Template Expression to AST (tentoast)

Experimental package, inspired by unified, for creating custom (abstract) syntax trees using javascript template strings.

About the Trees

Just like a unist, nodes are objects containing a string type field and optionally a children array (all "parent" nodes should have it set, even if it's empty). Nodes should use the value field if they have one and should not use the data field.

Unlike unists though, the tree roots are simply arrays, making it easier to merge them together at the same level without losing any potential associated fields.

Usage

Import the package and create an instance, optionally providing configuration:

import tentoast from 'tentoast'

const ttt = tentoast({
  // Defaults:
  converter: (val) => val, // Should return an array of nodes/ values, can return a single node/ non-array value.
  noSmartText: false,
  providers: {
    s: sectionProvider
  }
})

The returned function can then be used as a tag for template strings:

const tree = ttt`This is some ${'text'}. And here are some ${{type: 'strong', children: [{type: 'text', value: 'nodes'}]}}${{type: 'text', value: '!'}}`

The function runs all the template values through converter, merges the results together, and then converts any non-nodes to text nodes with a value of String(value). Finally, any neighboring text nodes are merged together and empty ones are removed (assuming noSmartText isn't truthy). The example above would return (with defaults):

[
  {
    "type": "text",
    "value": "This is some text. And here are some "
  },
  {
    "type": "strong",
    "children": [
      {
        "type": "text",
        "value": "nodes"
      }
    ]
  },
  {
    "type": "text",
    "value": "!"
  }
]

Node Interaction Providers

Tentoast also provides a nice way to expose other functions that interact with nodes but rely on tentoast functionality via the providers option. These should be functions that consume a tentoast instance and options object and return a value (generally a function) to be exposed on the instance under the same key as their provider from options. If you want to minimize typing while using these, you can always add a bit of boilerplate:

const {s, ps, ...} = ttt

These are the defaults (providers are also exported from the package), you can add/ override them with your own:

Sections (s: sectionProvider)

This produces section nodes composed of one section-header and one section-body children. The initial call passes the parameters to the tentoast instace to get the header children and returns a function that consumes the body arguments to produce the full section node in an array. For example:

const tree = 
ttt.s`This is a Section Header``\
This is the body!
It would usually have many lines, or possibly other ${{type: 'text', value: 'things.'}}`

produces:

[
  {
    "type": "section",
    "children": [
      {
        "type": "section-header",
        "children": [
          {
            "type": "text",
            "value": "This is a Section Header"
          }
        ]
      },
      {
        "type": "section-body",
        "children": [
          {
            "type": "text",
            "value": "This is the body!\nIt would usually have many lines, or possibly other things."
          }
        ]
      }
    ]
  }
]

For reference on creating your own interaction providers, here's the whole source for sectionProvider:

function sectionProvider(ttt, options) {
  return function(headerStrings, ...headerValues) {
    return function(bodyStrings, ...bodyValues) {
      return {
        "type": "section" ,
        "children": [
          {
            "type": "section-header",
            "children": ttt(headerStrings, ...headerValues)
          },
          {
            "type": "section-body",
            "children": ttt(bodyStrings, ...bodyValues)
          }
        ]
      }
    }
  }
}

Helper Functions

The tentoast package also exports a few helper functions that are used internally:

isNode(value)

Determines if a value is a node.

massageToArray(value)

Returns value if it's an array, otherwise returns [ value ].