Schema linting

GraphOS provides schema linting to help you enforce formatting conventions and other GraphQL best practices with every proposed change to your graph's schema.

• If you set up schema checks for your graph, linting runs as a separate check type alongside build and operation checks.
• You can also perform one-off linting with the Rover CLI.

Linter configuration

The GraphOS schema linter uses a predefined collection of rules to identify issues with proposed schema changes. The predefined collection includes schema composition rules. The graph-wide linter defaults you define apply to all variants of a particular graph.

To navigate to your linter configuration:

1. In GraphOS Studio, go to your graph's Checks page.
2. Click Configuration in the upper right to open the checks configuration page.
3. From the checks configuration page, open the Linter section.

This page organizes linter options into the following categories:

• General Linter Configuration provides high-level options, including disabling the linter entirely.
• Approved @tag names enables you to specify approved values for the name argument of the @tag directive. This directive is used most commonly with GraphOS contracts.
  • If you don't use the @tag directive, you can ignore this category.
  • Using a non-approved value for name raises the TAG_DIRECTIVE_USES_UNKNOWN_NAME violation.
• Rule Severity Configuration enables you to set the severity level for violations of each rule.

If you view this configuration for a single variant, each category displays a Use Graph Settings toggle in the upper right. If this toggle is enabled, the variant uses whatever graph-wide defaults are set for that category. At this time, the Use Graph Settings toggle is always enabled for all variants.

Setting severity levels

The Rules Severity Configuration category of your linter configuration displays all predefined rules and the current severity level for each. Click a rule's severity to set it to any of the following:

• Error: Any violation of this rule causes the associated linter check to fail.
  • This in turn causes the entire schema checks run to fail, which is useful for failing builds in CI.
• Warn: Violations of this rule are flagged in checks reports, but they don't cause the associated linter check to fail.
• Ignore: Violations of this rule are ignored entirely.

For information on specific rules, see the reference list of rules.

Running the linter

Schema linting runs automatically as part of your graph's schema checks. You can also perform one-off linting of local schema changes via the Rover CLI.

Linting via schema checks

If you set up schema checks for your graph, schema linting automatically runs as a separate check type alongside build and operation checks. You can view the results of all check types from your graph's Checks page in Studio. For example, the screenshot below shows successful build and operations checks with a failed linting check.

One-off linting

The Rover CLI provides subgraph lint and graph lint commands for running the GraphOS linter against your local schema changes.

• Use subgraph lint for subgraphs in a supergraph.
• Use graph lint for monographs (not recommended).

The rover subgraph lint and rover graph lint commands validate all linter rules except for composition rules. Use rover subgraph check or rover supergraph compose to validate composition rules locally.

rover subgraph lint --name products --schema ./products-schema.graphql my-graph@my-variant

The argument my-graph@my-variant in the example above is a graph ref that specifies the ID of the graph you're comparing your schema changes against, along with which variant you're comparing against.

Command options include:

Linter rules

See this reference list of rules.