add plug-in mechanism for load/dump pre resp. post-processing0.15.7

4 files changed, 39 insertions, 3 deletions

diff --git a/CHANGES b/CHANGES
index a401d38..9ef21b7 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,6 @@
+[0, 15, 7]: 2017-06-14
+  - add plug-in mechanism for load/dump pre resp. post-processing
+
 [0, 15, 6]: 2017-06-10
   - a set() with duplicate elements now throws error in rt loading
   - support for toplevel column zero literal/folded scalar in explicit documents
diff --git a/README.rst b/README.rst
index 89ee836..fa503a9 100644
--- a/README.rst
+++ b/README.rst
@@ -32,6 +32,9 @@ ChangeLog
 
 .. should insert NEXT: at the beginning of line for next key
 
+0.15.7 (2017-06-14):
+  - add plug-in mechanism for load/dump pre resp. post-processing
+
 0.15.6 (2017-06-10):
   - a set() with duplicate elements now throws error in rt loading
   - support for toplevel column zero literal/folded scalar in explicit documents
diff --git a/__init__.py b/__init__.py
index 1224815..ba29709 100644
--- a/__init__.py
+++ b/__init__.py
@@ -11,12 +11,13 @@ if False:  # MYPY
 
 _package_data = dict(
     full_package_name='ruamel.yaml',
-    version_info=(0, 15, 6),
-    __version__='0.15.6',
+    version_info=(0, 15, 7),
+    __version__='0.15.7',
     author='Anthon van der Neut',
     author_email='a.van.der.neut@ruamel.eu',
     description='ruamel.yaml is a YAML parser/emitter that supports roundtrip preservation of comments, seq/map flow style, and map key order',  # NOQA
     entry_points=None,
+    since=2014,
     extras_require={':platform_python_implementation=="CPython" and python_version<="2.7"': [
         'ruamel.ordereddict',
         ]},
@@ -49,6 +50,11 @@ _package_data = dict(
     read_the_docs='yaml',
     many_linux='libyaml-devel',
     supported=[(2, 7), (3, 3)],  # minimum
+    tox=dict(
+        env='*p',
+        deps='ruamel.std.pathlib',
+        fl8excl='_test/lib',
+    ),
 )  # type: Dict[Any, Any]
 
 version_info = _package_data['version_info']
diff --git a/main.py b/main.py
index c238d2d..6240d14 100644
--- a/main.py
+++ b/main.py
@@ -3,7 +3,11 @@
 from __future__ import absolute_import, unicode_literals
 
 import sys
+import os
 import warnings
+import glob
+from importlib import import_module
+
 
 import ruamel.yaml
 from ruamel.yaml.error import *                                # NOQA
@@ -40,7 +44,7 @@ enforce = object()
 # subset of abbreviations, which should all caps according to PEP8
 
 class YAML(object):
-    def __init__(self, _kw=enforce, typ=None, pure=False):
+    def __init__(self, _kw=enforce, typ=None, pure=False, plug_ins=None):
         # type: (Any, Any, Any) -> None
         """
         _kw: not used, forces keyword arguments in 2.7 (in 3 you can do (*, safe_load=..)
@@ -49,12 +53,17 @@ class YAML(object):
              'unsafe'  -> normal/unsafe Loader/Dumper
              'base'    -> baseloader
         pure: if True only use Python modules
+        plug_ins: a list of plug-in files
         """
         if _kw is not enforce:
             raise TypeError("{}.__init__() takes no positional argument but at least "
                             "one was given ({!r})".format(self.__class__.__name__, _kw))
 
         self.typ = 'rt' if typ is None else typ
+        self.plug_ins = []
+        for pu in ([] if plug_ins is None else plug_ins) + self.official_plug_ins():
+            file_name = pu.replace('/', '.')
+            self.plug_ins.append(import_module(file_name))
         self.Resolver = ruamel.yaml.resolver.VersionedResolver               # type: Any
         self.allow_unicode = True
         self.Reader = None       # type: Any
@@ -89,6 +98,14 @@ class YAML(object):
             self.Parser = ruamel.yaml.parser.Parser if pure or CParser is None else CParser
             self.Composer = ruamel.yaml.composer.Composer
             self.Constructor = ruamel.yaml.constructor.Constructor
+        else:
+            for module in self.plug_ins:
+                if getattr(module, 'typ', None) == self.typ:
+                    module.init_typ(self)
+                    break
+            else:
+                raise NotImplementedError(
+                    'typ "{}"not recognised (need to install plug-in?)'.format(self.typ))
         self.stream = None
         self.canonical = None
         self.indent = None
@@ -427,6 +444,13 @@ class YAML(object):
         else:
             return list(*args)
 
+    # helpers
+    def official_plug_ins(self):
+        bd = os.path.dirname(__file__)
+        gpbd = os.path.dirname(os.path.dirname(bd))
+        res = [x.replace(gpbd, '')[1:-3] for x in glob.glob(bd + '/*/yaml_plugin.py')]
+        return res
+
 
 ########################################################################################