Function nu_engine::eval_expression_with_input

pub fn eval_expression_with_input(
    engine_state: &EngineState, 
    stack: &mut Stack, 
    expr: &Expression, 
    input: PipelineData, 
    redirect_stdout: bool, 
    redirect_stderr: bool
) -> Result<PipelineData, ShellError>

Checks the expression to see if it’s a internal or external call. If so, passes the input into the call and gets out the result Otherwise, invokes the expression