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# Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
# For details: https://github.com/nedbat/coveragepy/blob/master/NOTICE.txt
"""Code parsing for coverage.py."""
from __future__ import annotations
import ast
import collections
import os
import re
import sys
import token
import tokenize
from types import CodeType
from typing import (
cast, Any, Callable, Dict, Iterable, List, Optional, Sequence, Set, Tuple,
)
from coverage import env
from coverage.bytecode import code_objects
from coverage.debug import short_stack
from coverage.exceptions import NoSource, NotPython
from coverage.misc import join_regex, nice_pair
from coverage.phystokens import generate_tokens
from coverage.types import Protocol, TArc, TLineNo
class PythonParser:
"""Parse code to find executable lines, excluded lines, etc.
This information is all based on static analysis: no code execution is
involved.
"""
def __init__(
self,
text: Optional[str] = None,
filename: Optional[str] = None,
exclude: Optional[str] = None,
) -> None:
"""
Source can be provided as `text`, the text itself, or `filename`, from
which the text will be read. Excluded lines are those that match
`exclude`, a regex string.
"""
assert text or filename, "PythonParser needs either text or filename"
self.filename = filename or "<code>"
if text is not None:
self.text: str = text
else:
from coverage.python import get_python_source
try:
self.text = get_python_source(self.filename)
except OSError as err:
raise NoSource(f"No source for code: '{self.filename}': {err}") from err
self.exclude = exclude
# The text lines of the parsed code.
self.lines: List[str] = self.text.split("\n")
# The normalized line numbers of the statements in the code. Exclusions
# are taken into account, and statements are adjusted to their first
# lines.
self.statements: Set[TLineNo] = set()
# The normalized line numbers of the excluded lines in the code,
# adjusted to their first lines.
self.excluded: Set[TLineNo] = set()
# The raw_* attributes are only used in this class, and in
# lab/parser.py to show how this class is working.
# The line numbers that start statements, as reported by the line
# number table in the bytecode.
self.raw_statements: Set[TLineNo] = set()
# The raw line numbers of excluded lines of code, as marked by pragmas.
self.raw_excluded: Set[TLineNo] = set()
# The line numbers of class definitions.
self.raw_classdefs: Set[TLineNo] = set()
# The line numbers of docstring lines.
self.raw_docstrings: Set[TLineNo] = set()
# Internal detail, used by lab/parser.py.
self.show_tokens = False
# A dict mapping line numbers to lexical statement starts for
# multi-line statements.
self._multiline: Dict[TLineNo, TLineNo] = {}
# Lazily-created arc data, and missing arc descriptions.
self._all_arcs: Optional[Set[TArc]] = None
self._missing_arc_fragments: Optional[TArcFragments] = None
def lines_matching(self, *regexes: str) -> Set[TLineNo]:
"""Find the lines matching one of a list of regexes.
Returns a set of line numbers, the lines that contain a match for one
of the regexes in `regexes`. The entire line needn't match, just a
part of it.
"""
combined = join_regex(regexes)
regex_c = re.compile(combined)
matches = set()
for i, ltext in enumerate(self.lines, start=1):
if regex_c.search(ltext):
matches.add(i)
return matches
def _raw_parse(self) -> None:
"""Parse the source to find the interesting facts about its lines.
A handful of attributes are updated.
"""
# Find lines which match an exclusion pattern.
if self.exclude:
self.raw_excluded = self.lines_matching(self.exclude)
# Tokenize, to find excluded suites, to find docstrings, and to find
# multi-line statements.
indent = 0
exclude_indent = 0
excluding = False
excluding_decorators = False
prev_toktype = token.INDENT
first_line = None
empty = True
first_on_line = True
nesting = 0
assert self.text is not None
tokgen = generate_tokens(self.text)
for toktype, ttext, (slineno, _), (elineno, _), ltext in tokgen:
if self.show_tokens: # pragma: debugging
print("%10s %5s %-20r %r" % (
tokenize.tok_name.get(toktype, toktype),
nice_pair((slineno, elineno)), ttext, ltext
))
if toktype == token.INDENT:
indent += 1
elif toktype == token.DEDENT:
indent -= 1
elif toktype == token.NAME:
if ttext == "class":
# Class definitions look like branches in the bytecode, so
# we need to exclude them. The simplest way is to note the
# lines with the "class" keyword.
self.raw_classdefs.add(slineno)
elif toktype == token.OP:
if ttext == ":" and nesting == 0:
should_exclude = (elineno in self.raw_excluded) or excluding_decorators
if not excluding and should_exclude:
# Start excluding a suite. We trigger off of the colon
# token so that the #pragma comment will be recognized on
# the same line as the colon.
self.raw_excluded.add(elineno)
exclude_indent = indent
excluding = True
excluding_decorators = False
elif ttext == "@" and first_on_line:
# A decorator.
if elineno in self.raw_excluded:
excluding_decorators = True
if excluding_decorators:
self.raw_excluded.add(elineno)
elif ttext in "([{":
nesting += 1
elif ttext in ")]}":
nesting -= 1
elif toktype == token.STRING and prev_toktype == token.INDENT:
# Strings that are first on an indented line are docstrings.
# (a trick from trace.py in the stdlib.) This works for
# 99.9999% of cases. For the rest (!) see:
# http://stackoverflow.com/questions/1769332/x/1769794#1769794
self.raw_docstrings.update(range(slineno, elineno+1))
elif toktype == token.NEWLINE:
if first_line is not None and elineno != first_line: # type: ignore[unreachable]
# We're at the end of a line, and we've ended on a
# different line than the first line of the statement,
# so record a multi-line range.
for l in range(first_line, elineno+1): # type: ignore[unreachable]
self._multiline[l] = first_line
first_line = None
first_on_line = True
if ttext.strip() and toktype != tokenize.COMMENT:
# A non-white-space token.
empty = False
if first_line is None:
# The token is not white space, and is the first in a statement.
first_line = slineno
# Check whether to end an excluded suite.
if excluding and indent <= exclude_indent:
excluding = False
if excluding:
self.raw_excluded.add(elineno)
first_on_line = False
prev_toktype = toktype
# Find the starts of the executable statements.
if not empty:
byte_parser = ByteParser(self.text, filename=self.filename)
self.raw_statements.update(byte_parser._find_statements())
# The first line of modules can lie and say 1 always, even if the first
# line of code is later. If so, map 1 to the actual first line of the
# module.
if env.PYBEHAVIOR.module_firstline_1 and self._multiline:
self._multiline[1] = min(self.raw_statements)
def first_line(self, lineno: TLineNo) -> TLineNo:
"""Return the first line number of the statement including `lineno`."""
