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#!/usr/bin/env python
#
# Copyright 2009 Facebook
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may
# not use this file except in compliance with the License. You may obtain
# a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
# License for the specific language governing permissions and limitations
# under the License.
"""A simple template system that compiles templates to Python code.
Basic usage looks like:
t = template.Template("<html>{{ myvalue }}</html>")
print t.generate(myvalue="XXX")
Loader is a class that loads templates from a root directory and caches
the compiled templates:
loader = template.Loader("/home/btaylor")
print loader.load("test.html").generate(myvalue="XXX")
We compile all templates to raw Python. Error-reporting is currently... uh,
interesting. Syntax for the templates
### base.html
<html>
<head>
<title>{% block title %}Default title{% end %}</title>
</head>
<body>
<ul>
{% for student in students %}
{% block student %}
<li>{{ escape(student.name) }}</li>
{% end %}
{% end %}
</ul>
</body>
</html>
### bold.html
{% extends "base.html" %}
{% block title %}A bolder title{% end %}
{% block student %}
<li><span style="bold">{{ escape(student.name) }}</span></li>
{% block %}
Unlike most other template systems, we do not put any restrictions on the
expressions you can include in your statements. if and for blocks get
translated exactly into Python, do you can do complex expressions like:
{% for student in [p for p in people if p.student and p.age > 23] %}
<li>{{ escape(student.name) }}</li>
{% end %}
Translating directly to Python means you can apply functions to expressions
easily, like the escape() function in the examples above. You can pass
functions in to your template just like any other variable:
### Python code
def add(x, y):
return x + y
template.execute(add=add)
### The template
{{ add(1, 2) }}
We provide the functions escape(), url_escape(), json_encode(), and squeeze()
to all templates by default.
"""
from __future__ import with_statement
import cStringIO
import datetime
import escape
import logging
import os.path
import re
class Template(object):
"""A compiled template.
We compile into Python from the given template_string. You can generate
the template from variables with generate().
"""
def __init__(self, template_string, name="<string>", loader=None,
compress_whitespace=None):
self.name = name
if compress_whitespace is None:
compress_whitespace = name.endswith(".html") or \
name.endswith(".js")
reader = _TemplateReader(name, template_string)
self.file = _File(_parse(reader))
self.code = self._generate_python(loader, compress_whitespace)
try:
self.compiled = compile(self.code, self.name, "exec")
except:
formatted_code = _format_code(self.code).rstrip()
logging.error("%s code:\n%s", self.name, formatted_code)
raise
def generate(self, **kwargs):
"""Generate this template with the given arguments."""
namespace = {
"escape": escape.xhtml_escape,
"url_escape": escape.url_escape,
"json_encode": escape.json_encode,
"squeeze": escape.squeeze,
"datetime": datetime,
}
namespace.update(kwargs)
exec self.compiled in namespace
execute = namespace["_execute"]
try:
return execute()
except:
formatted_code = _format_code(self.code).rstrip()
logging.error("%s code:\n%s", self.name, formatted_code)
raise
def _generate_python(self, loader, compress_whitespace):
buffer = cStringIO.StringIO()
try:
named_blocks = {}
ancestors = self._get_ancestors(loader)
ancestors.reverse()
for ancestor in ancestors:
ancestor.find_named_blocks(loader, named_blocks)
self.file.find_named_blocks(loader, named_blocks)
writer = _CodeWriter(buffer, named_blocks, loader, self,
compress_whitespace)
ancestors[0].generate(writer)
return buffer.getvalue()
finally:
buffer.close()
def _get_ancestors(self, loader):
ancestors = [self.file]
for chunk in self.file.body.chunks:
if isinstance(chunk, _ExtendsBlock):
if not loader:
raise ParseError("{% extends %} block found, but no "
"template loader")
template = loader.load(chunk.name, self.name)
ancestors.extend(template._get_ancestors(loader))
return ancestors
class Loader(object):
"""A template loader that loads from a single root directory.
You must use a template loader to use template constructs like
{% extends %} and {% include %}. Loader caches all templates after
they are loaded the first time.
