mercurial/formatter.py

hgweb: refactor the request draining code

The previous code for draining was only invoked in a few places in
the wire protocol. Behavior wasn't consist. Furthermore, it was
difficult to reason about.

With us converting the input stream to a capped reader, it is now
safe to always drain the input stream when its size is known because
we can never overrun the input and read into the next HTTP request.
The only question is "should we?"

This commit changes the draining code so every request is examined.
Draining now kicks in for a few requests where it wouldn't before.
But I think the code is sufficiently restricted so the behavior is
safe. Possibly the most dangerous part of this code is the issuing
of Connection: close for POST and PUT requests that don't have a
Content-Length. I don't think there are any such uses in our WSGI
application, so this should be safe.

In the near future, I plan to significantly refactor the WSGI
response handling. I anticipate this code evolving a bit. So any
minor regressions around draining or connection closing behavior
might be fixed as a result of that work.

All tests pass with this change. That scares me a bit because it
means we are lacking low-level tests for the HTTP protocol.

Differential Revision: https://phab.mercurial-scm.org/D2769

# formatter.py - generic output formatting for mercurial
#
# Copyright 2012 Matt Mackall <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

"""Generic output formatting for Mercurial

The formatter provides API to show data in various ways. The following
functions should be used in place of ui.write():

- fm.write() for unconditional output
- fm.condwrite() to show some extra data conditionally in plain output
- fm.context() to provide changectx to template output
- fm.data() to provide extra data to JSON or template output
- fm.plain() to show raw text that isn't provided to JSON or template output

To show structured data (e.g. date tuples, dicts, lists), apply fm.format*()
beforehand so the data is converted to the appropriate data type. Use
fm.isplain() if you need to convert or format data conditionally which isn't
supported by the formatter API.

To build nested structure (i.e. a list of dicts), use fm.nested().

See also https://www.mercurial-scm.org/wiki/GenericTemplatingPlan

fm.condwrite() vs 'if cond:':

In most cases, use fm.condwrite() so users can selectively show the data
in template output. If it's costly to build data, use plain 'if cond:' with
fm.write().

fm.nested() vs fm.formatdict() (or fm.formatlist()):

fm.nested() should be used to form a tree structure (a list of dicts of
lists of dicts...) which can be accessed through template keywords, e.g.
"{foo % "{bar % {...}} {baz % {...}}"}". On the other hand, fm.formatdict()
exports a dict-type object to template, which can be accessed by e.g.
"{get(foo, key)}" function.

Doctest helper:

>>> def show(fn, verbose=False, **opts):
...     import sys
...     from . import ui as uimod
...     ui = uimod.ui()
...     ui.verbose = verbose
...     ui.pushbuffer()
...     try:
...         return fn(ui, ui.formatter(pycompat.sysbytes(fn.__name__),
...                   pycompat.byteskwargs(opts)))
...     finally:
...         print(pycompat.sysstr(ui.popbuffer()), end='')

Basic example:

>>> def files(ui, fm):
...     files = [(b'foo', 123, (0, 0)), (b'bar', 456, (1, 0))]
...     for f in files:
...         fm.startitem()
...         fm.write(b'path', b'%s', f[0])
...         fm.condwrite(ui.verbose, b'date', b'  %s',
...                      fm.formatdate(f[2], b'%Y-%m-%d %H:%M:%S'))
...         fm.data(size=f[1])
...         fm.plain(b'\\n')
...     fm.end()
>>> show(files)
foo
bar
>>> show(files, verbose=True)
foo  1970-01-01 00:00:00
bar  1970-01-01 00:00:01
>>> show(files, template=b'json')
[
 {
  "date": [0, 0],
  "path": "foo",
  "size": 123
 },
 {
  "date": [1, 0],
  "path": "bar",
  "size": 456
 }
]
>>> show(files, template=b'path: {path}\\ndate: {date|rfc3339date}\\n')
path: foo
date: 1970-01-01T00:00:00+00:00
path: bar
date: 1970-01-01T00:00:01+00:00

Nested example:

>>> def subrepos(ui, fm):
...     fm.startitem()
...     fm.write(b'reponame', b'[%s]\\n', b'baz')
...     files(ui, fm.nested(b'files'))
...     fm.end()
>>> show(subrepos)
[baz]
foo
bar
>>> show(subrepos, template=b'{reponame}: {join(files % "{path}", ", ")}\\n')
baz: foo, bar
"""

from __future__ import absolute_import, print_function

import collections
import contextlib
import itertools
import os

from .i18n import _
from .node import (
    hex,
    short,
)

from . import (
    error,
    pycompat,
    templatefilters,
    templatekw,
    templater,
    util,
)
from .utils import dateutil

pickle = util.pickle

class _nullconverter(object):
    '''convert non-primitive data types to be processed by formatter'''

