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Configuring Project Files

The entry and project file patterns are the first and most important options. Getting those right is essential to get the most value and performance out of Knip.

The key takeaways of this page include:

  • If the defaults need adjustment, define targeted entry file patterns.
  • To find unused files, narrow down and add negated project patterns.
  • To exclude test and other non-production files, use production mode.
  • Use ignore patterns to exclude issues in matching files from the report.

Let’s dive in and expand on all of these.

Unused files

Files are reported as unused if they are in the set of project files, but not in the set of files resolved from the entry files:

unused files = project files - (entry files + resolved files)

See entry files to see where Knip looks for entry files. Read on to learn how to fine-tune the sets of entry and project files.

Negated patterns

Let’s take a look at using negated patterns for entry and project files. If you think there are too many files in the analysis, this could be the first step in selecting the right files for the analysis.

Say we need to explicitly add route files as entry files, except those starting with an underscore. Then we can use a negated pattern like so:

"entry": ["src/routes/*.ts", "!src/routes/_*.ts"]

If certain files are not part of our project source files and are unwantedly reported as unused files, we can use negated project patterns:

"entry": ["src/index.ts"],
"project": ["src/**/*.ts", "!src/exclude/**"]

By the way, we don’t want to simply add all files as entry files for two reasons:

  1. Knip does not report unused exports in entry files.
  2. Configuring entry and project files properly allows Knip to find unused files.

Ignore issues in specific files

Use ignore if a certain file contain unused exports that we want to ignore. For example, this might happen with a generated file that exports “everything” and we don’t want the unused exports of this file to be reported:

"entry": ["src/index.ts"],
"project": ["src/**/*.ts"],
"ignore": ["src/generated.ts"]

Exclude non-production files

In default mode, Knip includes all test files and other non-production files in the analysis. To find out what files, dependencies and exports are unused in production source files, use production mode.

How NOT to exclude test files from the analysis? For a better understanding of how Knip works, here’s a list of options that don’t work, and why:

❌   Don’t do this:

"ignore": ["**/*.test.js"]

This is not a good idea, since ignore patterns have only one goal: to exclude issues in matching files from the report. Files matching ignore patterns are not excluded from the analysis, only their issues are not reported. This also hurts performance, since the files are first analyzed, and eventually filtered out.

❌   Also don’t do this:

"entry": ["!**/*.test.js"]

This won’t help if dependencies like Vitest or Ava are listed, because their plugins will add test files as entry files anyway, which you can’t and shouldn’t undo or override here.

❌   Also don’t do this:

"project": ["!**/*.spec.ts"]

This won’t help either:

  1. The set of project files have only one goal: to find unused files. Negated project patterns do not exclude files from the analysis.
  2. Enabled plugins add (test) files as entry files, and their configuration remains unaffected. You’d need to disable the plugin or override its configuration instead.

✅   Do this:

Terminal window
knip --production

This will exclude test files from the analysis, so you can focus on production code.

Now, Knip might still report certain files like test utilities as unused. That’s because they’re still part of the set of project files. Those files should then be excluded in production mode:

"entry": ["src/index.ts!"],
"project": ["src/**/*.ts!", "!src/test-helpers/**!"]

Remember to keep adding the exclamation mark suffix! for production file patterns.

In rare occasions, for large projects where a single configuration for both default and production mode gets unwieldy, it might be interesting to consider using a separate configuration file for production mode:

Terminal window
knip --production --config knip.production.json

ISC License © 2024 Lars Kappert