community.general/lib/ansible/template/__init__.py

# (c) 2012-2014, Michael DeHaan <michael.dehaan@gmail.com>
#
# This file is part of Ansible
#
# Ansible is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# Ansible is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Ansible.  If not, see <http://www.gnu.org/licenses/>.

# Make coding more python3-ish
from __future__ import (absolute_import, division, print_function)
__metaclass__ = type

import ast
import re

from jinja2 import Environment
from jinja2.loaders import FileSystemLoader
from jinja2.exceptions import TemplateSyntaxError, UndefinedError
from jinja2.utils import concat as j2_concat
from jinja2.runtime import StrictUndefined

from ansible import constants as C
from ansible.errors import AnsibleError, AnsibleFilterError, AnsibleUndefinedVariable
from ansible.plugins import _basedirs, filter_loader, lookup_loader, test_loader
from ansible.template.safe_eval import safe_eval
from ansible.template.template import AnsibleJ2Template
from ansible.template.vars import AnsibleJ2Vars
from ansible.utils.debug import debug

from numbers import Number

__all__ = ['Templar']

# A regex for checking to see if a variable we're trying to
# expand is just a single variable name.

# Primitive Types which we don't want Jinja to convert to strings.
NON_TEMPLATED_TYPES = ( bool, Number )

JINJA2_OVERRIDE = '#jinja2:'

def _escape_backslashes(data, jinja_env):
    """Double backslashes within jinja2 expressions

    A user may enter something like this in a playbook::

      debug:
        msg: "Test Case 1\\3; {{ test1_name | regex_replace('^(.*)_name$', '\\1')}}"

    The string inside of the {{ gets interpreted multiple times First by yaml.
    Then by python.  And finally by jinja2 as part of it's variable.  Because
    it is processed by both python and jinja2, the backslash escaped
    characters get unescaped twice.  This means that we'd normally have to use
    four backslashes to escape that.  This is painful for playbook authors as
    they have to remember different rules for inside vs outside of a jinja2
    expression (The backslashes outside of the "{{ }}" only get processed by
    yaml and python.  So they only need to be escaped once).  The following
    code fixes this by automatically performing the extra quoting of
    backslashes inside of a jinja2 expression.

    """
    if '\\' in data and '{{' in data:
        new_data = []
        d2 = jinja_env.preprocess(data)
        in_var = False

        for token in jinja_env.lex(d2):
            if token[1] == 'variable_begin':
                in_var = True
                new_data.append(token[2])
            elif token[1] == 'variable_end':
                in_var = False
                new_data.append(token[2])
            elif in_var and token[1] == 'string':
                # Double backslashes only if we're inside of a jinja2 variable
                new_data.append(token[2].replace('\\','\\\\'))
            else:
                new_data.append(token[2])

        data = ''.join(new_data)

    return data

def _count_newlines_from_end(in_str):
    '''
    Counts the number of newlines at the end of a string. This is used during
    the jinja2 templating to ensure the count matches the input, since some newlines
    may be thrown away during the templating.
    '''

    try:
        i = len(in_str)
        j = i -1
        while in_str[j] == '\n':
            j -= 1
        return i - 1 - j
    except IndexError:
        # Uncommon cases: zero length string and string containing only newlines
        return i

class Templar:
    '''
    The main class for templating, with the main entry-point of template().
    '''

    def __init__(self, loader, shared_loader_obj=None, variables=dict()):
        self._loader              = loader
        self._filters             = None
        self._tests               = None
        self._available_variables = variables

        if loader:
            self._basedir = loader.get_basedir()
        else:
            self._basedir = './'

        if shared_loader_obj:
            self._filter_loader = getattr(shared_loader_obj, 'filter_loader')
            self._lookup_loader = getattr(shared_loader_obj, 'lookup_loader')
        else:
            self._filter_loader = filter_loader
            self._lookup_loader = lookup_loader

