Can't validate a json with a schema using an external schema file

user_3000434 0
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My issue

I need to validate a json file from a Json Schema. I have a main schema and this schema should load an external schema file to validate some part of the json.

For different reasons I can't merge them. I do need 2 schema file.

I am using a $ref statement as proposed in this doc:

https://docs.microsoft.com/en-us/powershell/module/microsoft.powershell.utility/test-json?view=powershell-7.2&WT.mc_id=DT-MVP-5004831

but whatever I try I have this error:

Cannot parse the JSON schema.

What I need

What is the right schema syntax to do this in my case.

Test case

I have this directories on my disk:

.
test.ps1
----/jsons
       params.json
----/schemas
       securities.json
       storages.json

I run validation from this pretty simple PowerShell (test.ps1):

# read json param
$testFile = Get-Content "./jsons/params.json" -Encoding UTF8 | convertfrom-json -Depth 50
$testee = $testFile.parameters | convertto-json

# read json schema
$schemasFile = (Get-ChildItem -Path "./schemas/storages.json").FullName

# test json from schema
$result = $testee | Test-Json -SchemaFile $schemasFile 

$result

My json (params.json):

{
    "parameters": {
        "storages": [
            {
                "comment": "Very important storage",
                "name": "fdlmsto",
                "securities": [
                    {
                        "comment": "Critical rule",
                        "kind": "MSI"
                    }
                ]
            }
        ]
    }
}

The main schema (storages.json):

{
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "$id": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "additionalProperties": false,
    "required": [
        "storages"
    ],
    "properties": {
        "storages": {
            "$id": "#/properties/storages",
            "type": "array",
            "additionalProperties": false,
            "items": [
                {
                    "$id": "#/properties/storages/items",
                    "type": "object",
                    "additionalProperties": false,
                    "required": [
                        "name",
                        "comment"
                    ],
                    "properties": {
                        "$ref": "#/schemas/securities.json",
                        "name": {
                            "type": "string",
                            "$id": "#/properties/storages/items/properties/name"
                        },
                        "comment": {
                            "type": "string",
                            "$id": "#/properties/storages/items/properties/comment"
                        }
                    }
                }
            ]
        }
    }
}

and the child schema (securities.json):

{
    "$schema": "http://json-schema.org/draft-04/schema#",
    "type": "object",
    "additionalProperties": false,
    "required": [
        "securities"
    ],
    "properties": {
        "securities": {
            "$id": "#/properties/securities",
            "type": "array",
            "additionalProperties": false,
            "items": {
                "$id": "/properties/securities/items",
                "anyOf": [
                    {
                        "$id": "#/properties/securities/items/anyOf/0",
                        "type": "object",
                        "additionalItems": false,
                        "additionalProperties": false,
                        "required": [
                            "kind",
                            "comment"
                        ],
                        "properties": {
                            "comment": {
                                "type": "string",
                                "$id": "#/properties/securities/items/anyOf/0/properties/comment"
                            },
                            "kind": {
                                "type": "string",
                                "$id": "#/properties/securities/items/anyOf/0/properties/kind"
                            }
                        }
                    }
                ]
            }
        }
    }
}

What I tested

I tested several syntaxe for $ref:

#/schemas/securities.json

./schemas/securities.json

/schemas/securities.json

....

I also tried to set the schema in the repository of test.ps1

I checked that this is the securities section that don't work

Thank you

I edit the question to leave what worked for me:

Change storages.json like this:

  "properties": {
                "securities": {
                    "$ref": "securities1.json#/securities"
                },
                "name": {
                    "type": "string"
                },
                "comment": {
                    "type": "string"
                }
            }

Change securities.json as:

{
    "securities": {
        "type": "array",
        "items": {
            "type": "object",
            "additionalProperties": false,
            "required": [
                "kind",
                "comment"
            ],
            "properties": {
                "comment": {
                    "type": "string"
                },
                "kind": {
                    "type": "string"
                }
            }
        }
    }
}

And of course I applied all changed suggested in the post

json-schema-validator jsonschema powershell json
2 Answers

It appears that the powershell cmdlet is powered by NJsonSchema, which at this stage doesn't support JSON Schema draft 2020-12.

There are several issues I see.

storages.json

  1. "$schema": "https://json-schema.org/draft/2020-12/schema" declares this is a draft 2020-12 schema. As your schema doesn't use any 2020-12 features, I'd suggest using draft 7 as it'll definitely be supported by NJsonSchema.
  2. Your schema is declaring itself to be the meta-schema with "$id": "https://json-schema.org/draft/2020-12/schema". The meta-schema is a special schema that validates other schemas. What you probably want here is just storages.json, or even better, a full URI like https://examp.le/schemas/storages.json. It's just an identifier though; it doesn't need to be downloadable.
  3. Remove the internal $ids. They're only specifying relative location and not providing any more detail. This kind of thing is generally calculated at runtime.
  4. Your $ref is wrong. #/schemas/securities.json is going to try to search for this location inside the current schema. You need a full URI here, and you'll want to declare that same URI as $id in securities.json as well. This may be what is producing the error.
  5. At #/properties/storages, you have "type": "array" and "additionalProperties": false. Maybe you meant additionalItems? additionalProperties only works on objects. (I also see this in securities.json at #/properties/securities.)
  6. Your use of items is an array. This will only validate the first item. I think you're wanting to validate all the items. If so, just use the schema as the value for items; don't wrap it in an array. (also seen in securities.json)

securities.json

  1. This schema uses draft 4, which is quite old and a bit incompatible with later drafts. Specifically, I see it's using $id in several places, which replaced draft 4's id in draft 6. Since draft 4 doesn't recognize $id, it'll probably ignore them. Moreover, $ref-ing between drafts isn't something that's required (or perhaps even addressed) by the specification. (I added some tests to the test suite around this only about a week ago.) As with storages.json I'd suggest using draft 7 here.
  2. As mentioned above, you'll want to add an $id to the root so that the $ref in storages.json can identify this schema properly.
  3. As with storages.json, remove the interal $ids; they're not providing any additional function.
  4. You use an anyOf but only declare a single schema. You don't need this. Just move the keywords in that subschema up to where the allOf is. 
    {
  "type": "object",
  "allOf": [ { ... } ]
}

// becomes

{
  "type": "object",
  ...
}

Sorry this sounds like a pile-on. I realize you might be new with JSON Schema. The learning curve can be pretty steep.

Instead of the documentation provided by MS, I'd use Understanding JSON Schema for how to write schemas. Use the MS docs only for how to use the cmdlet.

user_8787010

Just to add one point to the excellent answer above: the array form of items is not valid in 2020-12 anyway - it was replaced with prefixItems.

But the advice to use draft-07 throughout is the right advice, as is the advice to use the schema form of items anyway.

user_158454640
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