if lineno < 0:
lineno = -self._multiline.get(-lineno, -lineno)
else:
lineno = self._multiline.get(lineno, lineno)
return lineno
def first_lines(self, linenos: Iterable[TLineNo]) -> Set[TLineNo]:
"""Map the line numbers in `linenos` to the correct first line of the
statement.
Returns a set of the first lines.
"""
return {self.first_line(l) for l in linenos}
def translate_lines(self, lines: Iterable[TLineNo]) -> Set[TLineNo]:
"""Implement `FileReporter.translate_lines`."""
return self.first_lines(lines)
def translate_arcs(self, arcs: Iterable[TArc]) -> Set[TArc]:
"""Implement `FileReporter.translate_arcs`."""
return {(self.first_line(a), self.first_line(b)) for (a, b) in arcs}
def parse_source(self) -> None:
"""Parse source text to find executable lines, excluded lines, etc.
Sets the .excluded and .statements attributes, normalized to the first
line of multi-line statements.
"""
try:
self._raw_parse()
except (tokenize.TokenError, IndentationError, SyntaxError) as err:
if hasattr(err, "lineno"):
lineno = err.lineno # IndentationError
else:
lineno = err.args[1][0] # TokenError
raise NotPython(
f"Couldn't parse '{self.filename}' as Python source: " +
f"{err.args[0]!r} at line {lineno}"
) from err
self.excluded = self.first_lines(self.raw_excluded)
ignore = self.excluded | self.raw_docstrings
starts = self.raw_statements - ignore
self.statements = self.first_lines(starts) - ignore
def arcs(self) -> Set[TArc]:
"""Get information about the arcs available in the code.
Returns a set of line number pairs. Line numbers have been normalized
to the first line of multi-line statements.
"""
if self._all_arcs is None:
self._analyze_ast()
assert self._all_arcs is not None
return self._all_arcs
def _analyze_ast(self) -> None:
"""Run the AstArcAnalyzer and save its results.
`_all_arcs` is the set of arcs in the code.
"""
aaa = AstArcAnalyzer(self.text, self.raw_statements, self._multiline)
aaa.analyze()
self._all_arcs = set()
for l1, l2 in aaa.arcs:
fl1 = self.first_line(l1)
fl2 = self.first_line(l2)
if fl1 != fl2:
self._all_arcs.add((fl1, fl2))
self._missing_arc_fragments = aaa.missing_arc_fragments
def exit_counts(self) -> Dict[TLineNo, int]:
"""Get a count of exits from that each line.
Excluded lines are excluded.
"""
exit_counts: Dict[TLineNo, int] = collections.defaultdict(int)
for l1, l2 in self.arcs():
if l1 < 0:
# Don't ever report -1 as a line number
continue
if l1 in self.excluded:
# Don't report excluded lines as line numbers.
continue
if l2 in self.excluded:
# Arcs to excluded lines shouldn't count.
continue
exit_counts[l1] += 1
# Class definitions have one extra exit, so remove one for each:
for l in self.raw_classdefs:
# Ensure key is there: class definitions can include excluded lines.
if l in exit_counts:
exit_counts[l] -= 1
return exit_counts
def missing_arc_description(
self,
start: TLineNo,
end: TLineNo,
executed_arcs: Optional[Iterable[TArc]] = None,
) -> str:
"""Provide an English sentence describing a missing arc."""
if self._missing_arc_fragments is None:
self._analyze_ast()
assert self._missing_arc_fragments is not None
actual_start = start
if (
executed_arcs and
end < 0 and end == -start and
(end, start) not in executed_arcs and
(end, start) in self._missing_arc_fragments
):
# It's a one-line callable, and we never even started it,
# and we have a message about not starting it.
start, end = end, start
fragment_pairs = self._missing_arc_fragments.get((start, end), [(None, None)])
msgs = []
for smsg, emsg in fragment_pairs:
if emsg is None:
if end < 0:
# Hmm, maybe we have a one-line callable, let's check.
if (-end, end) in self._missing_arc_fragments:
return self.missing_arc_description(-end, end)
emsg = "didn't jump to the function exit"
else:
emsg = "didn't jump to line {lineno}"
emsg = emsg.format(lineno=end)
msg = f"line {actual_start} {emsg}"
if smsg is not None:
msg += f", because {smsg.format(lineno=actual_start)}"
msgs.append(msg)
return " or ".join(msgs)
class ByteParser:
"""Parse bytecode to understand the structure of code."""
def __init__(
self,
text: str,
code: Optional[CodeType] = None,
filename: Optional[str] = None,
) -> None:
self.text = text
if code is not None:
self.code = code
else:
assert filename is not None
try:
self.code = compile(text, filename, "exec", dont_inherit=True)
except SyntaxError as synerr:
raise NotPython(
"Couldn't parse '%s' as Python source: '%s' at line %d" % (
filename, synerr.msg, synerr.lineno or 0
)
) from synerr
def child_parsers(self) -> Iterable[ByteParser]:
"""Iterate over all the code objects nested within this one.
