Fix HTML permalink output path

packages/docusaurus-utils/src/__tests__/emitUtils.test.ts

@@ -7,6 +7,7 @@
 
 import {describe, expect, it, vi} from 'vitest';
 import path from 'path';
+import os from 'os';
 import fs from 'fs-extra';
 import {readOutputHTMLFile, generate} from '../emitUtils';
 
@@ -89,6 +90,15 @@ describe('readOutputHTMLFile', () => {
       ).then(String),
     ).resolves.toBe('htmlFile.html\n');
   });
+  it('reads file ending in .html with trailing slash true', async () => {
+    await expect(
+      readOutputHTMLFile(
+        '/htmlFile.html',
+        path.join(__dirname, '__fixtures__/build-snap'),
+        true,
+      ).then(String),
+    ).resolves.toBe('htmlFile.html\n');
+  });
   it('reads file ending in .html in folder containing .html', async () => {
     await expect(
       readOutputHTMLFile(
@@ -105,6 +115,20 @@ describe('readOutputHTMLFile', () => {
       ).then(String),
     ).resolves.toBe('nestedHtmlFile.html\n');
   });
+  it('reads index.html when the permalink path is a directory', async () => {
+    const tempDir = await fs.mkdtemp(path.join(os.tmpdir(), 'docusaurus-'));
+    try {
+      const dirPath = path.join(tempDir, 'dir.html');
+      await fs.ensureDir(dirPath);
+      await fs.writeFile(path.join(dirPath, 'index.html'), 'dir-index\n');
+
+      await expect(
+        readOutputHTMLFile('/dir.html', tempDir, undefined).then(String),
+      ).resolves.toBe('dir-index\n');
+    } finally {
+      await fs.remove(tempDir);
+    }
+  });
   // Can it ever happen?
   it('throws if file does not exist', async () => {
     await expect(

packages/docusaurus-utils/src/emitUtils.ts

@@ -82,24 +82,60 @@ export async function readOutputHTMLFile(
   outDir: string,
   trailingSlash: boolean | undefined,
 ): Promise<Buffer> {
-  const withTrailingSlashPath = path.join(outDir, permalink, 'index.html');
-  const withoutTrailingSlashPath = (() => {
-    const basePath = path.join(outDir, permalink.replace(/\/$/, ''));
-    const htmlSuffix = /\.html?$/i.test(basePath) ? '' : '.html';
-    return `${basePath}${htmlSuffix}`;
-  })();
+  const normalizedPermalink = permalink.replace(/\/$/, '');
+  const withTrailingSlashPath = path.join(
+    outDir,
+    normalizedPermalink,
+    'index.html',
+  );
+  const withoutTrailingSlashPath = path.join(outDir, normalizedPermalink);
+  const isHtmlPath = /\.html?$/i.test(normalizedPermalink);
 
-  const possibleHtmlPaths = [
-    trailingSlash !== false && withTrailingSlashPath,
-    trailingSlash !== true && withoutTrailingSlashPath,
-  ].filter((p): p is string => Boolean(p));
+  const possibleHtmlPaths = isHtmlPath
+    ? [withoutTrailingSlashPath]
+    : trailingSlash === true
+      ? [withTrailingSlashPath]
+      : trailingSlash === false
+        ? [`${withoutTrailingSlashPath}.html`]
+        : [withTrailingSlashPath, `${withoutTrailingSlashPath}.html`];
 
-  const HTMLPath = await findAsyncSequential(possibleHtmlPaths, fs.pathExists);
+  async function readCandidateHTMLFile(
+    candidatePath: string,
+  ): Promise<Buffer | null> {
+    if (!(await fs.pathExists(candidatePath))) {
+      return null;
+    }
+    try {
+      return await fs.readFile(candidatePath);
+    } catch (error) {
+      if ((error as NodeJS.ErrnoException)?.code !== 'EISDIR') {
+        throw error;
+      }
+    }
+
+    const candidateIndexPath = path.join(candidatePath, 'index.html');
+    if (await fs.pathExists(candidateIndexPath)) {
+      return fs.readFile(candidateIndexPath);
+    }
+
+    return null;
+  }
+
+  const HTMLPath = await findAsyncSequential(possibleHtmlPaths, async (p) =>
+    Boolean(await readCandidateHTMLFile(p)),
+  );
 
   if (!HTMLPath) {
     throw new Error(
-      `Expected output HTML file to be found at ${withTrailingSlashPath} for permalink ${permalink}.`,
+      `Expected output HTML file to be found at ${possibleHtmlPaths[0]} for permalink ${permalink}.`,
+    );
+  }
+
+  const content = await readCandidateHTMLFile(HTMLPath);
+  if (!content) {
+    throw new Error(
+      `Expected output HTML file to be found at ${HTMLPath} for permalink ${permalink}.`,
     );
   }
-  return fs.readFile(HTMLPath);
+  return content;
 }