Make sure that hermes-engine is updated with cocoapods. (#37148)

Summary:
Pull Request resolved: #37148

This should fix https://github.com/facebook/react-native/issue/36945, which is also causing annoyance when doing the releases

## Changelog:
[iOS][Changed] - Use contents of sdks/.hermesversion to let cocoapods recognize Hermes updates.

Reviewed By: cipolleschi

Differential Revision: D45394241

fbshipit-source-id: 972fbee8f954b90f7087bb232f922761c1639e06

packages/react-native/scripts/cocoapods/__tests__/jsengine-test.rb

@@ -105,7 +105,9 @@ def test_setupHermes_whenHermesScriptSucceeds_installsPods
         assert_equal($podInvocation["React-jsi"][:path], "../../ReactCommon/jsi")
         assert_equal($podInvocation["React-hermes"][:path], "../../ReactCommon/hermes")
         assert_equal($podInvocation["libevent"][:version], "~> 2.1.12")
-        assert_equal($podInvocation["hermes-engine"][:podspec], "../../sdks/hermes/hermes-engine.podspec")
+        hermes_engine_pod_invocation = $podInvocation["hermes-engine"]
+        assert_equal(hermes_engine_pod_invocation[:podspec], "../../sdks/hermes-engine/hermes-engine.podspec")
+        assert_equal(hermes_engine_pod_invocation[:tag], "")
     end
 
     def test_setupHermes_installsPods_installsFabricSubspecWhenFabricEnabled
@@ -118,7 +120,9 @@ def test_setupHermes_installsPods_installsFabricSubspecWhenFabricEnabled
         # Assert
         assert_equal($podInvocationCount, 4)
         assert_equal($podInvocation["React-jsi"][:path], "../../ReactCommon/jsi")
-        assert_equal($podInvocation["hermes-engine"][:podspec], "../../sdks/hermes/hermes-engine.podspec")
+        hermes_engine_pod_invocation = $podInvocation["hermes-engine"]
+        assert_equal(hermes_engine_pod_invocation[:podspec], "../../sdks/hermes-engine/hermes-engine.podspec")
+        assert_equal(hermes_engine_pod_invocation[:tag], "")
         assert_equal($podInvocation["React-hermes"][:path], "../../ReactCommon/hermes")
         assert_equal($podInvocation["libevent"][:version], "~> 2.1.12")
     end

packages/react-native/scripts/cocoapods/__tests__/test_utils/podSpy.rb

@@ -26,13 +26,14 @@ def podSpy_cleanUp
     $podInvocationCount = 0
 end
 
-def pod(name, version = nil, path: nil, configurations: nil, modular_headers: nil, podspec: nil)
+def pod(name, version = nil, path: nil, configurations: nil, modular_headers: nil, podspec: nil, tag: nil)
     $podInvocationCount += 1
     params = {}
     if version != nil then params[:version] = version end
     if path != nil then params[:path] = path end
     if configurations != nil then params[:configurations] = configurations end
     if modular_headers != nil then params[:modular_headers] = modular_headers end
     if podspec != nil then params[:podspec] = podspec end
+    if tag != nil then params[:tag] = tag end
     $podInvocation[name] = params
 end

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

@@ -30,7 +30,11 @@ def setup_hermes!(react_native_path: "../node_modules/react-native", fabric_enab
     abort unless prep_status == 0
 
     pod 'React-jsi', :path => "#{react_native_path}/ReactCommon/jsi"
-    pod 'hermes-engine', :podspec => "#{react_native_path}/sdks/hermes/hermes-engine.podspec"
+    # This `:tag => hermestag` below is only to tell CocoaPods to update hermes-engine when React Native version changes.
+    # We have custom logic to compute the source for hermes-engine. See sdks/hermes-engine/*
+    hermestag_file = File.join(react_native_path, "sdks", ".hermesversion")
+    hermestag = File.exist?(hermestag_file) ? File.read().strip : ''
+    pod 'hermes-engine', :podspec => "#{react_native_path}/sdks/hermes-engine/hermes-engine.podspec", :tag => hermestag
     pod 'React-hermes', :path => "#{react_native_path}/ReactCommon/hermes"
     pod 'libevent', '~> 2.1.12'
 end