diesel-rs/diesel · error

expected valid identifier, found

Error message

expected valid identifier, found `{0}`. Diesel automatically renames invalid identifiers, perhaps you meant to write `{0}_`?

What it means

A field name containing whitespace cannot be turned into a Rust identifier. The offending input is the field name with spaces; Diesel can rename other invalid identifiers, but whitespace is not supported.

Solutions

1. Rename the column so it contains no whitespace
2. Map the field explicitly to a valid Rust identifier
3. Remove spaces or use a different database column name

When it happens

Trigger: Thrown at diesel_attribute_parser/src/lib.rs:107 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of diesel-rs/diesel@6fa6ed01b2 (2026-09-07). Data as JSON: /api/errors/0a50be97530b7615. Report an issue: GitHub.

Appendix: source

Thrown at diesel_attribute_parser/src/lib.rs:107

    pub fn span(&self) -> Span {
        self.span
    }

    pub fn to_ident(&self) -> Result<Ident> {
        match syn::parse_str::<Ident>(&format!("r#{}", self.field_name)) {
            Ok(mut ident) => {
                ident.set_span(self.span);
                Ok(ident)
            }
            Err(_e) if self.field_name.contains(' ') => Err(syn::Error::new(
                self.span(),
                format!(
                    "expected valid identifier, found `{0}`. \
                 Diesel does not support column names with whitespaces yet",
                    self.field_name
                ),
            )),
            Err(_e) => Err(syn::Error::new(
                self.span(),
                format!(
                    "expected valid identifier, found `{0}`. \
                 Diesel automatically renames invalid identifiers, \
                 perhaps you meant to write `{0}_`?",
                    self.field_name
                ),
            )),
        }
    }
}

impl ToTokens for SqlIdentifier {
    fn to_tokens(&self, tokens: &mut TokenStream) {
        if self.field_name.starts_with("r#") {
            Ident::new_raw(&self.field_name[2..], self.span).to_tokens(tokens)
        } else {
            Ident::new(&self.field_name, self.span).to_tokens(tokens)

View on GitHub (pinned to 6fa6ed01b2)