tslint complaining “statements must be filtered with an if statement” when using switch

This made me curious, so I checked out the TSlint source code for this rule. It has a function called isFiltered which seems to only check for ts.SyntaxKind.IfStatement, not for ts.SyntaxKind.SwitchStatement.

function isFiltered({statements}: ts.Block): boolean {
    switch (statements.length) {
        case 0: return true;
        case 1: return statements[0].kind === ts.SyntaxKind.IfStatement;
        default:
            return statements[0].kind === ts.SyntaxKind.IfStatement && nodeIsContinue((statements[0] as ts.IfStatement).thenStatement);
    }

}

So unless you want to convert your object to an array, you’ll need to use a fix from the link you provided. Either Object.keys, or an if statement:

    for (const errorName in state.errors) {
      if (state.errors.hasOwnProperty(errorName)) {
        switch (errorName) {

The interesting thing is that you can have any kind of if statement and the error will go away. There is no check to see if you are calling hasOwnProperty.