Duplicate error with "coerceTypes" option

[jfstgermain]

There seems to be an issue with unsupported formats. I don't have control over what's passed in as a format for certain types in the json schema. I tried ignoring them (unknownFormats: 'ignore') and adding them (addFormat) as described below. I always end up getting duplicate error messages for the same fields. If I remove the format keyword in the schema, the problem disappears.
Any clue?

What version of Ajv are you using? Does the issue happen if you use the latest version?
5.0.0

Ajv options object

const ajv = new Ajv({
    removeAdditional: true,
    // unknownFormats: 'ignore',
    coerceTypes: 'array',
    allErrors: true,
    verbose: true,
});

JSON Schema

{
  "type": "number",
  "format": "double",
  "description": ""
}

Sample data

'lorem'

Your code

const ajv = new Ajv({
    removeAdditional: true,
    // unknownFormats: 'ignore',
    coerceTypes: 'array',
    allErrors: true,
    verbose: true,
});

ajv.addFormat('double', /.*/); // double format isn't standard.  Accept anything

const validate = ajv.compile({
  "type": "number",
  "format": "double",
  "description": ""
});

validate('lorem');
logger.error({ ajv: validate.errors });

Validation result, data AFTER validation, error messages

 [
      {
        "keyword": "type",
        "dataPath": "",
        "schemaPath": "#/type",
        "params": {
          "type": "number"
        },
        "message": "should be number",
        "schema": "number",
        "parentSchema": {
          "type": "number",
          "format": "double",
          "description": ""
        },
        "data": "lorem"
      },
      {
        "keyword": "type",
        "dataPath": "",
        "schemaPath": "#/type",
        "params": {
          "type": "number"
        },
        "message": "should be number",
        "schema": "number",
        "parentSchema": {
          "type": "number",
          "format": "double",
          "description": ""
        },
        "data": "lorem"
      }
    ]

What results did you expect?

 [
      {
        "keyword": "type",
        "dataPath": "",
        "schemaPath": "#/type",
        "params": {
          "type": "number"
        },
        "message": "should be number",
        "schema": "number",
        "parentSchema": {
          "type": "number",
          "format": "double",
          "description": ""
        },
        "data": "lorem"
      }
    ]

[epoberezkin]

@jfstgermain thank you. Option coerceTypes seems to be causing it when "type" is used in combination with any other keyword that may apply to a number, not necessarily format:

https://runkit.com/esp/58fe72cc29e27100129b2212

[epoberezkin]

fixed in 5.0.1 and in 4.11.8