Method _construct

pydantic/fields.py:480–569

Construct the final `FieldInfo` instance, by merging the possibly existing `FieldInfo` instances from the metadata. With the following example: ```python {test="skip" lint="skip"} class Model(BaseModel): f: Annotated[int, Gt(1), Field(description='desc', lt=2)]

(cls, metadata: list[Any], **attr_overrides: Any)

    @classmethod
    def _construct(cls, metadata: list[Any], **attr_overrides: Any) -> Self:
        """Construct the final `FieldInfo` instance, by merging the possibly existing `FieldInfo` instances from the metadata.

        With the following example:

        ```python {test="skip" lint="skip"}
        class Model(BaseModel):
            f: Annotated[int, Gt(1), Field(description='desc', lt=2)]
        ```

        `metadata` refers to the metadata elements of the `Annotated` form. This metadata is iterated over from left to right:

        - If the element is a `Field()` function (which is itself a `FieldInfo` instance), the field attributes (such as
          `description`) are saved to be set on the final `FieldInfo` instance.
          On the other hand, some kwargs (such as `lt`) are stored as `metadata` (see `FieldInfo.__init__()`, calling
          `FieldInfo._collect_metadata()`). In this case, the final metadata list is extended with the one from this instance.
        - Else, the element is considered as a single metadata object, and is appended to the final metadata list.

        Args:
            metadata: The list of metadata elements to merge together. If the `FieldInfo` instance to be constructed is for
                a field with an assigned `Field()`, this `Field()` assignment should be added as the last element of the
                provided metadata.
            **attr_overrides: Extra attributes that should be set on the final merged `FieldInfo` instance.

        Returns:
            The final merged `FieldInfo` instance.
        """
        merged_metadata: list[Any] = []
        merged_kwargs: dict[str, Any] = {}

        for meta in metadata:
            if isinstance(meta, FieldInfo):
                merged_metadata.extend(meta.metadata)

                new_js_extra: JsonDict | None = None
                current_js_extra = meta.json_schema_extra
                if current_js_extra is not None and 'json_schema_extra' in merged_kwargs:
                    # We need to merge `json_schema_extra`'s:
                    existing_js_extra = merged_kwargs['json_schema_extra']
                    if isinstance(existing_js_extra, dict):
                        if isinstance(current_js_extra, dict):
                            new_js_extra = {
                                **existing_js_extra,
                                **current_js_extra,
                            }
                        elif callable(current_js_extra):
                            warn(
                                'Composing `dict` and `callable` type `json_schema_extra` is not supported. '
                                'The `callable` type is being ignored. '
                                "If you'd like support for this behavior, please open an issue on pydantic.",
                                UserWarning,
                            )
                    elif callable(existing_js_extra) and isinstance(current_js_extra, dict):
                        warn(
                            'Composing `dict` and `callable` type `json_schema_extra` is not supported. '
                            'The `callable` type is being ignored. '
                            "If you'd like support for this behavior, please open an issue on pydantic.",
                            UserWarning,