Simple template

This is a templating language and engine for rendering Hypertemplates.

Hypertemplate is a template that:

• is logicless
• can traverse arbitrary JSON and render it
• can contain data that can be extracted and exposed to the application layer
• can be parsed and the input structure inferred

Example:

{{ metadata(JSON) }}
    {
        "template": "data/table.html" 
        "actions": [
            { "get": "query/get_sales.sql", "name": "Sales" }
            { "get": "query/get_purchases.sql", "name": "Purchases" }
        ]
    }
{{ end }}

SELECT
    [[ for key, col in columns ]]
        ${ col } --${ key }
    [[ end ]]
FROM ${ table_name }

We can infer from this example that the accepted schema is:

{
  "table_name": string,
  "columns": []string | map<key, value>
}

If we then pass an object with this structure, it will be correctly rendered by the engine. Notice that the columns can be an array of objects, or an hashmap/object.

• if it is array, then the key will be the index if that array
• if it is object, then the key will be the key to look in the object

Then we can traverse an object like this:

{
  "table_name": "countries",
  "columns": {
    "Country Name": "country_name",
    "Country Code":  "country_code",
    "Id": "id"
  }
}

Or like this:

{
  "table_name": "countries",
  "columns": ["country_name", "country_code", "id"]
}

Also there is the metadata(JSON) that exposes some data that can be relevant to this template to my application. I can use this data to find another template (this time HTML for example) and use the actions as a part of an input passed to it, along with the result of the query.

Also you can specify any format for the metadata that supports nesting arrays and hashmaps/objects/dictionaries, as long as the engine supports it.

The testing EBNF spec is in hypertempl.ebnf. The example templates are in the examples folder.

TODO

• Implementation in Rust - winnow
  • working parser
  • testing including examples
  • input inference
  • rendering
  • error handling - how to handle when someone creates an incorrect template
  • updating specification
• Implementation in Treesitter grammar