.

extensions/shared/element-to-php.js

@@ -0,0 +1,39 @@
+/**
+ * External dependencies
+ */
+import React from 'react';
+
+export * from '@wordpress/element';
+export { Platform, renderToString, RawHTML } from '@wordpress/element';
+
+// export * from '@wordpress/element/react';
+// export * from '@wordpress/element/react-platform';
+// export * from '@wordpress/element/utils';
+
+// How (and why) does this transform work?
+// The idea here is to replace every call to each of `@wordpress/i18n`'s translation functions
+// (`__()`, `_n()`, `_x()`, `_nx()`) with their PHP counterpart, wrapped in a `<?php ... ?>`
+// pseudo-tag, and using `echo` to output the var, plus some escaping for sanitization.
+// The most puzzling part might be the `echo`: after all, we can't know _how_ the translated
+// strings are used in the Javascript source -- e.g. they might be assigned to a variable
+// for later usage, rather than rendered directly.
+// The answer is that this happens during React's rendering (to static markup, in this case),
+// where the entire component logic is essentially flattened to a component string. This means
+// that even translated strings that have gone through any intermediate steps will end up in
+// that rendered markup -- and thus, we'll have our `<?php echo esc_html__( ... ) ?>`
+// statements right where they belong.
+// A note on implementation:
+// Ideally, our replaced translation function would simply return `<?php echo esc_html__( ... ) ?>`.
+// However, React sanitizes strings by escaping chars like `<`. As a consequence, we need to use
+// `dangerouslySetInnerHTML` to bypass the escaping. This also requires to be attached as a prop
+// to a DOM element. I've chosen `<span />` since this likely has the smallest footprint for
+// rendering strings (e.g. shouldn't normally get in the way of styling).
+
+// We have to stub `sprintf` with the identity function here, since the original
+// `sprintf from '@wordpress/i18n'` only accepts strings as its first argument -- but
+// our replaced translation functions return a React element (`<span />`, see above).
+// This means that our rendered markup will contain `sprintf`-style `%(placeholder)s`
+// for which we need to add an extra `str_replace()` step. This is done in `components.php`.
+// TODO: Provide a wrapper around `@wordpress/i18n`'s `sprintf` that accepts React elements
+// as first argument, and remove the `str_replace()` call in `components.php`.
+export const createInterpolateElement = x => x;

webpack.config.extensions.js

@@ -144,6 +144,10 @@ module.exports = [
 				/^@wordpress\/i18n$/,
 				path.join( __dirname, './extensions/shared/i18n-to-php' )
 			),
+			new webpack.NormalModuleReplacementPlugin(
+				/^@wordpress\/element$/,
+				path.join( __dirname, './extensions/shared/element-to-php' )
+			),
 			new StaticSiteGeneratorPlugin( {
 				// The following mocks are required to make `@wordpress/` npm imports work with server-side rendering.
 				// Hopefully, most of them can be dropped once https://github.com/WordPress/gutenberg/pull/16227 lands.