Mercurial > hg
view mercurial/vfs.py @ 31765:264baeef3588
show: new extension for displaying various repository data
Currently, Mercurial has a number of commands to show information. And,
there are features coming down the pipe that will introduce more
commands for showing information.
Currently, when introducing a new class of data or a view that we
wish to expose to the user, the strategy is to introduce a new command
or overload an existing command, sometimes both. For example, there is
a desire to formalize the wip/smartlog/underway/mine functionality that
many have devised. There is also a desire to introduce a "topics"
concept. Others would like views of "the current stack." In the
current model, we'd need a new command for wip/smartlog/etc (that
behaves a lot like a pre-defined alias of `hg log`). For topics,
we'd likely overload `hg topic[s]` to both display and manipulate
topics.
Adding new commands for every pre-defined query doesn't scale well
and pollutes `hg help`. Overloading commands to perform read-only and
write operations is arguably an UX anti-pattern: while having all
functionality for a given concept in one command is nice, having a
single command doing multiple discrete operations is not. Furthermore,
a user may be surprised that a command they thought was read-only
actually changes something.
We discussed this at the Mercurial 4.0 Sprint in Paris and decided that
having a single command where we could hang pre-defined views of
various data would be a good idea. Having such a command would:
* Help prevent an explosion of new query-related commands
* Create a clear separation between read and write operations
(mitigates footguns)
* Avoids overloading the meaning of commands that manipulate data
(bookmark, tag, branch, etc) (while we can't take away the
existing behavior for BC reasons, we now won't introduce this
behavior on new commands)
* Allows users to discover informational views more easily by
aggregating them in a single location
* Lowers the barrier to creating the new views (since the barrier
to creating a top-level command is relatively high)
So, this commit introduces the `hg show` command via the "show"
extension. This command accepts a positional argument of the
"view" to show. New views can be registered with a decorator. To
prove it works, we implement the "bookmarks" view, which shows a
table of bookmarks and their associated nodes.
We introduce a new style to hold everything used by `hg show`.
For our initial bookmarks view, the output varies from `hg bookmarks`:
* Padding is performed in the template itself as opposed to Python
* Revision integers are not shown
* shortest() is used to display a 5 character node by default (as
opposed to static 12 characters)
I chose to implement the "bookmarks" view first because it is simple
and shouldn't invite too much bikeshedding that detracts from the
evaluation of `hg show` itself. But there is an important point
to consider: we now have 2 ways to show a list of bookmarks. I'm not
a fan of introducing multiple ways to do very similar things. So it
might be worth discussing how we wish to tackle this issue for
bookmarks, tags, branches, MQ series, etc.
I also made the choice of explicitly declaring the default show
template not part of the standard BC guarantees. History has shown
that we make mistakes and poor choices with output formatting but
can't fix these mistakes later because random tools are parsing
output and we don't want to break these tools. Optimizing for human
consumption is one of my goals for `hg show`. So, by not covering
the formatting as part of BC, the barrier to future change is much
lower and humans benefit.
There are some improvements that can be made to formatting. For
example, we don't yet use label() in the templates. We obviously
want this for color. But I'm not sure if we should reuse the existing
log.* labels or invent new ones. I figure we can punt that to a
follow-up.
At the aforementioned Sprint, we discussed and discarded various
alternatives to `hg show`.
We considered making `hg log <view>` perform this behavior. The main
reason we can't do this is because a positional argument to `hg log`
can be a file path and if there is a conflict between a path name and
a view name, behavior is ambiguous. We could have introduced
`hg log --view` or similar, but we felt that required too much typing
(we don't want to require a command flag to show a view) and wasn't
very discoverable. Furthermore, `hg log` is optimized for showing
changelog data and there are things that `hg display` could display
that aren't changelog centric.
There were concerns about using "show" as the command name.
Some users already have a "show" alias that is similar to `hg export`.
There were also concerns that Git users adapted to `git show` would
be confused by `hg show`'s different behavior. The main difference
here is `git show` prints an `hg export` like view of the current
commit by default and `hg show` requires an argument. `git show`
can also display any Git object. `git show` does not support
displaying more complex views: just single objects. If we
implemented `hg show <hash>` or `hg show <identifier>`, `hg show`
would be a superset of `git show`. Although, I'm hesitant to do that
at this time because I view `hg show` as a higher-level querying
command and there are namespace collisions between valid identifiers
and registered views.
