Add no-segments-on-sliced-layers rule

.changeset/mean-pianos-cover.md

@@ -0,0 +1,6 @@
+---
+'@feature-sliced/steiger-plugin': minor
+'steiger': minor
+---
+
+Add no-segments-on-sliced-layers rule

README.md

@@ -66,6 +66,7 @@ Currently, Steiger is not extendable with more rules, though that will change in
   <tr> <td><a href="./packages/steiger-plugin-fsd/src/no-public-api-sidestep/README.md"><code>no-public-api-sidestep</code></a></td> <td>Forbid going around the public API of a slice to import directly from an internal module in a slice.</td> </tr>
   <tr> <td><a href="./packages/steiger-plugin-fsd/src/no-reserved-folder-names/README.md"><code>no-reserved-folder-names</code></a></td> <td>Forbid subfolders in segments that have the same name as other conventional segments.</td> </tr>
   <tr> <td><a href="./packages/steiger-plugin-fsd/src/no-segmentless-slices/README.md"><code>no-segmentless-slices</code></a></td> <td>Forbid slices that don't have any segments.</td> </tr>
+  <tr> <td><a href="./packages/steiger-plugin-fsd/src/no-segments-on-sliced-layers/README.md"><code>no-segments-on-sliced-layers</code></a></td> <td>Forbid segments (like ui, lib, api ...) that appear directly in sliced layer folders (entities, features, ...)</td> </tr>
   <tr> <td><a href="./packages/steiger-plugin-fsd/src/public-api/README.md"><code>public-api</code></a></td> <td>Require slices (and segments on sliceless layers like Shared) to have a public API definition.</td> </tr>
   <tr> <td><a href="./packages/steiger-plugin-fsd/src/repetitive-naming/README.md"><code>repetitive-naming</code></a></td> <td>Ensure that all entities are named consistently in terms of pluralization.</td> </tr>
   <tr> <td><a href="./packages/steiger-plugin-fsd/src/segments-by-purpose/README.md"><code>segments-by-purpose</code></a></td> <td>Discourage the use of segment names that group code by its essence, and instead encourage grouping by purpose</td> </tr>

packages/steiger-plugin-fsd/src/index.ts

@@ -7,6 +7,7 @@ import noLayerPublicApi from './no-layer-public-api/index.js'
 import noPublicApiSidestep from './no-public-api-sidestep/index.js'
 import noReservedFolderNames from './no-reserved-folder-names/index.js'
 import noSegmentlessSlices from './no-segmentless-slices/index.js'
+import noSegmentsOnSlicedLayers from './no-segments-on-sliced-layers/index.js'
 import publicApi from './public-api/index.js'
 import repetitiveNaming from './repetitive-naming/index.js'
 import segmentsByPurpose from './segments-by-purpose/index.js'
@@ -23,6 +24,7 @@ export default [
   noPublicApiSidestep,
   noReservedFolderNames,
   noSegmentlessSlices,
+  noSegmentsOnSlicedLayers,
   publicApi,
   repetitiveNaming,
   segmentsByPurpose,

packages/steiger-plugin-fsd/src/no-segments-on-sliced-layers/README.md

@@ -0,0 +1,47 @@
+# `no-segmentless-slices`
+
+Forbid segments that appear in direct children of sliced layers.
+
+Examples of project structures that pass this rule:
+
+```
+📂 shared
+  📂 ui
+    📄 index.ts
+  📂 lib
+    📄 index.ts
+📂 entities
+  📂 user
+    📂 ui
+    📂 model
+    📄 index.ts
+📂 pages
+  📂 home
+    📂 ui
+    📄 index.ts
+```
+
+Examples of project structures that fail this rule:
+
+```
+📂 shared
+  📂 ui
+    📄 index.ts
+  📂 lib
+    📄 index.ts
+📂 entities
+  📂 user
+    📂 ui
+    📂 model
+    📄 index.ts
+  📂 api // ❌
+    📄 index.ts
+📂 pages
+   📂 home
+     📂 ui
+     📄 index.ts
+```
+
+## Rationale
+
+Slices exist to partition code by business domain and entities. You can freely create and name them (e.g. `pages` home, profile and `entities` user, product, ...) based on your needs, application logic, company glossary, etc. Slices contain code of different type/purposes (segments) to implement their part of functionality. Segments (`ui`, `lib`, `api`) are simply a division of code by purpose, thus "ownerless" segments in sliced layers are not allowed since they need to be attached to some part of the business domain inside these layers.

