What causes "Failed to build BybitSetLeverageParams" in nautechsystems/nautilus_trader?

Inspect `BybitSetLeverageParams` for non-optional fields and add the missing setter to the chain

Failed to build BybitSetLeverageParams

Error message

Failed to build BybitSetLeverageParams

What it means

`set_leverage` builds `BybitSetLeverageParams` via derive_builder and panics through `expect` if `build()` fails, i.e. if a required field without a default is missing. The chain sets category, symbol, buy_leverage and sell_leverage; any remaining required field unset causes the panic.

Source

Thrown at crates/adapters/bybit/src/http/client.rs:1271

    /// Panics if required parameters are not provided (should not happen with current implementation).
    ///
    /// # References
    ///
    /// - <https://bybit-exchange.github.io/docs/v5/position/leverage>
    pub async fn set_leverage(
        &self,
        product_type: BybitProductType,
        symbol: &str,
        buy_leverage: &str,
        sell_leverage: &str,
    ) -> Result<BybitSetLeverageResponse, BybitHttpError> {
        let params = BybitSetLeverageParamsBuilder::default()
            .category(product_type)
            .symbol(symbol.to_string())
            .buy_leverage(buy_leverage.to_string())
            .sell_leverage(sell_leverage.to_string())
            .build()
            .expect("Failed to build BybitSetLeverageParams");

        let body = serde_json::to_vec(&params)?;
        self.send_request::<_, ()>(
            Method::POST,
            "/v5/position/set-leverage",
            None,
            Some(body),
            true,
        )
        .await
    }

    /// Switches position mode for a product type.
    ///
    /// # Errors
    ///
    /// Returns an error if:
    /// - Credentials are missing.

View on GitHub (pinned to 18893faf8b)

Solutions

Inspect `BybitSetLeverageParams` for non-optional fields and add the missing setter to the chain
After a crate upgrade, rebuild and address any newly required builder fields
Convert the `expect` to `?`/error mapping for graceful failure
Report a bug if it panics via the public `set_leverage` path

Example fix

// before
.build().expect("Failed to build BybitSetLeverageParams");
// after
.build().map_err(BybitHttpError::InvalidParams)?;

Defensive patterns

Strategy: validation

Validate before calling

// Validate leverage strings are numeric and within Bybit limits before calling
let b: f64 = buy_leverage.parse()?; let s: f64 = sell_leverage.parse()?;
assert!((1.0..=100.0).contains(&b) && (1.0..=100.0).contains(&s), "leverage out of range");

Try / catch

if let Err(e) = client.set_leverage(cat, sym, buy, sell).await { log::error!("set_leverage failed: {e}"); return Err(e.into()); }

Prevention

Format leverage as strings like "10" matching Bybit step rules
Ensure buy/sell leverage are equal unless using Bybit cross-margin semantics
Re-check builder field requirements after dependency upgrades

When it happens

Trigger: A newly added required field on `BybitSetLeverageParams` (e.g. a Bybit V5 API addition like `borrow_mode`) not set by this builder chain, so `build()` returns `Err` and the `expect` fires.

Common situations: Crate upgrade after Bybit adds a mandatory leverage parameter; constructing the builder manually and omitting a required setter.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

AI-assisted analysis of nautechsystems/nautilus_trader@18893faf8b (2026-09-08). Data as JSON: /api/errors/415a4ce2cfe0dc65. Report an issue: GitHub.