yRest Language Support

VS Code extension for yrest — the zero-config YAML-based REST API mock server.

Provides syntax highlighting, hover documentation, autocompletion and diagnostics for db.yml and *.yrest.yml files.

Features

Syntax highlighting

Highlights yrest-specific constructs on top of standard YAML:

Injections are also active in plain .yaml files and inside TypeScript/JavaScript (e.g. test setup files using yrest).

Hover documentation

Hover any yrest reserved key, relation type, alias or cardinality to see inline docs with a description and a minimal YAML example.

Covered tokens: _rel, _routes, _schema, all _rel keys (_type, _target, _foreignKey, _otherKey, _primaryKey, _through, _car-direct, _car-inverse, _nested), all _routes keys (_method, _path, _handler, _response, _scenarios, _otherwise, _delay, _error, _errorBody), response block keys (_status, _body, _headers), _when, relation types and aliases (many2one, m2o, one2one, o2o, many2many, m2m), cardinalities and +nested.

Hover and diagnostics also work inside TypeScript/JavaScript tagged template literals:

const db = yrest`
  users:
    - { id: 1, name: Ana }

  posts:
    - { id: 1, title: Hello, userId: 1 }

  _rel:
    posts:
      userId: users   # hover, autocomplete and validation work here
`;

Autocompletion

Context-aware completions trigger on Space and : — no Ctrl+Space needed:

Diagnostics

Validates on every save and keystroke:

• YAML syntax errors — with exact position from the yaml parser
• _rel entity names must match a root collection in the same file
• Relation targets (shorthand string or _target) must match a root collection
• _type must be many2one, one2one, many2many (or aliases m2o, o2o, m2m)
• _car-direct / _car-inverse must use 0..1, 1..1, 1..n or 0..n
• DSL strings are validated against the full compact format regex
• _routes bare keys — flags keys written without _ prefix inside _routes entries (method → use _method, path → use _path, status → use _status, etc.) at three nesting levels: route entry, _response/_otherwise block, and _scenarios entries

Supported files

The extension activates automatically for:

For any other filename, add to your VS Code settings:

"files.associations": { "mock.yml": "yrest" }

Syntax quick reference

Shorthand relation (level 1)

users:
  - { id: 1, name: Ana }

posts:
  - { id: 1, title: Hello world, userId: 1 }

_rel:
  posts:
    userId: users

Compact DSL (level 2 — type + cardinality)

users:
  - { id: 1, name: Ana }

tags:
  - { id: 1, name: typescript }

post_tags:
  - { postId: 1, tagId: 1 }

posts:
  - { id: 1, title: Hello world, userId: 1 }

_rel:
  posts:
    userId: "m2o:users[1..1->0..n]"
    tags: "m2m:tags@post_tags(postId,tagId)[0..n->0..n]+nested"

Verbose form (full control)

bookings:
  - { id: 1, date: "2026-01-15" }

payments:
  - { id: 1, bookingId: 1, amount: 150 }

_rel:
  payments:
    bookingId:
      _type: many2one
      _target: bookings
      _foreignKey: bookingId
      _car-direct: 1..1
      _car-inverse: 0..n
      _nested: true

Custom routes with scenarios and template variables

_routes:
  - _method: POST
    _path: /auth/login
    _scenarios:
      - _when:
          body.role: admin
        _response:
          _status: 200
          _body:
            token: "{{uuid}}"
            generatedAt: "{{now}}"
    _otherwise:
      _status: 401
      _body: { error: Invalid credentials }
    _delay: 300

  - _method: GET
    _path: /orders/:id/receipt
    _response:
      _status: 200
      _body:
        orderId: "{{params.id}}"
        issuedAt: "{{now}}"

Requirements

• VS Code ^1.90.0
• A db.yml file or any *.yrest.yml file following the yrest YAML format

No additional runtime dependencies are needed. The extension bundles its own yaml parser.

Roadmap

License

MIT — aggiovato