Function scan_parse_fallback

marimo/_ast/scanner.py:592–640

Fallback parser: scan for cell boundaries, parse each cell individually. Called when ast.parse() on the full file fails due to syntax errors. Returns a tuple of (nodes, scanner_generated_lines) where scanner_generated_lines contains the 1-indexed start line numbers of unparsable cel

(
    source: str, filepath: str
)

def scan_parse_fallback(
    source: str, filepath: str
) -> tuple[list[ast.stmt], frozenset[int]]:
    """Fallback parser: scan for cell boundaries, parse each cell individually.

    Called when ast.parse() on the full file fails due to syntax errors.
    Returns a tuple of (nodes, scanner_generated_lines) where
    scanner_generated_lines contains the 1-indexed start line numbers of
    unparsable cells created by the scanner (vs. pre-existing
    app._unparsable_cell() calls in the source).
    Returns ([], frozenset()) if no cell boundaries are found.
    """
    from marimo._ast.parse import ast_parse

    if not _has_cell_boundaries(source):
        return [], frozenset()

    scan = scan_notebook(source)

    nodes: list[ast.stmt] = []
    scanner_lines: set[int] = set()

    # Preamble
    if scan.preamble.strip():
        try:
            tree = ast_parse(scan.preamble, filename=filepath)
            nodes.extend(tree.body)
        except SyntaxError:
            raise  # Preamble errors are fatal

    # Cells
    for cell in scan.cells:
        try:
            cell_tree = ast_parse(cell.source, filename=filepath)
            ast.increment_lineno(cell_tree, cell.start_line - 1)
            nodes.extend(cell_tree.body)
        except SyntaxError:
            inner_code = _extract_body_code(cell.source, cell.kind)
            node = _build_unparsable_node(
                inner_code, cell.name, cell.start_line
            )
            scanner_lines.add(node.lineno)
            nodes.append(node)

    # Run guard
    if scan.run_guard_line is not None:
        nodes.append(_build_run_guard_node(scan.run_guard_line))

    return nodes, frozenset(scanner_lines)