Stop demanding public API from the App layer

packages/steiger-plugin-fsd/src/public-api/README.md

@@ -1,6 +1,6 @@
 # `public-api`
 
-Require slices (and segments on sliceless layers like Shared) to have a public API definition.
+Require slices (and segments on Shared) to have a public API definition.
 
 According to the _public API rule on slices_:
 

packages/steiger-plugin-fsd/src/public-api/index.spec.ts

@@ -130,3 +130,31 @@ it('reports errors on segments that are missing a public API', () => {
     },
   ])
 })
+
+it('reports no errors when the App layer is missing a public API', () => {
+  const root = parseIntoFsdRoot(`
+    📂 shared
+      📂 ui
+        📄 index.ts
+    📂 entities
+      📂 users
+        📂 ui
+        📄 index.ts
+      📂 posts
+        📂 ui
+        📄 index.ts
+    📂 features
+      📂 comments
+        📂 ui
+        📄 index.ts
+    📂 pages
+      📂 editor
+        📂 ui
+        📄 index.ts
+    📂 app
+      📂 providers
+      📂 styles
+  `)
+
+  expect(publicApi.check(root, { sourceFileExtension: 'ts' })).toEqual({ diagnostics: [] })
+})

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

@@ -11,6 +11,10 @@ const publicApi = {
 
     for (const [layerName, layer] of Object.entries(getLayers(root))) {
       if (!isSliced(layer)) {
+        if (layerName === 'app') {
+          // The app layer is the top-level layer, there's no need for public API.
+          continue
+        }
         for (const [segmentName, segment] of Object.entries(getSegments(layer))) {
           if (getIndex(segment) === undefined) {
             diagnostics.push({

packages/steiger/steiger.config.ts

@@ -1,5 +1,5 @@
 export default {
   rules: {
-    'public-api': 'off',
+    // 'public-api': 'off',
   },
 }