    # set to True if context object should be stored as item
    storecontext = False

    @staticmethod
    def formatdate(date, fmt):
        '''convert date tuple to appropriate format'''
        return date
    @staticmethod
    def formatdict(data, key, value, fmt, sep):
        '''convert dict or key-value pairs to appropriate dict format'''
        # use plain dict instead of util.sortdict so that data can be
        # serialized as a builtin dict in pickle output
        return dict(data)
    @staticmethod
    def formatlist(data, name, fmt, sep):
        '''convert iterable to appropriate list format'''
        return list(data)

class baseformatter(object):
    def __init__(self, ui, topic, opts, converter):
        self._ui = ui
        self._topic = topic
        self._style = opts.get("style")
        self._template = opts.get("template")
        self._converter = converter
        self._item = None
        # function to convert node to string suitable for this output
        self.hexfunc = hex
    def __enter__(self):
        return self
    def __exit__(self, exctype, excvalue, traceback):
        if exctype is None:
            self.end()
    def _showitem(self):
        '''show a formatted item once all data is collected'''
    def startitem(self):
        '''begin an item in the format list'''
        if self._item is not None:
            self._showitem()
        self._item = {}
    def formatdate(self, date, fmt='%a %b %d %H:%M:%S %Y %1%2'):
        '''convert date tuple to appropriate format'''
        return self._converter.formatdate(date, fmt)
    def formatdict(self, data, key='key', value='value', fmt=None, sep=' '):
        '''convert dict or key-value pairs to appropriate dict format'''
        return self._converter.formatdict(data, key, value, fmt, sep)
    def formatlist(self, data, name, fmt=None, sep=' '):
        '''convert iterable to appropriate list format'''
        # name is mandatory argument for now, but it could be optional if
        # we have default template keyword, e.g. {item}
        return self._converter.formatlist(data, name, fmt, sep)
    def context(self, **ctxs):
        '''insert context objects to be used to render template keywords'''
        ctxs = pycompat.byteskwargs(ctxs)
        assert all(k == 'ctx' for k in ctxs)
        if self._converter.storecontext:
            self._item.update(ctxs)
    def data(self, **data):
        '''insert data into item that's not shown in default output'''
        data = pycompat.byteskwargs(data)
        self._item.update(data)
    def write(self, fields, deftext, *fielddata, **opts):
        '''do default text output while assigning data to item'''
        fieldkeys = fields.split()
        assert len(fieldkeys) == len(fielddata)
        self._item.update(zip(fieldkeys, fielddata))
    def condwrite(self, cond, fields, deftext, *fielddata, **opts):
        '''do conditional write (primarily for plain formatter)'''
        fieldkeys = fields.split()
        assert len(fieldkeys) == len(fielddata)
        self._item.update(zip(fieldkeys, fielddata))
    def plain(self, text, **opts):
        '''show raw text for non-templated mode'''
    def isplain(self):
        '''check for plain formatter usage'''
        return False
    def nested(self, field):
        '''sub formatter to store nested data in the specified field'''
        self._item[field] = data = []
        return _nestedformatter(self._ui, self._converter, data)
    def end(self):
        '''end output for the formatter'''
        if self._item is not None:
            self._showitem()

def nullformatter(ui, topic):
    '''formatter that prints nothing'''
    return baseformatter(ui, topic, opts={}, converter=_nullconverter)

class _nestedformatter(baseformatter):
    '''build sub items and store them in the parent formatter'''
    def __init__(self, ui, converter, data):
        baseformatter.__init__(self, ui, topic='', opts={}, converter=converter)
        self._data = data
    def _showitem(self):
        self._data.append(self._item)

def _iteritems(data):
    '''iterate key-value pairs in stable order'''
    if isinstance(data, dict):
        return sorted(data.iteritems())
    return data

class _plainconverter(object):
    '''convert non-primitive data types to text'''

    storecontext = False

    @staticmethod
    def formatdate(date, fmt):
        '''stringify date tuple in the given format'''
        return dateutil.datestr(date, fmt)
    @staticmethod
    def formatdict(data, key, value, fmt, sep):
        '''stringify key-value pairs separated by sep'''
        prefmt = pycompat.identity
        if fmt is None:
            fmt = '%s=%s'
            prefmt = pycompat.bytestr
        return sep.join(fmt % (prefmt(k), prefmt(v))
                        for k, v in _iteritems(data))
    @staticmethod
    def formatlist(data, name, fmt, sep):
        '''stringify iterable separated by sep'''
        prefmt = pycompat.identity
        if fmt is None:
            fmt = '%s'
            prefmt = pycompat.bytestr
        return sep.join(fmt % prefmt(e) for e in data)

