Validate my array items satisfy certain criteria

[jamesbmorris92]

Hi All,

This is my first time posting so apologies if I'm posting in the wrong place. I'm trying to write a schema that essentially describes a database table and it's fields, the schema looks like this:

{
	"properties": {
		"viEntity": {
			"description": "",
			"type": "object",
			"properties": {
				"dbTableName": {
					"description": "The name of the database table for the entity.",
					"type": "string"
				},
				"fields": {
					"description": "The fields configured for this entity.",
					"type": "array",
					"minItems": 1,
					"items": {
						"type": "object",
						"properties": {
							"fieldName": {
								"description": "The name of the field.",
								"type": "string"
							},
							"role": {
								"type": "string",
								"description": "The flag indicating special properties of the field.",
								"default": "",
								"enum": ["", "primarykey", "lastmodifieddate"]
							}
					}
				}
			}
		}
	}
}

I want to validate that atleast one of my fields is marked as primarykey and one of them is marked as lastmodifieddate. When looking through the docs I saw the contains option which looked like it could be helpful but I haven't found a way of getting both of my constraints working with contain. Any help greatly appreciated.

[jdesrosiers]

Welcome! This is the perfect place to ask a question like this.

You have the right idea with contains. Are you saying that you got both constraints working, just not at the same time? You probably just need an allOf.

"allOf": [
  {
    "contains": { pk constraint }
  },
  {
    "contains": { lmd constraint }
  }
]

If that doesn't help. Please share more of what you've tried.

[jamesbmorris92]

thanks for the response, here's what I just tried (apologies for the massive JSON dumps):

{
    "properties": {
		"viEntity": {
			"description": "",
			"type": "object",
			"properties": {
				"dbTableName": {
					"description": "The name of the database table for the entity.",
					"type": "string"
				},
				"fields": {
					"description": "The fields configured for this entity.",
					"type": "array",
					"minItems": 1,
					"items": {
						"type": "object",
						"properties": {
							"fieldName": {
								"description": "The name of the field.",
								"type": "string"
							},
							"role": {
								"type": "string",
								"description": "The flag indicating special properties of the field.",
								"default": "",
								"enum": ["", "primarykey", "lastmodifieddate"]
							}
            }
          },
          "allOf": [
						{
							"contains": {
								"type": "object",
								"properties": {
									"role": {
										"const": "primarykey"
									}
								}
							},
							"minContains": 1,
							"maxContains": 1
						},
						{
							"contains": {
								"type": "object",
								"properties": {
									"role": {
										"const": "lastmodifieddate"
									}
								}
							},
							"minContains": 1,
							"maxContains": 1
						}
					]
                }
            }
        }
    }
}

And then with data:

{
    "dbTableName": "test_table",
    "fields": [
        {
            "role": "",
            "fieldName": "field_one"
        },
        {
            "role": "",
            "fieldName": "field_two"
        },
        {
            "role": "",
            "fieldName": "field_three"
        }
    ]
}

Using AJV to validate I get the following 8 errors:

