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xmledit-cookbook

This cookbook allows incremental editing of XML files. You must include the default recipe to ensure nokogiri and its dependencies are installed using the upstream community xml cookbook.

Here be dragons. This is definitely not idempotent, and is not the best way to manage a file in chef. clintoncwolfe has described why you should not use this. Please read his thoughts on the matter.

Specifically, this library cookbooks offers a resource and provider that can be called by the name xml_edit. This resource accepts XPath expressions and will perform the expected action on the very first node found.

Important notes

  • This cookbook supports chef 12.x and greater. For working Chef 11.x support, pin back to xmledit < 3.0.0.

  • If no XML nodes match the XPath expression, no actions will be performed. If a file cannot be found, this provider will raise an error by virtue of ::File raising an error.

  • This cookbook attempts to sidestep resource cloning issues by forcing the resource name to be something other than a path to a file to edit. This allows you to perform multiple edits to the same file by giving the resources unique names and providing the same path attribute value. You may also do a bulk edit, if you know in advance all the edits that should be happening to a file.

  • Including an XPath expression that is a match against the node's value that you want to replace (e.g. matching against [text=()=\'false\'] if you want to replace false with true) means that the underlying file resource will no longer be defined, vs. having a file resource that was defined but idempotently 'up to date'. Both styles are possible using this cookbook, depending on the XPath expressions you provide.

Supported actions

name description
replace replaces a target node (and all children) with a new fragment
append appends a new XML fragment to a parent target node
append_if_missing if target is found, replace with fragment, otherwise append fragment
remove remove gets rid of a target node
bulk pass a hash of the above actions, do them all and write file out once after

Supported attributes

These have no default values, and will cause a no-op if they are not specified or don't match a valid file or target.

name description
path path to the XML file to edit
target an xpath expression for the target node (see action replace and append_if_missing above)
parent an xpath expression for the parent of the target node (see actions append and append_if_missing above)
fragment a string that will be parsed into an XML fragment, for actions that add or update
edits an array of hashes, with each hash containing one or zero keys of: :action, :path, :targent, :parent, or :fragment
prepend true or false; If the action is appending, prepend to the front (parent.prepend_chidl) vs. the end (parent.add_child)

Checkout nokogiri's documentation on XPath and search to understand the syntax behind target and parent attributes.

Examples

Replace false with true in a file at /etc/application.xml containing <config><foo>false</foo></config>.

xml_edit 'set foo to true' do
  path '/etc/application.xml'
  target '/config/foo[text()=\'false\']'
  fragment '<foo>true</foo>'
  action :replace
end

xml_edit '/tmp/xmledit_bulk_test.xml' do
  edits [
    {action: :replace, target: '/foo/bar', fragment: '<bar>xyzzy</bar>'},
    {action: :append, parent: '/foo', target: '/foo/baz', fragment: '<baz>true</baz>'},
    {action: :remove, target: '/foo/hideme'},
    {action: :append_if_missing, parent: '/foo', target: '/foo/showme', fragment: '<showme/>'}
    ]
  action :bulk
end

TODO

  • Add an attribute for forcing an error when an xpath expr doesn't match

License

# 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.