Class LineCoverageVisitor

mypy/report.py:315–403

class LineCoverageVisitor(TraverserVisitor):
    def __init__(self, source: list[str]) -> None:
        self.source = source

        # For each line of source, we maintain a pair of
        #  * the indentation level of the surrounding function
        #    (-1 if not inside a function), and
        #  * whether the surrounding function is typed.
        # Initially, everything is covered at indentation level -1.
        self.lines_covered = [(-1, True) for l in source]

    # The Python AST has position information for the starts of
    # elements, but not for their ends. Fortunately the
    # indentation-based syntax makes it pretty easy to find where a
    # block ends without doing any real parsing.

    # TODO: Handle line continuations (explicit and implicit) and
    # multi-line string literals. (But at least line continuations
    # are normally more indented than their surrounding block anyways,
    # by PEP 8.)

    def indentation_level(self, line_number: int) -> int | None:
        """Return the indentation of a line of the source (specified by
        zero-indexed line number). Returns None for blank lines or comments."""
        line = self.source[line_number]
        indent = 0
        for char in list(line):
            if char == " ":
                indent += 1
            elif char == "\t":
                indent = 8 * ((indent + 8) // 8)
            elif char == "#":
                # Line is a comment; ignore it
                return None
            elif char == "\n":
                # Line is entirely whitespace; ignore it
                return None
            # TODO line continuation (\)
            else:
                # Found a non-whitespace character
                return indent
        # Line is entirely whitespace, and at end of file
        # with no trailing newline; ignore it
        return None

    def visit_func_def(self, defn: FuncDef) -> None:
        start_line = defn.line - 1
        start_indent = None
        # When a function is decorated, sometimes the start line will point to
        # whitespace or comments between the decorator and the function, so
        # we have to look for the start.
        while start_line < len(self.source):
            start_indent = self.indentation_level(start_line)
            if start_indent is not None:
                break
            start_line += 1
        # If we can't find the function give up and don't annotate anything.
        # Our line numbers are not reliable enough to be asserting on.