Allow schema to still validate even if AJV fails

[Alphadelta14]

I was trying to track down yet another StackOverflow error in AJV that wasn't fixed in #1260. But honestly, I would like to see this code be slightly more resilient to AJV since having a schema that isn't valid against the metaschema still is possible to do a lot of checking that is very valuable.

What does this PR do?

This captures a nasty RangeError (Maximum call stack size exceeded) that is possible in AJV when you have multiple local $ref's recursively referencing each other (while their $id has a full uri).
In that case, it just warns to the console and allows normal validation to continue. (note that having a schema resolution error causes the file to FULL STOP processing and no more validation hints are given).

What issues does this PR fix or reference?

If a file has a relative # yaml-language-server: $schema=./... and that schema has a $ref: "./path-b.schema.yaml" (with a full $id: "https://example.com/my/path-b.yaml") which may refer to a $ref: "./path-c.schema.yaml" (with a full $id: "https://example.com/my/path-c.yaml") that may refer back to path-a, AJV can end up being confused and cause infinite recursion.

Is it tested? How?

Multi-step recursion tested in vscode-yaml:

Details

cat > example.yaml <<'EXAMPLE'
# yaml-language-server: \$schema=./example.schema.yaml
# Here is my simple file
description: my top level description
blocks:
- text: some content lives here
EXAMPLE

cat > example.schema.yaml <<'EXSCHEMA'
# yaml-language-server: $schema=https://json-schema.org/draft/2020-12/schema
$schema: "https://json-schema.org/draft/2020-12/schema"
$id: "https://example.com/my/example.schema.yaml"
title: "My Example Schema"
description: "The root schema"
type: object
allOf:
  - $ref: "./top.schema.yaml"
EXSCHEMA

cat > top.schema.yaml <<'TOP'
# yaml-language-server: $schema=https://json-schema.org/draft/2020-12/schema
$schema: "https://json-schema.org/draft/2020-12/schema"
$id: "https://example.com/my/example.schema.yaml"
title: "Top-level items of the schema"
description: "Top-level items of the schema"
type: object
properties:
  description:
    type: string
    description: Human readable summary
  blocks:
    description: List of blocks
    type: array
    items:
      oneOf:
        - $ref: "./text.schema.yaml"
        - $ref: "./numerical.schema.yaml"
        - $ref: "./mixed.schema.yaml"
unevaluatedProperties: false
TOP

cat > text.schema.yaml <<'TEXT'
# yaml-language-server: $schema=https://json-schema.org/draft/2020-12/schema
$schema: "https://json-schema.org/draft/2020-12/schema"
$id: "https://example.com/my/text.schema.yaml"
title: "Text items"
description: "Text item blocks"
type: object
properties:
  text:
    type: string
required: [text]
additionalProperties: false
TEXT

cat > numerical.schema.yaml <<'NUM'
# yaml-language-server: $schema=https://json-schema.org/draft/2020-12/schema
$schema: "https://json-schema.org/draft/2020-12/schema"
$id: "https://example.com/my/numerical.schema.yaml"
title: "Numerical items"
description: "Numerical item blocks"
type: object
properties:
  number:
    type: number
  complex:
    type: string
additionalProperties: false
NUM

cat > mixed.schema.yaml <<'MIXED'
# yaml-language-server: $schema=https://json-schema.org/draft/2020-12/schema
$schema: "https://json-schema.org/draft/2020-12/schema"
$id: "https://example.com/my/numerical.schema.yaml"
title: "Mixed items"
description: "Mixed item blocks"
type: object
properties:
  multi:
    $ref: "#/$defs/multiItems"
required: [multi]
additionalProperties: false

$defs:
  multiItems:
    type: array
    items:
      oneOf:
        - $ref: "./text.schema.yaml"
        - $ref: "./numerical.schema.yaml"
        - $ref: "#/$defs/multiItems"
MIXED

So now you open up example.yaml and this particular case works well the first time. But if you comment out - $ref: "./text.schema.yaml", check that example.yaml goes to invalid, then uncomment it, it would have stopped working, but with my change, it now continues to work with a logged:

Schema '/path/to/test-schemas/example.schema.yaml' could not be fully validated: Maximum call stack size exceeded

[datho7561]

It might be better to report this as a warning or error on the text document and provide translations for this message, but I think this is good for now.

[datho7561]

Works well to fix the bug. Thanks, Heather!