check-jsonschema

A pre-commit hook for checking files against a JSONSchema, built using the python jsonschema package. The schema may be specified as a local or remote (HTTP or HTTPS) file.

Remote files are automatically downloaded and cached if possible.

Supported Hooks

The most generic hook is this one:

• check-jsonschema: Validate JSON or YAML files against a jsonschema on disk or fetched via HTTP(S)

• check-metaschema: Validate JSON Schema files against their matching metaschema, as specified in their "$schema" key

The following hooks check specific files against various schemas provided by SchemaStore and other sources:

• check-azure-pipelines: Validate Azure Pipelines config against the schema provided by Microsoft

• check-bamboo-spec: Validate Bamboo Specs against the schema provided by SchemaStore

• check-dependabot: Validate Dependabot Config (v2) against the schema provided by SchemaStore

• check-github-actions: Validate GitHub Actions against the schema provided by SchemaStore

• check-github-workflows: Validate GitHub Workflows against the schema provided by SchemaStore

• check-gitlab-ci: Validate GitLab CI config against the schema provided by SchemaStore

• check-readthedocs: Validate ReadTheDocs config against the schema provided by ReadTheDocs

• check-renovate: Validate Renovate config against the schema provided by Renovate (does not support renovate config in package.json)

• check-travis: Validate Travis Config against the schema provided by SchemaStore

Example Usage

Validate GitHub Workflows with Schemastore

You can use the schemastore github workflow schema to lint your GitHub workflow files. All you need to add to your .pre-commit-config.yaml is this:

- repo: https://github.com/python-jsonschema/check-jsonschema
  rev: 0.16.1
  hooks:
    - id: check-github-workflows

Applying an arbitrary schema to files

There is a more general hook available for running any jsonschema against a file or set of files. For example, to implement the GitHub workflow check manually, you could do this:

- repo: https://github.com/python-jsonschema/check-jsonschema
  rev: 0.16.1
  hooks:
    - id: check-jsonschema
      name: "Check GitHub Workflows"
      files: ^\.github/workflows/
      types: [yaml]
      args: ["--schemafile", "https://json.schemastore.org/github-workflow"]

And to check with the builtin schema that a GitHub workflow sets timeout-minutes on all jobs:

- repo: https://github.com/python-jsonschema/check-jsonschema
  rev: 0.16.1
  hooks:
    - id: check-jsonschema
      name: "Check GitHub Workflows set timeout-minutes"
      files: ^\.github/workflows/
      types: [yaml]
      args: ["--builtin-schema", "github-workflows-require-timeout"]

Standalone Usage

You can also pip install check-jsonschema to run the tool manually.

For full usage info:

check-jsonschema --help

CLI Options

These options apply both to standalone usage and pre-commit hook usage.

--schemafile

The path or URL for a file containing a schema to use.

This option is required unless --builtin-schema or --check-metaschema is used.

--builtin-schema

The name of a builtin schema from check-jsonschema to use. Use of this option replaces --schemafile, and the two are mutually exclusive.

The following values are valid and refer to vendored copies schemas from SchemaStore and other sources:

• vendor.azure-pipelines
• vendor.bamboo-spec
• vendor.dependabot
• vendor.github-actions
• vendor.github-workflows
• vendor.gitlab-ci
• vendor.readthedocs
• vendor.renovate
• vendor.travis

The following values refer to custom schemas:

• github-workflows-require-timeout -- This schema checks that a GitHub workflow explicitly sets timeout-minutes on all jobs. (The default value for this is 6 hours.)

--check-metaschema

Validate each instancefile as a JSON Schema, using the relevant metaschema defined in "$schema".

This option replaces --schemafile and --builtin-schema, and these options are mutually exclusive.

--default-filetype

The default filetype to assume on instance files when they are detected neither as JSON nor as YAML.

For example, pass --default-filetype yaml to instruct that files which have no extension should be treated as YAML.

By default, this is not set and files without a detected type of JSON or YAML will fail.

--data-transform

--data-transform applies a transformation to instancefiles before they are checked. The following transforms are supported:

• azure-pipelines: "Unpack" compile-time expressions for Azure Pipelines files, skipping them for the purposes of validation. This transformation is based on Microsoft's lanaguage-server for VSCode and how it handles expressions

-v, --verbose

Request more output.

-q, --quiet

Request less output.

-o, --output-format

Use this option to choose how the output is presented. Either as TEXT (the default) or JSON, as in -o JSON.

Downloading and Caching Options

By default, when --schemafile is used to refer to an http:// or https:// location, the schema is downloaded and cached based on the schema's Last-Modified time. The following options control caching behaviors.

--no-cache

Disable caching. Do not cache downloaded schemas.

--cache-filename

The name to use for caching a remote schema.

Defaults to using the last slash-delimited part of the URI.

"format" Validation Options

JSON Schema defines a "format" attribute for string fields but does not require that any validation for formats be applied.

check-jsonschema supports checking several "format"s by default. The following options can be used to control this behavior.

--disable-format

Disable all "format" checks.

Because "format" checking is not done by all JSON Schema tools, it is possible that a file may validate under a schema with a different tool, but fail with check-jsonschema if --disable-format is not set.

--format-regex

Set a mode for handling of the "regex" value for "format". The modes are as follows:

Error Handling Options

--show-all-validation-errors

Deprecated. Use --verbose instead.

--traceback-mode

By default, when an error is encountered, check-jsonschema will pretty-print the error and exit. Use --traceback-mode full to request the full traceback be printed, for debugging and troubleshooting.

Environment Variables

NO_COLOR

Set NO_COLOR=1 to explicitly turn off colorized output.

Optional Parsers

check-jsonschema comes with out-of-the-box support for the JSON and YAML file formats. Additional optional parsers may be installed, and are supported when present.

JSON5

In order to support JSON5 files, either the pyjson5 or json5 package must be installed.

In pre-commit-config.yaml, this can be done with additional_dependencies. For example,

- repo: https://github.com/python-jsonschema/check-jsonschema
  rev: 0.16.1
  hooks:
    - id: check-renovate
      additional_dependencies: ['pyjson5']

TOML

In order to support TOML files, the tomli package must be installed.

In pre-commit-config.yaml, this can be done with additional_dependencies. For example,

- repo: https://github.com/python-jsonschema/check-jsonschema
  rev: 0.16.1
  hooks:
    - id: check-jsonschema
      name: 'Check GitHub Workflows'
      files: ^mydata/
      types_or: [toml]
      args: ['--schemafile', 'schemas/toml-data.json']
      additional_dependencies: ['tomli']

The TOML format has support for dates and times as first-class types, meaning that they are parsed as part of the data format. check-jsonschema will convert the parsed data back into strings so that they can be checked by a schema. In general, the string conversion should be checkable using "format": "date-time", "format": "date", and "format": "time".