Guidance: Nested indexer [] within flow sequence

[evilrobot-01]

Is there any way to easily extend the parsing of flow sequence entries to allow values which contain the indexer [] characters? The requirement is simply to provide a string-type value in yaml, which is parsed in and ultimately passed to https://lodash.com/docs/#get to resolve a value within a particular object.

import YAML from 'yaml'

// Works when enclosed in quotes
YAML.parse('args: [ "$variable[0]", 100 ]')

// Required syntax
YAML.parse('args: [ $variable[0], 100 ]')

The second parse YAML.parse call results in:

YAMLParseError: Missing , or : between flow sequence items at line 1, column 18:

args: [ $variable[0], 100 ]
                 ^

[eemeli]

Short answer: not really, because the latter "required syntax" is not valid YAML.

Within flow collections, plain scalars cannot contain [] or {} characters: https://yaml.org/spec/1.2.2/#733-plain-style

They're fine is a block collection though:

YAML.parse(`
args:
  - $variable[0]
  - 100
`)
// { args: [ '$variable[0]', 100 ] }

[evilrobot-01]

Thanks for the reply! I had figured out that the block collection works but the flow syntax is preferred. Is there perhaps a way for me to add support somehow to meet a requirement, even if not technically valid yaml? Perhaps a custom tag could handle an entry when starting with $ or handle processing of args? 🙂

…

________________________________ From: Eemeli Aro ***@***.***> Sent: Saturday, November 12, 2022 12:48:30 AM To: eemeli/yaml ***@***.***> Cc: Frank Bell ***@***.***>; Author ***@***.***> Subject: Re: [eemeli/yaml] Guidance: Nested indexer [] within flow sequence (Discussion #423) Short answer: not really, because the latter "required syntax" is not valid YAML. Within flow collections, plain scalars cannot contain [] or {} characters: https://yaml.org/spec/1.2.2/#733-plain-style They're fine is a block collection though: YAML.parse(` args: - $variable[0] - 100 `) // { args: [ '$variable[0]', 100 ] } — Reply to this email directly, view it on GitHub<#423 (comment)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/AORABCW7JSYSTTU32VUONLTWH3SN5ANCNFSM6AAAAAAR5XZRUQ>. You are receiving this because you authored the thread.Message ID: ***@***.***>

[eemeli]

Not really, because this already happens in the lexer, and your input is ambiguous. Consider what happens here:

args: [ $variable[0], 100 ]
                   ^

If [] were allowed in scalar flow values, how could we know at that point whether the outer [...] collection was being closed or not?

[evilrobot-01]

I see, thank you. It seems the only way then would be if the lexer was somehow tolerant of nested [ ], perhaps by using a stack to track corresponding opening and closing brackets, but as you point out is invalid yaml.

…

________________________________ From: Eemeli Aro ***@***.***> Sent: Saturday, November 12, 2022 12:35:49 PM To: eemeli/yaml ***@***.***> Cc: Frank Bell ***@***.***>; Author ***@***.***> Subject: Re: [eemeli/yaml] Guidance: Nested indexer [] within flow sequence (Discussion #423) Not really, because this already happens in the lexer, and your input is ambiguous. Consider what happens here: args: [ $variable[0], 100 ] ^ If [] were allowed in scalar flow values, how could we know at that point whether the outer [...] collection was being closed or not? — Reply to this email directly, view it on GitHub<#423 (reply in thread)>, or unsubscribe<https://github.com/notifications/unsubscribe-auth/AORABCS3JK7PGNFWR2W5YODWH6FKLANCNFSM6AAAAAAR5XZRUQ>. You are receiving this because you authored the thread.Message ID: ***@***.***>