tests/test-template-engine.t

templater: add context.preload(t) to test if the specified template exists

I'm going to remove 'templ' from the resources dict because it is the only
resource that the caller can't provide. This also implies that putting
'templ' into the resources dict creates a reference cycle.

context.preload(t) will be used in place of templater.__contains__().

  $ cat > engine.py << EOF
  > 
  > from mercurial import (
  >     pycompat,
  >     templater,
  >     templateutil,
  > )
  > 
  > class mytemplater(templater.engine):
  >     def _load(self, t):
  >         return self._loader(t)
  > 
  >     def process(self, t, map):
  >         tmpl = self._load(t)
  >         props = self._defaults.copy()
  >         props.update(map)
  >         for k, v in props.items():
  >             if b'{{%s}}' % k not in tmpl:
  >                 continue
  >             if callable(v) and getattr(v, '_requires', None) is None:
  >                 props = self._resources.copy()
  >                 props.update(map)
  >                 v = v(**pycompat.strkwargs(props))
  >             elif callable(v):
  >                 v = v(self, props)
  >             v = templateutil.stringify(v)
  >             tmpl = tmpl.replace(b'{{%s}}' % k, v)
  >         yield tmpl
  > 
  > templater.engines[b'my'] = mytemplater
  > EOF
  $ hg init test
  $ echo '[extensions]' > test/.hg/hgrc
  $ echo "engine = `pwd`/engine.py" >> test/.hg/hgrc
  $ cd test
  $ cat > mymap << EOF
  > changeset = my:changeset.txt
  > EOF
  $ cat > changeset.txt << EOF
  > {{rev}} {{node}} {{author}}
  > EOF
  $ hg ci -Ama
  adding changeset.txt
  adding mymap
  $ hg log --style=./mymap
  0 97e5f848f0936960273bbf75be6388cd0350a32b test

  $ cat > changeset.txt << EOF
  > {{p1rev}} {{p1node}} {{p2rev}} {{p2node}}
  > EOF
  $ hg ci -Ama
  $ hg log --style=./mymap
  0 97e5f848f0936960273bbf75be6388cd0350a32b -1 0000000000000000000000000000000000000000
  -1 0000000000000000000000000000000000000000 -1 0000000000000000000000000000000000000000

invalid engine type:

  $ echo 'changeset = unknown:changeset.txt' > unknownenginemap
  $ hg log --style=./unknownenginemap
  abort: invalid template engine: unknown
  [255]

  $ cd ..