The iteration includes `self` as its first value.
"""
return (ByteParser(self.text, code=c) for c in code_objects(self.code))
def _line_numbers(self) -> Iterable[TLineNo]:
"""Yield the line numbers possible in this code object.
Uses co_lnotab described in Python/compile.c to find the
line numbers. Produces a sequence: l0, l1, ...
"""
if hasattr(self.code, "co_lines"):
for _, _, line in self.code.co_lines():
if line:
yield line
else:
# Adapted from dis.py in the standard library.
byte_increments = self.code.co_lnotab[0::2]
line_increments = self.code.co_lnotab[1::2]
last_line_num = None
line_num = self.code.co_firstlineno
byte_num = 0
for byte_incr, line_incr in zip(byte_increments, line_increments):
if byte_incr:
if line_num != last_line_num:
yield line_num
last_line_num = line_num
byte_num += byte_incr
if env.PYBEHAVIOR.negative_lnotab and line_incr >= 0x80:
line_incr -= 0x100
line_num += line_incr
if line_num != last_line_num:
yield line_num
def _find_statements(self) -> Iterable[TLineNo]:
"""Find the statements in `self.code`.
Produce a sequence of line numbers that start statements. Recurses
into all code objects reachable from `self.code`.
"""
for bp in self.child_parsers():
# Get all of the lineno information from this code.
yield from bp._line_numbers()
#
# AST analysis
#
class ArcStart(collections.namedtuple("Arc", "lineno, cause")):
"""The information needed to start an arc.
`lineno` is the line number the arc starts from.
`cause` is an English text fragment used as the `startmsg` for
AstArcAnalyzer.missing_arc_fragments. It will be used to describe why an
arc wasn't executed, so should fit well into a sentence of the form,
"Line 17 didn't run because {cause}." The fragment can include "{lineno}"
to have `lineno` interpolated into it.
"""
def __new__(cls, lineno: TLineNo, cause: Optional[str] = None) -> ArcStart:
return super().__new__(cls, lineno, cause)
class TAddArcFn(Protocol):
"""The type for AstArcAnalyzer.add_arc()."""
def __call__(
self,
start: TLineNo,
end: TLineNo,
smsg: Optional[str] = None,
emsg: Optional[str] = None,
) -> None:
...
TArcFragments = Dict[TArc, List[Tuple[Optional[str], Optional[str]]]]
class Block:
"""
Blocks need to handle various exiting statements in their own ways.
All of these methods take a list of exits, and a callable `add_arc`
function that they can use to add arcs if needed. They return True if the
exits are handled, or False if the search should continue up the block
stack.
"""
# pylint: disable=unused-argument
def process_break_exits(self, exits: Set[ArcStart], add_arc: TAddArcFn) -> bool:
"""Process break exits."""
# Because break can only appear in loops, and most subclasses
# implement process_break_exits, this function is never reached.
raise AssertionError
def process_continue_exits(self, exits: Set[ArcStart], add_arc: TAddArcFn) -> bool:
"""Process continue exits."""
# Because continue can only appear in loops, and most subclasses
# implement process_continue_exits, this function is never reached.
raise AssertionError
def process_raise_exits(self, exits: Set[ArcStart], add_arc: TAddArcFn) -> bool:
"""Process raise exits."""
return False
def process_return_exits(self, exits: Set[ArcStart], add_arc: TAddArcFn) -> bool:
"""Process return exits."""
return False
class LoopBlock(Block):
"""A block on the block stack representing a `for` or `while` loop."""
def __init__(self, start: TLineNo) -> None:
# The line number where the loop starts.
self.start = start
# A set of ArcStarts, the arcs from break statements exiting this loop.
self.break_exits: Set[ArcStart] = set()
def process_break_exits(self, exits: Set[ArcStart], add_arc: TAddArcFn) -> bool:
self.break_exits.update(exits)
return True
def process_continue_exits(self, exits: Set[ArcStart], add_arc: TAddArcFn) -> bool:
for xit in exits:
add_arc(xit.lineno, self.start, xit.cause)
return True
class FunctionBlock(Block):
"""A block on the block stack representing a function definition."""
def __init__(self, start: TLineNo, name: str) -> None:
# The line number where the function starts.
self.start = start
# The name of the function.
self.name = name
def process_raise_exits(self, exits: Set[ArcStart], add_arc: TAddArcFn) -> bool:
for xit in exits:
add_arc(
xit.lineno, -self.start, xit.cause,
f"didn't except from function {self.name!r}",
)
return True
def process_return_exits(self, exits: Set[ArcStart], add_arc: TAddArcFn) -> bool:
for xit in exits:
add_arc(
xit.lineno, -self.start, xit.cause,
f"didn't return from function {self.name!r}",
)
return True
class TryBlock(Block):
"""A block on the block stack representing a `try` block."""
def __init__(self, handler_start: Optional[TLineNo], final_start: Optional[TLineNo]) -> None:
# The line number of the first "except" handler, if any.
self.handler_start = handler_start
# The line number of the "finally:" clause, if any.
self.final_start = final_start
# The ArcStarts for breaks/continues/returns/raises inside the "try:"
# that need to route through the "finally:" clause.
self.break_from: Set[ArcStart] = set()
self.continue_from: Set[ArcStart] = set()
self.raise_from: Set[ArcStart] = set()
self.return_from: Set[ArcStart] = set()
def process_break_exits(self, exits: Set[ArcStart], add_arc: TAddArcFn) -> bool:
if self.final_start is not None:
self.break_from.update(exits)
return True
return False
def process_continue_exits(self, exits: Set[ArcStart], add_arc: TAddArcFn) -> bool:
if self.final_start is not None:
self.continue_from.update(exits)
return True
return False
def process_raise_exits(self, exits: Set[ArcStart], add_arc: TAddArcFn) -> bool:
if self.handler_start is not None:
for xit in exits:
add_arc(xit.lineno, self.handler_start, xit.cause)
else:
assert self.final_start is not None
self.raise_from.update(exits)
return True
def process_return_exits(self, exits: Set[ArcStart], add_arc: TAddArcFn) -> bool:
if self.final_start is not None:
self.return_from.update(exits)
return True
return False
class WithBlock(Block):
"""A block on the block stack representing a `with` block."""
