3.4.1

Bug Fixes:

• yaml-set (and the underlying Processor class) were unable to change nodes
  having a null (None) value to anything else. This changes how null/None
  values are handled by the Processor during node retrieval; they are no longer
  discarded, so you will receive None as the data of any retrieved NodeCoords
  for appropriate null/None leaf nodes.

Enhancements:

• Python 3.9 is now supported (because common testing tools finally work with
  Python 3.9).
• The node deletion capability of the yaml-set command is now part of the
  library. See Processor::delete_nodes(...) and
  Processor::delete_gathered_nodes(...) for details.
• The node aliasing capability of the yaml-set command is now part of the
  library. See Processor::alias_nodes(...) and
  Processor::alias_gathered_nodes(...) for details.
• The node tagging capability of the yaml-set command is now part of the
  library. See Processor::tag_nodes(...) and
  Processor::tag_gathered_nodes(...) for details.
• The library now supports loading YAML from String rather than only from file.
  Simply pass a new literal=True keyword parameter to
  Parsers::get_yaml_data(...) or Parsers::get_yaml_multidoc_data(...) to
  indicate that source is literal serialized (String) YAML data rather than a
  file-spec. This mode is implied when reading from STDIN (source is "-").
• The emitter_write_folded_fix.py patch file for ruamel.yaml has been removed
  in favor of an author-supplied solution to the problem --
  https://sourceforge.net/p/ruamel-yaml/tickets/383/ -- for which the patch was
  originally written.

Known Issues:

• ruamel.yaml version 0.17.x is a major refactoring effort by the project's
  owner. As such, only select versions will be marked as compatible with
  yamlpath. Such marking occurs in this project's dependencies list via the
  setup.py file. This is necessary because I use yamlpath in production
  environments where stability is paramount; I need the freedom to update
  yamlpath at-will without incurring any unexpected failures due to
  incompatible ruamel.yaml changes. I will try to test some -- but not all --
  ruamel.yaml releases from time to time and update yamlpath dependency
  compatibilities accordingly.
• ruamel.yaml version 0.17.4 somewhat resolves a previously reported issue --
  https://sourceforge.net/p/ruamel-yaml/tickets/351/ -- wherein certain
  arrangements of comments or new-lines within YAML files near aliased hash
  keys would cause a total loss of data when the stream was written to file.
  Now, the data is no longer entirely lost. However, the preceding comment or
  new-line is deleted when the stream is written to file. This is deemed to be
  an acceptable compromise, for now, because the alternative is to either lose
  the entire document or lose all attempted changes to the affected document.
  Until the issue is properly fixed, an XFAIL test will continue to be in the
  yamlpath unit test suite.