view mercurial/linelog.py @ 48687:f8f2ecdde4b5

branchmap: skip obsolete revisions while computing heads

It's time to make this part of core Mercurial obsolescence-aware.

Not considering obsolete revisions when computing heads is clearly what
Mercurial should do. But there are a couple of small issues:

- Let's say tip of the repo is obsolete. There are two ways of finding tiprev
  for branchcache (both are in use): looking at input data for update() and
  looking at computed heads after update(). Previously, repo tip would be
  tiprev of the branchcache. With this patch, an obsolete revision can no
  longer be tiprev. And depending on what way we use for finding tiprev (input
  data vs computed heads) we'll get a different result. This is relevant when
  recomputing cache key from cache contents, and may lead to updating cache for
  obsolete revisions multiple times (not from scratch, because it still would
  be considered valid for a subset of revisions in the repo).

- If all commits on a branch are obsolete, the branchcache will include that
  branch, but the list of heads will be empty (that's why there's now `if not
  heads` when recomputing tiprev/tipnode from cache contents). Having an entry
  for every branch is currently required for notify extension (and
  test-notify.t to pass), because notify doesn't handle revsets in its
  subscription config very well and will throw an error if e.g. a branch
  doesn't exist.

- Cloning static HTTP repos may try to stat() a non-existent obsstore file. The
  issue is that we now care about obsolescence during clone, but statichttpvfs
  doesn't implement a stat method, so a regular vfs.stat() is used, and it
  assumes that file is local and calls os.stat().  During a clone, we're trying
  to stat() .hg/store/obsstore, but in static HTTP case we provide a literal
  URL to the obsstore file on the remote as if it were a local file path. On
  windows it actually results in a failure in test-static-http.t.

The first issue is going to be addressed in a series dedicated to making sure
branchcache is properly and timely written on disk (it wasn't perfect even
before this patch, but there aren't enough tests to demonstrate that). The
second issue will be addressed in a future patch for notify extension that will
make it not raise an exception if a branch doesn't exist. And the third one was
partially addressed in the previous patch in this series and will be properly
fixed in a future patch when this series is accepted.

filteredhash() grows a keyword argument to make sure that branchcache is also
invalidated when there are new obsolete revisions in its repo view. This way
the on-disk cache format is unchanged and compatible between versions (although
it will obviously be recomputed when switching versions before/after this patch
and the repo has obsolete revisions).

There's one test that uses plain `hg up` without arguments while updated to a
pruned commit. To make this test pass, simply return current working directory
parent. Later in this series this code will be replaced by what prune command
does: updating to the closest non-obsolete ancestor.

Test changes:

test-branch-change.t: update branch head and cache update message. The head of
default listed in hg heads is changed because revision 2 was rewritten as 7,
and 1 is the closest ancestor on the same branch, so it's the head of default
now.

The cache invalidation message appears now because of the cache hash change,
since we're now accounting for obsolete revisions. Here's some context:

"served.hidden" repo filter means everything is visible (no filtered
revisions), so before this series branch2-served.hidden file would not contain
any cache hash, only revnum and node. Now it also has a hash when there are
obsolete changesets in the repo. The command that the message appears for is
changing branch of 5 and 6, which are now obsolete, so the cache hash changes.

In general, when cache is simply out-of-date, it can be updated using the old
version as a base. But if cache hash differs, then the cache for that
particular repo filter is recomputed (at least with the current
implementation). This is what happens here.

test-obsmarker-template.t: the pull reports 2 heads changed, but after that the
repo correctly sees only 1. The new message could be better, but it's still an
improvement over the previous one where hg pull suggested merging with an
obsolete revision.

test-obsolete.t: we can see these revisions in hg log --hidden, but they
shouldn't be considered heads even with --hidden.

test-rebase-obsolete{,2}.t: there were new heads created previously after
making new orphan changesets, but they weren't detected. Now we are properly
detecting and reporting them.

test-rebase-obsolete4.t: there's only one head now because the other head is
pruned and was falsely reported before.

test-static-http.t: add obsstore to the list of requested files. This file
doesn't exist on the remotes, but clients want it anyway (they get 404). This
is fine, because there are other nonexistent files that clients request, like
.hg/bookmarks or .hg/cache/tags2-served.

Differential Revision: https://phab.mercurial-scm.org/D12097

# linelog - efficient cache for annotate data
#
# Copyright 2018 Google LLC.
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
"""linelog is an efficient cache for annotate data inspired by SCCS Weaves.