"""
def __init__(self, root_directory):
self.root = os.path.abspath(root_directory)
self.templates = {}
def reset(self):
self.templates = {}
def resolve_path(self, name, parent_path=None):
if parent_path and not parent_path.startswith("<") and \
not parent_path.startswith("/") and \
not name.startswith("/"):
current_path = os.path.join(self.root, parent_path)
file_dir = os.path.dirname(os.path.abspath(current_path))
relative_path = os.path.abspath(os.path.join(file_dir, name))
if relative_path.startswith(self.root):
name = relative_path[len(self.root) + 1:]
return name
def load(self, name, parent_path=None):
name = self.resolve_path(name, parent_path=parent_path)
if name not in self.templates:
path = os.path.join(self.root, name)
f = open(path, "r")
self.templates[name] = Template(f.read(), name=name, loader=self)
f.close()
return self.templates[name]
class _Node(object):
def each_child(self):
return ()
def generate(self, writer):
raise NotImplementedError()
def find_named_blocks(self, loader, named_blocks):
for child in self.each_child():
child.find_named_blocks(loader, named_blocks)
class _File(_Node):
def __init__(self, body):
self.body = body
def generate(self, writer):
writer.write_line("def _execute():")
with writer.indent():
writer.write_line("_buffer = []")
self.body.generate(writer)
writer.write_line("return ''.join(_buffer)")
def each_child(self):
return (self.body,)
class _ChunkList(_Node):
def __init__(self, chunks):
self.chunks = chunks
def generate(self, writer):
for chunk in self.chunks:
chunk.generate(writer)
def each_child(self):
return self.chunks
class _NamedBlock(_Node):
def __init__(self, name, body=None):
self.name = name
self.body = body
def each_child(self):
return (self.body,)
def generate(self, writer):
writer.named_blocks[self.name].generate(writer)
def find_named_blocks(self, loader, named_blocks):
named_blocks[self.name] = self.body
_Node.find_named_blocks(self, loader, named_blocks)
class _ExtendsBlock(_Node):
def __init__(self, name):
self.name = name
class _IncludeBlock(_Node):
def __init__(self, name, reader):
self.name = name
self.template_name = reader.name
def find_named_blocks(self, loader, named_blocks):
included = loader.load(self.name, self.template_name)
included.file.find_named_blocks(loader, named_blocks)
def generate(self, writer):
included = writer.loader.load(self.name, self.template_name)
old = writer.current_template
writer.current_template = included
included.file.body.generate(writer)
writer.current_template = old
class _ApplyBlock(_Node):
def __init__(self, method, body=None):
self.method = method
self.body = body
def each_child(self):
return (self.body,)
def generate(self, writer):
method_name = "apply%d" % writer.apply_counter
writer.apply_counter += 1
writer.write_line("def %s():" % method_name)
with writer.indent():
writer.write_line("_buffer = []")
self.body.generate(writer)
writer.write_line("return ''.join(_buffer)")
writer.write_line("_buffer.append(%s(%s()))" % (
self.method, method_name))
class _ControlBlock(_Node):
def __init__(self, statement, body=None):
self.statement = statement
self.body = body
def each_child(self):
return (self.body,)
def generate(self, writer):
writer.write_line("%s:" % self.statement)
with writer.indent():
self.body.generate(writer)
class _IntermediateControlBlock(_Node):
def __init__(self, statement):
self.statement = statement
def generate(self, writer):
writer.write_line("%s:" % self.statement, writer.indent_size() - 1)
class _Statement(_Node):
def __init__(self, statement):
self.statement = statement
def generate(self, writer):
writer.write_line(self.statement)
class _Expression(_Node):
def __init__(self, expression):
self.expression = expression
def generate(self, writer):
writer.write_line("_tmp = %s" % self.expression)
writer.write_line("if isinstance(_tmp, str): _buffer.append(_tmp)")
writer.write_line("elif isinstance(_tmp, unicode): "
"_buffer.append(_tmp.encode('utf-8'))")
writer.write_line("else: _buffer.append(str(_tmp))")
class _Text(_Node):
def __init__(self, value):
self.value = value
def generate(self, writer):
value = self.value
# Compress lots of white space to a single character. If the whitespace
# breaks a line, have it continue to break a line, but just with a
# single \n character
if writer.compress_whitespace and "<pre>" not in value:
value = re.sub(r"([\t ]+)", " ", value)
value = re.sub(r"(\s*\n\s*)", "\n", value)
if value:
writer.write_line('_buffer.append(%r)' % value)
class ParseError(Exception):
"""Raised for template syntax errors."""