        # flags to determine whether certain failures during templating
        # should result in fatal errors being raised
        self._fail_on_lookup_errors    = True
        self._fail_on_filter_errors    = True
        self._fail_on_undefined_errors = C.DEFAULT_UNDEFINED_VAR_BEHAVIOR

        self.environment = Environment(
            trim_blocks=True,
            undefined=StrictUndefined,
            extensions=self._get_extensions(),
            finalize=self._finalize,
            loader=FileSystemLoader(self._basedir),
        )
        self.environment.template_class = AnsibleJ2Template

        self.SINGLE_VAR = re.compile(r"^%s\s*(\w*)\s*%s$" % (self.environment.variable_start_string, self.environment.variable_end_string))

    def _get_filters(self):
        '''
        Returns filter plugins, after loading and caching them if need be
        '''

        if self._filters is not None:
            return self._filters.copy()

        plugins = [x for x in self._filter_loader.all()]

        self._filters = dict()
        for fp in plugins:
            self._filters.update(fp.filters())
        self._filters.update(self._get_tests())

        return self._filters.copy()

    def _get_tests(self):
        '''
        Returns tests plugins, after loading and caching them if need be
        '''

        if self._tests is not None:
            return self._tests.copy()

        plugins = [x for x in test_loader.all()]

        self._tests = dict()
        for fp in plugins:
            self._tests.update(fp.tests())

        return self._tests.copy()

    def _get_extensions(self):
        '''
        Return jinja2 extensions to load.

        If some extensions are set via jinja_extensions in ansible.cfg, we try
        to load them with the jinja environment.
        '''

        jinja_exts = []
        if C.DEFAULT_JINJA2_EXTENSIONS:
            # make sure the configuration directive doesn't contain spaces
            # and split extensions in an array
            jinja_exts = C.DEFAULT_JINJA2_EXTENSIONS.replace(" ", "").split(',')

        return jinja_exts

    def set_available_variables(self, variables):
        '''
        Sets the list of template variables this Templar instance will use
        to template things, so we don't have to pass them around between
        internal methods.
        '''

        assert isinstance(variables, dict)
        self._available_variables = variables.copy()

    def template(self, variable, convert_bare=False, preserve_trailing_newlines=True, escape_backslashes=True, fail_on_undefined=None, overrides=None, convert_data=True):
        '''
        Templates (possibly recursively) any given data as input. If convert_bare is
        set to True, the given data will be wrapped as a jinja2 variable ('{{foo}}')
        before being sent through the template engine. 
        '''

        try:
            if convert_bare:
                variable = self._convert_bare_variable(variable)

            if isinstance(variable, basestring):
                result = variable
                if self._contains_vars(variable):

                    # Check to see if the string we are trying to render is just referencing a single
                    # var.  In this case we don't want to accidentally change the type of the variable
                    # to a string by using the jinja template renderer. We just want to pass it.
                    only_one = self.SINGLE_VAR.match(variable)
                    if only_one:
                        var_name = only_one.group(1)
                        if var_name in self._available_variables:
                            resolved_val = self._available_variables[var_name]
                            if isinstance(resolved_val, NON_TEMPLATED_TYPES):
                                return resolved_val
                            elif resolved_val is None:
                                return C.DEFAULT_NULL_REPRESENTATION

                    result = self._do_template(variable, preserve_trailing_newlines=preserve_trailing_newlines, escape_backslashes=escape_backslashes, fail_on_undefined=fail_on_undefined, overrides=overrides)

                    if convert_data:
                        # if this looks like a dictionary or list, convert it to such using the safe_eval method
                        if (result.startswith("{") and not result.startswith(self.environment.variable_start_string)) or \
                           result.startswith("[") or result in ("True", "False"):
                            eval_results = safe_eval(result, locals=self._available_variables, include_exceptions=True)
                            if eval_results[1] is None:
                                result = eval_results[0]
                            else:
                                # FIXME: if the safe_eval raised an error, should we do something with it?
                                pass

                return result

            elif isinstance(variable, (list, tuple)):
                return [self.template(v, convert_bare=convert_bare, preserve_trailing_newlines=preserve_trailing_newlines, fail_on_undefined=fail_on_undefined, overrides=overrides) for v in variable]
            elif isinstance(variable, dict):
                d = {}
                # we don't use iteritems() here to avoid problems if the underlying dict
                # changes sizes due to the templating, which can happen with hostvars
                for k in variable.keys():
                    d[k] = self.template(variable[k], convert_bare=convert_bare, preserve_trailing_newlines=preserve_trailing_newlines, fail_on_undefined=fail_on_undefined, overrides=overrides)
                return d
            else:
                return variable

        except AnsibleFilterError:
            if self._fail_on_filter_errors:
                raise
            else:
                return variable

    def _contains_vars(self, data):
        '''
        returns True if the data contains a variable pattern
        '''
        return self.environment.block_start_string in data or self.environment.variable_start_string in data

    def _convert_bare_variable(self, variable):
        '''
        Wraps a bare string, which may have an attribute portion (ie. foo.bar)
        in jinja2 variable braces so that it is evaluated properly.
        '''

        if isinstance(variable, basestring):
            contains_filters = "|" in variable
            first_part = variable.split("|")[0].split(".")[0].split("[")[0]
            if (contains_filters or first_part in self._available_variables) and self.environment.variable_start_string not in variable:
                return "%s%s%s" % (self.environment.variable_start_string, variable, self.environment.variable_end_string)