SCCS Weaves are an implementation of
https://en.wikipedia.org/wiki/Interleaved_deltas. See
mercurial/helptext/internals/linelog.txt for an exploration of SCCS weaves
and how linelog works in detail.

Here's a hacker's summary: a linelog is a program which is executed in
the context of a revision. Executing the program emits information
about lines, including the revision that introduced them and the line
number in the file at the introducing revision. When an insertion or
deletion is performed on the file, a jump instruction is used to patch
in a new body of annotate information.
"""
from __future__ import absolute_import, print_function

import abc
import struct

from .thirdparty import attr
from . import pycompat

_llentry = struct.Struct(b'>II')


class LineLogError(Exception):
    """Error raised when something bad happens internally in linelog."""


@attr.s
class lineinfo(object):
    # Introducing revision of this line.
    rev = attr.ib()
    # Line number for this line in its introducing revision.
    linenum = attr.ib()
    # Private. Offset in the linelog program of this line. Used internally.
    _offset = attr.ib()


@attr.s
class annotateresult(object):
    rev = attr.ib()
    lines = attr.ib()
    _eof = attr.ib()

    def __iter__(self):
        return iter(self.lines)


class _llinstruction(object):  # pytype: disable=ignored-metaclass

    __metaclass__ = abc.ABCMeta

    @abc.abstractmethod
    def __init__(self, op1, op2):
        pass

    @abc.abstractmethod
    def __str__(self):
        pass

    def __repr__(self):
        return str(self)

    @abc.abstractmethod
    def __eq__(self, other):
        pass

    @abc.abstractmethod
    def encode(self):
        """Encode this instruction to the binary linelog format."""

    @abc.abstractmethod
    def execute(self, rev, pc, emit):
        """Execute this instruction.

        Args:
          rev: The revision we're annotating.
          pc: The current offset in the linelog program.
          emit: A function that accepts a single lineinfo object.

        Returns:
          The new value of pc. Returns None if exeuction should stop
          (that is, we've found the end of the file.)
        """


class _jge(_llinstruction):
    """If the current rev is greater than or equal to op1, jump to op2."""

    def __init__(self, op1, op2):
        self._cmprev = op1
        self._target = op2

    def __str__(self):
        return 'JGE %d %d' % (self._cmprev, self._target)

    def __eq__(self, other):
        return (
            type(self) == type(other)
            and self._cmprev == other._cmprev
            and self._target == other._target
        )

    def encode(self):
        return _llentry.pack(self._cmprev << 2, self._target)

    def execute(self, rev, pc, emit):
        if rev >= self._cmprev:
            return self._target
        return pc + 1


class _jump(_llinstruction):
    """Unconditional jumps are expressed as a JGE with op1 set to 0."""

    def __init__(self, op1, op2):
        if op1 != 0:
            raise LineLogError(b"malformed JUMP, op1 must be 0, got %d" % op1)
        self._target = op2

    def __str__(self):
        return 'JUMP %d' % (self._target)

    def __eq__(self, other):
        return type(self) == type(other) and self._target == other._target

    def encode(self):
        return _llentry.pack(0, self._target)

    def execute(self, rev, pc, emit):
        return self._target


class _eof(_llinstruction):
    """EOF is expressed as a JGE that always jumps to 0."""

    def __init__(self, op1, op2):
        if op1 != 0:
            raise LineLogError(b"malformed EOF, op1 must be 0, got %d" % op1)
        if op2 != 0:
            raise LineLogError(b"malformed EOF, op2 must be 0, got %d" % op2)

    def __str__(self):
        return r'EOF'

    def __eq__(self, other):
        return type(self) == type(other)

    def encode(self):
        return _llentry.pack(0, 0)

    def execute(self, rev, pc, emit):
        return None


class _jl(_llinstruction):
    """If the current rev is less than op1, jump to op2."""

    def __init__(self, op1, op2):
        self._cmprev = op1
        self._target = op2

    def __str__(self):
        return 'JL %d %d' % (self._cmprev, self._target)

    def __eq__(self, other):
        return (
            type(self) == type(other)
            and self._cmprev == other._cmprev
            and self._target == other._target
        )

    def encode(self):
        return _llentry.pack(1 | (self._cmprev << 2), self._target)

    def execute(self, rev, pc, emit):
        if rev < self._cmprev:
            return self._target
        return pc + 1


class _line(_llinstruction):
    """Emit a line."""

