markdown_viewer: jump to anchor position when clicking on an anchor link

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 ### Added
 
 - TCSS styles `layer` and `layers` can be strings https://github.com/Textualize/textual/pull/3169
+- `MarkdownViewer` now correctly handles anchors in links https://github.com/Textualize/textual/pull/2941
 
 ### Changed
 
@@ -21,6 +22,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 - Fixed flicker when calling pop_screen multiple times https://github.com/Textualize/textual/issues/3126
 - Fixed setting styles.layout not updating https://github.com/Textualize/textual/issues/3047
+- Fixed a crash in `MarkdownViewer` when clicking on a link containing an anchor https://github.com/Textualize/textual/issues/3094
 
 ## [0.35.1]
 

src/textual/widgets/_markdown.py

@@ -966,7 +966,22 @@ async def forward(self) -> None:
 
     async def _on_markdown_link_clicked(self, message: Markdown.LinkClicked) -> None:
         message.stop()
-        await self.go(message.href)
+        if message.href.find("#") == -1:
+            await self.go(message.href)
+        else:
+            link, anchor = message.href.split("#", 1)
+            await self.go(link)
+
+            def scroll_to_anchor() -> None:
+                toc = self.table_of_contents.table_of_contents
+                assert toc is not None
+                for _, name, block_id in toc:
+                    if name.lower().replace(" ", "-") == anchor:
+                        block = self.query_one(f"#{block_id}", MarkdownBlock)
+                        self.scroll_to_widget(block, top=True)
+                        break
+
+            self.call_later(scroll_to_anchor)
 
     def watch_show_table_of_contents(self, show_table_of_contents: bool) -> None:
         self.set_class(show_table_of_contents, "-show-table-of-contents")

tests/test_markdownviewer.md

@@ -0,0 +1,15 @@
+* [First](test_markdownviewer.md#first)
+* [Second](test_markdownviewer.md#second)
+* [Third](test_markdownviewer.md#third)
+
+# First
+
+The first.
+
+# Second
+
+The second.
+
+# Third
+
+The third.

tests/test_markdownviewer.py

@@ -0,0 +1,25 @@
+from pathlib import Path
+
+from textual.app import App, ComposeResult
+from textual.geometry import Offset
+from textual.widgets import Markdown, MarkdownViewer
+
+class MarkdownViewerApp(App[None]):
+
+    def compose(self) -> ComposeResult:
+        yield MarkdownViewer()
+
+    async def on_mount(self) -> None:
+        self.query_one(MarkdownViewer).show_table_of_contents = False
+        await self.query_one(MarkdownViewer).go(
+            Path(__file__).with_suffix(".md")
+        )
+
+
+async def test_markdown_viewer_anchor_link() -> None:
+    """Test https://github.com/Textualize/textual/issues/3094"""
+    async with MarkdownViewerApp().run_test() as pilot:
+        # There's not really anything to test *for* here, but the lack of an
+        # exception is the win (before the fix this is testing it would have
+        # been FileNotFoundError).
+        await pilot.click(Markdown, Offset(2, 1))