pass
class _CodeWriter(object):
def __init__(self, file, named_blocks, loader, current_template,
compress_whitespace):
self.file = file
self.named_blocks = named_blocks
self.loader = loader
self.current_template = current_template
self.compress_whitespace = compress_whitespace
self.apply_counter = 0
self._indent = 0
def indent(self):
return self
def indent_size(self):
return self._indent
def __enter__(self):
self._indent += 1
return self
def __exit__(self, *args):
assert self._indent > 0
self._indent -= 1
def write_line(self, line, indent=None):
if indent == None:
indent = self._indent
for i in xrange(indent):
self.file.write(" ")
print >> self.file, line
class _TemplateReader(object):
def __init__(self, name, text):
self.name = name
self.text = text
self.line = 0
self.pos = 0
def find(self, needle, start=0, end=None):
assert start >= 0, start
pos = self.pos
start += pos
if end is None:
index = self.text.find(needle, start)
else:
end += pos
assert end >= start
index = self.text.find(needle, start, end)
if index != -1:
index -= pos
return index
def consume(self, count=None):
if count is None:
count = len(self.text) - self.pos
newpos = self.pos + count
self.line += self.text.count("\n", self.pos, newpos)
s = self.text[self.pos:newpos]
self.pos = newpos
return s
def remaining(self):
return len(self.text) - self.pos
def __len__(self):
return self.remaining()
def __getitem__(self, key):
if type(key) is slice:
size = len(self)
start, stop, step = slice.indices(size)
if start is None: start = self.pos
else: start += self.pos
if stop is not None: stop += self.pos
return self.text[slice(start, stop, step)]
elif key < 0:
return self.text[key]
else:
return self.text[self.pos + key]
def __str__(self):
return self.text[self.pos:]
def _format_code(code):
lines = code.splitlines()
format = "%%%dd %%s\n" % len(repr(len(lines) + 1))
return "".join([format % (i + 1, line) for (i, line) in enumerate(lines)])
def _parse(reader, in_block=None):
body = _ChunkList([])
while True:
# Find next template directive
curly = 0
while True:
curly = reader.find("{", curly)
if curly == -1 or curly + 1 == reader.remaining():
# EOF
if in_block:
raise ParseError("Missing {%% end %%} block for %s" %
in_block)
body.chunks.append(_Text(reader.consume()))
return body
# If the first curly brace is not the start of a special token,
# start searching from the character after it
if reader[curly + 1] not in ("{", "%"):
curly += 1
continue
# When there are more than 2 curlies in a row, use the
# innermost ones. This is useful when generating languages
# like latex where curlies are also meaningful
if (curly + 2 < reader.remaining() and
reader[curly + 1] == '{' and reader[curly + 2] == '{'):
curly += 1
continue
break
# Append any text before the special token
if curly > 0:
body.chunks.append(_Text(reader.consume(curly)))
start_brace = reader.consume(2)
line = reader.line
# Expression
if start_brace == "{{":
end = reader.find("}}")
if end == -1 or reader.find("\n", 0, end) != -1:
raise ParseError("Missing end expression }} on line %d" % line)
contents = reader.consume(end).strip()
reader.consume(2)
if not contents:
raise ParseError("Empty expression on line %d" % line)
body.chunks.append(_Expression(contents))
continue
# Block
assert start_brace == "{%", start_brace
end = reader.find("%}")
if end == -1 or reader.find("\n", 0, end) != -1:
raise ParseError("Missing end block %%} on line %d" % line)
contents = reader.consume(end).strip()
reader.consume(2)
if not contents:
raise ParseError("Empty block tag ({%% %%}) on line %d" % line)
operator, space, suffix = contents.partition(" ")
suffix = suffix.strip()
# Intermediate ("else", "elif", etc) blocks
intermediate_blocks = {
"else": set(["if", "for", "while"]),
"elif": set(["if"]),
"except": set(["try"]),
"finally": set(["try"]),
}
allowed_parents = intermediate_blocks.get(operator)
if allowed_parents is not None:
if not in_block:
raise ParseError("%s outside %s block" %
(operator, allowed_parents))
if in_block not in allowed_parents:
raise ParseError("%s block cannot be attached to %s block" % (operator, in_block))
body.chunks.append(_IntermediateControlBlock(contents))
continue
# End tag
elif operator == "end":
if not in_block:
raise ParseError("Extra {%% end %%} block on line %d" % line)
return body
elif operator in ("extends", "include", "set", "import", "comment"):
if operator == "comment":
continue
if operator == "extends":
suffix = suffix.strip('"').strip("'")
if not suffix:
raise ParseError("extends missing file path on line %d" % line)
block = _ExtendsBlock(suffix)
elif operator == "import":
if not suffix:
raise ParseError("import missing statement on line %d" % line)
block = _Statement(contents)
elif operator == "include":
suffix = suffix.strip('"').strip("'")
if not suffix:
raise ParseError("include missing file path on line %d" % line)
block = _IncludeBlock(suffix, reader)
elif operator == "set":
if not suffix:
raise ParseError("set missing statement on line %d" % line)
block = _Statement(suffix)
body.chunks.append(block)
continue
elif operator in ("apply", "block", "try", "if", "for", "while"):
# parse inner body recursively
block_body = _parse(reader, operator)
if operator == "apply":
if not suffix:
raise ParseError("apply missing method name on line %d" % line)
block = _ApplyBlock(suffix, block_body)
elif operator == "block":
if not suffix:
raise ParseError("block missing name on line %d" % line)
block = _NamedBlock(suffix, block_body)
else:
block = _ControlBlock(contents, block_body)
body.chunks.append(block)
continue
else:
raise ParseError("unknown operator: %r" % operator)
|
