432 lines
15 KiB
Python
432 lines
15 KiB
Python
import bisect
|
|
import enum
|
|
import enum
|
|
import logging
|
|
import typing
|
|
from dataclasses import dataclass
|
|
|
|
from . import parser
|
|
|
|
|
|
@dataclass
|
|
class TokenValue:
|
|
kind: str
|
|
start: int
|
|
end: int
|
|
|
|
|
|
@dataclass
|
|
class Tree:
|
|
name: str | None
|
|
start: int
|
|
end: int
|
|
children: typing.Tuple["Tree | TokenValue", ...]
|
|
|
|
|
|
@dataclass
|
|
class ParseError:
|
|
message: str
|
|
start: int
|
|
end: int
|
|
|
|
|
|
ParseStack = list[typing.Tuple[int, TokenValue | Tree | None]]
|
|
|
|
|
|
recover_log = logging.getLogger("parser.recovery")
|
|
|
|
|
|
class RepairAction(enum.Enum):
|
|
Base = "bas"
|
|
Insert = "ins"
|
|
Delete = "del"
|
|
Shift = "sft"
|
|
|
|
|
|
class RepairStack(typing.NamedTuple):
|
|
state: int
|
|
parent: "RepairStack | None"
|
|
|
|
@classmethod
|
|
def from_stack(cls, stack: ParseStack) -> "RepairStack":
|
|
if len(stack) == 0:
|
|
raise ValueError("Empty stack")
|
|
|
|
result: RepairStack | None = None
|
|
for item in stack:
|
|
result = RepairStack(state=item[0], parent=result)
|
|
|
|
assert result is not None
|
|
return result
|
|
|
|
def pop(self, n: int) -> "RepairStack":
|
|
s = self
|
|
while n > 0:
|
|
s = s.parent
|
|
n -= 1
|
|
assert s is not None, "Stack underflow"
|
|
|
|
return s
|
|
|
|
def flatten(self) -> list[int]:
|
|
stack = self
|
|
result: list[int] = []
|
|
while stack is not None:
|
|
result.append(stack.state)
|
|
stack = stack.parent
|
|
return result
|
|
|
|
def push(self, state: int) -> "RepairStack":
|
|
return RepairStack(state, self)
|
|
|
|
def handle_token(
|
|
self, table: parser.ParseTable, token: str
|
|
) -> typing.Tuple["RepairStack | None", bool]:
|
|
rl = recover_log
|
|
|
|
stack = self
|
|
while True:
|
|
action = table.actions[stack.state].get(token)
|
|
if action is None:
|
|
return None, False
|
|
|
|
match action:
|
|
case parser.Shift():
|
|
rl.debug(f"{stack.state}: SHIFT -> {action.state}")
|
|
return stack.push(action.state), False
|
|
|
|
case parser.Accept():
|
|
rl.debug(f"{stack.state}: ACCEPT")
|
|
return stack, True # ?
|
|
|
|
case parser.Reduce():
|
|
rl.debug(f"{stack.state}: REDUCE {action.name} {action.count} ")
|
|
new_stack = stack.pop(action.count)
|
|
rl.debug(f" -> {new_stack.state}")
|
|
new_state = table.gotos[new_stack.state][action.name]
|
|
rl.debug(f" goto {new_state}")
|
|
stack = new_stack.push(new_state)
|
|
|
|
case parser.Error():
|
|
assert False, "Explicit error found in repair"
|
|
|
|
case _:
|
|
typing.assert_never(action)
|
|
|
|
|
|
class Repair:
|
|
repair: RepairAction
|
|
cost: int
|
|
stack: RepairStack
|
|
value: str | None
|
|
parent: "Repair | None"
|
|
shifts: int
|
|
success: bool
|
|
|
|
def __init__(self, repair, cost, stack, parent, advance=0, value=None, success=False):
|
|
self.repair = repair
|
|
self.cost = cost
|
|
self.stack = stack
|
|
self.parent = parent
|
|
self.value = value
|
|
self.success = success
|
|
self.advance = advance
|
|
|
|
if parent is not None:
|
|
self.cost += parent.cost
|
|
self.advance += parent.advance
|
|
|
|
if self.advance >= 3:
|
|
self.success = True
|
|
|
|
def __repr__(self):
|
|
valstr = f"({self.value})" if self.value is not None else ""
|
|
return f"<Repair {self.repair.value}{valstr} cost:{self.cost} advance:{self.advance}>"
|
|
|
|
def neighbors(
|
|
self,
|
|
table: parser.ParseTable,
|
|
input: list[TokenValue],
|
|
start: int,
|
|
):
|
|
input_index = start + self.advance
|
|
current_token = input[input_index].kind
|
|
|
|
rl = recover_log
|
|
if rl.isEnabledFor(logging.INFO):
|
|
valstr = f"({self.value})" if self.value is not None else ""
|
|
rl.debug(f"{self.repair.value}{valstr} @ {self.cost} input:{input_index}")
|
|
rl.debug(f" {','.join(str(s) for s in self.stack.flatten())}")
