-school-data][0]: query[ConstantScore(*:*)],from[0],size[20]: Parse Failure [No mapping found for [advantage] in order to sort on]]; }]","status":400}

…t-1.0.12/lib/elasticsearch/transport/transport/base.rb: 135:in `__raise_transport_error'
…t-1.0.12/lib/elasticsearch/transport/transport/base.rb: 227:in `perform_request'
…/lib/elasticsearch/transport/transport/http/faraday.rb:  20:in `perform_request'
…transport-1.0.12/lib/elasticsearch/transport/client.rb: 119:in `perform_request'
…rch-api-1.0.12/lib/elasticsearch/api/actions/search.rb: 159:in `search'
                       /home/vcap/app/lib/data_magic.rb:  82:in `search'

[ultrasaurus]

Indeed, seems to be someone experimenting with the API. I can reproduce locally with 4 years of College Scorecard data:

http://localhost:3000/v1/schools?sort=advantage:desc

Definitely a bug

[ultrasaurus]

note: in general sort does work. Using the dafault cities data in sample-data, this works: http://localhost:3000/v1/cities?sort=population:desc

However, this doesn't: http://localhost:3000/v1/cities?sort=whatever:desc

this is an issue with error reporting when you try to sort by a field that is not available.