Interpolation of {{value}} is incorrect when using `field: "@key"`

[egrimstad]

Describe the bug
When using field: @key in order to lint the keys in an object (as documented here: https://docs.stoplight.io/docs/spectral/d3482ff0ccae9-rules#then), for example for linting allowed response codes, the resulting error is bugged. It prints an Object {} as the interpolation for {{value}}, and the range is not what I expect.

To Reproduce

I added the following test to packages/core/src/__tests__/linter.test.ts:

Test

  test('should work with @key', async () => {
    const message = '404 must be equal to one of the allowed values: "200", "400"';

    spectral.setRuleset({
      rules: {
        rule1: {
          given: '$.responses',
          then: {
            field: '@key',
            function: enumeration,
            functionOptions: {
              values: ['200', '400'],
            },
          },
        },
      },
    });

    const document = new Document(
      `responses:
  "200":
    description: "ok"
  "404":
    description: "not found"`,
      Parsers.Yaml,
    );

    const result = await spectral.run(document);

    expect(result).toEqual([
      expect.objectContaining({
        code: 'rule1',
        message,
        severity: DiagnosticSeverity.Warning,
        path: ['responses', '404'],
        range: {
          end: {
            line: 7,
            character: 3,
          },
          start: {
            character: 3,
            line: 3,
          },
        },
      }),
    ]);
  });

Test results

    expect(received).toEqual(expected) // deep equality

    - Expected  - 5
    + Received  + 6

    @@ -1,20 +1,21 @@
      Array [
    -   ObjectContaining {
    +   Object {
          "code": "rule1",
    -     "message": "404 must be equal to one of the allowed values: \"200\", \"400\"",
    +     "documentationUrl": undefined,
    +     "message": "Object{} must be equal to one of the allowed values: \"200\", \"400\"",
          "path": Array [
            "responses",
            "404",
          ],
          "range": Object {
            "end": Object {
    -         "character": 7,
    -         "line": 3,
    +         "character": 28,
    +         "line": 4,
            },
            "start": Object {
    -         "character": 3,
    +         "character": 8,
              "line": 3,
            },
          },
          "severity": 1,
        },

So there are two bugs:

1. I expected message to interpolate the relevant key "400", but it just gets evaluated to Object{}.
2. I expected the range to only enclose the key, but it seems to refer to the entire block, or something. This is especially confusing for the github-actions formatter.

Environment (remove any that are not applicable):

• Library version: Tested on develop, but also observed on 6.15.0.
• OS: Linux

Additional info:
The same bug also occurs when using the JSONPath syntax: $.responses.*~ for given and no field, which is part of the "jsonpath-plus" syntax as I understand it, and not standard.

I tried to look at the implementation to see if I could easily fix it, but it did not seem to be that straightforward. But I suppose it needs to be fixed in lintNode.ts#processTargetResults, maybe?