|
|
|
|
state = self.stack.state
|
|
|
|
# For insert: go through all the actions and run all the possible
|
|
# reduce/accepts on them. This will generate a *new stack* which we
|
|
# then capture with an "Insert" repair action. Do not manipuate the
|
|
# input stream.
|
|
#
|
|
# For shift: produce a repair that consumes the current input token,
|
|
# advancing the input stream, and manipulating the stack as
|
|
# necessary, producing a new version of the stack. Count up the
|
|
# number of successful shifts.
|
|
for token in table.actions[state].keys():
|
|
rl.debug(f" token: {token}")
|
|
new_stack, success = self.stack.handle_token(table, token)
|
|
if new_stack is None:
|
|
# Not clear why this is necessary, but I think state merging
|
|
# causes us to occasionally have reduce actions that lead to
|
|
# errors. It's not a bug, technically, to insert a reduce in
|
|
# a table that leads to a syntax error... "I don't know what
|
|
# happens but I do know that if I see this I'm at the end of
|
|
# this production I'm in!"
|
|
continue
|
|
|
|
if token == current_token:
|
|
rl.debug(f" generate shift {token}")
|
|
yield Repair(
|
|
repair=RepairAction.Shift,
|
|
parent=self,
|
|
stack=new_stack,
|
|
cost=0, # Shifts are free.
|
|
advance=1, # Move forward by one.
|
|
success=success,
|
|
)
|
|
|
|
# Never generate an insert for EOF, that might cause us to cut
|
|
# off large parts of the tree!
|
|
if token != "$":
|
|
rl.debug(f" generate insert {token}")
|
|
yield Repair(
|
|
repair=RepairAction.Insert,
|
|
value=token,
|
|
parent=self,
|
|
stack=new_stack,
|
|
cost=1, # TODO: Configurable token costs
|
|
success=success,
|
|
)
|
|
|
|
# For delete: produce a repair that just advances the input token
|
|
# stream, but does not manipulate the stack at all. Obviously we can
|
|
# only do this if we aren't at the end of the stream. Do not generate
|
|
# a "delete" if the previous repair was an "insert". (Only allow
|
|
# delete-insert pairs, not insert-delete, because they are
|
|
# symmetrical and therefore a waste of time and memory.)
|
|
if self.repair != RepairAction.Insert and current_token != "$":
|
|
rl.debug(f" generate delete")
|
|
yield Repair(
|
|
repair=RepairAction.Delete,
|
|
parent=self,
|
|
stack=self.stack,
|
|
cost=2, # TODO: Configurable token costs
|
|
advance=1,
|
|
)
|
|
|
|
|
|
def recover(table: parser.ParseTable, input: list[TokenValue], start: int, stack: ParseStack):
|
|
rl = recover_log
|
|
initial = Repair(
|
|
repair=RepairAction.Base,
|
|
cost=0,
|
|
stack=RepairStack.from_stack(stack),
|
|
parent=None,
|
|
)
|
|
|
|
todo_queue = [[initial]]
|
|
level = 0
|
|
while level < len(todo_queue):
|
|
queue_index = 0
|
|
queue = todo_queue[level]
|
|
while queue_index < len(queue):
|
|
repair = queue[queue_index]
|
|
|
|
# NOTE: This is guaranteed to be the cheapest possible success-
|
|
# there can be no success cheaper than this one. Since
|
|
# we're going to pick one arbitrarily, this one might as
|
|
# well be it.
|
|
if repair.success:
|
|
repairs: list[Repair] = []
|
|
while repair is not None:
|
|
repairs.append(repair)
|
|
repair = repair.parent
|
|
repairs.reverse()
|
|
if rl.isEnabledFor(logging.INFO):
|
|
rl.info("Recovered with actions:")
|
|
for repair in repairs:
|
|
rl.info(" " + repr(repair))
|
|
return repairs
|
|
|
|
for neighbor in repair.neighbors(table, input, start):
|
|
for _ in range((neighbor.cost - len(todo_queue)) + 1):
|
|
todo_queue.append([])
|
|
todo_queue[neighbor.cost].append(neighbor)
|
|
|
|
queue_index += 1
|
|
level += 1
|
|
|
|
|
|
action_log = logging.getLogger("parser.action")
|
|
|
|
|
|
class TokenStream(typing.Protocol):
|
|
def tokens(self) -> list[typing.Tuple[parser.Terminal, int, int]]:
|
|
"""The tokens in the stream, in the form (terminal, start, length)."""
|
|
...
|
|
|
|
def lines(self) -> list[int]:
|
|
"""The offsets of line breaks in the tokens. (The end of line 0 is at
|
|
index 0, etc.)"""
|
|
...
