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Add a --react-native-package option to vendor-hermes command #287

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Merged
merged 2 commits into from
Oct 26, 2025
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Merged

Add a --react-native-package option to vendor-hermes command #287

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d47ee08
Add --react-native-package option to "vendor-hermes" command
kraenhansen Oct 23, 2025
fc30bd3
Allow overriding REACT_NATIVE_OVERRIDE_HERMES_DIR externally
kraenhansen Oct 23, 2025
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5 changes: 5 additions & 0 deletions .changeset/chatty-states-build.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
"react-native-node-api": patch
---

Add --react-native-package option to "vendor-hermes" command, allowing caller to choose the package to download hermes into
23 changes: 15 additions & 8 deletions packages/host/scripts/patch-hermes.rb
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Expand Up @@ -4,13 +4,20 @@
raise "React Native Node-API cannot reliably patch JSI when React Native Core is prebuilt."
end

VENDORED_HERMES_DIR ||= `npx react-native-node-api vendor-hermes --silent '#{Pod::Config.instance.installation_root}'`.strip
if Dir.exist?(VENDORED_HERMES_DIR)
Pod::UI.info "Hermes vendored into #{VENDORED_HERMES_DIR.inspect}"
else
raise "Hermes patching failed. Please check the output above for errors."
if ENV['REACT_NATIVE_OVERRIDE_HERMES_DIR'].nil?
VENDORED_HERMES_DIR ||= `npx react-native-node-api vendor-hermes --silent '#{Pod::Config.instance.installation_root}'`.strip
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Is there any reason for this to be ||= rather than =? As VENDORED_HERMES_DIR is a local variable, I think it can only be unset at this point?

Suggested change
VENDORED_HERMES_DIR ||= `npx react-native-node-api vendor-hermes --silent '#{Pod::Config.instance.installation_root}'`.strip
VENDORED_HERMES_DIR = `npx react-native-node-api vendor-hermes --silent '#{Pod::Config.instance.installation_root}'`.strip

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It's my understanding that Ruby scripts aren't caching requires the same way Node.js would.

I had this originally because it prevents re-execution of the command if the .rb file is (transitively) "required" multiple times.

Comment on lines +7 to +8
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Summary of the proposed behaviour for my benefit:

  • If ENV.REACT_NATIVE_OVERRIDE_HERMES_DIR is defined:
    • The env var is used as-is.
    • The script checks whether the directory is exists.
      • If it exists, then good to go.
      • If not, an exception is raised.
  • If ENV.REACT_NATIVE_OVERRIDE_HERMES_DIR is not defined
    • npx react-native-node-api vendor-hermes --silent is called, ultimately vendoring Hermes for react-native (regardless of whether the user is using react-native or react-native-macos.
    • That vendored directory gets set as the value for ENV.REACT_NATIVE_OVERRIDE_HERMES_DIR.

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Exactly and I agree it would be ideal if we didn't vendor for react-native if this was driven by a MacOS app. Let's make that happen in a follow-up PR, ideally when we actually have a MacOS app in the repo, testing that flow.

# Signal the patched Hermes to React Native
ENV['BUILD_FROM_SOURCE'] = 'true'
ENV['REACT_NATIVE_OVERRIDE_HERMES_DIR'] = VENDORED_HERMES_DIR
elsif Dir.exist?(ENV['REACT_NATIVE_OVERRIDE_HERMES_DIR'])
# Setting an override path implies building from source
ENV['BUILD_FROM_SOURCE'] = 'true'
end

# Signal the patched Hermes to React Native
ENV['BUILD_FROM_SOURCE'] = 'true'
ENV['REACT_NATIVE_OVERRIDE_HERMES_DIR'] = VENDORED_HERMES_DIR
if !ENV['REACT_NATIVE_OVERRIDE_HERMES_DIR'].empty?
if Dir.exist?(ENV['REACT_NATIVE_OVERRIDE_HERMES_DIR'])
Pod::UI.info "[Node-API] Using overridden Hermes in #{ENV['REACT_NATIVE_OVERRIDE_HERMES_DIR'].inspect}"
else
raise "Hermes patching failed: Expected override to exist in #{ENV['REACT_NATIVE_OVERRIDE_HERMES_DIR'].inspect}"
end
end
31 changes: 25 additions & 6 deletions packages/host/src/node/cli/hermes.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -5,18 +5,24 @@ import path from "node:path";
import {
chalk,
Command,
Option,
oraPromise,
spawn,
UsageError,
wrapAction,
prettyPath,
} from "@react-native-node-api/cli-utils";
import { packageDirectorySync } from "pkg-dir";
import { packageDirectory } from "pkg-dir";
import { readPackage } from "read-pkg";

const HOST_PACKAGE_ROOT = path.resolve(__dirname, "../../..");
// FIXME: make this configurable with reasonable fallback before public release
const HERMES_GIT_URL = "https://github.com/kraenhansen/hermes.git";

const platformOption = new Option(
"--react-native-package <package-name>",
"The React Native package to vendor Hermes into",
).default("react-native");

export const command = new Command("vendor-hermes")
.argument("[from]", "Path to a file inside the app package", process.cwd())
.option("--silent", "Don't print anything except the final path", false)
Expand All @@ -25,12 +31,20 @@ export const command = new Command("vendor-hermes")
"Don't check timestamps of input files to skip unnecessary rebuilds",
false,
)
.addOption(platformOption)
.action(
wrapAction(async (from, { force, silent }) => {
const appPackageRoot = packageDirectorySync({ cwd: from });
wrapAction(async (from, { force, silent, reactNativePackage }) => {
const appPackageRoot = await packageDirectory({ cwd: from });
assert(appPackageRoot, "Failed to find package root");

const { dependencies = {} } = await readPackage({ cwd: appPackageRoot });
assert(
Object.keys(dependencies).includes(reactNativePackage),
`Expected app to have a dependency on the '${reactNativePackage}' package`,
);

const reactNativePath = path.dirname(
require.resolve("react-native/package.json", {
require.resolve(reactNativePackage + "/package.json", {
// Ensures we'll be patching the React Native package actually used by the app
paths: [appPackageRoot],
}),
Expand All @@ -40,6 +54,11 @@ export const command = new Command("vendor-hermes")
"sdks",
".hermesversion",
);
assert(
fs.existsSync(hermesVersionPath),
`Expected a file with a Hermes version at ${prettyPath(hermesVersionPath)}`,
);

const hermesVersion = fs.readFileSync(hermesVersionPath, "utf8").trim();
if (!silent) {
console.log(`Using Hermes version: ${hermesVersion}`);
Expand All @@ -50,7 +69,7 @@ export const command = new Command("vendor-hermes")
"ReactCommon/jsi/jsi/",
);

const hermesPath = path.join(HOST_PACKAGE_ROOT, "hermes");
const hermesPath = path.join(reactNativePath, "sdks", "node-api-hermes");
if (force && fs.existsSync(hermesPath)) {
await oraPromise(
fs.promises.rm(hermesPath, { recursive: true, force: true }),
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