<SYSTEM>Guides: Migrate from Steiger: Replace Steiger with the fsd preset. Each Steiger rule has a rule of the same name, with examples, and the differences are listed.</SYSTEM>

# Migrate from Steiger

> Replace Steiger with the fsd preset. Each Steiger rule has a rule of the same name, with examples, and the differences are listed.

Steiger is the linter of Feature-Sliced Design. Archangel’s `fsd` preset has a rule for each of Steiger’s 21 rules, with the same name and a link to Steiger’s page for it. A test in the archangel repository runs Steiger and the preset on the same repositories, and compares the files that each one reports.

[Feature-Sliced Design](/archangel/guides/feature-sliced-design/) tells you how to use the preset. This page tells you how to move from Steiger.

## The config before

steiger.config.ts

```ts
import { defineConfig } from 'steiger';
import fsd from '@feature-sliced/steiger-plugin';


export default defineConfig([
  ...fsd.configs.recommended,
  {
    rules: {
      'fsd/insignificant-slice': 'off',
    },
  },
]);
```

## The config after

archangel.config.ts

```ts
import { defineConfig, fsd } from '@enhance-eng/archangel';


export default defineConfig({
  extends: [fsd({ root: 'src' })],
  off: ['fsd/insignificant-slice'],
});
```

| Steiger                          | archangel                                                                                         |
| -------------------------------- | ------------------------------------------------------------------------------------------------- |
| `...fsd.configs.recommended`     | `extends: [fsd({ root: 'src' })]`                                                                 |
| All rules on                     | `fsd({ root: 'src', strict: true })`                                                              |
| `'fsd/<rule>': 'off'`            | `off: ['fsd/<rule>']`                                                                             |
| `'fsd/<rule>': 'warn'`           | No equivalent. A rule is on or off.                                                               |
| `ignores: [...]`                 | `ignore: [...]` in the config, in `.gitignore` syntax. It removes the files from the whole check. |
| `files: [...]` with a rule `off` | Write a rule with the same name as the preset rule. Your rule replaces it.                        |
| A second FSD root                | A second `fsd({ root, name })` with its own `name`, for example `fsd-admin`.                      |

## Run it

1. Check the repository:

   Terminal

   ```ansi
   $ npx archangel check
   error[may-not-import]: src/features/login/ui/login-form.ts may not import "../../signup", because files in "features" may not import "all of (fsd/features, not src/features/*/@x/**)" in a different instance
    --> src/features/login/ui/login-form.ts:1:28
     |
   1 | import { signupLink } from '../../signup';
     |                            ^^^^^^^^^^^^^^ remove the import, or move the code to files that may import it
     |
     = note: rule: fsd/forbidden-imports
     = note: reason: A module may import only from layers below its own, and a slice not from another slice of its layer, except through @x.
     = note: see: https://feature-sliced.github.io/steiger/rules/forbidden-imports


   checked 8 files and 8 imports: 1 problem
     fsd/shared matches nothing in this repository
     fsd/entities matches nothing in this repository
     fsd/widgets matches nothing in this repository
     fsd/processes matches nothing in this repository
   For what a code means, run `archangel docs may-not-import`.
   ```

   The feature `login` imports the feature `signup`, so `fsd/forbidden-imports` refuses it. The lines that say “matches nothing” are parts of the preset with no files. A repository usually has only some layers, so these lines are not errors.

2. Run `npx archangel test`. It checks the examples of each preset rule in your repository, under the preset’s `root`, with your tsconfig.

3. Remove Steiger when the results are the same.

## The rules

Each rule name has the prefix of the preset, `fsd/` by default. The rules that Steiger recommends are on by default. `strict: true` adds the four rules that Steiger has as options.

| Steiger rule                       | archangel rule                     | On             |
| ---------------------------------- | ---------------------------------- | -------------- |
| `fsd/forbidden-imports`            | `fsd/forbidden-imports`            | Default        |
| `fsd/no-public-api-sidestep`       | `fsd/no-public-api-sidestep`       | Default        |
| `fsd/public-api`                   | `fsd/public-api`                   | Default        |
| `fsd/no-layer-public-api`          | `fsd/no-layer-public-api`          | Default        |
| `fsd/no-reserved-folder-names`     | `fsd/no-reserved-folder-names`     | Default        |
| `fsd/no-segmentless-slices`        | `fsd/no-segmentless-slices`        | Default        |
| `fsd/no-segments-on-sliced-layers` | `fsd/no-segments-on-sliced-layers` | Default        |
| `fsd/no-ui-in-app`                 | `fsd/no-ui-in-app`                 | Default        |
| `fsd/segments-by-purpose`          | `fsd/segments-by-purpose`          | Default        |
| `fsd/no-processes`                 | `fsd/no-processes`                 | Default        |
| `fsd/typo-in-layer-name`           | `fsd/typo-in-layer-name`           | Default        |
| `fsd/ambiguous-slice-names`        | `fsd/ambiguous-slice-names`        | Default        |
| `fsd/inconsistent-naming`          | `fsd/inconsistent-naming`          | Default        |
| `fsd/insignificant-slice`          | `fsd/insignificant-slice`          | Default        |
| `fsd/repetitive-naming`            | `fsd/repetitive-naming`            | Default        |
| `fsd/excessive-slicing`            | `fsd/excessive-slicing`            | Default        |
| `fsd/shared-lib-grouping`          | `fsd/shared-lib-grouping`          | Default        |
| `fsd/no-higher-level-imports`      | `fsd/no-higher-level-imports`      | `strict: true` |
| `fsd/no-cross-imports`             | `fsd/no-cross-imports`             | `strict: true` |
| `fsd/import-locality`              | `fsd/import-locality`              | `strict: true` |
| `fsd/no-wildcard-exports`          | `fsd/no-wildcard-exports`          | `strict: true` |

The rules about imports and folders are built-in conditions of archangel. The seven rules about names and counts, from `typo-in-layer-name` to `shared-lib-grouping`, are conditions of the preset’s plugin, and they read the whole tree as Steiger does.

## Results that change

These differences are on purpose. The test that compares the two tools names each one.

* **A slice is any folder in a sliced layer.** The built-in rules take each folder directly in Entities, Features, Widgets or Pages as a slice, with or without segments. They do not know slice groups. Steiger finds a slice by the segments inside it. The plugin rules find slices and slice groups as Steiger does.
* **Each folder in `shared/ui` and `shared/lib` needs an index file.** `fsd/public-api` asks for it even when the segment has an index file of its own. Steiger checks those folders only when the segment has none.
* **A misspelt layer is reported beside the real one.** `fsd/typo-in-layer-name` reports `src/featurez` even when `src/features` exists. Steiger then reports nothing.
* **A layer has its exact name.** The built-in rules take only a folder named exactly as a layer. Steiger also reads `1_shared` or `_app` as a layer.
* **Code outside the layers is checked too.** `fsd/no-public-api-sidestep` checks imports from files outside the layers, such as tests. A deep import from a test is still a sidestep. Steiger reads only the files in the layers.
* **A re-export is an import.** Each rule counts `export ... from` as an import, because a re-export loads the module.

One tool for more rules

Steiger checks Feature-Sliced Design only. With archangel, you can add your own tables and rules next to the preset, in the same config, and check them in one run.