Critical bug-risk: Poorly formed nilness guards

[philipjonsen]

DESCRIPTION
Poorly formed nilness guards can be fatal as they might lead to unwanted panic because of nil pointer dereferences. Depending on the binary expression, the logic might not work as expected because of the poorly formed guards. In a binary expression, it is crucial to creating good nilness guards so that executing the other operand in the expression is safe.

BAD PRACTICE:
if cmd == nil && cmd.Execute() == 0 {
// do something
}

if cmd != nil || cmd.Execute() == 0 {
// do something
}

RECOMMENDED:
if cmd != nil && cmd.Execute() == 0 {
// do something
}

if cmd == nil || cmd.Execute() == 0 {
// do something
}

Problematic code to fix: /shentu/blob/master/app/export.go#L75-L75