new format_str option in vfield

tests/test_variableparameters.py

@@ -292,6 +292,21 @@ def test_unit_forammter():
     assert fmt(np.zeros((2, 2, 2))) == "(((0, 0), (0, 0)), ((0, 0), (0, 0)))"
 
 
+def test_format_str():
+    """format_str takes precedence"""
+
+    @vdataclass
+    class Conf:
+        x: Variable = vfield(default=123456789)
+        y: Variable = vfield(default=123456789, decimals=2)
+        z: Variable = vfield(default=123456789, decimals=2, format_str="d")
+
+    conf = Conf()
+    assert conf.x.format(0) == "x=1.235e+08"
+    assert conf.y.format(0) == "y=1.2e+08"
+    assert conf.z.format(0) == "z=123456789"
+
+
 def test_param_formatting():
     """formatting is always respected"""