108 lines
3.7 KiB
Python
108 lines
3.7 KiB
Python
# Copyright 2015 Canonical Ltd.
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# This file is part of cloud-init. See LICENCE file for license information.
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#
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# vi: ts=4 expandtab
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import collections
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import os
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import re
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try:
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import jinja2
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from jinja2 import Template as JTemplate
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JINJA_AVAILABLE = True
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except (ImportError, AttributeError):
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JINJA_AVAILABLE = False # noqa
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from cloudinit import logging
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LOG = logging.getLogger(__name__)
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TYPE_MATCHER = re.compile(r"##\s*template:(.*)", re.I)
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BASIC_MATCHER = re.compile(r'\$\{([A-Za-z0-9_.]+)\}|\$([A-Za-z0-9_.]+)')
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def basic_render(content, params):
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"""This does simple replacement of bash variable like templates.
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It identifies patterns like ${a} or $a and can also identify patterns like
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${a.b} or $a.b which will look for a key 'b' in the dictionary rooted
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by key 'a'.
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"""
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def replacer(match):
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# Only 1 of the 2 groups will actually have a valid entry.
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name = match.group(1) or match.group(2)
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if name is None:
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# not sure how this can possibly occur
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raise RuntimeError("Match encountered but no valid group present")
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path = collections.deque(name.split("."))
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selected_params = params
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while len(path) > 1:
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key = path.popleft()
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if not isinstance(selected_params, dict):
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raise TypeError(
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"Can not traverse into non-dictionary '%s' of type %s "
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"while looking for subkey '%s'" %
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(selected_params, type(selected_params), key))
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selected_params = selected_params[key]
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key = path.popleft()
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if not isinstance(selected_params, dict):
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raise TypeError("Can not extract key '%s' from non-dictionary"
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" '%s' of type %s"
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% (key, selected_params, type(selected_params)))
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return str(selected_params[key])
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return BASIC_MATCHER.sub(replacer, content)
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def detect_template(text):
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def jinja_render(content, params):
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# keep_trailing_newline is in jinja2 2.7+, not 2.6
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add = "\n" if content.endswith("\n") else ""
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return JTemplate(content,
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undefined=jinja2.StrictUndefined,
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trim_blocks=True).render(**params) + add
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if "\n" in text:
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ident, rest = text.split("\n", 1)
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else:
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ident = text
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rest = ''
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type_match = TYPE_MATCHER.match(ident)
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if not type_match:
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return ('basic', basic_render, text)
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else:
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template_type = type_match.group(1).lower().strip()
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if template_type not in ('jinja', 'basic'):
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raise ValueError("Unknown template rendering type '%s' requested"
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% template_type)
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if template_type == 'jinja' and not JINJA_AVAILABLE:
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raise ValueError("Template requested jinja as renderer, but Jinja "
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"is not available.")
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elif template_type == 'jinja' and JINJA_AVAILABLE:
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return ('jinja', jinja_render, rest)
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# Only thing left over is the basic renderer (it is always available).
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return ('basic', basic_render, rest)
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def render_from_file(fn, params, encoding='utf-8'):
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with open(fn, 'rb') as fh:
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content = fh.read()
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content = content.decode(encoding)
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_, renderer, content = detect_template(content)
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return renderer(content, params)
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def render_to_file(fn, outfn, params, mode=0o644, encoding='utf-8'):
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contents = render_from_file(fn, params, encoding=encoding)
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with open(outfn, 'wb') as fh:
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fh.write(contents.encode(encoding))
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os.chmod(outfn, mode)
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def render_string(content, params):
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_, renderer, content = detect_template(content)
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return renderer(content, params)
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