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Contributing to z-schema

z-schema is a JSON Schema validator (draft-04 through draft-2020-12) written in TypeScript. This skill covers the development workflow, codebase navigation, and common contribution tasks.

Repository setup

git clone --recursive https://github.com/zaggino/z-schema.git
cd z-schema
npm install

If already cloned without --recursive (needed for the json-schema-spec/ submodule):

git submodule update --init --recursive

Quality checks

Run all checks before pushing:

npm run lint:check      # ESLint
npm run format:check    # Prettier
npm run build           # TypeScript + Rollup
npm run build:tests     # Type-check tests
npm test                # Vitest (node + browser)

Pre-commit hooks auto-run lint + format on staged files. Pre-push hooks run build + type-check.

Codebase map

src/
  index.ts              → Public API (all exports)
  z-schema.ts           → Factory + ZSchema/ZSchemaSafe/ZSchemaAsync/ZSchemaAsyncSafe
  z-schema-base.ts      → Core validation orchestration
  schema-compiler.ts    → $ref resolution, id collection, schema compilation
  schema-validator.ts   → Schema-level validation against meta-schemas
  json-validation.ts    → Validation orchestration (validate, recurse*, collectEvaluated)
  validation/            → Keyword validators split by category
    shared.ts            → Shared types (JsonValidatorFn), vocab helpers, caching utilities
    type.ts              → type, enum, const validators
    numeric.ts           → multipleOf, minimum, maximum, exclusiveMin/Max validators
    string.ts            → minLength, maxLength, pattern, format, content* validators
    array.ts             → items, prefixItems, contains, min/maxItems, uniqueItems validators
    object.ts            → properties, patternProperties, additionalProperties, required, etc.
    combinators.ts       → allOf, anyOf, oneOf, not, if/then/else validators
    ref.ts               → $dynamicRef/$recursiveRef resolution helpers
  schema-cache.ts       → Schema caching by URI/id
  errors.ts             → Error codes (Errors object) + ValidateError class
  format-validators.ts  → Built-in + custom format validators
  report.ts             → Error accumulation (Report, SchemaErrorDetail)
  json-schema.ts        → Common JSON Schema definitions + helpers
  json-schema-versions.ts → Draft-specific type unions + version mappings
  z-schema-options.ts   → Options interface + defaults + normalizeOptions
  z-schema-reader.ts    → Schema reader type
  z-schema-versions.ts  → Registers bundled meta-schemas into cache
  utils/                → Pure utilities (array, clone, json, uri, etc.)
  schemas/              → Bundled meta-schemas (generated at build time)

Validation pipeline

1. Schema compilation (schema-compiler.ts): resolves $ref, collects id/$id, registers in cache
2. Schema validation (schema-validator.ts): validates schema against its meta-schema
3. JSON validation (json-validation.ts + validation/*.ts): validates data against compiled schema — type checks, constraints, combiners (allOf/anyOf/oneOf/), tracking, format checks. Keyword validators are split into modules under by category

Common tasks

Adding a new error code

1. Add the error to the Errors object in src/errors.ts:

   MY_NEW_ERROR: 'Description with {0} placeholder',

2. Use report.addError('MY_NEW_ERROR', [param]) in the validation logic.

3. Write tests verifying the error code is produced.

Adding a new format validator

1. Write the validator function in src/format-validators.ts:

   const myFormatValidator: FormatValidatorFn = (input: unknown) => { if (typeof input !== 'string') return true; return /^pattern$/.test(input); };

2. Register it in the inbuiltValidators record:

   const inbuiltValidators = { // ...existing 'my-format': myFormatValidator, };

3. Add tests in test/spec/format-validators.spec.ts.

Adding a new option

1. Add the option to ZSchemaOptions in src/z-schema-options.ts.
2. Add a default value in defaultOptions.
3. If the option is part of strictMode, add it to the strictMode block in normalizeOptions.
4. Document it in docs/options.md.
5. Write tests.

Implementing a new JSON Schema keyword

1. Add validation logic in the appropriate src/validation/*.ts module (e.g., array.ts for array keywords, object.ts for object keywords, combinators.ts for applicators) or src/schema-validator.ts (for schema-level validation). The orchestration layer in src/json-validation.ts calls into these modules.

2. Guard with a draft version check if the keyword is draft-specific.

3. Remove relevant entries from excludedFiles/excludedTests in test/spec/json-schema-test-suite.common.ts.

Modifying existing behavior

1. Find the relevant module using the codebase map above.
2. Make changes following code conventions (see below).
3. Run the full test suite — regressions often appear in other drafts.

Test framework

• Vitest with globals: true.
• Two projects: node and browser (Playwright: Chromium, Firefox, WebKit).
• Tests live in test/spec/.

File naming

Running tests

npm test                                                        # all
npm run test:node                                               # node only
npx vitest run --silent=false --project node -t "draft4/type"   # single test
npm run test:coverage                                           # coverage

Test pattern

import { ZSchema } from '../../src/z-schema.ts';

describe('Feature Name', () => {
  it('should accept valid data', () => {
    const validator = ZSchema.create();
    expect(validator.validate('hello', { type: 'string' })).toBe(true);
  });

  it('should reject invalid data', () => {
    const validator = ZSchema.create();
    const { valid, err } = validator.validateSafe(42, { type: 'string' });
    expect(valid).toBe(false);
    expect(err?.details?.[0]?.code).toBe('INVALID_TYPE');
  });
});

JSON Schema Test Suite

Official test cases loaded via test/spec/json-schema-test-suite.common.ts. To enable tests for a newly implemented feature, remove entries from excludedFiles / excludedTests and confirm they pass.

Code conventions

• TypeScript strict: true, ESM with .js import extensions in src/
• .ts import extensions in test/ (via allowImportingTsExtensions)
• import type for type-only imports (enforced by ESLint)
• Import order: type-only → side-effect → node builtins → packages → relative
• Prettier: 120 char width, single quotes, trailing commas (es5), semicolons
• Classes/types: PascalCase — functions/variables: camelCase — errors: UPPER_SNAKE_CASE

PR checklist

- [ ] Branch from `main`
- [ ] Changes follow code conventions
- [ ] npm run lint:check passes
- [ ] npm run format:check passes
- [ ] npm run build passes
- [ ] npm run build:tests passes
- [ ] npm test passes (node + browser)
- [ ] New public types/values exported through src/index.ts
- [ ] New features have tests
- [ ] docs/ updated if public API changed
- [ ] JSON Schema Test Suite entries un-excluded if applicable

Reference files

• references/architecture-details.md — Full module dependency diagram, factory pattern, build outputs, and internal types

Weekly Installs

52

Repository

zaggino/z-schema

GitHub Stars

342

First Seen

Feb 27, 2026

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