There is also a prefix collision with `hg showconfig`, which is an
alias of `hg config`.
We also considered `hg view`, but that is already used by the "hgk"
extension.
`hg display` was also proposed at one point. It has a prefix collision
with `hg diff`. General consensus was "show" or "view" are the best
verbs. And since "view" was taken, "show" was chosen.
There are a number of inline TODOs in this patch. Some of these
represent decisions yet to be made. Others represent features
requiring non-trivial complexity. Rather than bloat the patch or
invite additional bikeshedding, I figured I'd document future
enhancements via TODO so we can get a minimal implmentation landed.
Something is better than nothing.
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Fri, 24 Mar 2017 19:19:00 -0700 |
parents | f80d9ddc40f3 |
children | d74b0cff94a9 20bac46f7744 |
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# vfs.py - Mercurial 'vfs' classes # # Copyright Matt Mackall <mpm@selenic.com> # # This software may be used and distributed according to the terms of the # GNU General Public License version 2 or any later version. from __future__ import absolute_import import contextlib import errno import os import shutil import stat import tempfile import threading from .i18n import _ from . import ( error, osutil, pathutil, pycompat, util, ) class abstractvfs(object): """Abstract base class; cannot be instantiated""" def __init__(self, *args, **kwargs): '''Prevent instantiation; don't call this from subclasses.''' raise NotImplementedError('attempted instantiating ' + str(type(self))) def tryread(self, path): '''gracefully return an empty string for missing files''' try: return self.read(path) except IOError as inst: if inst.errno != errno.ENOENT: raise return "" def tryreadlines(self, path, mode='rb'): '''gracefully return an empty array for missing files''' try: return self.readlines(path, mode=mode) except IOError as inst: if inst.errno != errno.ENOENT: raise return [] @util.propertycache def open(self): '''Open ``path`` file, which is relative to vfs root. Newly created directories are marked as "not to be indexed by the content indexing service", if ``notindexed`` is specified for "write" mode access. ''' return self.__call__ def read(self, path): with self(path, 'rb') as fp: return fp.read() def readlines(self, path, mode='rb'): with self(path, mode=mode) as fp: return fp.readlines() def write(self, path, data, backgroundclose=False): with self(path, 'wb', backgroundclose=backgroundclose) as fp: return fp.write(data) def writelines(self, path, data, mode='wb', notindexed=False): with self(path, mode=mode, notindexed=notindexed) as fp: return fp.writelines(data) def append(self, path, data): with self(path, 'ab') as fp: return fp.write(data) def basename(self, path): """return base element of a path (as os.path.basename would do) This exists to allow handling of strange encoding if needed.""" return os.path.basename(path) def chmod(self, path, mode): return os.chmod(self.join(path), mode) def dirname(self, path): """return dirname element of a path (as os.path.dirname would do) This exists to allow handling of strange encoding if needed.""" return os.path.dirname(path) def exists(self, path=None): return os.path.exists(self.join(path)) def fstat(self, fp): return util.fstat(fp) def isdir(self, path=None): return os.path.isdir(self.join(path)) def isfile(self, path=None): return os.path.isfile(self.join(path)) def islink(self, path=None): return os.path.islink(self.join(path)) def isfileorlink(self, path=None): '''return whether path is a regular file or a symlink Unlike isfile, this doesn't follow symlinks.''' try: st = self.lstat(path) except OSError: return False mode = st.st_mode return stat.S_ISREG(mode) or stat.S_ISLNK(mode) def reljoin(self, *paths): """join various elements of a path together (as os.path.join would do) The vfs base is not injected so that path stay relative. This exists to allow handling of strange encoding if needed.""" return os.path.join(*paths) def split(self, path): """split top-most element of a path (as os.path.split would do) This exists to allow handling of strange encoding if needed.""" return os.path.split(path) def lexists(self, path=None): return os.path.lexists(self.join(path)) def lstat(self, path=None): return os.lstat(self.join(path)) def listdir(self, path=None): return os.listdir(self.join(path)) def makedir(self, path=None, notindexed=True): return util.makedir(self.join(path), notindexed) def