    def __init__(self, op1, op2):
        # This line was introduced by this revision number.
        self._rev = op1
        # This line had the specified line number in the introducing revision.
        self._origlineno = op2

    def __str__(self):
        return 'LINE %d %d' % (self._rev, self._origlineno)

    def __eq__(self, other):
        return (
            type(self) == type(other)
            and self._rev == other._rev
            and self._origlineno == other._origlineno
        )

    def encode(self):
        return _llentry.pack(2 | (self._rev << 2), self._origlineno)

    def execute(self, rev, pc, emit):
        emit(lineinfo(self._rev, self._origlineno, pc))
        return pc + 1


def _decodeone(data, offset):
    """Decode a single linelog instruction from an offset in a buffer."""
    try:
        op1, op2 = _llentry.unpack_from(data, offset)
    except struct.error as e:
        raise LineLogError(b'reading an instruction failed: %r' % e)
    opcode = op1 & 0b11
    op1 = op1 >> 2
    if opcode == 0:
        if op1 == 0:
            if op2 == 0:
                return _eof(op1, op2)
            return _jump(op1, op2)
        return _jge(op1, op2)
    elif opcode == 1:
        return _jl(op1, op2)
    elif opcode == 2:
        return _line(op1, op2)
    raise NotImplementedError(b'Unimplemented opcode %r' % opcode)


class linelog(object):
    """Efficient cache for per-line history information."""

    def __init__(self, program=None, maxrev=0):
        if program is None:
            # We pad the program with an extra leading EOF so that our
            # offsets will match the C code exactly. This means we can
            # interoperate with the C code.
            program = [_eof(0, 0), _eof(0, 0)]
        self._program = program
        self._lastannotate = None
        self._maxrev = maxrev

    def __eq__(self, other):
        return (
            type(self) == type(other)
            and self._program == other._program
            and self._maxrev == other._maxrev
        )

    def __repr__(self):
        return '<linelog at %s: maxrev=%d size=%d>' % (
            hex(id(self)),
            self._maxrev,
            len(self._program),
        )

    def debugstr(self):
        fmt = '%%%dd %%s' % len(str(len(self._program)))
        return pycompat.sysstr(b'\n').join(
            fmt % (idx, i) for idx, i in enumerate(self._program[1:], 1)
        )

    @classmethod
    def fromdata(cls, buf):
        if len(buf) % _llentry.size != 0:
            raise LineLogError(
                b"invalid linelog buffer size %d (must be a multiple of %d)"
                % (len(buf), _llentry.size)
            )
        expected = len(buf) / _llentry.size
        fakejge = _decodeone(buf, 0)
        if isinstance(fakejge, _jump):
            maxrev = 0
        elif isinstance(fakejge, (_jge, _jl)):
            maxrev = fakejge._cmprev
        else:
            raise LineLogError(
                'Expected one of _jump, _jge, or _jl. Got %s.'
                % type(fakejge).__name__
            )
        assert isinstance(fakejge, (_jump, _jge, _jl))  # help pytype
        numentries = fakejge._target
        if expected != numentries:
            raise LineLogError(
                b"corrupt linelog data: claimed"
                b" %d entries but given data for %d entries"
                % (expected, numentries)
            )
        instructions = [_eof(0, 0)]
        for offset in pycompat.xrange(1, numentries):
            instructions.append(_decodeone(buf, offset * _llentry.size))
        return cls(instructions, maxrev=maxrev)

    def encode(self):
        hdr = _jge(self._maxrev, len(self._program)).encode()
        return hdr + b''.join(i.encode() for i in self._program[1:])

    def clear(self):
        self._program = []
        self._maxrev = 0
        self._lastannotate = None

    def replacelines_vec(self, rev, a1, a2, blines):
        return self.replacelines(
            rev, a1, a2, 0, len(blines), _internal_blines=blines
        )

    def replacelines(self, rev, a1, a2, b1, b2, _internal_blines=None):
        """Replace lines [a1, a2) with lines [b1, b2)."""
        if self._lastannotate:
            # TODO(augie): make replacelines() accept a revision at
            # which we're editing as well as a revision to mark
            # responsible for the edits. In hg-experimental it's
            # stateful like this, so we're doing the same thing to
            # retain compatibility with absorb until that's imported.
            ar = self._lastannotate
        else:
            ar = self.annotate(rev)
            #        ar = self.annotate(self._maxrev)
        if a1 > len(ar.lines):
            raise LineLogError(
                b'%d contains %d lines, tried to access line %d'
                % (rev, len(ar.lines), a1)
            )
        elif a1 == len(ar.lines):
            # Simulated EOF instruction since we're at EOF, which
            # doesn't have a "real" line.
            a1inst = _eof(0, 0)
            a1info = lineinfo(0, 0, ar._eof)
        else:
            a1info = ar.lines[a1]
            a1inst = self._program[a1info._offset]
        programlen = self._program.__len__
        oldproglen = programlen()
        appendinst = self._program.append