[
    {
        "instancePath": "/viEntity/fields/0/role",
        "schemaPath": "#/properties/viEntity/properties/fields/allOf/0/contains/properties/role/const",
        "keyword": "const",
        "params": {
            "allowedValue": "primarykey"
        },
        "message": "must be equal to constant",
        "schema": "primarykey",
        "parentSchema": {
            "const": "primarykey"
        },
        "data": ""
    },
    {
        "instancePath": "/viEntity/fields/1/role",
        "schemaPath": "#/properties/viEntity/properties/fields/allOf/0/contains/properties/role/const",
        "keyword": "const",
        "params": {
            "allowedValue": "primarykey"
        },
        "message": "must be equal to constant",
        "schema": "primarykey",
        "parentSchema": {
            "const": "primarykey"
        },
        "data": ""
    },
    {
        "instancePath": "/viEntity/fields/2/role",
        "schemaPath": "#/properties/viEntity/properties/fields/allOf/0/contains/properties/role/const",
        "keyword": "const",
        "params": {
            "allowedValue": "primarykey"
        },
        "message": "must be equal to constant",
        "schema": "primarykey",
        "parentSchema": {
            "const": "primarykey"
        },
        "data": ""
    },
    {
        "instancePath": "/viEntity/fields",
        "schemaPath": "#/properties/viEntity/properties/fields/allOf/0/contains",
        "keyword": "contains",
        "params": {
            "minContains": 1,
            "maxContains": 1
        },
        "message": "must contain at least 1 and no more than 1 valid item(s)",
        "schema": {
            "type": "object",
            "properties": {
                "role": {
                    "const": "primarykey"
                }
            }
        },
        "parentSchema": {
            "contains": {
                "type": "object",
                "properties": {
                    "role": {
                        "const": "primarykey"
                    }
                }
            },
            "minContains": 1,
            "maxContains": 1
        },
        "data": [
            {
                "role": "",
                "fieldName": "field_one"
            },
            {
                "role": "",
                "fieldName": "field_two"
            },
            {
                "role": "",
                "fieldName": "field_three"
            }
        ]
    },
    {
        "instancePath": "/viEntity/fields/0/role",
        "schemaPath": "#/properties/viEntity/properties/fields/allOf/1/contains/properties/role/const",
        "keyword": "const",
        "params": {
            "allowedValue": "lastmodifieddate"
        },
        "message": "must be equal to constant",
        "schema": "lastmodifieddate",
        "parentSchema": {
            "const": "lastmodifieddate"
        },
        "data": ""
    },
    {
        "instancePath": "/viEntity/fields/1/role",
        "schemaPath": "#/properties/viEntity/properties/fields/allOf/1/contains/properties/role/const",
        "keyword": "const",
        "params": {
            "allowedValue": "lastmodifieddate"
        },
        "message": "must be equal to constant",
        "schema": "lastmodifieddate",
        "parentSchema": {
            "const": "lastmodifieddate"
        },
        "data": ""
    },
    {
        "instancePath": "/viEntity/fields/2/role",
        "schemaPath": "#/properties/viEntity/properties/fields/allOf/1/contains/properties/role/const",
        "keyword": "const",
        "params": {
            "allowedValue": "lastmodifieddate"
        },
        "message": "must be equal to constant",
        "schema": "lastmodifieddate",
        "parentSchema": {
            "const": "lastmodifieddate"
        },
        "data": ""
    },
    {
        "instancePath": "/viEntity/fields",
        "schemaPath": "#/properties/viEntity/properties/fields/allOf/1/contains",
        "keyword": "contains",
        "params": {
            "minContains": 1,
            "maxContains": 1
        },
        "message": "must contain at least 1 and no more than 1 valid item(s)",
        "schema": {
            "type": "object",
            "properties": {
                "role": {
                    "const": "lastmodifieddate"
                }
            }
        },
        "parentSchema": {
            "contains": {
                "type": "object",
                "properties": {
                    "role": {
                        "const": "lastmodifieddate"
                    }
                }
            },
            "minContains": 1,
            "maxContains": 1
        },
        "data": [
            {
                "role": "",
                "fieldName": "field_one"
            },
            {
                "role": "",
                "fieldName": "field_two"
            },
            {
                "role": "",
                "fieldName": "field_three"
            }
        ]
    }
]

So of the 8 total errors, there are three that say every field must be equal to primarykey and then three errors that say that every field must be equal to lastmodifieddate. The other two are errors that say the fields array must contain one item that satisfies the primarykey / lastmodifieddate criteria.

When I set a field_one to primarykey and field_two to lastmodifieddate the errors go away i.e. the data is now valid. As I type this I'm starting to wonder if this is perhaps a question for AJV or does JSON schema have the concept describing every way that data isn't valid against a schema?

[jdesrosiers]

Yeah, the schema is ok. It looks like the issue you're having is that the error output isn't very helpful. Yes, that would be an ajv concern. You can create an issue over there to see if they can improve this experience, but I'm not sure how much they can do given their flat output structure. The only thing I can think of that might help is to move the individual item errors so they're nested in the contains error.

JSON Schema defines an output format called "detailed" that's nested and can make this case a little more clear, but ajv doesn't implement that format.

[jamesbmorris92]

@jdesrosiers thank you for taking the time to work through this with me and for maintaining JSON schema :)