def __init__(self, start: TLineNo) -> None:
# We only ever use this block if it is needed, so that we don't have to
# check this setting in all the methods.
assert env.PYBEHAVIOR.exit_through_with
# The line number of the with statement.
self.start = start
# The ArcStarts for breaks/continues/returns/raises inside the "with:"
# that need to go through the with-statement while exiting.
self.break_from: Set[ArcStart] = set()
self.continue_from: Set[ArcStart] = set()
self.return_from: Set[ArcStart] = set()
def _process_exits(
self,
exits: Set[ArcStart],
add_arc: TAddArcFn,
from_set: Optional[Set[ArcStart]] = None,
) -> bool:
"""Helper to process the four kinds of exits."""
for xit in exits:
add_arc(xit.lineno, self.start, xit.cause)
if from_set is not None:
from_set.update(exits)
return True
def process_break_exits(self, exits: Set[ArcStart], add_arc: TAddArcFn) -> bool:
return self._process_exits(exits, add_arc, self.break_from)
def process_continue_exits(self, exits: Set[ArcStart], add_arc: TAddArcFn) -> bool:
return self._process_exits(exits, add_arc, self.continue_from)
def process_raise_exits(self, exits: Set[ArcStart], add_arc: TAddArcFn) -> bool:
return self._process_exits(exits, add_arc)
def process_return_exits(self, exits: Set[ArcStart], add_arc: TAddArcFn) -> bool:
return self._process_exits(exits, add_arc, self.return_from)
class NodeList(ast.AST):
"""A synthetic fictitious node, containing a sequence of nodes.
This is used when collapsing optimized if-statements, to represent the
unconditional execution of one of the clauses.
"""
def __init__(self, body: Sequence[ast.AST]) -> None:
self.body = body
self.lineno = body[0].lineno
# TODO: some add_arcs methods here don't add arcs, they return them. Rename them.
# TODO: the cause messages have too many commas.
# TODO: Shouldn't the cause messages join with "and" instead of "or"?
def _make_expression_code_method(noun: str) -> Callable[[AstArcAnalyzer, ast.AST], None]:
"""A function to make methods for expression-based callable _code_object__ methods."""
def _code_object__expression_callable(self: AstArcAnalyzer, node: ast.AST) -> None:
start = self.line_for_node(node)
self.add_arc(-start, start, None, f"didn't run the {noun} on line {start}")
self.add_arc(start, -start, None, f"didn't finish the {noun} on line {start}")
return _code_object__expression_callable
class AstArcAnalyzer:
"""Analyze source text with an AST to find executable code paths."""
def __init__(
self,
text: str,
statements: Set[TLineNo],
multiline: Dict[TLineNo, TLineNo],
) -> None:
self.root_node = ast.parse(text)
# TODO: I think this is happening in too many places.
self.statements = {multiline.get(l, l) for l in statements}
self.multiline = multiline
# Turn on AST dumps with an environment variable.
# $set_env.py: COVERAGE_AST_DUMP - Dump the AST nodes when parsing code.
dump_ast = bool(int(os.environ.get("COVERAGE_AST_DUMP", 0)))
if dump_ast: # pragma: debugging
# Dump the AST so that failing tests have helpful output.
print(f"Statements: {self.statements}")
print(f"Multiline map: {self.multiline}")
ast_dump(self.root_node)
self.arcs: Set[TArc] = set()
# A map from arc pairs to a list of pairs of sentence fragments:
# { (start, end): [(startmsg, endmsg), ...], }
#
# For an arc from line 17, they should be usable like:
# "Line 17 {endmsg}, because {startmsg}"
self.missing_arc_fragments: TArcFragments = collections.defaultdict(list)
self.block_stack: List[Block] = []
# $set_env.py: COVERAGE_TRACK_ARCS - Trace possible arcs added while parsing code.
self.debug = bool(int(os.environ.get("COVERAGE_TRACK_ARCS", 0)))
def analyze(self) -> None:
"""Examine the AST tree from `root_node` to determine possible arcs.
This sets the `arcs` attribute to be a set of (from, to) line number
pairs.
"""
for node in ast.walk(self.root_node):
node_name = node.__class__.__name__
code_object_handler = getattr(self, "_code_object__" + node_name, None)
if code_object_handler is not None:
code_object_handler(node)
def add_arc(
self,
start: TLineNo,
end: TLineNo,
smsg: Optional[str] = None,
emsg: Optional[str] = None,
) -> None:
"""Add an arc, including message fragments to use if it is missing."""
if self.debug: # pragma: debugging
print(f"\nAdding possible arc: ({start}, {end}): {smsg!r}, {emsg!r}")
print(short_stack(limit=10))
self.arcs.add((start, end))
if smsg is not None or emsg is not None:
self.missing_arc_fragments[(start, end)].append((smsg, emsg))
def nearest_blocks(self) -> Iterable[Block]:
"""Yield the blocks in nearest-to-farthest order."""
return reversed(self.block_stack)
def line_for_node(self, node: ast.AST) -> TLineNo:
"""What is the right line number to use for this node?
This dispatches to _line__Node functions where needed.
