Highlight unused code in Pull Requests as a warning

.github/workflows/ci-tests.yml

@@ -63,6 +63,32 @@ jobs:
           ./Derived/*
         key: ${{ github.run_id }}-dependencies
 
+  unused:
+    name: Periphery
+    runs-on: macos-latest
+    needs: [tuist-generation, changes]
+    steps:
+      - uses: actions/checkout@v3
+      - uses: maxim-lobanov/setup-xcode@v1
+        with:
+          xcode-version: ${{ env.XCODE_VERSION }}
+      - name: Retrieve Build Cache
+        uses: actions/cache@v3
+        with:
+          path: |
+            ./ApolloDev.xcodeproj
+            ./ApolloDev.xcworkspace
+            ./Derived/*
+          key: ${{ github.run_id }}-dependencies
+          fail-on-cache-miss: true
+      - name: Install Periphery
+        run: |
+          brew install peripheryapp/periphery/periphery
+
+      - name: Run Periphery
+        run: |
+          ruby scripts/periphery.rb
+
   run-swift-builds:
     runs-on: macos-latest
     timeout-minutes: 15

.periphery.yml

@@ -0,0 +1,21 @@
+retain_public: true
+schemes:
+- ApolloAPI
+- ApolloCodegenLib
+- ApolloPagination
+- ApolloSQLite
+- ApolloWebSocket
+- ApolloWrapper
+- CodegenCLI
+- apollo-ios-cli
+targets:
+- Apollo.Apollo
+- Apollo.ApolloAPI
+- Apollo.ApolloSQLite
+- Apollo.ApolloWebSocket
+- ApolloCodegen.ApolloCodegenLib
+- ApolloCodegen.CodegenCLI
+- ApolloCodegenLibWrapper
+- ApolloPagination.ApolloPagination
+- ApolloWrapper
+workspace: ApolloDev.xcworkspace

scripts/periphery.rb

@@ -0,0 +1,12 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+output = `periphery scan --relative-results`
+# This can be simplified in the future to `periphery scan --relative-results --format github-actions`
+# https://github.com/peripheryapp/periphery/pull/746
+title = 'Unused Code'
+output
+  .split("\n").select { |line| line.include?('.swift') }
+  .map { |line| line.split(':', 5) }
+  .map { |parts| "::warning file=#{parts[0]},line=#{parts[1]},col=#{parts[2]},title=#{title}::#{parts[4].strip}" }
+  .each { |warning| puts warning }