makedirs(self, path=None, mode=None): return util.makedirs(self.join(path), mode) def makelock(self, info, path): return util.makelock(info, self.join(path)) def mkdir(self, path=None): return os.mkdir(self.join(path)) def mkstemp(self, suffix='', prefix='tmp', dir=None, text=False): fd, name = tempfile.mkstemp(suffix=suffix, prefix=prefix, dir=self.join(dir), text=text) dname, fname = util.split(name) if dir: return fd, os.path.join(dir, fname) else: return fd, fname def readdir(self, path=None, stat=None, skip=None): return osutil.listdir(self.join(path), stat, skip) def readlock(self, path): return util.readlock(self.join(path)) def rename(self, src, dst, checkambig=False): """Rename from src to dst checkambig argument is used with util.filestat, and is useful only if destination file is guarded by any lock (e.g. repo.lock or repo.wlock). """ dstpath = self.join(dst) oldstat = checkambig and util.filestat(dstpath) if oldstat and oldstat.stat: ret = util.rename(self.join(src), dstpath) newstat = util.filestat(dstpath) if newstat.isambig(oldstat): # stat of renamed file is ambiguous to original one newstat.avoidambig(dstpath, oldstat) return ret return util.rename(self.join(src), dstpath) def readlink(self, path): return os.readlink(self.join(path)) def removedirs(self, path=None): """Remove a leaf directory and all empty intermediate ones """ return util.removedirs(self.join(path)) def rmtree(self, path=None, ignore_errors=False, forcibly=False): """Remove a directory tree recursively If ``forcibly``, this tries to remove READ-ONLY files, too. """ if forcibly: def onerror(function, path, excinfo): if function is not os.remove: raise # read-only files cannot be unlinked under Windows s = os.stat(path) if (s.st_mode & stat.S_IWRITE) != 0: raise os.chmod(path, stat.S_IMODE(s.st_mode) | stat.S_IWRITE) os.remove(path) else: onerror = None return shutil.rmtree(self.join(path), ignore_errors=ignore_errors, onerror=onerror) def setflags(self, path, l, x): return util.setflags(self.join(path), l, x) def stat(self, path=None): return os.stat(self.join(path)) def unlink(self, path=None): return util.unlink(self.join(path)) def tryunlink(self, path=None): """Attempt to remove a file, ignoring missing file errors.""" util.tryunlink(self.join(path)) def unlinkpath(self, path=None, ignoremissing=False): return util.unlinkpath(self.join(path), ignoremissing=ignoremissing) def utime(self, path=None, t=None): return os.utime(self.join(path), t) def walk(self, path=None, onerror=None): """Yield (dirpath, dirs, files) tuple for each directories under path ``dirpath`` is relative one from the root of this vfs. This uses ``os.sep`` as path separator, even you specify POSIX style ``path``. "The root of this vfs" is represented as empty ``dirpath``. """ root = os.path.normpath(self.join(None)) # when dirpath == root, dirpath[prefixlen:] becomes empty # because len(dirpath) < prefixlen. prefixlen = len(pathutil.normasprefix(root)) for dirpath, dirs, files in os.walk(self.join(path), onerror=onerror): yield (dirpath[prefixlen:], dirs, files) @contextlib.contextmanager def backgroundclosing(self, ui, expectedcount=-1): """Allow files to be closed asynchronously. When this context manager is active, ``backgroundclose`` can be passed to ``__call__``/``open`` to result in the file possibly being closed asynchronously, on a background thread. """ # This is an arbitrary restriction and could be changed if we ever # have a use case. vfs = getattr(self, 'vfs', self) if getattr(vfs, '_backgroundfilecloser', None): raise error.Abort( _('can only have 1 active background file closer')) with backgroundfilecloser(ui, expectedcount=expectedcount) as bfc: try: vfs._backgroundfilecloser = bfc yield bfc finally: vfs._backgroundfilecloser = None class vfs(abstractvfs): '''Operate files relative to a base directory This class is used to hide the details of COW semantics and remote file access from higher level code. ''' def __init__(self, base, audit=True, expandpath=False, realpath=False): if expandpath: base = util.expandpath(base) if realpath: base = os.path.realpath(base) self.base = base self.mustaudit = audit self.createmode = None self._trustnlink = None @property def mustaudit(self): return self._audit @mustaudit.setter def mustaudit(self, onoff): self._audit = onoff if onoff: self.audit = pathutil.pathauditor(self.base) else: self.audit = util.always @util.propertycache def _cansymlink(self): return util.checklink(self.base) @util.propertycache def _chmod(self): return