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

Verify all non-Option fields of `BybitBorrowParams` are set on the builder

Failed to build BybitBorrowParams

Error message

Failed to build BybitBorrowParams

What it means

`borrow` builds `BybitBorrowParams` (coin + amount) and panics via `expect` when `build()` fails, which derive_builder signals only when a required field is missing. Both `coin` and `amount` are set in the chain, so a panic indicates a struct/builder mismatch — typically a new required field or an internal bug.

Source

Thrown at crates/adapters/bybit/src/http/client.rs:1386

    /// - Insufficient collateral for the borrow.
    ///
    /// # Panics
    ///
    /// Panics if the parameter builder fails (should never happen with valid inputs).
    ///
    /// # References
    ///
    /// - <https://bybit-exchange.github.io/docs/v5/account/borrow>
    pub async fn borrow(
        &self,
        coin: &str,
        amount: &str,
    ) -> Result<BybitBorrowResponse, BybitHttpError> {
        let params = BybitBorrowParamsBuilder::default()
            .coin(coin.to_string())
            .amount(amount.to_string())
            .build()
            .expect("Failed to build BybitBorrowParams");

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

    /// Manually repays borrowed coins without asset conversion.
    ///
    /// # Errors
    ///
    /// Returns an error if:
    /// - Credentials are missing.
    /// - The request fails.
    /// - Called during the hourly interest-calculation window (mm:04:00-mm:05:30 UTC each hour).
    /// - Insufficient spot balance for repayment.
    ///
    /// # Panics
    ///

View on GitHub (pinned to 18893faf8b)

Solutions

Verify all non-Option fields of `BybitBorrowParams` are set on the builder
After upgrading, re-check this call site against the updated struct
Replace `expect` with `?` mapping to `BybitHttpError`
Report as a bug if it fires via public `borrow`

Example fix

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

Defensive patterns

Strategy: validation

Validate before calling

// coin and amount are required for borrow
assert!(!coin.is_empty() && !amount.is_empty(), "coin and amount are required");
assert!(amount.parse::<Decimal>().is_ok(), "amount must be a decimal string");

Try / catch

match client.borrow(coin, amount).await { Ok(r) => r, Err(e) => { log::error!("borrow failed: {e}"); return Err(e.into()); } }

Prevention

Pass coin and amount explicitly; never rely on defaults
Validate amount parses as Decimal and is > 0
Check borrowable quota via the borrow API before borrowing

When it happens

Trigger: `BybitBorrowParams` gains an additional required field not set here (e.g. a new mandatory borrow parameter), or the raw builder is used without `coin`/`amount`.

Common situations: Post-upgrade schema drift; hand-rolling the builder in custom trading logic and omitting a 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/eaef8e84d4dd493a. Report an issue: GitHub.