JSON key can have special character

[brianchu]

Use case

Unfortunately, the JSON data I got from the server has structure and naming like this:

{
"data" : {
"some-key": "some value",
"some-other-key-you-know-can-look-like-this": "value can have t-h-i-s thing too",
"okkey": "ok value"
}
}

When I try to access the JSON via saved context

@{data.some-key} it doesn't work.

For other result without the hyphen "-", it work.

Proposal

• Allow special character.
• I was curious, since they're purely data, why there is a limit of that? Will there be ever a chance of them as variable?
• Given it may be difficult to change public server response, can we do a transformation (if yes, where to add?) of, say, replacing "-" with "_" (which is allowed as stated in your doc). Can that be done via a customized deserializer?

[Tiagoperes]

Hi @brianchu, this is a problem that arrises from the definition of the grammar for Beagle expressions:

Grammar

Below, "`" is used to group symbols and "/" to represent regular expressions. "|", outside a regular expression, means or.

Expression = @{Operation | Value}
Operation = Name(`Params | )`
Name = /\w[\w\d_]*/
Params = `Param,Params` | Param)
Param = Operation | Value
Value = State | Literal
State = /^(?!(true$|false$|null$|'|\d))[a-z|A-Z|_](\w|(\[\d+\])|(\.\w))*$/
Literal = String | Number | true | false | null
String = /^'([^'\\]|(\\.))*'$/
Number = /^\d+$/

Problem

Any accessed property is identified by State in the grammar, and just like most programming languages, you can't have symbols like space, plus, minus (hyphen), space, brackets, etc. This is so we don't mix a variable access with some other syntax element.

In truth, considering we don't currently use the minus operator, we could support hyphen on keys without any issue. But, it wouldn't solve the other scenarios and we'd be preventing us from extending the language to include infix operators in the future.

We are currently developing some new server driven libraries to work with SwiftUI and Compose. In these new libraries we'll extend the grammar to include new functionalities, one of them is dynamic state access, which will solve this issue; example: "myState['my-key $*-with-special-characters']". Unfortunately, we can't bring this to Beagle yet, considering it would require a very high amount of work and we have other priorities (like the aforementioned libs).

A solution that can be used now

As you said, one solution is to do a transformation before accessing it. This can be done via a custom operation.

First, you should create a custom operation in the frontend. I'm gonna give you an example on React:

function sanitizeKey(key: string): string {
  // replaces both hyphens and spaces with underscores
  return key.replace(/[\s\-]/g, '_')
}
  
function sanitize(data?: any): any {
  if (Array.isArray(data)) {
    return data.map(sanitize)
  }
  if (data != null && typeof data == 'object') {
    let result: object = {}
    Object.keys(data).forEach(key => {
      result[sanitizeKey(key)] = sanitize(data[key])
    })
    return result
  }
  return data
}

let beagle = createBeagleUIService({
  baseUrl: '',
  customOperations: {
    sanitize,
  },
  components: {},
})

Then, in the backend, assuming you're setting a Beagle Context from a sendRequest action, you should use the new operation before setting the context (I'll call it result in the next example):

{
  "_beagleAction_": "beagle:sendRequest",
  "url": "your_url",
  "onSuccess": [{
    "_beagleAction_": "beagle:setContext",
    "contextId": "result",
    "value": "@{sanitize(onSuccess.data)}"
  }]
}

Another solution that can be used now

You can also create a custom operation called get:

function get(data: any, key: string): any {
  return (data != null && typeof data == 'object') ? data[key] : null
}

let beagle = createBeagleUIService({
  baseUrl: '',
  customOperations: {
    get,
  },
  components: {},
})

Then, in the backend, you can access the data with this custom operation (I'll assume your context is called result):

{
  "_beagleComponent_": "beagle:text",
  "text": "get(result, 'some-other-key-you-know-can-look-like-this')",
}

The only problem with this approach is that, if your data is deeply nested, you'll have a lot of nested calls to get.

[Tiagoperes]

I'm closing this issue due to inactivity. Please, fell free to reopen this if necessary.