warn on incorrect YAML 1.1 floats

2 files changed, 35 insertions, 3 deletions

diff --git a/constructor.py b/constructor.py
index c957cd0..aa77b47 100644
--- a/constructor.py
+++ b/constructor.py
@@ -11,7 +11,8 @@ import sys
 import types
 import warnings
 
-from ruamel.yaml.error import (MarkedYAMLError, MarkedYAMLFutureWarning)
+from ruamel.yaml.error import (MarkedYAMLError, MarkedYAMLFutureWarning,
+                               MantissaNoDotYAML1_1Warning)
 from ruamel.yaml.nodes import *                               # NOQA
 from ruamel.yaml.nodes import (SequenceNode, MappingNode, ScalarNode)
 from ruamel.yaml.compat import (utf8, builtins_module, to_str, PY2, PY3,  # NOQA
@@ -411,8 +412,8 @@ class SafeConstructor(BaseConstructor):
 
     def construct_yaml_float(self, node):
         # type: (Any) -> float
-        value_s = to_str(self.construct_scalar(node))
-        value_s = value_s.replace('_', '').lower()
+        value_so = to_str(self.construct_scalar(node))
+        value_s = value_so.replace('_', '').lower()
         sign = +1
         if value_s[0] == '-':
             sign = -1
@@ -432,6 +433,11 @@ class SafeConstructor(BaseConstructor):
                 base *= 60
             return sign * value
         else:
+            if self.resolver.processing_version != (1, 2) and 'e' in value_s:
+                # value_s is lower case independent of input
+                mantissa, exponent = value_s.split('e')
+                if '.' not in mantissa:
+                    warnings.warn(MantissaNoDotYAML1_1Warning(node, value_so))
             return sign * float(value_s)
 
     if PY3:
diff --git a/error.py b/error.py
index 4faab94..4658f8e 100644
--- a/error.py
+++ b/error.py
@@ -193,6 +193,32 @@ In most other cases you should consider using 'safe_load(stream)'"""
 warnings.simplefilter('once', UnsafeLoaderWarning)
 
 
+class MantissaNoDotYAML1_1Warning(YAMLWarning):
+    def __init__(self, node, flt_str):
+        self.node = node
+        self.flt = flt_str
+
+    def __str__(self):
+        line = self.node.start_mark.line
+        col = self.node.start_mark.column
+        return """
+In YAML 1.1 floating point values should have a dot ('.') in their mantissa.
+See the Floating-Point Language-Independent Type for YAML™ Version 1.1 specification
+( http://yaml.org/type/float.html ). This dot is not required for JSON nor for YAML 1.2
+
+Correct your float: "{}" on line: {}, column: {}
+
+or alternatively include the following in your code:
+
+  import warnings
+  warnings.simplefilter('ignore', ruamel.yaml.error.MantissaNoDotYAML1_1Warning)
+
+""".format(self.flt, line, col)
+
+
+warnings.simplefilter('once', MantissaNoDotYAML1_1Warning)
+
+
 class YAMLFutureWarning(Warning):
     pass