Named Arguments

Named arguments at call sites

When you call a function or constructor with two or more arguments, pass them by name:

// Do
drawReferenceBand(
    chartContext = chartContext,
    orientation = ChartOrientation.VERTICAL,
    config = band,
    textMeasurer = textMeasurer,
)

// Don't
drawReferenceBand(chartContext, ChartOrientation.VERTICAL, band, textMeasurer)

Named arguments make call sites self-documenting, prevent silent breakage when parameters are reordered, and are mandatory for any boolean or multiple same-typed arguments (where position is easy to get wrong).

Scope

Applies to calls with 2+ value arguments. Exempt (naming adds noise or isn't possible):

• Single-argument calls — remember { … }, require(cond), listOf(x), it.copy().
• A trailing lambda that is the only "argument" written outside the parens — dataList.fastForEachIndexed { i, v -> … }, Modifier.drawBehind { … }. If a call has other value args plus a trailing lambda, name the value args: measure(text = s, style = style).
• Operators / infix — a to b, a + b, x..y, a.coerceIn(0f, 1f) (infix-like stdlib scale functions are fine positional).
• vararg spreads and calls where the callee can't accept names (some Java interop).
• Simple geometry/value constructors are encouraged but not required when the order is a strong convention: Offset(x, y), Size(w, h), Color(0xFF…), CornerRadius(r, r).

Applying it

• New/changed multi-arg calls: write them named from the start.
• When you edit a file, name the multi-arg calls in the code you touch (don't rewrite the whole file just for this).
• Commit gate: a staged diff that adds a positional 2+-arg call (outside the exemptions) is not ready. commit-with-stats checks for it.

Note: no formatter converts positional calls to named automatically — the parameter names come from each callee's signature. Adopt this incrementally (every file you touch) rather than in one bulk rewrite; the gate keeps new code compliant.

Quick check on a staged diff (manual review — the callee's real param names must be filled in):

git diff --cached -U0 -- '*.kt' | grep -E '^\+' | grep -E '\b[a-z][A-Za-z]*\([^)]*,[^)=]*\)'