Intercept webbrowser open requests for local html files as well as …

…localhost (#4178)

Addresses #4118 

Hooks into the new `'show-html-file'` comm path to display html files
opened with the `webbrowser` python module in the viewer pane.

Previously we overrode the `webbrowser` opening to forward localhost
servers, so this just adds a condition to check for html files and do a
similar thing.

Here's an example of it working on a bokeh plot that previously used to
open in an external browser:
<img width="1115" alt="image"
src="https://github.com/user-attachments/assets/d258ae4e-f8d2-449a-8490-b99bb282aaca">


Rough edges:
- Bokeh widget doesn't seem to care about the size of the viewer pane.


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extensions/positron-python/README.md

@@ -47,11 +47,11 @@ pyright
 Install the test requirements that are used in CI:
 
 ```sh
-pip install -r ../build/pinned-test-requirements.txt
+pip install -r python_files/positron/pinned-test-requirements.txt
 ```
 
 Run Positron's unit tests with [pytest](https://docs.pytest.org/en/8.0.x/):
 
 ```sh
-pytest python_files/positron/
+python -m pytest python_files/positron/
 ```

extensions/positron-python/python_files/positron/positron_ipykernel/tests/test_ui.py

@@ -66,6 +66,10 @@ def show_url_event(url: str) -> Dict[str, Any]:
     return json_rpc_notification("show_url", {"url": url})
 
 
+def show_html_file_event(path: str, is_plot: bool) -> Dict[str, Any]:
+    return json_rpc_notification("show_html_file", {"path": path, "is_plot": is_plot})
+
+
 def test_comm_open(ui_service: UiService) -> None:
     # Double-check that comm is not yet open
     assert ui_service._comm is None
@@ -149,7 +153,24 @@ def test_shutdown(ui_service: UiService, ui_comm: DummyComm) -> None:
 
 @pytest.mark.parametrize(
     ("url", "expected"),
-    [("https://google.com", []), ("localhost:8000", [show_url_event("localhost:8000")])],
+    [
+        ("https://google.com", []),
+        ("localhost:8000", [show_url_event("localhost:8000")]),
+        # Unix path
+        (
+            "file://hello/my/friend.html",
+            [show_html_file_event("file://hello/my/friend.html", False)],
+        ),
+        # Windows path
+        (
+            "file:///C:/Users/username/Documents/index.htm",
+            [show_html_file_event("file:///C:/Users/username/Documents/index.htm", False)],
+        ),
+        # Not a local html file
+        ("http://example.com/page.html", []),
+        # Not an html file
+        ("file:///C:/Users/username/Documents/file.txt", []),
+    ],
 )
 def test_viewer_webbrowser_does_not_open(
     url, expected, shell: PositronShell, ui_comm: DummyComm, ui_service: UiService

extensions/positron-python/python_files/positron/positron_ipykernel/ui.py

@@ -23,7 +23,7 @@
     UiFrontendEvent,
     WorkingDirectoryParams,
 )
-from .utils import JsonData, JsonRecord, alias_home
+from .utils import JsonData, JsonRecord, alias_home, is_local_html_file
 
 logger = logging.getLogger(__name__)
 
@@ -179,6 +179,18 @@ def open(self, url, new=0, autoraise=True):
         if not self._comm:
             return False
 
+        # If url is pointing to an HTML file, route to the ShowHtmlFile comm
+        if is_local_html_file(url):
+            self._comm.send_event(
+                name=UiFrontendEvent.ShowHtmlFile,
+                payload={
+                    "path": url,
+                    # TODO: Figure out if the file being displayed is a plot or not.
+                    "is_plot": False,
+                },
+            )
+            return True
+
         for addr in _localhosts:
             if addr in url:
                 event = ShowUrlParams(url=url)

extensions/positron-python/python_files/positron/positron_ipykernel/utils.py

@@ -25,6 +25,7 @@
     Union,
     cast,
 )
+from urllib.parse import urlparse, unquote
 
 JsonData = Union[Dict[str, "JsonData"], List["JsonData"], str, int, float, bool, None]
 JsonRecord = Dict[str, JsonData]
@@ -384,3 +385,23 @@ def positron_ipykernel_usage():
     "numpy.cdouble",
     "numpy.clongdouble",
 ]
+
+
+def is_local_html_file(url: str) -> bool:
+    """Check if a URL points to a local HTML file."""
+    try:
+        parsed_url = urlparse(unquote(url))
+
+        # Check if it's a file scheme
+        if parsed_url.scheme not in ("file"):
+            return False
+
+        # Check if the path contains the .html or .htm extensions
+        path = parsed_url.path.lower()
+        if any(ext in path for ext in (".html", ".htm")):
+            return True
+
+        return False
+
+    except Exception:
+        return False