string type arrays handling dates

[JimmyHurrah]

I was trying to add response schemas to a production app using nullable dates and fastify. I noticed that type arrays would not work with string for dates while it worked fine when not using type arrays.

{                                                                  
   type: 'object',                                                 
   properties: {                                                  
     date: { type: 'string' }                                  
   }                                                            
}

works for dates and will produce

function $main(obj) {
  var json = '{'
  var addComma = false
  if (obj['date'] !== undefined) {
    if (addComma) {
      json += ','
    }
    addComma = true
    json += '"date":'
    json += $asString(obj['date'])
  }
  json += '}'
  return json
}

while

{                                                                  
   type: 'object',                                                 
   properties: {                                                  
     date: { type: ['string'] }                                  
   }                                                            
}

does not work and will produce

function $main(obj) {
  var json = '{'
  var addComma = false
  if (obj['date'] !== undefined) {
    if (addComma) {
      json += ','
    }
    addComma = true
    json += '"date":'

    if (ajv.validate({ type: 'string'}, obj['date']))
      json += $asString(obj['date'])
  }
  json += '}'
  return json
}

since Date is of type object Ajv.validate({ type: 'string'}, someDate) will fail and not get passed to $asString

With the fix the produced function looks like this:

function $main(obj) {
  var json = '{'
  var addComma = false
  if (obj['date'] !== undefined) {
    if (addComma) {
      json += ','
    }
    addComma = true
    json += '"date":'
    if (obj['date'] instanceof Date || ajv.validate({ type: 'string' }, obj['date']))
      json += $asString(obj['date'])
    else json += null
  }
  json += '}'
  return json
}

I also added an else case so it will always produce valid json.

Benchmark before

JSON.stringify array x 2,712 ops/sec ±1.00% (84 runs sampled)
fast-json-stringify array x 3,440 ops/sec ±1.03% (87 runs sampled)
fast-json-stringify-uglified array x 3,466 ops/sec ±0.96% (88 runs sampled)
JSON.stringify long string x 11,898 ops/sec ±1.01% (85 runs sampled)
fast-json-stringify long string x 11,693 ops/sec ±1.55% (87 runs sampled)
fast-json-stringify-uglified long string x 11,703 ops/sec ±1.19% (87 runs sampled)
JSON.stringify short string x 3,984,047 ops/sec ±1.08% (87 runs sampled)
fast-json-stringify short string x 7,459,043 ops/sec ±0.84% (85 runs sampled)
fast-json-stringify-uglified short string x 7,442,658 ops/sec ±1.02% (87 runs sampled)
JSON.stringify obj x 1,204,803 ops/sec ±1.04% (86 runs sampled)
fast-json-stringify obj x 3,049,330 ops/sec ±1.08% (90 runs sampled)
fast-json-stringify-uglified obj x 3,101,949 ops/sec ±0.93% (89 runs sampled)

Benchmark after

JSON.stringify array x 2,713 ops/sec ±1.01% (86 runs sampled)
fast-json-stringify array x 3,454 ops/sec ±1.41% (89 runs sampled)
fast-json-stringify-uglified array x 3,482 ops/sec ±0.85% (87 runs sampled)
JSON.stringify long string x 11,848 ops/sec ±1.02% (87 runs sampled)
fast-json-stringify long string x 11,780 ops/sec ±0.79% (87 runs sampled)
fast-json-stringify-uglified long string x 11,724 ops/sec ±1.08% (85 runs sampled)
JSON.stringify short string x 3,954,375 ops/sec ±0.83% (88 runs sampled)
fast-json-stringify short string x 7,493,674 ops/sec ±0.81% (85 runs sampled)
fast-json-stringify-uglified short string x 7,417,784 ops/sec ±0.86% (87 runs sampled)
JSON.stringify obj x 1,204,706 ops/sec ±0.94% (86 runs sampled)
fast-json-stringify obj x 3,069,088 ops/sec ±1.05% (85 runs sampled)
fast-json-stringify-uglified obj x 3,095,127 ops/sec ±1.00% (85 runs sampled)

[JimmyHurrah]

@mcollina @delvedor Any feedback on this?

[mcollina]

Why is this call to ajv needed? I would refrain from doing so. Callling ajv is costly.

[JimmyHurrah]

@mcollina I'm not sure really. All I have done is to check if the data is a Date when the type is string. the ajv stuff was there before already.