fix(core): preserve Interpolate children semantics (#7103)

* fix(core): preserve Interpolate children semantics

* fix

* fix again

packages/docusaurus/src/client/exports/Interpolate.tsx

@@ -9,7 +9,6 @@ import React, {isValidElement, type ReactNode} from 'react';
 import type {
   InterpolateProps,
   InterpolateValues,
-  ExtractInterpolatePlaceholders,
 } from '@docusaurus/Interpolate';
 
 /*
@@ -18,8 +17,6 @@ We don't ship a markdown parser nor a feature-complete i18n library on purpose.
 More details here: https://github.com/facebook/docusaurus/pull/4295
 */
 
-const ValueFoundMarker = '{}'; // does not care much
-
 // If all the values are plain strings, then interpolate returns a simple string
 export function interpolate<Str extends string>(
   text: Str,
@@ -36,46 +33,26 @@ export function interpolate<Str extends string, Value extends ReactNode>(
   text: Str,
   values?: InterpolateValues<Str, Value>,
 ): ReactNode {
-  const elements: (Value | string)[] = [];
-
-  const processedText = text.replace(
-    // eslint-disable-next-line prefer-named-capture-group
-    /\{(\w+)\}/g,
-    (match, key: ExtractInterpolatePlaceholders<Str>) => {
-      const value = values?.[key];
-
-      if (typeof value !== 'undefined') {
-        const element = isValidElement(value)
-          ? value
-          : // For non-React elements: basic primitive->string conversion
-            String(value);
-        elements.push(element);
-        return ValueFoundMarker;
+  // eslint-disable-next-line prefer-named-capture-group
+  const segments = text.split(/(\{\w+\})/).map((seg, index) => {
+    // Odd indices (1, 3, 5...) of the segments are (potentially) interpolatable
+    if (index % 2 === 1) {
+      const value = values?.[seg.slice(1, -1) as keyof typeof values];
+      if (value !== undefined) {
+        return value;
       }
-      return match; // no match? add warning?
-    },
-  );
-
-  // No interpolation to be done: just return the text
-  if (elements.length === 0) {
-    return text;
+      // No match: add warning? There's no way to "escape" interpolation though
+    }
+    return seg;
+  });
+  if (segments.some((seg) => isValidElement(seg))) {
+    return segments
+      .map((seg, index) =>
+        isValidElement(seg) ? React.cloneElement(seg, {key: index}) : seg,
+      )
+      .filter((seg) => seg !== '');
   }
-  // Basic string interpolation: returns interpolated string
-  if (elements.every((el): el is string => typeof el === 'string')) {
-    return processedText
-      .split(ValueFoundMarker)
-      .reduce<string>(
-        (str, value, index) => str.concat(value).concat(elements[index] ?? ''),
-        '',
-      );
-  }
-  // JSX interpolation: returns ReactNode
-  return processedText.split(ValueFoundMarker).map((value, index) => (
-    <React.Fragment key={index}>
-      {value}
-      {elements[index]}
-    </React.Fragment>
-  ));
+  return segments.join('');
 }
 
 export default function Interpolate<Str extends string>({
@@ -83,9 +60,10 @@ export default function Interpolate<Str extends string>({
   values,
 }: InterpolateProps<Str>): JSX.Element {
   if (typeof children !== 'string') {
-    console.warn('Illegal <Interpolate> children', children);
     throw new Error(
-      'The Docusaurus <Interpolate> component only accept simple string values',
+      `The Docusaurus <Interpolate> component only accept simple string values. Received: ${
+        isValidElement(children) ? 'React element' : typeof children
+      }`,
     );
   }
   return <>{interpolate(children, values)}</>;

packages/docusaurus/src/client/exports/__tests__/Interpolate.test.tsx

@@ -130,7 +130,7 @@ describe('<Interpolate>', () => {
         </Interpolate>,
       ),
     ).toThrowErrorMatchingInlineSnapshot(
-      `"The Docusaurus <Interpolate> component only accept simple string values"`,
+      `"The Docusaurus <Interpolate> component only accept simple string values. Received: React element"`,
     );
   });
 });

packages/docusaurus/src/client/exports/__tests__/__snapshots__/Interpolate.test.tsx.snap

@@ -8,62 +8,48 @@ exports[`<Interpolate> acceptance test 1`] = `
   <span>
     today
   </span>,
-  "? Another {unprovidedValue}!",
+  "? Another ",
+  "{unprovidedValue}",
+  "!",
 ]
 `;
 
 exports[`interpolate acceptance test 1`] = `
 [
-  <React.Fragment>
-    Hello 
-    Sébastien
-  </React.Fragment>,
-  <React.Fragment>
-     how are you 
-    <span>
-      today
-    </span>
-  </React.Fragment>,
-  <React.Fragment>
-    ? Another {unprovidedValue}!
-  </React.Fragment>,
+  "Hello ",
+  "Sébastien",
+  " how are you ",
+  <span>
+    today
+  </span>,
+  "? Another ",
+  "{unprovidedValue}",
+  "!",
 ]
 `;
 
 exports[`interpolate placeholders with JSX values 1`] = `
 [
-  <React.Fragment>
-    Hello 
-    <b>
-      Sébastien
-    </b>
-  </React.Fragment>,
-  <React.Fragment>
-     how are you 
-    <span>
-      today
-    </span>
-  </React.Fragment>,
-  <React.Fragment>
-    ?
-  </React.Fragment>,
+  "Hello ",
+  <b>
+    Sébastien
+  </b>,
+  " how are you ",
+  <span>
+    today
+  </span>,
+  "?",
 ]
 `;
 
 exports[`interpolate placeholders with mixed vales 1`] = `
 [
-  <React.Fragment>
-    Hello 
-    Sébastien
-  </React.Fragment>,
-  <React.Fragment>
-     how are you 
-    <span>
-      today
-    </span>
-  </React.Fragment>,
-  <React.Fragment>
-    ?
-  </React.Fragment>,
+  "Hello ",
+  "Sébastien",
+  " how are you ",
+  <span>
+    today
+  </span>,
+  "?",
 ]
 `;

website/_dogfooding/_pages tests/error-boundary-tests.tsx

@@ -7,6 +7,7 @@
 
 import React from 'react';
 import Layout from '@theme/Layout';
+import Interpolate from '@docusaurus/Interpolate';
 
 import ErrorBoundaryTestButton from '@site/src/components/ErrorBoundaryTestButton';
 
@@ -22,6 +23,9 @@ export default function ErrorBoundaryTests(): JSX.Element {
               Crash inside layout
             </ErrorBoundaryTestButton>
           </div>
+          <Interpolate values={{foo: <span>FooFoo</span>, bar: <b>BarBar</b>}}>
+            {'{foo} is {bar}'}
+          </Interpolate>
         </main>
       </Layout>
     </>