formatter: provide hint of context keys required by template

This allows us to create ctx objects only if necessary.

I tried another idea which is to populate ctx from 'repo' and 'node' value
on demand. It worked, but seemed unnecessarily complicated. So I chose a
simpler one.

The datafields argument is a space-separated string for consistency with
fm.write() API.

mercurial/formatter.py

@@ -1,627 +1,649 b''
 # 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', tmpl=b'{reponame}'))
 ...     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 contextlib
 import itertools
 import os
 
 from .i18n import _
 from .node import (
     hex,
     short,
 )
 from .thirdparty import (
     attr,
 )
 
 from . import (
     error,
     pycompat,
     templatefilters,
+    templatefuncs,
     templatekw,
     templater,
     templateutil,
     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 wrapnested(data, tmpl, sep):
         '''wrap nested data by appropriate type'''
         return data
     @staticmethod
     def formatdate(date, fmt):
         '''convert date tuple to appropriate format'''
         # timestamp can be float, but the canonical form should be int
         ts, tz = date
         return (int(ts), tz)
     @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._opts = opts
         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 contexthint(self, datafields):
+        '''set of context object keys to be required given datafields set'''
+        return set()
     def context(self, **ctxs):
         '''insert context objects to be used to render template keywords'''
         ctxs = pycompat.byteskwargs(ctxs)
         assert all(k in {'ctx', 'fctx'} for k in ctxs)
         if self._converter.storecontext:
             self._item.update(ctxs)
     def datahint(self):
         '''set of field names to be referenced'''
         return set()
     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, tmpl=None, sep=''):
         '''sub formatter to store nested data in the specified field'''
         data = []
         self._item[field] = self._converter.wrapnested(data, tmpl, sep)
         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, opts):
     '''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 wrapnested(data, tmpl, sep):
         raise error.ProgrammingError('plainformatter should never be nested')
     @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, tmpl=None, sep=''):
         # 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 wrapnested(data, tmpl, sep):
         '''wrap nested data by templatable type'''
         return templateutil.mappinglist(data, tmpl=tmpl, sep=sep)
     @staticmethod
     def formatdate(date, fmt):
         '''return date tuple'''
         return templateutil.date(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 templateutil.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 templateutil.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]
         self._out.write(self._t.render(ref, item))
 
     @util.propertycache
     def _symbolsused(self):
         return self._t.symbolsuseddefault()
 
+    def contexthint(self, datafields):
+        '''set of context object keys to be required by the template, given
+        datafields overridden by immediate values'''
+        requires = set()
+        ksyms, fsyms = self._symbolsused
+        ksyms = ksyms - set(datafields.split())  # exclude immediate fields
+        symtables = [(ksyms, templatekw.keywords),
+                     (fsyms, templatefuncs.funcs)]
+        for syms, table in symtables:
+            for k in syms:
+                f = table.get(k)
+                if not f:
+                    continue
+                requires.update(getattr(f, '_requires', ()))
+        if 'repo' in requires:
+            requires.add('ctx')  # there's no API to pass repo to formatter
+        return requires & {'ctx', 'fctx'}
+
     def datahint(self):
         '''set of field names to be referenced from the template'''
         return self._symbolsused[0]
 
     def end(self):
         baseformatter.end(self)
         self._renderitem('docfooter', {})
 
 @attr.s(frozen=True)
 class templatespec(object):
     ref = attr.ib()
     tmpl = attr.ib()
     mapfile = attr.ib()
 
 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
 
 class templateresources(templater.resourcemapper):
     """Resource mapper designed for the default templatekw and function"""
 
     def __init__(self, ui, repo=None):
         self._resmap = {
             'cache': {},  # for templatekw/funcs to store reusable data
             'repo': repo,
             'ui': ui,
         }
 
     def availablekeys(self, context, mapping):
         return {k for k, g in self._gettermap.iteritems()
                 if g(self, context, mapping, k) is not None}
 
     def knownkeys(self):
         return self._knownkeys
 
     def lookup(self, context, mapping, key):
         get = self._gettermap.get(key)
         if not get:
             return None
         return get(self, context, mapping, key)
 
     def populatemap(self, context, origmapping, newmapping):
         mapping = {}
         if self._hasctx(newmapping):
             mapping['revcache'] = {}  # per-ctx cache
         if (('node' in origmapping or self._hasctx(origmapping))
             and ('node' in newmapping or self._hasctx(newmapping))):
             orignode = templateutil.runsymbol(context, origmapping, 'node')
             mapping['originalnode'] = orignode
         return mapping
 
     def _getsome(self, context, mapping, key):
         v = mapping.get(key)
         if v is not None:
             return v
         return self._resmap.get(key)
 
     def _hasctx(self, mapping):
         return 'ctx' in mapping or 'fctx' in mapping
 
     def _getctx(self, context, mapping, key):
         ctx = mapping.get('ctx')
         if ctx is not None:
             return ctx
         fctx = mapping.get('fctx')
         if fctx is not None:
             return fctx.changectx()
 
     def _getrepo(self, context, mapping, key):
         ctx = self._getctx(context, mapping, 'ctx')
         if ctx is not None:
             return ctx.repo()
         return self._getsome(context, mapping, key)
 
     _gettermap = {
         'cache': _getsome,
         'ctx': _getctx,
         'fctx': _getsome,
         'repo': _getrepo,
         'revcache': _getsome,
         'ui': _getsome,
     }
     _knownkeys = set(_gettermap.keys())
 
 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):
     """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, fm._opts)
     else:
         return _neverending(fm)