Handlespy

Handlespy is a simple Node.js library to inspect Handlebars templates for required variables. This is accomplished by iterating over the AST produced by the handlebars parser.

It also provides a helper to verify that a payload contains all required variables.

Installation

npm install handlespy
# or
yarn add handlespy

Usage

const { getRequiredVariables, getMissingVariables } = require('handlespy')

const template = `
A simple handlebar template containing a variable ({{someVariable}}) and a loop :

{{#each someLoop}}
- {{someProperty}}
{{/each}}
`

const requiredVariables = getRequiredVariables(template)
/*
[
  'someVariable',
  { loopVariable: 'someLoop', properties: [ 'someProperty' ] }
]
*/

const completePayload = {
  someVariable: 'Test',
  someLoop: [{ someProperty: 'Another test' }]
}

const incompletePayload = {
  // missing someVariable,
  someLoop: [
    { someProperty: 'Another test' },
    { unsupportedProperty: 'Final test' }, // someLoop[1] is missing the required someProperty
  ]
}

const test1 = getMissingVariables(completePayload, requiredVariables)
// []
const test2 = getMissingVariables(incompletePayload, requiredVariables)
/*
[ 'someVariable', 'someLoop[1].someProperty' ]
*/

API

getRequiredVariables

• expects : (String) A handlebars template
• returns : (Array) The required variables

Each item in the returned array can either be a string (denoting a simple variable), or an object (denoting an each loop) containing the following :

• loopVariable (String) : the name of the variable
• properties (Array) : the required properties on the looped variable
  • loops can be nested, so properties can contain another object with loopVariable and properties
  • if only this is used in the loop, properties is an empty array

getMissingVariables

• expects :
  • (Object) The payload to check
  • One of the following :
    • (String) A handlebars template
    • (Array) or a required variables specification as returned by getRequiredVariables
• returns : (Array) The missing variables

Each item in the returned array is a string, which can be of either of the following formats :

• missingVariable : variable is missing in the payload
• missingArray[] : a variable, which is used in an each loop, is present in the payload but isn't an array
• item[2].missingProperty : an item in an array is missing a required properties

Contributing

If you find any bug or missing functionality in handlespy, don't hesitate to create an issue ! If you can provide a PR with a failing test, this would help greatly in solving the issue :)

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