        # the variable didn't meet the conditions to be converted,
        # so just return it as-is
        return variable

    def _finalize(self, thing):
        '''
        A custom finalize method for jinja2, which prevents None from being returned
        '''
        return thing if thing is not None else ''

    def _lookup(self, name, *args, **kwargs):
        instance = self._lookup_loader.get(name.lower(), loader=self._loader, templar=self)

        if instance is not None:
            from ansible.utils.listify import listify_lookup_plugin_terms
            loop_terms = listify_lookup_plugin_terms(terms=args, templar=self, loader=self._loader, fail_on_undefined=True, convert_bare=False)
            # safely catch run failures per #5059
            try:
                ran = instance.run(loop_terms, variables=self._available_variables, **kwargs)
            except (AnsibleUndefinedVariable, UndefinedError) as e:
                raise AnsibleUndefinedVariable(e)
            except Exception as e:
                if self._fail_on_lookup_errors:
                    raise
                ran = None
            if ran:
                ran = ",".join(ran)
            return ran
        else:
            raise AnsibleError("lookup plugin (%s) not found" % name)

    def _do_template(self, data, preserve_trailing_newlines=True, escape_backslashes=True, fail_on_undefined=None, overrides=None):

        # For preserving the number of input newlines in the output (used
        # later in this method)
        data_newlines = _count_newlines_from_end(data)

        if fail_on_undefined is None:
            fail_on_undefined = self._fail_on_undefined_errors

        try:
            # allows template header overrides to change jinja2 options.
            if overrides is None:
                myenv = self.environment.overlay()
            else:
                myenv = self.environment.overlay(overrides)

            # Get jinja env overrides from template
            if data.startswith(JINJA2_OVERRIDE):
                eol = data.find('\n')
                line = data[len(JINJA2_OVERRIDE):eol]
                data = data[eol+1:]
                for pair in line.split(','):
                    (key,val) = pair.split(':')
                    key = key.strip()
                    setattr(myenv, key, ast.literal_eval(val.strip()))

            #FIXME: add tests
            myenv.filters.update(self._get_filters())
            myenv.tests.update(self._get_tests())

            if escape_backslashes:
                # Allow users to specify backslashes in playbooks as "\\"
                # instead of as "\\\\".
                data = _escape_backslashes(data, myenv)

            try:
                t = myenv.from_string(data)
            except TemplateSyntaxError as e:
                raise AnsibleError("template error while templating string: %s" % str(e))
            except Exception as e:
                if 'recursion' in str(e):
                    raise AnsibleError("recursive loop detected in template string: %s" % data)
                else:
                    return data

            t.globals['lookup']   = self._lookup
            t.globals['finalize'] = self._finalize

            jvars = AnsibleJ2Vars(self, t.globals)

            new_context = t.new_context(jvars, shared=True)
            rf = t.root_render_func(new_context)

            try:
                res = j2_concat(rf)
            except TypeError as te:
                if 'StrictUndefined' in str(te):
                    raise AnsibleUndefinedVariable(
                        "Unable to look up a name or access an attribute in template string. " + \
                        "Make sure your variable name does not contain invalid characters like '-'."
                    )
                else:
                    debug("failing because of a type error, template data is: %s" % data)
                    raise AnsibleError("an unexpected type error occurred. Error was %s" % te)

            if preserve_trailing_newlines:
                # The low level calls above do not preserve the newline
                # characters at the end of the input data, so we use the
                # calculate the difference in newlines and append them
                # to the resulting output for parity
                #
                # jinja2 added a keep_trailing_newline option in 2.7 when
                # creating an Environment.  That would let us make this code
                # better (remove a single newline if
                # preserve_trailing_newlines is False).  Once we can depend on
                # that version being present, modify our code to set that when
                # initializing self.environment and remove a single trailing
                # newline here if preserve_newlines is False.
                res_newlines = _count_newlines_from_end(res)
                if data_newlines > res_newlines:
                    res += '\n' * (data_newlines - res_newlines)

            return res
        except (UndefinedError, AnsibleUndefinedVariable) as e:
            if fail_on_undefined:
                raise AnsibleUndefinedVariable(e)
            else:
                #TODO: return warning about undefined var
                return data