fix: ensure correct markdown serialization (#7016)

## 📝 Summary

Continuation of #7013
Very aggressive verification that markdown correctly serializes now.

---------

Co-authored-by: Myles Scolnick <[email protected]>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: 3 people

marimo/_ast/codegen.py

@@ -183,6 +183,7 @@ def format_markdown(cell: CellImpl) -> str:
         # We can blanket replace, because cell.markdown is not set
         # on f-strings with values.
         markdown = markdown.replace("{", "{{").replace("}", "}}")
+    markdown = markdown.replace('""', '"\\"')
 
     # We always use """ as per front end.
     body = construct_markdown_call(markdown, '"""', tag)

marimo/_ast/load.py

@@ -35,6 +35,15 @@
 
 @dataclass
 class LoadResult:
+    """Result of attempting to load a marimo notebook.
+
+    status can be one of:
+     - empty: No content, or only comments / a doc string
+     - has_errors: Parsed, but has marimo-specific errors (**can load!!**)
+     - invalid: Could not be parsed as a marimo notebook (**cannot load**)
+     - valid: Parsed and valid marimo notebook
+    """
+
     status: Literal["empty", "has_errors", "invalid", "valid"] = "empty"
     notebook: Optional[NotebookSerialization] = None
     contents: Optional[str] = None

tests/_ast/codegen_data/_test_not_parsable.py

@@ -0,0 +1,2 @@
+# INTENTIONALLY BROKEN!
+print("hello world

tests/_ast/codegen_data/_test_parse_error_in_notebook.py

@@ -0,0 +1,27 @@
+import marimo
+
+__generated_with = "0.17.4"
+app = marimo.App(width="medium")
+
+
+@app.cell
+def _(mo):
+    mo.md("""
+    r"""Markdown cell with error"""
+    """)
+    return
+
+
+@app.cell
+def _():
+    import marimo as mo
+    return (mo,)
+
+
+@app.cell
+def _():
+    return
+
+
+if __name__ == "__main__":
+    app.run()

tests/_ast/codegen_data/test_get_app_kwargs.py

@@ -1,5 +1,4 @@
 import marimo
-
 app = marimo.App(
     app_title="title",
     auto_download="html",