Update __repr__ for initial-default and write-default (#2287)

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Closes #1853 

This adds a new repr function that ensures that `initial-default` and
`write-default` will not appear if they are None. Unfortunately, this
functionality isn't baked into Pydantic.

# Rationale for this change
__repr__ changes may be breaking.

# Are these changes tested?
Tests included.

# Are there any user-facing changes?

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Author: rambleraptor

pyiceberg/types.py

@@ -340,8 +340,8 @@ class NestedField(IcebergType):
     field_type: SerializeAsAny[IcebergType] = Field(alias="type")
     required: bool = Field(default=False)
     doc: Optional[str] = Field(default=None, repr=False)
-    initial_default: Optional[DefaultValue] = Field(alias="initial-default", default=None, repr=False)  # type: ignore
-    write_default: Optional[DefaultValue] = Field(alias="write-default", default=None, repr=False)  # type: ignore
+    initial_default: Optional[DefaultValue] = Field(alias="initial-default", default=None, repr=True)  # type: ignore
+    write_default: Optional[DefaultValue] = Field(alias="write-default", default=None, repr=True)  # type: ignore
 
     @field_validator("field_type", mode="before")
     def convert_field_type(cls, v: Any) -> IcebergType:
@@ -401,6 +401,21 @@ def __str__(self) -> str:
         req = "required" if self.required else "optional"
         return f"{self.field_id}: {self.name}: {req} {self.field_type}{doc}"
 
+    def __repr__(self) -> str:
+        """Return the string representation of the NestedField class."""
+        parts = [
+            f"field_id={self.field_id}",
+            f"name={self.name!r}",
+            f"field_type={self.field_type!r}",
+            f"required={self.required}",
+        ]
+        if self.initial_default is not None:
+            parts.append(f"initial_default={self.initial_default!r}")
+        if self.write_default is not None:
+            parts.append(f"write_default={self.write_default!r}")
+
+        return f"NestedField({', '.join(parts)})"
+
     def __getnewargs__(self) -> Tuple[int, str, IcebergType, bool, Optional[str]]:
         """Pickle the NestedField class."""
         return (self.field_id, self.name, self.field_type, self.required, self.doc)

tests/test_types.py

@@ -525,6 +525,21 @@ def test_repr_decimal() -> None:
     assert repr(DecimalType(19, 25)) == "DecimalType(precision=19, scale=25)"
 
 
+def test_repr_nested_field_default_nones_should_not_appear() -> None:
+    assert (
+        repr(NestedField(1, "required_field", StringType(), required=False, initial_default=None, write_default=None))
+        == "NestedField(field_id=1, name='required_field', field_type=StringType(), required=False)"
+    )
+    assert (
+        repr(NestedField(1, "required_field", StringType(), required=False, initial_default="hello", write_default=None))
+        == "NestedField(field_id=1, name='required_field', field_type=StringType(), required=False, initial_default='hello')"
+    )
+    assert (
+        repr(NestedField(1, "required_field", StringType(), required=False, initial_default="hello", write_default="bye"))
+        == "NestedField(field_id=1, name='required_field', field_type=StringType(), required=False, initial_default='hello', write_default='bye')"
+    )
+
+
 def test_serialization_nestedfield() -> None:
     expected = '{"id":1,"name":"required_field","type":"string","required":true,"doc":"this is a doc"}'
     actual = NestedField(1, "required_field", StringType(), True, "this is a doc").model_dump_json()