Fix REACT_NATIVE_PATH resolution when Pods/ is a symlink (facebook#56453)

Summary:
Pull Request resolved: facebook#56453

**Problem**

On Meta's virtual filesystem, we've started making `Pods/` a symlink for performance reasons.

The `REACT_NATIVE_PATH` Xcode build setting was constructed as `${PODS_ROOT}/../<relative_path>`, assuming that `${PODS_ROOT}/..` equals the Podfile directory (`ios/`). When `Pods/` is a symlink to a different filesystem depth, Xcode resolves `${PODS_ROOT}` to the physical target, and `..` traverses the wrong tree — landing one directory too high and producing a nonexistent path.

This broke four Xcode script phases at build time: `hermes-engine`, `ReactNativeDependencies`, `React-Core-prebuilt`, and `ReactCodegen`.

**Root cause**

The `$PODS_ROOT/..` idiom appears in four independent locations across Ruby, JavaScript, and shell layers. Each assumes the Pods directory is a direct child of the Podfile directory, which breaks when Pods/ is a symlink to a different filesystem depth.

**Fix**

All four sites are patched with the same approach: a new `PODFILE_DIR` Xcode build setting (set to the absolute Podfile directory path at pod install time) replaces the broken `$PODS_ROOT/..` derivation, with a fallback to the old behavior for backward compatibility.

**Changed files**

- **react_native_pods.rb** — Constructs the `REACT_NATIVE_PATH` build setting in `react_native_post_install`. Now resolves both the Pods directory and the react-native path to their real (physical) filesystem locations via `Pathname#realpath` before computing the relative path. Also adds the new `PODFILE_DIR` build setting.
- **with-environment.sh** — Sourced by script phases to set up `NODE_BINARY`. Located `.xcode.env` via `$PODS_ROOT/../.xcode.env`. Now uses `$PODFILE_DIR` with fallback.
- **script_phases.rb** — Ruby ERB template that generates shell scripts for codegen build phases. Used `pushd "$PODS_ROOT/../"` to derive the Podfile directory. Now uses `$PODFILE_DIR` with fallback.
- **generateReactCodegenPodspec.js** — JavaScript template that generates the ReactCodegen.podspec "Generate Specs" script phase. Had its own hardcoded `pushd "$PODS_ROOT/../"`. Now uses `$PODFILE_DIR` with fallback.

Reviewed By: cipolleschi

Differential Revision: D100830088

fbshipit-source-id: b92e83e8491b9e947245e149f0fe8f4b3b81c2ad

Author: huntie

packages/react-native/scripts/codegen/generate-artifacts-executor/generateReactCodegenPodspec.js

@@ -82,10 +82,16 @@ function codegenScripts(appPath /*: string */, baseOutputPath /*: string */) {
     baseOutputPath,
     REACT_NATIVE_PACKAGE_ROOT_FOLDER,
   );
+  // Use PODFILE_DIR (set by react_native_post_install) to locate the Podfile
+  // directory. PODS_ROOT/.. does not work when Pods/ is a symlink.
   return `<<-SCRIPT
-pushd "$PODS_ROOT/../" > /dev/null
-RCT_SCRIPT_POD_INSTALLATION_ROOT=$(pwd)
-popd >/dev/null
+if [ -n "$PODFILE_DIR" ]; then
+  RCT_SCRIPT_POD_INSTALLATION_ROOT="$PODFILE_DIR"
+else
+  pushd "$PODS_ROOT/../" > /dev/null
+  RCT_SCRIPT_POD_INSTALLATION_ROOT=$(pwd)
+  popd >/dev/null
+fi
 
 export RCT_SCRIPT_RN_DIR="$RCT_SCRIPT_POD_INSTALLATION_ROOT/${relativeReactNativeRootFolder}"
 export RCT_SCRIPT_APP_PATH="$RCT_SCRIPT_POD_INSTALLATION_ROOT/${relativeAppPath.length === 0 ? '.' : relativeAppPath}"

packages/react-native/scripts/react_native_pods.rb

@@ -531,7 +531,16 @@ def react_native_post_install(
   ReactNativePodsUtils.fix_library_search_paths(installer)
   ReactNativePodsUtils.update_search_paths(installer)
   ReactNativePodsUtils.set_build_setting(installer, build_setting: "USE_HERMES", value: use_hermes())
-  ReactNativePodsUtils.set_build_setting(installer, build_setting: "REACT_NATIVE_PATH", value: File.join("${PODS_ROOT}", "..", react_native_path))
+  # Compute REACT_NATIVE_PATH relative to PODS_ROOT using real (physical)
+  # paths, so the relative traversal is correct even when Pods/ is a symlink.
+  pods_dir_real = Pathname.new(Pod::Config.instance.sandbox_root.to_s).realpath
+  rn_absolute = File.expand_path(react_native_path, Pod::Config.instance.installation_root.to_s)
+  rn_real = Pathname.new(rn_absolute).realpath
+  rn_relative_to_pods = rn_real.relative_path_from(pods_dir_real)
+  ReactNativePodsUtils.set_build_setting(installer, build_setting: "REACT_NATIVE_PATH", value: File.join("${PODS_ROOT}", rn_relative_to_pods.to_s))
+  # Store the Podfile directory as a build setting so that shell scripts can
+  # locate it without relying on PODS_ROOT/.. (breaks when Pods/ is a symlink).
+  ReactNativePodsUtils.set_build_setting(installer, build_setting: "PODFILE_DIR", value: Pod::Config.instance.installation_root.to_s)
   ReactNativePodsUtils.set_build_setting(installer, build_setting: "SWIFT_ACTIVE_COMPILATION_CONDITIONS", value: ['$(inherited)', 'DEBUG'], config_name: "Debug")
 
   if (ENV['RCT_REMOVE_LEGACY_ARCH'] == '1')

packages/react-native/scripts/react_native_pods_utils/script_phases.rb

@@ -35,9 +35,15 @@ def get_script_phases_no_codegen_discovery(options)
 
 def get_script_template(react_native_path, export_vars={})
     template =<<~EOS
-        pushd "$PODS_ROOT/../" > /dev/null
-        RCT_SCRIPT_POD_INSTALLATION_ROOT=$(pwd)
-        popd >/dev/null
+        # Use PODFILE_DIR (set by react_native_post_install) to locate the
+        # Podfile directory. PODS_ROOT/.. does not work when Pods/ is a symlink.
+        if [ -n "$PODFILE_DIR" ]; then
+          RCT_SCRIPT_POD_INSTALLATION_ROOT="$PODFILE_DIR"
+        else
+          pushd "$PODS_ROOT/../" > /dev/null
+          RCT_SCRIPT_POD_INSTALLATION_ROOT=$(pwd)
+          popd >/dev/null
+        fi
         <% export_vars.each do |(varname, value)| %>
         export <%= varname -%>=<%= value -%>
         <% end %>

packages/react-native/scripts/xcode/with-environment.sh

@@ -17,7 +17,13 @@ NODE_BINARY=$(command -v node || echo "")
 export NODE_BINARY
 
 # Override the default with the global environment
-ENV_PATH="$PODS_ROOT/../.xcode.env"
+# Use PODFILE_DIR (set by react_native_post_install) to locate .xcode.env.
+# PODS_ROOT/.. does not work when Pods/ is a symlink.
+if [ -n "$PODFILE_DIR" ]; then
+    ENV_PATH="$PODFILE_DIR/.xcode.env"
+else
+    ENV_PATH="$PODS_ROOT/../.xcode.env"
+fi
 if [ -f "$ENV_PATH" ]; then
     source "$ENV_PATH"
 fi