Implement no-processes

README.md

@@ -68,6 +68,7 @@ Currently, Steiger is not extendable with more rules, though that will change in
   <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>
   <tr> <td><a href="./packages/steiger-plugin-fsd/src/shared-lib-grouping/README.md"><code>shared-lib-grouping</code></a></td> <td>Forbid having too many ungrouped modules in <code>shared/lib</code>.</td> </tr>
+  <tr> <td><a href="./packages/steiger-plugin-fsd/src/no-processes/README.md"><code>no-processes</code></a></td> <td>Discourage the use of the deprecated Processes layer.</td> </tr>
 </tbody>
 </table>
 

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

@@ -11,6 +11,7 @@ import publicApi from './public-api/index.js'
 import repetitiveNaming from './repetitive-naming/index.js'
 import segmentsByPurpose from './segments-by-purpose/index.js'
 import sharedLibGrouping from './shared-lib-grouping/index.js'
+import noProcesses from './no-processes/index.js'
 
 export default [
   ambiguousSliceNames,
@@ -26,6 +27,7 @@ export default [
   repetitiveNaming,
   segmentsByPurpose,
   sharedLibGrouping,
+  noProcesses,
 ]
 
 export type { Diagnostic, Context, Fix, Rule, RuleResult } from './types.js'

packages/steiger-plugin-fsd/src/no-processes/README.md

@@ -0,0 +1,49 @@
+# `no-processes`
+
+Discourage the use of the deprecated Processes layer.
+
+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
+📂 pages
+  📂 home
+    📂 ui
+    📄 index.ts
+📂 processes // ❌
+  📂 cart
+```
+
+## Rationale
+
+The Processes layer was deprecated because there weren't enough use cases to justify its exitsence.
+
+If your project has this layer, consider moving the code from this layer into App or Features.

packages/steiger-plugin-fsd/src/no-processes/index.spec.ts

@@ -0,0 +1,51 @@
+import { expect, it } from 'vitest'
+
+import noProcesses from './index.js'
+import { parseIntoFsdRoot } from '../_lib/prepare-test.js'
+
+it('reports no errors on a project without the Processes layer', () => {
+  const root = parseIntoFsdRoot(`
+    📂 shared
+      📂 ui
+        📄 index.ts
+      📂 lib
+        📄 index.ts
+    📂 entities
+      📂 user
+        📂 ui
+        📂 model
+        📄 index.ts
+    📂 pages
+      📂 home
+        📂 ui
+        📄 index.ts
+  `)
+
+  expect(noProcesses.check(root)).toEqual({ diagnostics: [] })
+})
+
+it('reports errors on a project with the Processes layer', () => {
+  const root = parseIntoFsdRoot(`
+    📂 shared
+      📂 ui
+        📄 index.ts
+      📂 lib
+        📄 index.ts
+    📂 entities
+      📂 user
+        📂 ui
+        📂 model
+        📄 index.ts
+    📂 pages
+      📂 home
+        📂 ui
+        📄 index.ts
+    📂 processes
+      📂 cart
+        📂 ui
+        📄 index.ts
+  `)
+
+  const diagnostics = noProcesses.check(root).diagnostics
+  expect(diagnostics).toEqual([{ message: 'Layer "processes" is deprecated, avoid using it' }])
+})

packages/steiger-plugin-fsd/src/no-processes/index.ts

@@ -0,0 +1,23 @@
+import { basename } from 'node:path'
+import type { Diagnostic, Rule } from '../types.js'
+
+const noProcesses = {
+  name: 'no-processes',
+  check(root) {
+    const diagnostics: Array<Diagnostic> = []
+
+    const processesLayer = root.children.find(
+      (child) => child.type === 'folder' && basename(child.path) === 'processes',
+    )
+
+    if (processesLayer !== undefined) {
+      diagnostics.push({
+        message: 'Layer "processes" is deprecated, avoid using it',
+      })
+    }
+
+    return { diagnostics }
+  },
+} satisfies Rule
+
+export default noProcesses

packages/steiger/README.md

@@ -68,6 +68,7 @@ Currently, Steiger is not extendable with more rules, though that will change in
   <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>
   <tr> <td><a href="./packages/steiger-plugin-fsd/src/shared-lib-grouping/README.md"><code>shared-lib-grouping</code></a></td> <td>Forbid having too many ungrouped modules in <code>shared/lib</code>.</td> </tr>
+  <tr> <td><a href="./packages/steiger-plugin-fsd/src/no-processes/README.md"><code>no-processes</code></a></td> <td>Discourage the use of the deprecated Processes layer.</td> </tr>
 </tbody>
 </table>