Control Flow

Control flow is one of the most important parts of Pureline.

Pureline standardizes clarity and structure, not identical syntax across languages. Java, JavaScript, TypeScript, and Go use explicit blocks for control flow. Languages with established readable shorthand, such as Crystal postfix guards, may use that shorthand when the condition and action remain simple.

PL-CF-001

Prefer Guard Clauses

Preferred java

if (request == null) {
    return Result.empty();
}

if (!request.valid()) {
    return Result.invalid();
}

var session = sessions.create(request.user());
return executor.execute(session, request);

Avoid java

if (request != null) {
    if (request.valid()) {
        var session = sessions.create(request.user());
        return executor.execute(session, request);
    } else {
        return Result.invalid();
    }
}

return Result.empty();

The happy path should remain as close to the base indentation level as possible.

PL-CF-002

Avoid else

Avoid java

if (valid) {
    execute();
} else {
    reject();
}

Prefer java

if (!valid) {
    reject();
    return;
}

execute();

A ternary expression may be used for simple value selection java

var state = valid ? State.READY : State.INVALID;

Complex nested ternaries are not Pureline.

PL-CF-003

Explicit Blocks in Brace-Based Languages

In Java, JavaScript, TypeScript, Go, and other brace-based languages, control-flow bodies use explicit blocks.

Not Pureline java

if (!valid) return;

Also not Pureline java

if (!valid)
    return;

Pureline java

if (!valid) {
    return;
}

The same principle applies to for, while, and comparable control-flow constructs.

This rule does not ban idiomatic shorthand in languages where that shorthand is a normal, readable part of the language. Crystal postfix guards such as return unless valid are Pureline-compliant when kept simple.