"""
node_name = node.__class__.__name__
handler = cast(
Optional[Callable[[ast.AST], TLineNo]],
getattr(self, "_line__" + node_name, None)
)
if handler is not None:
return handler(node)
else:
return node.lineno
def _line_decorated(self, node: ast.FunctionDef) -> TLineNo:
"""Compute first line number for things that can be decorated (classes and functions)."""
lineno = node.lineno
if env.PYBEHAVIOR.trace_decorated_def or env.PYBEHAVIOR.def_ast_no_decorator:
if node.decorator_list:
lineno = node.decorator_list[0].lineno
return lineno
def _line__Assign(self, node: ast.Assign) -> TLineNo:
return self.line_for_node(node.value)
_line__ClassDef = _line_decorated
def _line__Dict(self, node: ast.Dict) -> TLineNo:
if node.keys:
if node.keys[0] is not None:
return node.keys[0].lineno
else:
# Unpacked dict literals `{**{"a":1}}` have None as the key,
# use the value in that case.
return node.values[0].lineno
else:
return node.lineno
_line__FunctionDef = _line_decorated
_line__AsyncFunctionDef = _line_decorated
def _line__List(self, node: ast.List) -> TLineNo:
if node.elts:
return self.line_for_node(node.elts[0])
else:
return node.lineno
def _line__Module(self, node: ast.Module) -> TLineNo:
if env.PYBEHAVIOR.module_firstline_1:
return 1
elif node.body:
return self.line_for_node(node.body[0])
else:
# Empty modules have no line number, they always start at 1.
return 1
# The node types that just flow to the next node with no complications.
OK_TO_DEFAULT = {
"AnnAssign", "Assign", "Assert", "AugAssign", "Delete", "Expr", "Global",
"Import", "ImportFrom", "Nonlocal", "Pass",
}
def add_arcs(self, node: ast.AST) -> Set[ArcStart]:
"""Add the arcs for `node`.
Return a set of ArcStarts, exits from this node to the next. Because a
node represents an entire sub-tree (including its children), the exits
from a node can be arbitrarily complex::
if something(1):
if other(2):
doit(3)
else:
doit(5)
There are two exits from line 1: they start at line 3 and line 5.
"""
node_name = node.__class__.__name__
handler = cast(
Optional[Callable[[ast.AST], Set[ArcStart]]],
getattr(self, "_handle__" + node_name, None)
)
if handler is not None:
return handler(node)
else:
# No handler: either it's something that's ok to default (a simple
# statement), or it's something we overlooked.
if env.TESTING:
if node_name not in self.OK_TO_DEFAULT:
raise RuntimeError(f"*** Unhandled: {node}") # pragma: only failure
# Default for simple statements: one exit from this node.
return {ArcStart(self.line_for_node(node))}
def add_body_arcs(
self,
body: Sequence[ast.AST],
from_start: Optional[ArcStart] = None,
prev_starts: Optional[Set[ArcStart]] = None
) -> Set[ArcStart]:
"""Add arcs for the body of a compound statement.
`body` is the body node. `from_start` is a single `ArcStart` that can
be the previous line in flow before this body. `prev_starts` is a set
of ArcStarts that can be the previous line. Only one of them should be
given.
Returns a set of ArcStarts, the exits from this body.
"""
if prev_starts is None:
assert from_start is not None
prev_starts = {from_start}
for body_node in body:
lineno = self.line_for_node(body_node)
first_line = self.multiline.get(lineno, lineno)
if first_line not in self.statements:
maybe_body_node = self.find_non_missing_node(body_node)
if maybe_body_node is None:
continue
body_node = maybe_body_node
lineno = self.line_for_node(body_node)
for prev_start in prev_starts:
self.add_arc(prev_start.lineno, lineno, prev_start.cause)
prev_starts = self.add_arcs(body_node)
return prev_starts
def find_non_missing_node(self, node: ast.AST) -> Optional[ast.AST]:
"""Search `node` looking for a child that has not been optimized away.
This might return the node you started with, or it will work recursively
to find a child node in self.statements.
Returns a node, or None if none of the node remains.
"""
# This repeats work just done in add_body_arcs, but this duplication
# means we can avoid a function call in the 99.9999% case of not
# optimizing away statements.
lineno = self.line_for_node(node)
first_line = self.multiline.get(lineno, lineno)
if first_line in self.statements:
return node
missing_fn = cast(
Optional[Callable[[ast.AST], Optional[ast.AST]]],
getattr(self, "_missing__" + node.__class__.__name__, None)
)
if missing_fn is not None:
ret_node = missing_fn(node)
else:
ret_node = None
return ret_node
# Missing nodes: _missing__*
#
# Entire statements can be optimized away by Python. They will appear in
# the AST, but not the bytecode. These functions are called (by
# find_non_missing_node) to find a node to use instead of the missing
# node. They can return None if the node should truly be gone.
def _missing__If(self, node: ast.If) -> Optional[ast.AST]:
# If the if-node is missing, then one of its children might still be
# here, but not both. So return the first of the two that isn't missing.
# Use a NodeList to hold the clauses as a single node.
non_missing = self.find_non_missing_node(NodeList(node.body))
if non_missing:
return non_missing
if node.orelse:
return self.find_non_missing_node(NodeList(node.orelse))
return None
def _missing__NodeList(self, node: NodeList) -> Optional[ast.AST]:
# A NodeList might be a mixture of missing and present nodes. Find the
# ones that are present.
non_missing_children = []
for child in node.body:
maybe_child = self.find_non_missing_node(child)
if maybe_child is not None:
non_missing_children.append(maybe_child)
# Return the simplest representation of the present children.
if not non_missing_children:
return None
if len(non_missing_children) == 1:
return non_missing_children[0]
return NodeList(non_missing_children)
def _missing__While(self, node: ast.While) -> Optional[ast.AST]:
body_nodes = self.find_non_missing_node(NodeList(node.body))
if not body_nodes:
return None
# Make a synthetic While-true node.
new_while = ast.While()
new_while.lineno = body_nodes.lineno
new_while.test = ast.Name()
new_while.test.lineno = body_nodes.lineno
new_while.test.id = "True"
assert hasattr(body_nodes, "body")
new_while.body = body_nodes.body
new_while.orelse = []
return new_while
def is_constant_expr(self, node: ast.AST) -> Optional[str]:
"""Is this a compile-time constant?"""
