feat(mdx): resolve @site/* markdown links, fix resolution priority bugs (#11397)

Author: slorber

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

@@ -75,4 +75,60 @@ describe('resolveMarkdownLinkPathname', () => {
     test('api/classes/divine_uri.URI.md', '/docs/api/classes/uri');
     test('another.md', '/docs/another');
   });
+
+  it('uses relative file paths in priority - Fix #11099', () => {
+    // Unit test to fix bug https://github.com/facebook/docusaurus/issues/11099
+
+    const context: Context = {
+      siteDir: '.',
+      sourceFilePath: 'docs/test/file.mdx',
+      contentPaths: {
+        contentPath: 'docs',
+        contentPathLocalized: 'i18n/docs-localized',
+      },
+      sourceToPermalink: new Map(
+        Object.entries({
+          '@site/docs/file.mdx': '/docs/file',
+          '@site/docs/test/file.mdx': '/docs/test/file',
+        }),
+      ),
+    };
+
+    function test(linkPathname: string, expectedOutput: string) {
+      const output = resolveMarkdownLinkPathname(linkPathname, context);
+      expect(output).toEqual(expectedOutput);
+    }
+
+    test('./file.mdx', '/docs/test/file');
+    test('file.mdx', '/docs/test/file');
+  });
+
+  it('can resolve @site/ links', () => {
+    const context: Context = {
+      siteDir: '.',
+      sourceFilePath: 'docs/test/file.mdx',
+      contentPaths: {
+        contentPath: 'docs',
+        contentPathLocalized: 'i18n/docs-localized',
+      },
+      sourceToPermalink: new Map(
+        Object.entries({
+          '@site/docs/file.mdx': '/docs/file',
+          '@site/docs/dir with spaces/file.mdx': '/docs/dir-with-spaces/file',
+        }),
+      ),
+    };
+
+    function test(linkPathname: string, expectedOutput: string) {
+      const output = resolveMarkdownLinkPathname(linkPathname, context);
+      expect(output).toEqual(expectedOutput);
+    }
+
+    test('@site/docs/file.mdx', '/docs/file');
+    test('@site/docs/dir with spaces/file.mdx', '/docs/dir-with-spaces/file');
+    test(
+      '@site/docs/dir%20with%20spaces/file.mdx',
+      '/docs/dir-with-spaces/file',
+    );
+  });
 });

packages/docusaurus-utils/src/markdownLinks.ts

@@ -47,9 +47,6 @@ export type SourceToPermalink = Map<
   string // Permalink: "/docs/content"
 >;
 
-// Note this is historical logic extracted during a 2024 refactor
-// The algo has been kept exactly as before for retro compatibility
-// See also https://github.com/facebook/docusaurus/pull/10168
 export function resolveMarkdownLinkPathname(
   linkPathname: string,
   context: {
@@ -60,20 +57,45 @@ export function resolveMarkdownLinkPathname(
   },
 ): string | null {
   const {sourceFilePath, sourceToPermalink, contentPaths, siteDir} = context;
-  const sourceDirsToTry: string[] = [];
-  // ./file.md and ../file.md are always relative to the current file
-  if (!linkPathname.startsWith('./') && !linkPathname.startsWith('../')) {
-    sourceDirsToTry.push(...getContentPathList(contentPaths), siteDir);
+
+  // If the link is already @site aliased, there's no need to resolve it
+  if (linkPathname.startsWith('@site/')) {
+    return sourceToPermalink.get(decodeURIComponent(linkPathname)) ?? null;
   }
-  // /file.md is never relative to the source file path
-  if (!linkPathname.startsWith('/')) {
-    sourceDirsToTry.push(path.dirname(sourceFilePath));
+
+  // Get the dirs to "look into", ordered by priority, when resolving the link
+  function getSourceDirsToTry() {
+    // /file.md is always resolved from
+    // - the plugin content paths,
+    // - then siteDir
+    if (linkPathname.startsWith('/')) {
+      return [...getContentPathList(contentPaths), siteDir];
+    }
+    // ./file.md and ../file.md are always resolved from
+    // - the current file dir
+    else if (linkPathname.startsWith('./') || linkPathname.startsWith('../')) {
+      return [path.dirname(sourceFilePath)];
+    }
+    // file.md is resolved from
+    // - the current file dir,
+    // - then from the plugin content paths,
+    // - then siteDir
+    else {
+      return [
+        path.dirname(sourceFilePath),
+        ...getContentPathList(contentPaths),
+        siteDir,
+      ];
+    }
   }
 
