[Issue #1493] Update search schema to disallow empty filters

[chouinar]

Summary

Fixes #1493

Time to review: 5 mins

Changes proposed

Updated search schema logic to disallow:

1. Empty one_of lists
2. Empty filter lists

Context for reviewers

These changes remove a few edge cases that have undefined / difficult to define behavior if we allow them (ie. what do we do if a list is empty, opportunity_status in [ ]). Rather than try to sort out what the behavior might mean / modify a users search request and interpret what we think they probably mean, we don't allow that type of request and chalk it up to user error in constructing a request.

Note that this does not modify the behavior of just not passing filters, that's still perfectly fine, we just want to avoid being passed filters that are half-built. See the additional section below for what is / isn't allowed.

Additional information

An example request looks like:

{
  "filters": {
    "agency": {
      "one_of": [
        "US-ABC",
        "HHS"
      ]
    },
    "applicant_type": {
      "one_of": [
        "state_governments",
        "county_governments",
        "individuals"
      ]
    },
    "funding_category": {
      "one_of": [
        "recovery_act",
        "arts",
        "natural_resources"
      ]
    },
    "funding_instrument": {
      "one_of": [
        "cooperative_agreement",
        "grant"
      ]
    },
    "opportunity_status": {
      "one_of": [
        "forecasted",
        "posted"
      ]
    }
  },
  "pagination": {
    "order_by": "opportunity_id",
    "page_offset": 1,
    "page_size": 25,
    "sort_direction": "descending"
  },
  "query": "research"
}

Technically only the pagination is required, and so you can also pass us:

{
  "pagination": {
    "order_by": "opportunity_id",
    "page_offset": 1,
    "page_size": 25,
    "sort_direction": "descending"
  }
}

Error cases

However, the following are now no longer allowed.

An empty list

logically this wouldn't ever return results as the intersection of an empty set always is nothing

{
  "filters": {
    "agency": {
      "one_of": []
    }
  },

  "pagination": {
    "order_by": "opportunity_id",
    "page_offset": 1,
    "page_size": 25,
    "sort_direction": "descending"
  }
}

Which returns:

{
  "data": {},
  "errors": [
    {
      "field": "filters.agency.one_of",
      "message": "Shorter than minimum length 1.",
      "type": "min_length"
    }
  ],
  "message": "Validation error",
  "status_code": 422
}

An empty set of filter rules for a field

this technically doesn't cause issues, but lets us be more flexible in our implementation

{
  "filters": {
    "agency": {
    }
  },

  "pagination": {
    "order_by": "opportunity_id",
    "page_offset": 1,
    "page_size": 25,
    "sort_direction": "descending"
  }
}

Which returns:

{
  "data": {},
  "errors": [
    {
      "field": "filters.agency",
      "message": "At least one filter rule must be provided.",
      "type": "invalid"
    }
  ],
  "message": "Validation error",
  "status_code": 422
}

[coilysiren]

Good thinking 👍🏼 and thanks for the PR description examples, I was confused until I saw them.