Cache prebuilt iOS binaries in ~/Library/Caches/ReactNative

Currently, Hermes, ReactNativeDependencies, and ReactNativeCore
tarballs are cached only inside the Pods/ directory. This means
every clean `pod install` (or deleting the Pods folder) triggers
a full re-download from Maven, even if the same version was already
downloaded before.

This adds a shared cache layer at ~/Library/Caches/ReactNative/.
On first download, tarballs are saved to the shared cache. On
subsequent pod installs, if the local Pods cache is empty but the
shared cache has the tarball, it is copied locally instead of
re-downloaded. This benefits:
- Clean installs after deleting Pods/
- Multiple projects using the same React Native version
- CI environments with a persistent home directory

Added descriptive log messages for each scenario (local hit,
shared cache hit, cache miss + download) to aid debugging.

Author: cipolleschi

packages/react-native/scripts/cocoapods/rncore.rb

@@ -173,15 +173,36 @@ def self.podspec_source_download_prebuilt_nightly_tarball(version)
         return {:http => url}
     end
 
+    def self.shared_cache_dir()
+        return File.join(Dir.home, "Library", "Caches", "ReactNative")
+    end
+
     def self.download_rncore_tarball(react_native_path, tarball_url, version, configuration)
-        destination_path = configuration == nil ?
-            "#{artifacts_dir()}/reactnative-core-#{version}.tar.gz" :
-            "#{artifacts_dir()}/reactnative-core-#{version}-#{configuration}.tar.gz"
+        filename = configuration == nil ?
+            "reactnative-core-#{version}.tar.gz" :
+            "reactnative-core-#{version}-#{configuration}.tar.gz"
+        destination_path = "#{artifacts_dir()}/#{filename}"
+
+        if File.exist?(destination_path)
+          rncore_log("Tarball #{filename} already exists in Pods. Skipping download.")
+          return destination_path
+        end
 
-        unless File.exist?(destination_path)
+        `mkdir -p "#{artifacts_dir()}"`
+
+        cached_path = File.join(shared_cache_dir(), filename)
+        if File.exist?(cached_path)
+          rncore_log("Cache hit: copying #{filename} from shared cache (#{shared_cache_dir()})")
+          FileUtils.cp(cached_path, destination_path)
+        else
+          rncore_log("Cache miss: downloading #{filename} from #{tarball_url}")
           # Download to a temporary file first so we don't cache incomplete downloads.
           tmp_file = "#{artifacts_dir()}/reactnative-core.download"
-          `mkdir -p "#{artifacts_dir()}" && curl "#{tarball_url}" -Lo "#{tmp_file}" && mv "#{tmp_file}" "#{destination_path}"`
+          `curl "#{tarball_url}" -Lo "#{tmp_file}" && mv "#{tmp_file}" "#{destination_path}"`
+          # Save to shared cache for future use
+          `mkdir -p "#{shared_cache_dir()}"`
+          FileUtils.cp(destination_path, cached_path)
+          rncore_log("Saved #{filename} to shared cache (#{shared_cache_dir()})")
         end
 
         return destination_path

packages/react-native/scripts/cocoapods/rndependencies.rb

@@ -208,15 +208,36 @@ def self.podspec_source_download_prebuilt_nightly_tarball(version)
         return {:http => url}
     end
 
+    def self.shared_cache_dir()
+        return File.join(Dir.home, "Library", "Caches", "ReactNative")
+    end
+
     def self.download_rndeps_tarball(react_native_path, tarball_url, version, configuration)
-        destination_path = configuration == nil ?
-            "#{artifacts_dir()}/reactnative-dependencies-#{version}.tar.gz" :
-            "#{artifacts_dir()}/reactnative-dependencies-#{version}-#{configuration}.tar.gz"
+        filename = configuration == nil ?
+            "reactnative-dependencies-#{version}.tar.gz" :
+            "reactnative-dependencies-#{version}-#{configuration}.tar.gz"
+        destination_path = "#{artifacts_dir()}/#{filename}"
+
+        if File.exist?(destination_path)
+          rndeps_log("Tarball #{filename} already exists in Pods. Skipping download.")
+          return destination_path
+        end
 
-        unless File.exist?(destination_path)
+        `mkdir -p "#{artifacts_dir()}"`
+
+        cached_path = File.join(shared_cache_dir(), filename)
+        if File.exist?(cached_path)
+          rndeps_log("Cache hit: copying #{filename} from shared cache (#{shared_cache_dir()})")
+          FileUtils.cp(cached_path, destination_path)
+        else
+          rndeps_log("Cache miss: downloading #{filename} from #{tarball_url}")
           # Download to a temporary file first so we don't cache incomplete downloads.
           tmp_file = "#{artifacts_dir()}/reactnative-dependencies.download"
-          `mkdir -p "#{artifacts_dir()}" && curl "#{tarball_url}" -Lo "#{tmp_file}" && mv "#{tmp_file}" "#{destination_path}"`
+          `curl "#{tarball_url}" -Lo "#{tmp_file}" && mv "#{tmp_file}" "#{destination_path}"`
+          # Save to shared cache for future use
+          `mkdir -p "#{shared_cache_dir()}"`
+          FileUtils.cp(destination_path, cached_path)
+          rndeps_log("Saved #{filename} to shared cache (#{shared_cache_dir()})")
         end
 
         return destination_path

packages/react-native/sdks/hermes-engine/hermes-utils.rb

@@ -221,16 +221,38 @@ def download_stable_hermes(react_native_path, version, configuration)
     download_hermes_tarball(react_native_path, tarball_url, version, configuration)
 end
 
+def shared_cache_dir()
+    return File.join(Dir.home, "Library", "Caches", "ReactNative")
+end
+
 def download_hermes_tarball(react_native_path, tarball_url, version, configuration)
-    destination_path = configuration == nil ?
-        "#{artifacts_dir()}/hermes-ios-#{version}.tar.gz" :
-        "#{artifacts_dir()}/hermes-ios-#{version}-#{configuration}.tar.gz"
+    filename = configuration == nil ?
+        "hermes-ios-#{version}.tar.gz" :
+        "hermes-ios-#{version}-#{configuration}.tar.gz"
+    destination_path = "#{artifacts_dir()}/#{filename}"
+
+    if File.exist?(destination_path)
+      hermes_log("Tarball #{filename} already exists in Pods. Skipping download.", :info)
+      return destination_path
+    end
 
-    unless File.exist?(destination_path)
+    `mkdir -p "#{artifacts_dir()}"`
+
+    cached_path = File.join(shared_cache_dir(), filename)
+    if File.exist?(cached_path)
+      hermes_log("Cache hit: copying #{filename} from shared cache (#{shared_cache_dir()})", :info)
+      FileUtils.cp(cached_path, destination_path)
+    else
+      hermes_log("Cache miss: downloading #{filename} from #{tarball_url}", :info)
       # Download to a temporary file first so we don't cache incomplete downloads.
       tmp_file = "#{artifacts_dir()}/hermes-ios.download"
-      `mkdir -p "#{artifacts_dir()}" && curl "#{tarball_url}" -Lo "#{tmp_file}" && mv "#{tmp_file}" "#{destination_path}"`
+      `curl "#{tarball_url}" -Lo "#{tmp_file}" && mv "#{tmp_file}" "#{destination_path}"`
+      # Save to shared cache for future use
+      `mkdir -p "#{shared_cache_dir()}"`
+      FileUtils.cp(destination_path, cached_path)
+      hermes_log("Saved #{filename} to shared cache (#{shared_cache_dir()})", :info)
     end
+
     return destination_path
 end