class plainformatter(baseformatter):
    '''the default text output scheme'''
    def __init__(self, ui, out, topic, opts):
        baseformatter.__init__(self, ui, topic, opts, _plainconverter)
        if ui.debugflag:
            self.hexfunc = hex
        else:
            self.hexfunc = short
        if ui is out:
            self._write = ui.write
        else:
            self._write = lambda s, **opts: out.write(s)
    def startitem(self):
        pass
    def data(self, **data):
        pass
    def write(self, fields, deftext, *fielddata, **opts):
        self._write(deftext % fielddata, **opts)
    def condwrite(self, cond, fields, deftext, *fielddata, **opts):
        '''do conditional write'''
        if cond:
            self._write(deftext % fielddata, **opts)
    def plain(self, text, **opts):
        self._write(text, **opts)
    def isplain(self):
        return True
    def nested(self, field):
        # nested data will be directly written to ui
        return self
    def end(self):
        pass

class debugformatter(baseformatter):
    def __init__(self, ui, out, topic, opts):
        baseformatter.__init__(self, ui, topic, opts, _nullconverter)
        self._out = out
        self._out.write("%s = [\n" % self._topic)
    def _showitem(self):
        self._out.write('    %s,\n' % pycompat.byterepr(self._item))
    def end(self):
        baseformatter.end(self)
        self._out.write("]\n")

class pickleformatter(baseformatter):
    def __init__(self, ui, out, topic, opts):
        baseformatter.__init__(self, ui, topic, opts, _nullconverter)
        self._out = out
        self._data = []
    def _showitem(self):
        self._data.append(self._item)
    def end(self):
        baseformatter.end(self)
        self._out.write(pickle.dumps(self._data))

class jsonformatter(baseformatter):
    def __init__(self, ui, out, topic, opts):
        baseformatter.__init__(self, ui, topic, opts, _nullconverter)
        self._out = out
        self._out.write("[")
        self._first = True
    def _showitem(self):
        if self._first:
            self._first = False
        else:
            self._out.write(",")

        self._out.write("\n {\n")
        first = True
        for k, v in sorted(self._item.items()):
            if first:
                first = False
            else:
                self._out.write(",\n")
            u = templatefilters.json(v, paranoid=False)
            self._out.write('  "%s": %s' % (k, u))
        self._out.write("\n }")
    def end(self):
        baseformatter.end(self)
        self._out.write("\n]\n")

class _templateconverter(object):
    '''convert non-primitive data types to be processed by templater'''

    storecontext = True

    @staticmethod
    def formatdate(date, fmt):
        '''return date tuple'''
        return date
    @staticmethod
    def formatdict(data, key, value, fmt, sep):
        '''build object that can be evaluated as either plain string or dict'''
        data = util.sortdict(_iteritems(data))
        def f():
            yield _plainconverter.formatdict(data, key, value, fmt, sep)
        return templatekw.hybriddict(data, key=key, value=value, fmt=fmt, gen=f)
    @staticmethod
    def formatlist(data, name, fmt, sep):
        '''build object that can be evaluated as either plain string or list'''
        data = list(data)
        def f():
            yield _plainconverter.formatlist(data, name, fmt, sep)
        return templatekw.hybridlist(data, name=name, fmt=fmt, gen=f)

class templateformatter(baseformatter):
    def __init__(self, ui, out, topic, opts):
        baseformatter.__init__(self, ui, topic, opts, _templateconverter)
        self._out = out
        spec = lookuptemplate(ui, topic, opts.get('template', ''))
        self._tref = spec.ref
        self._t = loadtemplater(ui, spec, defaults=templatekw.keywords,
                                resources=templateresources(ui),
                                cache=templatekw.defaulttempl)
        self._parts = templatepartsmap(spec, self._t,
                                       ['docheader', 'docfooter', 'separator'])
        self._counter = itertools.count()
        self._renderitem('docheader', {})

    def _showitem(self):
        item = self._item.copy()
        item['index'] = index = next(self._counter)
        if index > 0:
            self._renderitem('separator', {})
        self._renderitem(self._tref, item)

    def _renderitem(self, part, item):
        if part not in self._parts:
            return
        ref = self._parts[part]

        # TODO: add support for filectx
        props = {}
        # explicitly-defined fields precede templatekw
        props.update(item)
        if 'ctx' in item:
            # but template resources must be always available
            props['repo'] = props['ctx'].repo()
            props['revcache'] = {}
        props = pycompat.strkwargs(props)
        g = self._t(ref, **props)
        self._out.write(templater.stringify(g))

    def end(self):
        baseformatter.end(self)
        self._renderitem('docfooter', {})

templatespec = collections.namedtuple(r'templatespec',
                                      r'ref tmpl mapfile')

def lookuptemplate(ui, topic, tmpl):
    """Find the template matching the given -T/--template spec 'tmpl'

    'tmpl' can be any of the following:

     - a literal template (e.g. '{rev}')
     - a map-file name or path (e.g. 'changelog')
     - a reference to [templates] in config file
     - a path to raw template file

    A map file defines a stand-alone template environment. If a map file
    selected, all templates defined in the file will be loaded, and the
    template matching the given topic will be rendered. Aliases won't be
    loaded from user config, but from the map file.