util.checkexec(self.base) def _fixfilemode(self, name): if self.createmode is None or not self._chmod: return os.chmod(name, self.createmode & 0o666) def __call__(self, path, mode="r", text=False, atomictemp=False, notindexed=False, backgroundclose=False, checkambig=False): '''Open ``path`` file, which is relative to vfs root. Newly created directories are marked as "not to be indexed by the content indexing service", if ``notindexed`` is specified for "write" mode access. If ``backgroundclose`` is passed, the file may be closed asynchronously. It can only be used if the ``self.backgroundclosing()`` context manager is active. This should only be specified if the following criteria hold: 1. There is a potential for writing thousands of files. Unless you are writing thousands of files, the performance benefits of asynchronously closing files is not realized. 2. Files are opened exactly once for the ``backgroundclosing`` active duration and are therefore free of race conditions between closing a file on a background thread and reopening it. (If the file were opened multiple times, there could be unflushed data because the original file handle hasn't been flushed/closed yet.) ``checkambig`` argument is passed to atomictemplfile (valid only for writing), and is useful only if target file is guarded by any lock (e.g. repo.lock or repo.wlock). ''' if self._audit: r = util.checkosfilename(path) if r: raise error.Abort("%s: %r" % (r, path)) self.audit(path) f = self.join(path) if not text and "b" not in mode: mode += "b" # for that other OS nlink = -1 if mode not in ('r', 'rb'): dirname, basename = util.split(f) # If basename is empty, then the path is malformed because it points # to a directory. Let the posixfile() call below raise IOError. if basename: if atomictemp: util.makedirs(dirname, self.createmode, notindexed) return util.atomictempfile(f, mode, self.createmode, checkambig=checkambig) try: if 'w' in mode: util.unlink(f) nlink = 0 else: # nlinks() may behave differently for files on Windows # shares if the file is open. with util.posixfile(f): nlink = util.nlinks(f) if nlink < 1: nlink = 2 # force mktempcopy (issue1922) except (OSError, IOError) as e: if e.errno != errno.ENOENT: raise nlink = 0 util.makedirs(dirname, self.createmode, notindexed) if nlink > 0: if self._trustnlink is None: self._trustnlink = nlink > 1 or util.checknlink(f) if nlink > 1 or not self._trustnlink: util.rename(util.mktempcopy(f), f) fp = util.posixfile(f, mode) if nlink == 0: self._fixfilemode(f) if checkambig: if mode in ('r', 'rb'): raise error.Abort(_('implementation error: mode %s is not' ' valid for checkambig=True') % mode) fp = checkambigatclosing(fp) if backgroundclose: if not self._backgroundfilecloser: raise error.Abort(_('backgroundclose can only be used when a ' 'backgroundclosing context manager is active') ) fp = delayclosedfile(fp, self._backgroundfilecloser) return fp def symlink(self, src, dst): self.audit(dst) linkname = self.join(dst) util.tryunlink(linkname) util.makedirs(os.path.dirname(linkname), self.createmode) if self._cansymlink: try: os.symlink(src, linkname) except OSError as err: raise OSError(err.errno, _('could not symlink to %r: %s') % (src, err.strerror), linkname) else: self.write(dst, src) def join(self, path, *insidef): if path: return os.path.join(self.base, path, *insidef) else: return self.base opener = vfs class auditvfs(object): def __init__(self, vfs): self.vfs = vfs @property def mustaudit(self): return self.vfs.mustaudit @mustaudit.setter def mustaudit(self, onoff): self.vfs.mustaudit = onoff @property def options(self): return self.vfs.options @options.setter def options(self, value): self.vfs.options = value class filtervfs(abstractvfs, auditvfs): '''Wrapper vfs for filtering filenames with a function.''' def __init__(self, vfs, filter): auditvfs.__init__(self, vfs) self._filter = filter def __call__(self, path, *args, **kwargs): return self.vfs(self._filter(path), *args, **kwargs) def join(self, path, *insidef): if path: return self.vfs.join(self._filter(self.vfs.reljoin(path, *insidef))) else: return self.vfs.join(path) filteropener = filtervfs class readonlyvfs(abstractvfs, auditvfs): '''Wrapper vfs preventing any writing.''' def __init__(self, vfs): auditvfs.__init__(self, vfs) def __call__(self, path, mode='r', *args, **kw): if mode not in ('r', 'rb'): raise error.Abort(_('this vfs is read only')) return self.vfs(path, mode, *args, **kw) def join(self, path, *insidef): return self.vfs.join(path, *insidef) class closewrapbase(object): """Base class of wrapper, which hooks closing Do not instantiate outside of the vfs layer. """ def __init__(self, fh): object.