-  const aliasedSourceMatch = sourceDirsToTry
+  const sourcesToTry = getSourceDirsToTry()
     .map((sourceDir) => path.join(sourceDir, decodeURIComponent(linkPathname)))
-    .map((source) => aliasedSitePath(source, siteDir))
-    .find((source) => sourceToPermalink.has(source));
+    .map((source) => aliasedSitePath(source, siteDir));
+
+  const aliasedSourceMatch = sourcesToTry.find((source) =>
+    sourceToPermalink.has(source),
+  );
 
   return aliasedSourceMatch
     ? sourceToPermalink.get(aliasedSourceMatch) ?? null

website/_dogfooding/_docs tests/tests/links/resolution/index.mdx

@@ -0,0 +1,19 @@
+# Link resolution tests
+
+## Test for issue [#11099](https://github.com/facebook/docusaurus/issues/11099)
+
+These links should target the root `index.mdx` file:
+
+[`/index.mdx`](/index.mdx)
+
+[`@site/_dogfooding/_docs tests/index.mdx`](@site/_dogfooding/_docs%20tests/index.mdx)
+
+These links should target the current `index.mdx` file:
+
+[`/tests/links/index.mdx`](/tests/links/resolution/index.mdx)
+
+[`@site/_dogfooding/_docs tests/tests/links/resolution/index.mdx`](@site/_dogfooding/_docs%20tests/tests/links/resolution/index.mdx)
+
+[`index.mdx`](index.mdx)
+
+[`./index.mdx`](./index.mdx)

website/docs/guides/markdown-features/markdown-features-links.mdx

@@ -29,13 +29,17 @@ Reference to another [document in a subfolder](subfolder/doc3.mdx).
 
 Relative file paths are resolved against the current file's directory. Absolute file paths, on the other hand, are resolved relative to the **content root**, usually `docs/`, `blog/`, or [localized ones](../../i18n/i18n-tutorial.mdx) like `i18n/zh-Hans/plugin-content-docs/current`.
 
-Absolute file paths can also be relative to the site directory. However, beware that links that begin with `/docs/` or `/blog/` are **not portable** as you would need to manually update them if you create new doc versions or localize them.
+Here are some examples of file path links and how they get resolved, assuming the current file is `website/docs/category/source.mdx`:
 
-```md
-You can write [links](/otherFolder/doc4.mdx) relative to the content root (`/docs/`).
+- `[link](./target.mdx)` is resolved from the current file's directory `website/docs/category`.
+- `[link](../target.mdx)` is resolved from the parent file's directory `website/docs`.
+- `[link](/target.mdx)` is resolved from the docs content root `website/docs`, using in priority the localized docs.
+- `[link](target.mdx)` is resolved from the current directory `website/docs/category`, then from the docs content roots, then from the site root.
 
-You can also write [links](/docs/otherFolder/doc4.mdx) relative to the site directory, but it's not recommended.
-```
+Absolute file paths can also be relative to the site directory. However, beware that links that begin with `/docs/`, `/blog/` or `@site/` are **not portable** as you would need to manually update them if you create new doc versions or localize them:
+
+- `[link](/docs/target.mdx)` is resolved from the site root `website` (⚠️ less portable).
+- `[link](@site/docs/target.mdx)` is relative to the site root `website` (⚠️ less portable).
 
 Using relative _file_ paths (with `.md` extensions) instead of relative _URL_ links provides the following benefits: