Re: [RFC PATCH 2/3] trace2: Add a JSON schema for trace2 events

> Define a JSON schema[1] that can be used to validate trace2 event
> objects. This can be used to add regression tests to verify that the
> event output format does not change unexpectedly.
> 
> Two versions of the schema are provided:
> * event_schema.json is more permissive. It verifies that all expected
>    fields are present in each trace event, but it allows traces to have
>    unexpected additional fields. This allows the schema to be specified
>    more concisely by factoring out the common fields into a reusable
>    sub-schema.
> * strict_schema.json is more restrictive. It verifies that all expected
>    fields are present and no unexpected fields are present in each trace
>    event. Due to this additional restriction, the common fields cannot be
>    factored out into a re-usable subschema (at least as-of draft-07) [2],
>    and must be repeated for each event definition.
> 

> +
> +		"data-json_event": {
> +			"allOf": [
> +				{ "$ref": "#/definitions/event_common_fields" },
> +				{
> +					"properties": {
> +						"event": { "const": "data-json" },
> +						"repo": { "type": "integer" },
> +						"t_abs": { "type": "number" },
> +						"t_rel": { "type": "number" },
> +						"nesting": { "type": "integer" },
> +						"category": { "type": "string" },
> +						"key": { "type": "string" },
> +						"value": true
> +					},
> +					"required": [
> +						"event", "t_abs", "t_rel", "nesting", "category", "key",
> +						"value"
> +					]
> +				}
> +			]
> +		}
> +	},