__setattr__(self, r'_origfh', fh) def __getattr__(self, attr): return getattr(self._origfh, attr) def __setattr__(self, attr, value): return setattr(self._origfh, attr, value) def __delattr__(self, attr): return delattr(self._origfh, attr) def __enter__(self): return self._origfh.__enter__() def __exit__(self, exc_type, exc_value, exc_tb): raise NotImplementedError('attempted instantiating ' + str(type(self))) def close(self): raise NotImplementedError('attempted instantiating ' + str(type(self))) class delayclosedfile(closewrapbase): """Proxy for a file object whose close is delayed. Do not instantiate outside of the vfs layer. """ def __init__(self, fh, closer): super(delayclosedfile, self).__init__(fh) object.__setattr__(self, r'_closer', closer) def __exit__(self, exc_type, exc_value, exc_tb): self._closer.close(self._origfh) def close(self): self._closer.close(self._origfh) class backgroundfilecloser(object): """Coordinates background closing of file handles on multiple threads.""" def __init__(self, ui, expectedcount=-1): self._running = False self._entered = False self._threads = [] self._threadexception = None # Only Windows/NTFS has slow file closing. So only enable by default # on that platform. But allow to be enabled elsewhere for testing. defaultenabled = pycompat.osname == 'nt' enabled = ui.configbool('worker', 'backgroundclose', defaultenabled) if not enabled: return # There is overhead to starting and stopping the background threads. # Don't do background processing unless the file count is large enough # to justify it. minfilecount = ui.configint('worker', 'backgroundcloseminfilecount', 2048) # FUTURE dynamically start background threads after minfilecount closes. # (We don't currently have any callers that don't know their file count) if expectedcount > 0 and expectedcount < minfilecount: return # Windows defaults to a limit of 512 open files. A buffer of 128 # should give us enough headway. maxqueue = ui.configint('worker', 'backgroundclosemaxqueue', 384) threadcount = ui.configint('worker', 'backgroundclosethreadcount', 4) ui.debug('starting %d threads for background file closing\n' % threadcount) self._queue = util.queue(maxsize=maxqueue) self._running = True for i in range(threadcount): t = threading.Thread(target=self._worker, name='backgroundcloser') self._threads.append(t) t.start() def __enter__(self): self._entered = True return self def __exit__(self, exc_type, exc_value, exc_tb): self._running = False # Wait for threads to finish closing so open files don't linger for # longer than lifetime of context manager. for t in self._threads: t.join() def _worker(self): """Main routine for worker thread.""" while True: try: fh = self._queue.get(block=True, timeout=0.100) # Need to catch or the thread will terminate and # we could orphan file descriptors. try: fh.close() except Exception as e: # Stash so can re-raise from main thread later. self._threadexception = e except util.empty: if not self._running: break def close(self, fh): """Schedule a file for closing.""" if not self._entered: raise error.Abort(_('can only call close() when context manager ' 'active')) # If a background thread encountered an exception, raise now so we fail # fast. Otherwise we may potentially go on for minutes until the error # is acted on. if self._threadexception: e = self._threadexception self._threadexception = None raise e # If we're not actively running, close synchronously. if not self._running: fh.close() return self._queue.put(fh, block=True, timeout=None) class checkambigatclosing(closewrapbase): """Proxy for a file object, to avoid ambiguity of file stat See also util.filestat for detail about "ambiguity of file stat". This proxy is useful only if the target file is guarded by any lock (e.g. repo.lock or repo.wlock) Do not instantiate outside of the vfs layer. """ def __init__(self, fh): super(checkambigatclosing, self).__init__(fh) object.__setattr__(self, r'_oldstat', util.filestat(fh.name)) def _checkambig(self): oldstat = self._oldstat if oldstat.stat: newstat = util.filestat(self._origfh.name) if newstat.isambig(oldstat): # stat of changed file is ambiguous to original one newstat.avoidambig(self._origfh.name, oldstat) def __exit__(self, exc_type, exc_value, exc_tb): self._origfh.__exit__(exc_type, exc_value, exc_tb) self._checkambig() def close(self): self._origfh.close() self._checkambig()