        # insert
        blineinfos = []
        bappend = blineinfos.append
        if b1 < b2:
            # Determine the jump target for the JGE at the start of
            # the new block.
            tgt = oldproglen + (b2 - b1 + 1)
            # Jump to skip the insert if we're at an older revision.
            appendinst(_jl(rev, tgt))
            for linenum in pycompat.xrange(b1, b2):
                if _internal_blines is None:
                    bappend(lineinfo(rev, linenum, programlen()))
                    appendinst(_line(rev, linenum))
                else:
                    newrev, newlinenum = _internal_blines[linenum]
                    bappend(lineinfo(newrev, newlinenum, programlen()))
                    appendinst(_line(newrev, newlinenum))
        # delete
        if a1 < a2:
            if a2 > len(ar.lines):
                raise LineLogError(
                    b'%d contains %d lines, tried to access line %d'
                    % (rev, len(ar.lines), a2)
                )
            elif a2 == len(ar.lines):
                endaddr = ar._eof
            else:
                endaddr = ar.lines[a2]._offset
            if a2 > 0 and rev < self._maxrev:
                # If we're here, we're deleting a chunk of an old
                # commit, so we need to be careful and not touch
                # invisible lines between a2-1 and a2 (IOW, lines that
                # are added later).
                endaddr = ar.lines[a2 - 1]._offset + 1
            appendinst(_jge(rev, endaddr))
        # copy instruction from a1
        a1instpc = programlen()
        appendinst(a1inst)
        # if a1inst isn't a jump or EOF, then we need to add an unconditional
        # jump back into the program here.
        if not isinstance(a1inst, (_jump, _eof)):
            appendinst(_jump(0, a1info._offset + 1))
        # Patch instruction at a1, which makes our patch live.
        self._program[a1info._offset] = _jump(0, oldproglen)

        # Update self._lastannotate in place. This serves as a cache to avoid
        # expensive "self.annotate" in this function, when "replacelines" is
        # used continuously.
        if len(self._lastannotate.lines) > a1:
            self._lastannotate.lines[a1]._offset = a1instpc
        else:
            assert isinstance(a1inst, _eof)
            self._lastannotate._eof = a1instpc
        self._lastannotate.lines[a1:a2] = blineinfos
        self._lastannotate.rev = max(self._lastannotate.rev, rev)

        if rev > self._maxrev:
            self._maxrev = rev

    def annotate(self, rev):
        pc = 1
        lines = []
        executed = 0
        # Sanity check: if instructions executed exceeds len(program), we
        # hit an infinite loop in the linelog program somehow and we
        # should stop.
        while pc is not None and executed < len(self._program):
            inst = self._program[pc]
            lastpc = pc
            pc = inst.execute(rev, pc, lines.append)
            executed += 1
        if pc is not None:
            raise LineLogError(
                r'Probably hit an infinite loop in linelog. Program:\n'
                + self.debugstr()
            )
        ar = annotateresult(rev, lines, lastpc)
        self._lastannotate = ar
        return ar

    @property
    def maxrev(self):
        return self._maxrev

    # Stateful methods which depend on the value of the last
    # annotation run. This API is for compatiblity with the original
    # linelog, and we should probably consider refactoring it.
    @property
    def annotateresult(self):
        """Return the last annotation result. C linelog code exposed this."""
        return [(l.rev, l.linenum) for l in self._lastannotate.lines]

    def getoffset(self, line):
        return self._lastannotate.lines[line]._offset

    def getalllines(self, start=0, end=0):
        """Get all lines that ever occurred in [start, end).

        Passing start == end == 0 means "all lines ever".

        This works in terms of *internal* program offsets, not line numbers.
        """
        pc = start or 1
        lines = []
        # only take as many steps as there are instructions in the
        # program - if we don't find an EOF or our stop-line before
        # then, something is badly broken.
        for step in pycompat.xrange(len(self._program)):
            inst = self._program[pc]
            nextpc = pc + 1
            if isinstance(inst, _jump):
                nextpc = inst._target
            elif isinstance(inst, _eof):
                return lines
            elif isinstance(inst, (_jl, _jge)):
                pass
            elif isinstance(inst, _line):
                lines.append((inst._rev, inst._origlineno))
            else:
                raise LineLogError(b"Illegal instruction %r" % inst)
            if nextpc == end:
                return lines
            pc = nextpc
        raise LineLogError(b"Failed to perform getalllines")