probo/contrib/claude/go-style.md

Go Style

Layout and readability rules for Go source. (Error handling, naming, and imports are covered in AGENTS.md / other guides.)

Call expressions and argument lists

In the Go spec, a call is a primary expression f(a1, a2, … an) where f is the function value (or method value) and a1 … an are arguments passed to the matching parameters.

Treat the argument list as either single-line or multiline — never mixed:

• Single-line call — the entire call, from the callee through the closing ), fits on one source line. Any argument may be a short expression (including a one-line composite literal or conversion).
• Multiline call — if any argument is written across multiple lines (e.g. a multi-line composite literal, function literal, or other expression that contains a line break), then every argument must start on its own line: one argument per line at the top level of that argument list. The closing ) is on its own line after the last argument (with a trailing comma after the final argument when the list is multiline).

Do not place some arguments on the same line as the opening ( while others continue on following lines.

// Good — entire call on one line
id := gid.New(tenantID, "Foo")

// Good — multiline argument list; each argument on its own line
svc, err := foo.NewService(
	ctx,
	db,
	logger,
	foo.Config{
		Interval: 10 * time.Second,
		MaxRetry: 3,
	},
)

// Good — function literal argument is multiline, so the name argument is on its own line too
t.Run(
	"handoff with custom tool name",
	func(t *testing.T) {
		t.Parallel()
		// ...
	},
)

// Bad — mixed: first arguments on the callee line, last argument is a multiline composite literal
svc, err := foo.NewService(ctx, db, logger, foo.Config{
	Interval: 10 * time.Second,
})

The same rule applies to method calls x.M(a1, …) — the receiver is already bound; the rule applies to the argument list after the method name.