node_name = node.__class__.__name__
if node_name in ["Constant", "NameConstant", "Num"]:
return "Num"
elif isinstance(node, ast.Name):
if node.id in ["True", "False", "None", "__debug__"]:
return "Name"
return None
# In the fullness of time, these might be good tests to write:
# while EXPR:
# while False:
# listcomps hidden deep in other expressions
# listcomps hidden in lists: x = [[i for i in range(10)]]
# nested function definitions
# Exit processing: process_*_exits
#
# These functions process the four kinds of jump exits: break, continue,
# raise, and return. To figure out where an exit goes, we have to look at
# the block stack context. For example, a break will jump to the nearest
# enclosing loop block, or the nearest enclosing finally block, whichever
# is nearer.
def process_break_exits(self, exits: Set[ArcStart]) -> None:
"""Add arcs due to jumps from `exits` being breaks."""
for block in self.nearest_blocks(): # pragma: always breaks
if block.process_break_exits(exits, self.add_arc):
break
def process_continue_exits(self, exits: Set[ArcStart]) -> None:
"""Add arcs due to jumps from `exits` being continues."""
for block in self.nearest_blocks(): # pragma: always breaks
if block.process_continue_exits(exits, self.add_arc):
break
def process_raise_exits(self, exits: Set[ArcStart]) -> None:
"""Add arcs due to jumps from `exits` being raises."""
for block in self.nearest_blocks():
if block.process_raise_exits(exits, self.add_arc):
break
def process_return_exits(self, exits: Set[ArcStart]) -> None:
"""Add arcs due to jumps from `exits` being returns."""
for block in self.nearest_blocks(): # pragma: always breaks
if block.process_return_exits(exits, self.add_arc):
break
# Handlers: _handle__*
#
# Each handler deals with a specific AST node type, dispatched from
# add_arcs. Handlers return the set of exits from that node, and can
# also call self.add_arc to record arcs they find. These functions mirror
# the Python semantics of each syntactic construct. See the docstring
# for add_arcs to understand the concept of exits from a node.
#
# Every node type that represents a statement should have a handler, or it
# should be listed in OK_TO_DEFAULT.
def _handle__Break(self, node: ast.Break) -> Set[ArcStart]:
here = self.line_for_node(node)
break_start = ArcStart(here, cause="the break on line {lineno} wasn't executed")
self.process_break_exits({break_start})
return set()
def _handle_decorated(self, node: ast.FunctionDef) -> Set[ArcStart]:
"""Add arcs for things that can be decorated (classes and functions)."""
main_line: TLineNo = node.lineno
last: Optional[TLineNo] = node.lineno
decs = node.decorator_list
if decs:
if env.PYBEHAVIOR.trace_decorated_def or env.PYBEHAVIOR.def_ast_no_decorator:
last = None
for dec_node in decs:
dec_start = self.line_for_node(dec_node)
if last is not None and dec_start != last:
self.add_arc(last, dec_start)
last = dec_start
assert last is not None
if env.PYBEHAVIOR.trace_decorated_def:
self.add_arc(last, main_line)
last = main_line
if env.PYBEHAVIOR.trace_decorator_line_again:
for top, bot in zip(decs, decs[1:]):
self.add_arc(self.line_for_node(bot), self.line_for_node(top))
self.add_arc(self.line_for_node(decs[0]), main_line)
self.add_arc(main_line, self.line_for_node(decs[-1]))
# The definition line may have been missed, but we should have it
# in `self.statements`. For some constructs, `line_for_node` is
# not what we'd think of as the first line in the statement, so map
# it to the first one.
if node.body:
body_start = self.line_for_node(node.body[0])
body_start = self.multiline.get(body_start, body_start)
for lineno in range(last+1, body_start):
if lineno in self.statements:
self.add_arc(last, lineno)
last = lineno
# The body is handled in collect_arcs.
assert last is not None
return {ArcStart(last)}
_handle__ClassDef = _handle_decorated
def _handle__Continue(self, node: ast.Continue) -> Set[ArcStart]:
here = self.line_for_node(node)
continue_start = ArcStart(here, cause="the continue on line {lineno} wasn't executed")
self.process_continue_exits({continue_start})
return set()
def _handle__For(self, node: ast.For) -> Set[ArcStart]:
start = self.line_for_node(node.iter)
self.block_stack.append(LoopBlock(start=start))
from_start = ArcStart(start, cause="the loop on line {lineno} never started")
exits = self.add_body_arcs(node.body, from_start=from_start)
# Any exit from the body will go back to the top of the loop.
for xit in exits:
self.add_arc(xit.lineno, start, xit.cause)
my_block = self.block_stack.pop()
assert isinstance(my_block, LoopBlock)
exits = my_block.break_exits
from_start = ArcStart(start, cause="the loop on line {lineno} didn't complete")
if node.orelse:
else_exits = self.add_body_arcs(node.orelse, from_start=from_start)
exits |= else_exits
else:
