Control Flow Braces

Control-flow braces

Charty always braces the bodies of control-flow statements and the branches of if/else used as a value expression. A single guarded statement or a terse ternary-style if is easy to misread or to break when a second line is added later, so we never write the braceless form.

Rule

Every if, else if, else, for, and while body is wrapped in { } — including a body that is a single statement, the one-line form, and an if/else whose value is assigned, returned, or passed as an argument.

Banned (braceless body or branch):

if (width > maxWidth) maxWidth = width
if (range == 0f) return bottom
for (point in points) draw(point)
if (a) b() else c()
val label = if (v == v.toLong().toFloat()) v.toLong().toString() else v.toString()
fun sweep(total: Float): Float = if (total > 0f) value / total else 0f
foo(bar = if (enabled) onClick else null)

Required (braced):

if (width > maxWidth) {
    maxWidth = width
}
for (point in points) {
    draw(point)
}
val label =
    if (v == v.toLong().toFloat()) {
        v.toLong().toString()
    } else {
        v.toString()
    }
fun sweep(total: Float): Float =
    if (total > 0f) {
        value / total
    } else {
        0f
    }
foo(
    bar =
        if (enabled) {
            onClick
        } else {
            null
        },
)

Inside a string template, brace the branches in place (it cannot span lines): "${if (n == 1) { "" } else { "s" }}".

Not covered by this rule

• when branches — a single-expression branch stays as arm -> expression; do not add braces (else -> is a when branch, not an if/else).
• Elvis / single-expression functions with no if (fun f() = expr, x ?: return) — not control-flow, not affected. But when the single-expression body is an if/else, brace its branches as shown above.

Applying it

• When you write or edit a control-flow statement, brace its body even if it is one line.
• When editing nearby code, convert any braceless if/for/while you touch to the braced form.
• This is a commit gate: a staged diff that adds a braceless control-flow body is not ready. commit-with-stats checks for it.

Quick self-check on a staged diff (flags added if (...)/for (...)/while (...) lines whose body is on the same line without an opening brace — review each hit):

git diff --cached -U0 -- '*.kt' | grep -E '^\+' \
  | grep -E '\b(if|for|while)\s*\(' \
  | grep -vE '\{\s*$' | grep -vE '\)\s*$' \
  | grep -vE '=\s*if|=\s*when|return (if|when)'

Every line it prints should be inspected: if it is a braceless statement body, add braces; expression forms and when arms are fine.