Disallow multi-line 'if', 'while' and 'for' conditionals

[yokuze]

Long if statement conditionals are sometimes broken up into multiple lines to avoid having a single long line. However, the result is difficult to read and leads to some unusual indentation issues. Consider these examples:

https://github.com/eslint/eslint/blob/3e522be/lib/rules/indent.js#L656 and

if (node.parent && (
         node.parent.type === "FunctionExpression" ||
         node.parent.type === "FunctionDeclaration" ||
         node.parent.type === "ArrowFunctionExpression"
)) {
{
    checkIndentInFunctionBlock(node);
    return;
}

and https://github.com/eslint/eslint/blob/3e522be/lib/rules/indent.js#L466

if (calleeNode.parent &&
    (calleeNode.parent.type === "Property" ||
    calleeNode.parent.type === "ArrayExpression")) {
    // If function is part of array or object, comma can be put at left
    indent = getNodeIndent(calleeNode, false, false);
}

and https://github.com/eslint/eslint/blob/3e522be/lib/rules/indent.js#L422

            while (
                stmt.type === "UnaryExpression" && (
                    stmt.operator === "!" ||
                    stmt.operator === "~" ||
                    stmt.operator === "+" ||
                    stmt.operator === "-") ||
                stmt.type === "AssignmentExpression" ||
                stmt.type === "LogicalExpression" ||
                stmt.type === "SequenceExpression" ||
                stmt.type === "VariableDeclarator") {

                stmt = stmt.parent;
            }

Find and enable an existing rule or create a new plugin that disallows multi-line conditionals in if, else if, for and while statements.

[yokuze]

Fixed with: silvermine/eslint-plugin-silvermine#3