packages/steiger-plugin-fsd/src/no-segments-on-sliced-layers/index.spec.ts

@@ -0,0 +1,99 @@
+import { describe, expect, it } from 'vitest'
+
+import noSegmentsOnSlicedLayers from './index.js'
+import { joinFromRoot, parseIntoFsdRoot } from '../_lib/prepare-test.js'
+
+describe('no-segments-on-sliced-layers rule', () => {
+  it('reports no errors on a project where the sliced layers has no segments in direct children', () => {
+    const root = parseIntoFsdRoot(`
+      📂 shared
+        📂 ui
+          📄 index.ts
+        📂 i18n
+          📄 index.ts
+      📂 entities
+        📂 user
+          📂 ui
+            📄 Name.tsx
+          📂 api
+            📄 useCurrentUser.ts
+          📄 index.ts
+        📂 document
+          📂 api
+            📄 useDocument.ts
+      📂 pages
+        📂 home
+          📂 ui
+          📄 index.ts
+    `)
+
+    expect(noSegmentsOnSlicedLayers.check(root)).toEqual({ diagnostics: [] })
+  })
+
+  it('reports errors on a project where the "Entities" layer has segments in direct children', () => {
+    const root = parseIntoFsdRoot(`
+      📂 shared
+        📂 ui
+          📄 index.ts
+        📂 i18n
+          📄 index.ts
+      📂 entities
+        📂 user
+          📄 index.ts
+          📄 Name.tsx
+        📂 ui
+          📄 index.ts
+      📂 features
+        📂 user
+          📂 ui
+            📄 LogIn.tsx
+            📄 index.ts
+          📄 index.ts
+        📂 api
+          📄 index.ts
+      📂 widgets
+        📂 footer
+          📂 ui
+            📄 Footer.tsx
+            📄 index.ts
+          📄 index.ts
+        📂 config
+          📄 index.ts
+      📂 pages
+        📂 home
+          📂 ui
+          📄 index.ts
+        📂 settings
+          📂 profile
+            📄 ProfilePage.tsx
+            📄 index.ts
+        📂 lib
+          📄 index.ts
+    `)
+
+    const diagnostics = noSegmentsOnSlicedLayers.check(root).diagnostics
+
+    expect(diagnostics).toEqual([
+      {
+        message:
+          'Conventional segment "ui" found as a direct child of a sliced layer. Consider moving it inside a slice or to another layer.',
+        location: { path: joinFromRoot('entities', 'ui') },
+      },
+      {
+        message:
+          'Conventional segment "api" found as a direct child of a sliced layer. Consider moving it inside a slice or to another layer.',
+        location: { path: joinFromRoot('features', 'api') },
+      },
+      {
+        message:
+          'Conventional segment "config" found as a direct child of a sliced layer. Consider moving it inside a slice or to another layer.',
+        location: { path: joinFromRoot('widgets', 'config') },
+      },
+      {
+        message:
+          'Conventional segment "lib" found as a direct child of a sliced layer. Consider moving it inside a slice or to another layer.',
+        location: { path: joinFromRoot('pages', 'lib') },
+      },
+    ])
+  })
+})

packages/steiger-plugin-fsd/src/no-segments-on-sliced-layers/index.ts

@@ -0,0 +1,32 @@
+import { getLayers, isSliced, conventionalSegmentNames } from '@feature-sliced/filesystem'
+import { type Diagnostic, Rule } from '@steiger/types'
+
+const noSegmentsOnSlicedLayers = {
+  name: 'no-segments-on-sliced-layers',
+  check(root) {
+    const diagnostics: Array<Diagnostic> = []
+    const layers = Object.values(getLayers(root))
+
+    for (const layer of layers) {
+      if (isSliced(layer)) {
+        for (const directChild of layer.children) {
+          if (directChild.type === 'folder') {
+            const folderName = directChild.path.split('/').pop()
+            const isConventionalSegment = folderName && conventionalSegmentNames.includes(folderName)
+
+            if (isConventionalSegment) {
+              diagnostics.push({
+                message: `Conventional segment "${folderName}" found as a direct child of a sliced layer. Consider moving it inside a slice or to another layer.`,
+                location: { path: directChild.path },
+              })
+            }
+          }
+        }
+      }
+    }
+
+    return { diagnostics }
+  },
+} satisfies Rule
+
+export default noSegmentsOnSlicedLayers

packages/steiger/README.md

@@ -66,6 +66,7 @@ Currently, Steiger is not extendable with more rules, though that will change in
   <tr> <td><a href="./packages/steiger-plugin-fsd/src/no-public-api-sidestep/README.md"><code>no-public-api-sidestep</code></a></td> <td>Forbid going around the public API of a slice to import directly from an internal module in a slice.</td> </tr>
   <tr> <td><a href="./packages/steiger-plugin-fsd/src/no-reserved-folder-names/README.md"><code>no-reserved-folder-names</code></a></td> <td>Forbid subfolders in segments that have the same name as other conventional segments.</td> </tr>
   <tr> <td><a href="./packages/steiger-plugin-fsd/src/no-segmentless-slices/README.md"><code>no-segmentless-slices</code></a></td> <td>Forbid slices that don't have any segments.</td> </tr>
+  <tr> <td><a href="./packages/steiger-plugin-fsd/src/no-segments-on-sliced-layers/README.md"><code>no-segments-on-sliced-layers</code></a></td> <td>Forbid segments (like ui, lib, api ...) that appear directly in sliced layer folders (entities, features, ...)</td> </tr>
   <tr> <td><a href="./packages/steiger-plugin-fsd/src/public-api/README.md"><code>public-api</code></a></td> <td>Require slices (and segments on sliceless layers like Shared) to have a public API definition.</td> </tr>
   <tr> <td><a href="./packages/steiger-plugin-fsd/src/repetitive-naming/README.md"><code>repetitive-naming</code></a></td> <td>Ensure that all entities are named consistently in terms of pluralization.</td> </tr>
   <tr> <td><a href="./packages/steiger-plugin-fsd/src/segments-by-purpose/README.md"><code>segments-by-purpose</code></a></td> <td>Discourage the use of segment names that group code by its essence, and instead encourage grouping by purpose</td> </tr>

packages/steiger/src/models/config.ts

@@ -14,6 +14,7 @@ export const schema = z.object({
         'no-public-api-sidestep',
         'no-reserved-folder-names',
         'no-segmentless-slices',
+        'no-segments-on-sliced-layers',
         'public-api',
         'repetitive-naming',
         'segments-by-purpose',