ty/docs/rules.md

Rules

Rules are individual checks that ty performs to detect common issues in your code, such as incompatible assignments, missing imports, or invalid type annotations. Each rule focuses on a specific pattern and can be turned on or off depending on your project’s needs.

!!! tip

See [rules](./reference/rules.md) for an enumeration of all supported rules.

Rule levels

Each rule has a configurable level:

• error: violations are reported as errors and ty exits with an exit code of 1 if there's any.
• warn: violations are reported as warnings. Depending on your configuration, ty exits with an exit code of 0 if there are only warning violations (default) or 1 when using --error-on-warning.
• ignore: the rule is turned off

You can configure the level for each rule on the command line using the --warn, --error, and --ignore flags. For example:

ty check \
  --warn unused-ignore-comment \        # Make `unused-ignore-comment` a warning
  --ignore redundant-cast \             # Disable `redundant-cast`
  --error possibly-unbound-attribute \  # Error on `possibly-unbound-attribute`
  --error possibly-unbound-import       # Error on `possibly-unbound-import`

The options can be repeated. Subsequent options override earlier options.

Rule levels can also be changed in the rules section of a configuration file.

For example, the following is equivalent to the command above:

[tool.ty.rules]
unused-ignore-comment = "warn"
redundant-cast = "ignore"
possibly-unbound-attribute = "error"
possibly-unbound-import = "error"