Add option for initial warning cell in try examples directive

docs/directives/try_examples.md

@@ -118,6 +118,7 @@ The `try_examples` directive has options
 * `:example_class:` An html class to attach to the outer container for the rendered
 examples content and embedded notebook. This can be used in a custom css file to allow
 for more precise customization, eg. different button styles across different examples.
+* `:warning_text:` Prepend a markdown cell to the notebook containing this text, styled to make it clear this is intended as a warning.
 
 Here's an example with some options set
 
@@ -126,6 +127,7 @@ Here's an example with some options set
     :button_text: Try it in your browser!
     :height: 400px
     :example_class: blue-bottom
+    :warning_text: Interactive examples are experimental and may not always work as expected.
 
     The button text has changed and the height now exceeds the size of the content.
 
@@ -148,6 +150,7 @@ and here is the result
     :button_text: Try it in your browser!
     :height: 400px
     :example_class: blue-bottom
+    :warning_text: Interactive examples are experimental and may not always work as expected.
 
     The button text has changed and the height now exceeds the size of the content.
 
@@ -195,13 +198,14 @@ the section header for an examples section will prevent a directive from being i
 allowing for specification of examples sections which should not be made interactive.
 
 
-The button text and theme can be set globally with the config variables
-`try_examples_global_button_text`, and `try_examples_global_theme`.
+The button text, theme, and warning text can be set globally with the config variables
+`try_examples_global_button_text`, `try_examples_global_theme`, and `try_examples_global_warning_text`.
 
 ```python
 global_enable_try_examples = True
 try_examples_global_button_text = "Try it in your browser!"
 try_examples_global_height = "200px"
+try_examples_global_warning_text = "Interactive examples are experimental and may not always work as expected."
 ```
 
 There is no option to set a global specific height because the proper height

jupyterlite_sphinx/_try_examples.py

@@ -3,13 +3,17 @@
 import re
 
 
-def examples_to_notebook(input_lines):
+def examples_to_notebook(input_lines, *, warning_text=None):
     """Parse examples section of a docstring and convert to Jupyter notebook.
 
     Parameters
     ----------
     input_lines : iterable of str.
-                  Lines within
+
+    warning_text : str[Optional]
+        If given, add a markdown cell at the top of the generated notebook
+        containing the given text. The cell will be styled to indicate that
+        this is a warning.
 
     Returns
     -------
@@ -44,6 +48,12 @@ def examples_to_notebook(input_lines):
     """
     nb = nbf.v4.new_notebook()
 
+    if warning_text is not None:
+        # Two newlines \n\n signal that the inner content should be parsed as
+        # markdown.
+        warning = f"<div class='alert alert-warning'>\n\n{warning_text}\n\n</div>"
+        nb.cells.append(new_markdown_cell(warning))
+
     code_lines = []
     md_lines = []
     output_lines = []

jupyterlite_sphinx/jupyterlite_sphinx.py

@@ -368,6 +368,7 @@ class TryExamplesDirective(SphinxDirective):
         "theme": directives.unchanged,
         "button_text": directives.unchanged,
         "example_class": directives.unchanged,
+        "warning_text": directives.unchanged,
     }
 
     def run(self):
@@ -382,6 +383,7 @@ def run(self):
         button_text = self.options.pop("button_text", "Try it with Jupyterlite!")
         height = self.options.pop("height", None)
         example_class = self.options.pop("example_class", "")
+        warning_text = self.options.pop("warning_text", None)
 
         # We need to get the relative path back to the documentation root from
         # whichever file the docstring content is in.
@@ -404,7 +406,7 @@ def run(self):
         self.state.nested_parse(self.content, self.content_offset, content_node)
 
         if notebook_unique_name is None:
-            nb = examples_to_notebook(self.content)
+            nb = examples_to_notebook(self.content, warning_text=warning_text)
             self.content = None
             notebooks_dir = Path(self.env.app.srcdir) / CONTENT_DIR
             notebook_unique_name = f"{uuid4()}.ipynb".replace("-", "_")
@@ -506,6 +508,7 @@ def _process_autodoc_docstrings(app, what, name, obj, options, lines):
     try_examples_options = {
         "theme": app.config.try_examples_global_theme,
         "button_text": app.config.try_examples_global_button_text,
+        "warning_text": app.config.try_examples_global_warning_text,
     }
     try_examples_options = {
         key: value for key, value in try_examples_options.items() if value is not None
@@ -614,6 +617,7 @@ def setup(app):
 
     app.add_config_value("global_enable_try_examples", default=False, rebuild=True)
     app.add_config_value("try_examples_global_theme", default=None, rebuild=True)
+    app.add_config_value("try_examples_global_warning_text", default=None, rebuild=True)
     app.add_config_value(
         "try_examples_global_button_text",
         default=None,