Fix parsing of floats with implicit leading zero (#847)

Author: mauvilsa

CHANGELOG.rst

@@ -20,6 +20,8 @@ Fixed
 - Positional arguments with ``nargs="*"`` or ``nargs="?"`` now correctly allow
   default values, matching standard argparse behavior (`#846
   <https://github.com/omni-us/jsonargparse/pull/846>`__).
+- Parsing of floats with implicit leading zero (e.g. ``-.5``) not working (`#847
+  <https://github.com/omni-us/jsonargparse/pull/847>`__).
 
 Changed
 ^^^^^^^

jsonargparse/_loaders_dumpers.py

@@ -176,6 +176,13 @@ def json_or_yaml_load(value):
     return json_load(value)
 
 
+def basic_json_or_yaml_load(value):
+    loaded_value = load_basic(value)
+    if loaded_value is not not_loaded:
+        return loaded_value
+    return json_or_yaml_load(value)
+
+
 json_or_yaml_loader_exceptions = get_loader_exceptions("yaml" if pyyaml_available else "json")
 
 

jsonargparse/_typehints.py

@@ -62,8 +62,8 @@
     validating_defaults,
 )
 from ._loaders_dumpers import (
+    basic_json_or_yaml_load,
     get_loader_exceptions,
-    json_or_yaml_load,
     json_or_yaml_loader_exceptions,
     load_value,
 )
@@ -800,7 +800,7 @@ def adapt_typehints(
     elif typehint in leaf_types:
         if isinstance(val, str) and typehint is not str:
             with suppress(*json_or_yaml_loader_exceptions):
-                val = json_or_yaml_load(val)
+                val = basic_json_or_yaml_load(val)
         if typehint is float and isinstance(val, int) and not isinstance(val, bool):
             val = float(val)
         if not isinstance(val, typehint) or (typehint in (int, float) and isinstance(val, bool)):

jsonargparse_tests/test_typehints.py

@@ -151,6 +151,14 @@ def test_float_scientific_notation(parser):
     assert 1e-3 == parser.parse_args(["--num=1e-3"]).num
 
 
+@parser_modes
+def test_float_implicit_leading_zero(parser):
+    parser.parser_mode = "yaml"
+    parser.add_argument("--num", type=float)
+    assert 0.5 == parser.parse_args(["--num=.5"]).num
+    assert -0.5 == parser.parse_args(["--num=-.5"]).num
+
+
 def test_complex_number(parser):
     parser.add_argument("--complex", type=complex)
     cfg = parser.parse_args(["--complex=(2+3j)"])