# No else clause: exit from the for line.
exits.add(from_start)
return exits
_handle__AsyncFor = _handle__For
_handle__FunctionDef = _handle_decorated
_handle__AsyncFunctionDef = _handle_decorated
def _handle__If(self, node: ast.If) -> Set[ArcStart]:
start = self.line_for_node(node.test)
from_start = ArcStart(start, cause="the condition on line {lineno} was never true")
exits = self.add_body_arcs(node.body, from_start=from_start)
from_start = ArcStart(start, cause="the condition on line {lineno} was never false")
exits |= self.add_body_arcs(node.orelse, from_start=from_start)
return exits
if sys.version_info >= (3, 10):
def _handle__Match(self, node: ast.Match) -> Set[ArcStart]:
start = self.line_for_node(node)
last_start = start
exits = set()
had_wildcard = False
for case in node.cases:
case_start = self.line_for_node(case.pattern)
pattern = case.pattern
while isinstance(pattern, ast.MatchOr):
pattern = pattern.patterns[-1]
if isinstance(pattern, ast.MatchAs):
had_wildcard = True
self.add_arc(last_start, case_start, "the pattern on line {lineno} always matched")
from_start = ArcStart(
case_start,
cause="the pattern on line {lineno} never matched",
)
exits |= self.add_body_arcs(case.body, from_start=from_start)
last_start = case_start
if not had_wildcard:
exits.add(from_start)
return exits
def _handle__NodeList(self, node: NodeList) -> Set[ArcStart]:
start = self.line_for_node(node)
exits = self.add_body_arcs(node.body, from_start=ArcStart(start))
return exits
def _handle__Raise(self, node: ast.Raise) -> Set[ArcStart]:
here = self.line_for_node(node)
raise_start = ArcStart(here, cause="the raise on line {lineno} wasn't executed")
self.process_raise_exits({raise_start})
# `raise` statement jumps away, no exits from here.
return set()
def _handle__Return(self, node: ast.Return) -> Set[ArcStart]:
here = self.line_for_node(node)
return_start = ArcStart(here, cause="the return on line {lineno} wasn't executed")
self.process_return_exits({return_start})
# `return` statement jumps away, no exits from here.
return set()
def _handle__Try(self, node: ast.Try) -> Set[ArcStart]:
if node.handlers:
handler_start = self.line_for_node(node.handlers[0])
else:
handler_start = None
if node.finalbody:
final_start = self.line_for_node(node.finalbody[0])
else:
final_start = None
# This is true by virtue of Python syntax: have to have either except
# or finally, or both.
assert handler_start is not None or final_start is not None
try_block = TryBlock(handler_start, final_start)
self.block_stack.append(try_block)
start = self.line_for_node(node)
exits = self.add_body_arcs(node.body, from_start=ArcStart(start))
# We're done with the `try` body, so this block no longer handles
# exceptions. We keep the block so the `finally` clause can pick up
# flows from the handlers and `else` clause.
if node.finalbody:
try_block.handler_start = None
if node.handlers:
# If there are `except` clauses, then raises in the try body
# will already jump to them. Start this set over for raises in
# `except` and `else`.
try_block.raise_from = set()
else:
self.block_stack.pop()
handler_exits: Set[ArcStart] = set()
if node.handlers:
last_handler_start: Optional[TLineNo] = None
for handler_node in node.handlers:
handler_start = self.line_for_node(handler_node)
if last_handler_start is not None:
self.add_arc(last_handler_start, handler_start)
last_handler_start = handler_start
from_cause = "the exception caught by line {lineno} didn't happen"
from_start = ArcStart(handler_start, cause=from_cause)
handler_exits |= self.add_body_arcs(handler_node.body, from_start=from_start)
if node.orelse:
exits = self.add_body_arcs(node.orelse, prev_starts=exits)
exits |= handler_exits
if node.finalbody:
self.block_stack.pop()
final_from = ( # You can get to the `finally` clause from:
exits | # the exits of the body or `else` clause,
try_block.break_from | # or a `break`,
try_block.continue_from | # or a `continue`,
try_block.raise_from | # or a `raise`,
try_block.return_from # or a `return`.
)
final_exits = self.add_body_arcs(node.finalbody, prev_starts=final_from)
if try_block.break_from:
if env.PYBEHAVIOR.finally_jumps_back:
for break_line in try_block.break_from:
lineno = break_line.lineno
cause = break_line.cause.format(lineno=lineno)
for final_exit in final_exits:
self.add_arc(final_exit.lineno, lineno, cause)
breaks = try_block.break_from
else:
breaks = self._combine_finally_starts(try_block.break_from, final_exits)
self.process_break_exits(breaks)
if try_block.continue_from:
if env.PYBEHAVIOR.finally_jumps_back:
for continue_line in try_block.continue_from:
lineno = continue_line.lineno
cause = continue_line.cause.format(lineno=lineno)
for final_exit in final_exits:
self.add_arc(final_exit.lineno, lineno, cause)
continues = try_block.continue_from
else:
continues = self._combine_finally_starts(try_block.continue_from, final_exits)
self.process_continue_exits(continues)
if try_block.raise_from:
self.process_raise_exits(
self._combine_finally_starts(try_block.raise_from, final_exits)
)
if try_block.return_from:
if env.PYBEHAVIOR.finally_jumps_back:
for return_line in try_block.return_from:
lineno = return_line.lineno
cause = return_line.cause.format(lineno=lineno)
for final_exit in final_exits:
self.add_arc(final_exit.lineno, lineno, cause)
returns = try_block.return_from
else:
returns = self._combine_finally_starts(try_block.return_from, final_exits)
self.process_return_exits(returns)
if exits:
# The finally clause's exits are only exits for the try block
# as a whole if the try block had some exits to begin with.
exits = final_exits
return exits
def _combine_finally_starts(self, starts: Set[ArcStart], exits: Set[ArcStart]) -> Set[ArcStart]:
"""Helper for building the cause of `finally` branches.
"finally" clauses might not execute their exits, and the causes could
be due to a failure to execute any of the exits in the try block. So
we use the causes from `starts` as the causes for `exits`.
