Fix PyYAML 5.1 Loader= warnings

Per [1] upstream docs, we should use safe loader where we can.
For parsing '!eval' we need full loader though.  So use Loaders
appropriately.

Slightly inconvenient is to write this thing portably because
FullLoader isn't available in old PyYAML versions.

[1] https://msg.pyyaml.org/load

Fixes: #93

NEWS

@@ -6,6 +6,8 @@ New in 1.3:
 
   - Added 'fedora-30' config, and rawhide moved to 'fedora-31'.
 
+  - Compatibility fixes for new PyYAML 5.1.
+
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 New in 1.2:

distgen/config.py

@@ -35,11 +35,14 @@ def __recursive_load(pm, stack, filename):
 
     import yaml
     try:
-        yaml_data = yaml.load(pm.open_file(
-            filename,
-            fail=True,
-            file_desc="configuration file",
-        ))
+        yaml_data = yaml.load(
+            pm.open_file(
+                filename,
+                fail=True,
+                file_desc="configuration file",
+            ),
+            Loader=yaml.SafeLoader,
+        )
     except yaml.YAMLError as exc:
         fatal("Error in configuration file: {0}".format(exc))
 

distgen/generator.py

@@ -2,6 +2,7 @@
 import sys
 import imp
 import jinja2
+import functools
 
 from distgen.err import fatal
 from distgen.pathmanager import PathManager
@@ -195,6 +196,32 @@ def _recursive_render_spec(self, s, max_passes=25, **kwargs):
 
         return s
 
+    def _enhanced_yaml_module(self, sysconfig):
+
+        # NOTE: This is soo ugly, sorry for that, in future we need to modify
+        # PyYAML to let us specify callbacks, somehow.  But for now, import
+        # yaml right here (local import) to be able to add the
+        # constructors/representers **only** locally (don't modify global
+        # context).
+        def _eval_node(loader, node):
+            return str(eval(str(loader.construct_scalar(node)), {
+                'project': self.project,
+                'config': sysconfig,
+                'macros': sysconfig['macros'],
+            }))
+
+        import yaml
+        try:
+            yaml.add_constructor(u'!eval', _eval_node, yaml.FullLoader)
+            yaml.dg_load = functools.partial(yaml.load, Loader=yaml.FullLoader)
+        except AttributeError:
+            # Older versions of PyYAML don't have yaml.FullLoader, remove this
+            # once we don't have to deal with those.
+            yaml.add_constructor(u'!eval', _eval_node)
+            yaml.dg_load = yaml.load
+
+        return yaml
+
     def render(self, specfiles, multispec, multispec_selectors, template,
                config, cmd_cfg, output, confdirs=None,
                explicit_macros={}, max_passes=1):
@@ -227,20 +254,7 @@ def render(self, specfiles, multispec, multispec_selectors, template,
         self.vars_fill_variables(explicit_macros, sysconfig)
         sysconfig = merge_yaml(sysconfig, explicit_macros)
 
-        # NOTE: This is soo ugly, sorry for that, in future we need to modify
-        # PyYAML to let us specify callbacks, somehow.  But for now, import
-        # yaml right here to be able to add the constructors/representers
-        # "locally".
-        import yaml
-
-        def _eval_node(loader, node):
-            return str(eval(str(loader.construct_scalar(node)), {
-                'project': self.project,
-                'config': sysconfig,
-                'macros': sysconfig['macros'],
-            }))
-
-        yaml.add_constructor(u'!eval', _eval_node)
+        yaml = self._enhanced_yaml_module(sysconfig)
 
         spec = {}
         for specfile in specfiles or []:
@@ -253,7 +267,7 @@ def _eval_node(loader, node):
                 fatal("Spec file {0} not found".format(specfile))
 
             try:
-                specdata = yaml.load(specfd)
+                specdata = yaml.dg_load(specfd)
                 spec = merge_yaml(spec, specdata)
             except yaml.YAMLError as exc:
                 fatal("Error in spec file: {0}".format(exc))

distgen/multispec.py

@@ -33,7 +33,7 @@ def __init__(self, data):
     def from_path(cls, project_dir, path):
         pm = PathManager([])
         fd = pm.open_file(path, [project_dir], fail=True)
-        data = yaml.load(fd)
+        data = yaml.load(fd, Loader=yaml.SafeLoader)
         return cls(data)
 
     def _process(self):

tests/unittests/test_multispec.py

@@ -28,7 +28,7 @@ def test_from_path_nok(self):
 
     def test_validate(self):
         with open(os.path.join(ms_fixtures, 'complex.yaml')) as f:
-            Multispec(yaml.load(f))._validate()
+            Multispec(yaml.load(f, Loader=yaml.SafeLoader))._validate()
 
     def test_has_spec_group(self):
         ms = Multispec.from_path(ms_fixtures, 'complex.yaml')