|
|
|
|
|
|
class Parser:
|
|
# Our stack is a stack of tuples, where the first entry is the state
|
|
# number and the second entry is the 'value' that was generated when the
|
|
# state was pushed.
|
|
table: parser.ParseTable
|
|
|
|
def __init__(self, table):
|
|
self.table = table
|
|
|
|
def parse(self, tokens: TokenStream) -> typing.Tuple[Tree | None, list[str]]:
|
|
input_tokens = tokens.tokens()
|
|
input: list[TokenValue] = [
|
|
TokenValue(kind=kind.value, start=start, end=start + length)
|
|
for (kind, start, length) in input_tokens
|
|
]
|
|
|
|
eof = 0 if len(input) == 0 else input[-1].end
|
|
input = input + [TokenValue(kind="$", start=eof, end=eof)]
|
|
input_index = 0
|
|
|
|
stack: ParseStack = [(0, None)]
|
|
result: Tree | None = None
|
|
errors: list[ParseError] = []
|
|
|
|
al = action_log
|
|
while True:
|
|
current_token = input[input_index]
|
|
current_state = stack[-1][0]
|
|
|
|
action = self.table.actions[current_state].get(current_token.kind, parser.Error())
|
|
if al.isEnabledFor(logging.INFO):
|
|
al.info(
|
|
"{stack: <30} {input: <15} {action: <5}".format(
|
|
stack=repr([s[0] for s in stack[-5:]]),
|
|
input=current_token.kind,
|
|
action=repr(action),
|
|
)
|
|
)
|
|
|
|
match action:
|
|
case parser.Accept():
|
|
r = stack[-1][1]
|
|
assert isinstance(r, Tree)
|
|
result = r
|
|
break
|
|
|
|
case parser.Reduce(name=name, count=size, transparent=transparent):
|
|
children: list[TokenValue | Tree] = []
|
|
if size > 0:
|
|
for _, c in stack[-size:]:
|
|
if c is None:
|
|
continue
|
|
elif isinstance(c, Tree) and c.name is None:
|
|
children.extend(c.children)
|
|
else:
|
|
children.append(c)
|
|
del stack[-size:]
|
|
|
|
start = children[0].start
|
|
end = children[-1].end
|
|
|
|
else:
|
|
start = end = current_token.start
|
|
|
|
value = Tree(
|
|
name=name if not transparent else None,
|
|
start=start,
|
|
end=end,
|
|
children=tuple(children),
|
|
)
|
|
|
|
goto = self.table.gotos[stack[-1][0]].get(name)
|
|
assert goto is not None
|
|
stack.append((goto, value))
|
|
|
|
case parser.Shift():
|
|
stack.append((action.state, current_token))
|
|
input_index += 1
|
|
|
|
case parser.Error():
|
|
if current_token.kind == "$":
|
|
message = "Syntax error: Unexpected end of file"
|
|
else:
|
|
message = f"Syntax error: unexpected symbol {current_token.kind}"
|
|
|
|
errors.append(
|
|
ParseError(
|
|
message=message,
|
|
start=current_token.start,
|
|
end=current_token.end,
|
|
)
|
|
)
|
|
|
|
repairs = recover(self.table, input, input_index, stack)
|
|
|
|
# If we were unable to find a repair sequence, then just
|
|
# quit here; we have what we have. We *should* do our
|
|
# best to generate a tree, but I'm not sure if we can?
|
|
if repairs is None:
|
|
break
|
|
|
|
# If we were *were* able to find a repair, apply it to
|
|
# the token stream and continue moving. It is guaranteed
|
|
# that we will not generate an error until we get to the
|
|
# end of the stream that we found.
|
|
cursor = input_index
|
|
for repair in repairs:
|
|
match repair.repair:
|
|
case RepairAction.Base:
|
|
# Don't need to do anything here, this is
|
|
# where we started.
|
|
pass
|
|
|
|
case RepairAction.Insert:
|
|
# Insert a token into the stream.
|
|
# Need to advance the cursor to compensate.
|
|
assert repair.value is not None
|
|
pos = input[cursor].end
|
|
input.insert(
|
|
cursor, TokenValue(kind=repair.value, start=pos, end=pos)
|
|
)
|
|
cursor += 1
|
|
|
|
case RepairAction.Delete:
|
|
del input[cursor]
|
|
|
|
case RepairAction.Shift:
|
|
# Just consume the token where we are.
|
|
cursor += 1
|
|
|
|
case _:
|
|
typing.assert_never(repair.repair)
|
|
|
|
case _:
|
|
typing.assert_never(action)
|
|
|
|
# All done.
|
|
error_strings = []
|
|
if errors:
|
|
lines = tokens.lines()
|
|
for parse_error in errors:
|
|
line_index = bisect.bisect_left(lines, parse_error.start)
|
|
if line_index == 0:
|
|
col_start = 0
|
|
else:
|
|
col_start = lines[line_index - 1] + 1
|
|
column_index = parse_error.start - col_start
|
|
line_index += 1
|
|
|
|
error_strings.append(f"{line_index}:{column_index}: {parse_error.message}")
|
|
|
|
return (result, error_strings)
|