Camel case function does not accommodate uppercase single letter words at the end of a property name

[SensibleWood]

Describe the bug

When using the built-in function casing with the argument camel Spectral raises an error when it encounters a single, uppercase word at the end of the camel-cased string. For example:

• coordinateX
• scaleY

To Reproduce

Using the following OpenAPI document:

openapi: 3.0.3
info:
  title: Spectral evidence
  description: Noddy API to use in Spectral ticket
  version: 0.0.1
paths:
  /:
    get:
      responses:
        "200":
          description: OK
          content:
            application/json:
              schema:
                type: object
                properties:
                  coordinateX:
                    type: string
                  scaleY:
                    type: string

And the following ruleset:

extends: spectral:oas
rules:
  operation-operationId: off
  oas3-api-servers: off
  info-contact: off
  operation-description: off
  operation-tags: off
  camel-case-enforcement:
    message: "Property is not named in lower camel case: {{path}}, {{property}}"
    severity: error
    given: $..[?(@.type === 'object' && @.properties)].properties.*~
    then:
      function: casing
      functionOptions:
        type: camel

Executing Spectral gives the following output:

➜  spectral-evidence spectral lint --ruleset ./evidence.yaml openapi.yaml
OpenAPI 3.x detected

/Users/chris/Documents/git/github/spectral-evidence/openapi.yaml
 22:31  error  camel-case-enforcement  Property is not named in lower camel case: #/paths/~1/get/responses/200/content/application~1json/schema/properties/coordinateX, coordinateX  paths./.get.responses[200].content.application/json.schema.properties.coordinateX
 24:26  error  camel-case-enforcement  Property is not named in lower camel case: #/paths/~1/get/responses/200/content/application~1json/schema/properties/scaleY, scaleY            paths./.get.responses[200].content.application/json.schema.properties.scaleY

✖ 2 problems (2 errors, 0 warnings, 0 infos, 0 hints)

➜  spectral-evidence

I think this is the root of the issue: here - the regex should allow end of line I guess i.e. ([a-z{__DIGITS__}]+|$)

Expected behavior

The ruleset should not raise the camel-case-enforcement errors as semantically the property names are correct.

Environment:

• Node version: 12.20.0
• Library version: 5.7.2
• OS: macOs Catalina 10.15.7