# Copyright 2018 The dm_control Authors.

#

# 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.

# ============================================================================

"""Functions for parsing XML into an MJCF object model."""

import os

import sys

from dm_control.mjcf import constants

from dm_control.mjcf import debugging

from dm_control.mjcf import element

from lxml import etree

from dm_control.utils import io as resources

def from_xml_string(xml_string, escape_separators=False,

model_dir='', resolve_references=True, assets=None):

"""Parses an XML string into an MJCF object model.

Args:

xml_string: An XML string representing an MJCF model.

escape_separators: (optional) A boolean, whether to replace '/' characters

in element identifiers. If `False`, any '/' present in the XML causes

a ValueError to be raised.

model_dir: (optional) Path to the directory containing the model XML file.

This is used to prefix the paths of all asset files.

resolve_references: (optional) A boolean indicating whether the parser

should attempt to resolve reference attributes to a corresponding element.

assets: (optional) A dictionary of pre-loaded assets, of the form

`{filename: bytestring}`. If present, PyMJCF will search for assets in

this dictionary before attempting to load them from the filesystem.

Returns:

An `mjcf.RootElement`.

"""

xml_root = etree.fromstring(xml_string)

return _parse(xml_root, escape_separators,

model_dir=model_dir,

resolve_references=resolve_references,

assets=assets)

def from_file(file_handle, escape_separators=False,

model_dir='', resolve_references=True, assets=None):

"""Parses an XML file into an MJCF object model.

Args:

file_handle: A Python file-like handle.

escape_separators: (optional) A boolean, whether to replace '/' characters

in element identifiers. If `False`, any '/' present in the XML causes

a ValueError to be raised.

model_dir: (optional) Path to the directory containing the model XML file.

This is used to prefix the paths of all asset files.

resolve_references: (optional) A boolean indicating whether the parser

should attempt to resolve reference attributes to a corresponding element.

assets: (optional) A dictionary of pre-loaded assets, of the form

`{filename: bytestring}`. If present, PyMJCF will search for assets in

this dictionary before attempting to load them from the filesystem.

Returns:

An `mjcf.RootElement`.

"""

xml_root = etree.parse(file_handle).getroot()

return _parse(xml_root, escape_separators,

model_dir=model_dir,

resolve_references=resolve_references,

assets=assets)

def from_path(path, escape_separators=False, resolve_references=True,

assets=None, model_dir=None):

"""Parses an XML file into an MJCF object model.

Args:

path: A path to an XML file. This path should be loadable using

`resources.GetResource`.

escape_separators: (optional) A boolean, whether to replace '/' characters

in element identifiers. If `False`, any '/' present in the XML causes

a ValueError to be raised.

resolve_references: (optional) A boolean indicating whether the parser

should attempt to resolve reference attributes to a corresponding element.

assets: (optional) A dictionary of pre-loaded assets, of the form

`{filename: bytestring}`. If present, PyMJCF will search for assets in

this dictionary before attempting to load them from the filesystem.

model_dir: (optional) Path to the directory containing the model XML file.

This is used to prefix the paths of all asset files.

Returns:

An `mjcf.RootElement`.

"""

if model_dir is None:

model_dir, _ = os.path.split(path)

contents = resources.GetResource(path)

xml_root = etree.fromstring(contents)

return _parse(xml_root, escape_separators,

model_dir=model_dir, resolve_references=resolve_references,

assets=assets)

def _parse(xml_root, escape_separators=False,

model_dir='', resolve_references=True, assets=None):

"""Parses a complete MJCF model from an XML.

Args:

xml_root: An `etree.Element` object.

escape_separators: (optional) A boolean, whether to replace '/' characters

in element identifiers. If `False`, any '/' present in the XML causes

a ValueError to be raised.

model_dir: (optional) Path to the directory containing the model XML file.

This is used to prefix the paths of all asset files.

resolve_references: (optional) A boolean indicating whether the parser

should attempt to resolve reference attributes to a corresponding element.

assets: (optional) A dictionary of pre-loaded assets, of the form

`{filename: bytestring}`. If present, PyMJCF will search for assets in

this dictionary before attempting to load them from the filesystem.

Returns:

An `mjcf.RootElement`.

Raises:

ValueError: If `xml_root`'s tag is not 'mujoco.*'.

"""

assets = assets or {}

if not xml_root.tag.startswith('mujoco'):

raise ValueError('Root element of the XML should be <mujoco.*>: got <{}>'

.format(xml_root.tag))

with debugging.freeze_current_stack_trace():

# Recursively parse any included XML files.

to_include = []

for include_tag in xml_root.findall('include'):

try:

# First look for the path to the included XML file in the assets dict.

path_or_xml_string = assets[include_tag.attrib['file']]

parsing_func = from_xml_string

except KeyError:

# If it's not present in the assets dict then attempt to load the XML

# from the filesystem.

path_or_xml_string = os.path.join(model_dir, include_tag.attrib['file'])

parsing_func = from_path

included_mjcf = parsing_func(

path_or_xml_string,

escape_separators=escape_separators,

resolve_references=resolve_references,

assets=assets, model_dir=model_dir)

to_include.append(included_mjcf)

# We must remove <include/> tags before parsing the main XML file, since

# these are a schema violation.

xml_root.remove(include_tag)

# Parse the main XML file.

try:

model = xml_root.attrib.pop('model')

except KeyError:

model = None

mjcf_root = element.RootElement(

model=model, model_dir=model_dir, assets=assets)

_parse_children(xml_root, mjcf_root, escape_separators)

# Merge in the included XML files.

for included_mjcf in to_include:

# The included MJCF might have been automatically assigned a model name

# that conficts with that of `mjcf_root`, so we override it here.

included_mjcf.model = mjcf_root.model

mjcf_root.include_copy(included_mjcf)

if resolve_references:

mjcf_root.resolve_references()

return mjcf_root

def _parse_children(xml_element, mjcf_element, escape_separators=False):

"""Parses all children of a given XML element into an MJCF element.

Args:

xml_element: The source `etree.Element` object.

mjcf_element: The target `mjcf.Element` object.

escape_separators: (optional) A boolean, whether to replace '/' characters

in element identifiers. If `False`, any '/' present in the XML causes

a ValueError to be raised.

"""

for xml_child in xml_element:

if xml_child.tag is etree.Comment or xml_child.tag is etree.PI:

continue

try:

child_spec = mjcf_element.spec.children[xml_child.tag]

if escape_separators:

attributes = {}

for name, value in xml_child.attrib.items():

new_value = value.replace(

constants.PREFIX_SEPARATOR_ESCAPE,

constants.PREFIX_SEPARATOR_ESCAPE * 2)

new_value = new_value.replace(

constants.PREFIX_SEPARATOR, constants.PREFIX_SEPARATOR_ESCAPE)

attributes[name] = new_value

else:

attributes = dict(xml_child.attrib)

if child_spec.repeated or child_spec.on_demand:

mjcf_child = mjcf_element.add(xml_child.tag, **attributes)

else:

mjcf_child = getattr(mjcf_element, xml_child.tag)

mjcf_child.set_attributes(**attributes)

except: # pylint: disable=bare-except

err_type, err, traceback = sys.exc_info()

raise err_type(

f'Line {xml_child.sourceline}: error while parsing element '

f'<{xml_child.tag}>: {err}').with_traceback(traceback)

_parse_children(xml_child, mjcf_child, escape_separators)