Mini Shell

"""
Custom YAML loading in Salt
"""

import re

import yaml  # pylint: disable=blacklisted-import
from yaml.constructor import ConstructorError
from yaml.nodes import MappingNode, SequenceNode

import salt.utils.stringutils

try:
    yaml.Loader = yaml.CLoader
    yaml.Dumper = yaml.CDumper
except Exception:  # pylint: disable=broad-except
    pass


__all__ = ["SaltYamlSafeLoader", "load", "safe_load"]


# with code integrated from https://gist.github.com/844388
class SaltYamlSafeLoader(yaml.SafeLoader):
    """
    Create a custom YAML loader that uses the custom constructor. This allows
    for the YAML loading defaults to be manipulated based on needs within salt
    to make things like sls file more intuitive.
    """

    def __init__(self, stream, dictclass=dict):
        super().__init__(stream)
        if dictclass is not dict:
            # then assume ordered dict and use it for both !map and !omap
            self.add_constructor("tag:yaml.org,2002:map", type(self).construct_yaml_map)
            self.add_constructor(
                "tag:yaml.org,2002:omap", type(self).construct_yaml_map
            )
        self.add_constructor("tag:yaml.org,2002:str", type(self).construct_yaml_str)
        self.add_constructor(
            "tag:yaml.org,2002:python/unicode", type(self).construct_unicode
        )
        self.add_constructor("tag:yaml.org,2002:timestamp", type(self).construct_scalar)
        self.dictclass = dictclass

    def construct_yaml_map(self, node):
        data = self.dictclass()
        yield data
        value = self.construct_mapping(node)
        data.update(value)

    def construct_unicode(self, node):
        return node.value

    def construct_mapping(self, node, deep=False):
        """
        Build the mapping for YAML
        """
        if not isinstance(node, MappingNode):
            raise ConstructorError(
                None,
                None,
                f"expected a mapping node, but found {node.id}",
                node.start_mark,
            )

        self.flatten_mapping(node)

        context = "while constructing a mapping"
        mapping = self.dictclass()
        for key_node, value_node in node.value:
            key = self.construct_object(key_node, deep=deep)
            try:
                hash(key)
            except TypeError:
                raise ConstructorError(
                    context,
                    node.start_mark,
                    f"found unacceptable key {key_node.value}",
                    key_node.start_mark,
                )
            value = self.construct_object(value_node, deep=deep)
            if key in mapping:
                raise ConstructorError(
                    context,
                    node.start_mark,
                    f"found conflicting ID '{key}'",
                    key_node.start_mark,
                )
            mapping[key] = value
        return mapping

    def construct_scalar(self, node):
        """
        Verify integers and pass them in correctly is they are declared
        as octal
        """
        if node.tag == "tag:yaml.org,2002:int":
            if node.value == "0":
                pass
            elif node.value.startswith("0") and not node.value.startswith(("0b", "0x")):
                node.value = node.value.lstrip("0")
                # If value was all zeros, node.value would have been reduced to
                # an empty string. Change it to '0'.
                if node.value == "":
                    node.value = "0"
        elif node.tag == "tag:yaml.org,2002:str":
            # If any string comes in as a quoted unicode literal, eval it into
            # the proper unicode string type.
            if re.match(r'^u([\'"]).+\1$', node.value, flags=re.IGNORECASE):
                node.value = eval(node.value, {}, {})  # pylint: disable=W0123
        return super().construct_scalar(node)

    def construct_yaml_str(self, node):
        value = self.construct_scalar(node)
        return salt.utils.stringutils.to_unicode(value)

    def fetch_plain(self):
        """
        Handle unicode literal strings which appear inline in the YAML
        """
        orig_line = self.line
        orig_column = self.column
        orig_pointer = self.pointer
        try:
            return super().fetch_plain()
        except yaml.scanner.ScannerError as exc:
            problem_line = self.line
            problem_column = self.column
            problem_pointer = self.pointer
            if exc.problem == "found unexpected ':'":
                # Reset to prior position
                self.line = orig_line
                self.column = orig_column
                self.pointer = orig_pointer
                if self.peek(0) == "u":
                    # Might be a unicode literal string, check for 2nd char and
                    # call the appropriate fetch func if it's a quote
                    quote_char = self.peek(1)
                    if quote_char in ("'", '"'):
                        # Skip the "u" prefix by advancing the column and
                        # pointer by 1
                        self.column += 1
                        self.pointer += 1
                        if quote_char == "'":
                            return self.fetch_single()
                        else:
                            return self.fetch_double()
                    else:
                        # This wasn't a unicode literal string, so the caught
                        # exception was correct. Restore the old position and
                        # then raise the caught exception.
                        self.line = problem_line
                        self.column = problem_column
                        self.pointer = problem_pointer
            # Raise the caught exception
            raise exc

    def flatten_mapping(self, node):
        merge = []
        index = 0
        while index < len(node.value):
            key_node, value_node = node.value[index]

            if key_node.tag == "tag:yaml.org,2002:merge":
                del node.value[index]
                if isinstance(value_node, MappingNode):
                    self.flatten_mapping(value_node)
                    merge.extend(value_node.value)
                elif isinstance(value_node, SequenceNode):
                    submerge = []
                    for subnode in value_node.value:
                        if not isinstance(subnode, MappingNode):
                            raise ConstructorError(
                                "while constructing a mapping",
                                node.start_mark,
                                "expected a mapping for merging, but found {}".format(
                                    subnode.id
                                ),
                                subnode.start_mark,
                            )
                        self.flatten_mapping(subnode)
                        submerge.append(subnode.value)
                    submerge.reverse()
                    for value in submerge:
                        merge.extend(value)
                else:
                    raise ConstructorError(
                        "while constructing a mapping",
                        node.start_mark,
                        "expected a mapping or list of mappings for merging, but"
                        " found {}".format(value_node.id),
                        value_node.start_mark,
                    )
            elif key_node.tag == "tag:yaml.org,2002:value":
                key_node.tag = "tag:yaml.org,2002:str"
                index += 1
            else:
                index += 1
        if merge:
            # Here we need to discard any duplicate entries based on key_node
            existing_nodes = [name_node.value for name_node, value_node in node.value]
            mergeable_items = [x for x in merge if x[0].value not in existing_nodes]

            node.value = mergeable_items + node.value


def load(stream, Loader=SaltYamlSafeLoader):
    return yaml.load(stream, Loader=Loader)


def safe_load(stream, Loader=SaltYamlSafeLoader):
    """
    .. versionadded:: 2018.3.0

    Helper function which automagically uses our custom loader.
    """
    return yaml.load(stream, Loader=Loader)