    If no map file selected, all templates in [templates] section will be
    available as well as aliases in [templatealias].
    """

    # looks like a literal template?
    if '{' in tmpl:
        return templatespec('', tmpl, None)

    # perhaps a stock style?
    if not os.path.split(tmpl)[0]:
        mapname = (templater.templatepath('map-cmdline.' + tmpl)
                   or templater.templatepath(tmpl))
        if mapname and os.path.isfile(mapname):
            return templatespec(topic, None, mapname)

    # perhaps it's a reference to [templates]
    if ui.config('templates', tmpl):
        return templatespec(tmpl, None, None)

    if tmpl == 'list':
        ui.write(_("available styles: %s\n") % templater.stylelist())
        raise error.Abort(_("specify a template"))

    # perhaps it's a path to a map or a template
    if ('/' in tmpl or '\\' in tmpl) and os.path.isfile(tmpl):
        # is it a mapfile for a style?
        if os.path.basename(tmpl).startswith("map-"):
            return templatespec(topic, None, os.path.realpath(tmpl))
        with util.posixfile(tmpl, 'rb') as f:
            tmpl = f.read()
        return templatespec('', tmpl, None)

    # constant string?
    return templatespec('', tmpl, None)

def templatepartsmap(spec, t, partnames):
    """Create a mapping of {part: ref}"""
    partsmap = {spec.ref: spec.ref}  # initial ref must exist in t
    if spec.mapfile:
        partsmap.update((p, p) for p in partnames if p in t)
    elif spec.ref:
        for part in partnames:
            ref = '%s:%s' % (spec.ref, part)  # select config sub-section
            if ref in t:
                partsmap[part] = ref
    return partsmap

def loadtemplater(ui, spec, defaults=None, resources=None, cache=None):
    """Create a templater from either a literal template or loading from
    a map file"""
    assert not (spec.tmpl and spec.mapfile)
    if spec.mapfile:
        frommapfile = templater.templater.frommapfile
        return frommapfile(spec.mapfile, defaults=defaults, resources=resources,
                           cache=cache)
    return maketemplater(ui, spec.tmpl, defaults=defaults, resources=resources,
                         cache=cache)

def maketemplater(ui, tmpl, defaults=None, resources=None, cache=None):
    """Create a templater from a string template 'tmpl'"""
    aliases = ui.configitems('templatealias')
    t = templater.templater(defaults=defaults, resources=resources,
                            cache=cache, aliases=aliases)
    t.cache.update((k, templater.unquotestring(v))
                   for k, v in ui.configitems('templates'))
    if tmpl:
        t.cache[''] = tmpl
    return t

def templateresources(ui, repo=None):
    """Create a dict of template resources designed for the default templatekw
    and function"""
    return {
        'cache': {},  # for templatekw/funcs to store reusable data
        'ctx': None,
        'repo': repo,
        'revcache': None,  # per-ctx cache; set later
        'ui': ui,
    }

def formatter(ui, out, topic, opts):
    template = opts.get("template", "")
    if template == "json":
        return jsonformatter(ui, out, topic, opts)
    elif template == "pickle":
        return pickleformatter(ui, out, topic, opts)
    elif template == "debug":
        return debugformatter(ui, out, topic, opts)
    elif template != "":
        return templateformatter(ui, out, topic, opts)
    # developer config: ui.formatdebug
    elif ui.configbool('ui', 'formatdebug'):
        return debugformatter(ui, out, topic, opts)
    # deprecated config: ui.formatjson
    elif ui.configbool('ui', 'formatjson'):
        return jsonformatter(ui, out, topic, opts)
    return plainformatter(ui, out, topic, opts)

@contextlib.contextmanager
def openformatter(ui, filename, topic, opts):
    """Create a formatter that writes outputs to the specified file

    Must be invoked using the 'with' statement.
    """
    with util.posixfile(filename, 'wb') as out:
        with formatter(ui, out, topic, opts) as fm:
            yield fm

@contextlib.contextmanager
def _neverending(fm):
    yield fm

def maybereopen(fm, filename, opts):
    """Create a formatter backed by file if filename specified, else return
    the given formatter

    Must be invoked using the 'with' statement. This will never call fm.end()
    of the given formatter.
    """
    if filename:
        return openformatter(fm._ui, filename, fm._topic, opts)
    else:
        return _neverending(fm)