"""
causes = []
for start in sorted(starts):
if start.cause is not None:
causes.append(start.cause.format(lineno=start.lineno))
cause = " or ".join(causes)
exits = {ArcStart(xit.lineno, cause) for xit in exits}
return exits
def _handle__While(self, node: ast.While) -> Set[ArcStart]:
start = to_top = self.line_for_node(node.test)
constant_test = self.is_constant_expr(node.test)
top_is_body0 = False
if constant_test:
top_is_body0 = True
if env.PYBEHAVIOR.keep_constant_test:
top_is_body0 = False
if top_is_body0:
to_top = self.line_for_node(node.body[0])
self.block_stack.append(LoopBlock(start=to_top))
from_start = ArcStart(start, cause="the condition on line {lineno} was never true")
exits = self.add_body_arcs(node.body, from_start=from_start)
for xit in exits:
self.add_arc(xit.lineno, to_top, xit.cause)
exits = set()
my_block = self.block_stack.pop()
assert isinstance(my_block, LoopBlock)
exits.update(my_block.break_exits)
from_start = ArcStart(start, cause="the condition on line {lineno} was never false")
if node.orelse:
else_exits = self.add_body_arcs(node.orelse, from_start=from_start)
exits |= else_exits
else:
# No `else` clause: you can exit from the start.
if not constant_test:
exits.add(from_start)
return exits
def _handle__With(self, node: ast.With) -> Set[ArcStart]:
start = self.line_for_node(node)
if env.PYBEHAVIOR.exit_through_with:
self.block_stack.append(WithBlock(start=start))
exits = self.add_body_arcs(node.body, from_start=ArcStart(start))
if env.PYBEHAVIOR.exit_through_with:
with_block = self.block_stack.pop()
assert isinstance(with_block, WithBlock)
with_exit = {ArcStart(start)}
if exits:
for xit in exits:
self.add_arc(xit.lineno, start)
exits = with_exit
if with_block.break_from:
self.process_break_exits(
self._combine_finally_starts(with_block.break_from, with_exit)
)
if with_block.continue_from:
self.process_continue_exits(
self._combine_finally_starts(with_block.continue_from, with_exit)
)
if with_block.return_from:
self.process_return_exits(
self._combine_finally_starts(with_block.return_from, with_exit)
)
return exits
_handle__AsyncWith = _handle__With
# Code object dispatchers: _code_object__*
#
# These methods are used by analyze() as the start of the analysis.
# There is one for each construct with a code object.
def _code_object__Module(self, node: ast.Module) -> None:
start = self.line_for_node(node)
if node.body:
exits = self.add_body_arcs(node.body, from_start=ArcStart(-start))
for xit in exits:
self.add_arc(xit.lineno, -start, xit.cause, "didn't exit the module")
else:
# Empty module.
self.add_arc(-start, start)
self.add_arc(start, -start)
def _code_object__FunctionDef(self, node: ast.FunctionDef) -> None:
start = self.line_for_node(node)
self.block_stack.append(FunctionBlock(start=start, name=node.name))
exits = self.add_body_arcs(node.body, from_start=ArcStart(-start))
self.process_return_exits(exits)
self.block_stack.pop()
_code_object__AsyncFunctionDef = _code_object__FunctionDef
def _code_object__ClassDef(self, node: ast.ClassDef) -> None:
start = self.line_for_node(node)
self.add_arc(-start, start)
exits = self.add_body_arcs(node.body, from_start=ArcStart(start))
for xit in exits:
self.add_arc(
xit.lineno, -start, xit.cause,
f"didn't exit the body of class {node.name!r}",
)
_code_object__Lambda = _make_expression_code_method("lambda")
_code_object__GeneratorExp = _make_expression_code_method("generator expression")
if env.PYBEHAVIOR.comprehensions_are_functions:
_code_object__DictComp = _make_expression_code_method("dictionary comprehension")
_code_object__SetComp = _make_expression_code_method("set comprehension")
_code_object__ListComp = _make_expression_code_method("list comprehension")
# Code only used when dumping the AST for debugging.
SKIP_DUMP_FIELDS = ["ctx"]
def _is_simple_value(value: Any) -> bool:
"""Is `value` simple enough to be displayed on a single line?"""
return (
value in [None, [], (), {}, set(), frozenset(), Ellipsis] or
isinstance(value, (bytes, int, float, str))
)
def ast_dump(
node: ast.AST,
depth: int = 0,
print: Callable[[str], None] = print, # pylint: disable=redefined-builtin
) -> None:
"""Dump the AST for `node`.
This recursively walks the AST, printing a readable version.
"""
indent = " " * depth
lineno = getattr(node, "lineno", None)
if lineno is not None:
linemark = f" @ {node.lineno},{node.col_offset}"
if hasattr(node, "end_lineno"):
assert hasattr(node, "end_col_offset")
linemark += ":"
if node.end_lineno != node.lineno:
linemark += f"{node.end_lineno},"
linemark += f"{node.end_col_offset}"
else:
linemark = ""
head = f"{indent}<{node.__class__.__name__}{linemark}"
named_fields = [
(name, value)
for name, value in ast.iter_fields(node)
if name not in SKIP_DUMP_FIELDS
]
if not named_fields:
print(f"{head}>")
elif len(named_fields) == 1 and _is_simple_value(named_fields[0][1]):
field_name, value = named_fields[0]
print(f"{head} {field_name}: {value!r}>")
else:
print(head)
if 0:
print("{}# mro: {}".format( # type: ignore[unreachable]
indent, ", ".join(c.__name__ for c in node.__class__.__mro__[1:]),
))
next_indent = indent + " "
for field_name, value in named_fields:
prefix = f"{next_indent}{field_name}:"
if _is_simple_value(value):
print(f"{prefix} {value!r}")
elif isinstance(value, list):
print(f"{prefix} [")
for n in value:
if _is_simple_value(n):
print(f"{next_indent} {n!r}")
else:
ast_dump(n, depth + 8, print=print)
print(f"{next_indent}]")
else:
print(prefix)
ast_dump(value, depth + 8, print=print)
print(f"{indent}>")