all fields of tuple structs must be annotated with…

Error message

all fields of tuple structs must be annotated with `#[diesel(column_name)]`

What it means

When deriving a diesel struct mapping (e.g. `Queryable`, `Insertable`) on a tuple struct, every field must carry an explicit `#[diesel(column_name = ...)]`, since tuple fields have no usable column-name source. `FieldName::Unnamed` without a column_name attribute reaches `column_name()` and raises this error at field.rs:163.

Solutions

Annotate every field with `#[diesel(column_name = the_column)]`.
Prefer a named struct, which infers column names from field names automatically.
For a newtype over one column, verify the derive supports inference for your case or keep the explicit annotation.

Example fix

// before
#[derive(Queryable)]
pub struct UserRow(pub i32, pub String);

// after
#[derive(Queryable)]
pub struct UserRow(
  #[diesel(column_name = id)] pub i32,
  #[diesel(column_name = name)] pub String,
);

Defensive patterns

Strategy: validation

Validate before calling

// For tuple structs, every positional field needs a column_name:
// struct Row(#[diesel(column_name = id)] i32, #[diesel(column_name = name)] String);

Prevention

Prefer named structs so column names are inferred from field names.
When using tuple structs, annotate every field with `#[diesel(column_name = ...)]`.
Re-check annotations after converting a named struct to a tuple struct.

When it happens

Trigger: Deriving diesel traits on a tuple struct where at least one positional field lacks `#[diesel(column_name = ...)]`.

Common situations: Newtype wrappers around a single column where the author assumed the derive would infer the column; partially annotated tuple structs; converting a named struct to a tuple struct without moving the attributes.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

AI-assisted analysis of diesel-rs/diesel@6fa6ed01b2 (2026-09-07). Data as JSON: /api/errors/2c19cdf0e5ad4dc9. Report an issue: GitHub.

Appendix: source

Thrown at diesel_derives/src/field.rs:163

            treat_none_as_null,
            serialize_as,
            deserialize_as,
            select_expression,
            select_expression_type,
            embed,
            skip_insertion,
            skip_update,
        })
    }

    pub fn column_name(&self) -> Result<SqlIdentifier> {
        let identifier = self.column_name.as_ref().map(|a| a.item.clone());
        if let Some(identifier) = identifier {
            Ok(identifier)
        } else {
            match self.name {
                FieldName::Named(ref x) => Ok(x.into()),
                FieldName::Unnamed(ref x) => Err(syn::Error::new(
                    x.span(),
                    "all fields of tuple structs must be annotated with `#[diesel(column_name)]`",
                )),
            }
        }
    }

    pub fn ty_for_deserialize(&self) -> &Type {
        if let Some(AttributeSpanWrapper { item: value, .. }) = &self.deserialize_as {
            value
        } else {
            &self.ty
        }
    }

    pub(crate) fn embed(&self) -> bool {
        self.embed.as_ref().map(|a| a.item).unwrap_or(false)
    }

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