diff --git a/README.md b/README.md index 122edb7..6f4279b 100644 --- a/README.md +++ b/README.md @@ -7,22 +7,25 @@ Duration Check A Go linter to detect cases where two `time.Duration` values are being multiplied in possibly erroneous ways. -For example, consider the following (highly contrived) function: +Consider the following (highly contrived) code: ```go -func waitFor(someDuration time.Duration) { - timeToWait := someDuration * time.Second - time.Sleep(timeToWait) +func waitForSeconds(someDuration time.Duration) { + timeToWait := someDuration * time.Second + fmt.Printf("Waiting for %s\n", timeToWait) +} + +func main() { + waitForSeconds(5) // waits for 5 seconds + waitForSeconds(5 * time.Second) // waits for 1388888h 53m 20s } ``` -Although the above code would compile without any errors, its runtime behaviour would almost certainly be incorrect. -A caller would reasonably expect `waitFor(5 * time.Seconds)` to wait for ~5 seconds but they would actually end up -waiting for ~1,388,889 hours. +Both invocations of the function are syntactically correct but the second one is probably not what most people want. +In this contrived example it is quite easy to spot the mistake. However, if the incorrect `waitForSeconds` invocation is +nested deep within a complex piece of code that runs in the background, the mistake could go unnoticed for months (which +is exactly what happened in a production backend system of fairly well-known software service). -The above example is just for illustration purposes only. The problem is glaringly obvious in such a simple function -and even the greenest Gopher would discover the issue immediately. However, imagine a much more complicated function -with many more lines and it is not inconceivable that such logic errors could go unnoticed. See the [test cases](testdata/src/a/a.go) for more examples of the types of errors detected by the linter. diff --git a/durationcheck.go b/durationcheck.go index 7f7008e..c47b3a7 100644 --- a/durationcheck.go +++ b/durationcheck.go @@ -150,6 +150,9 @@ func isAcceptableNestedExpr(pass *analysis.Pass, n ast.Expr) bool { case *ast.Ident: return isAcceptableIdent(pass, e) case *ast.CallExpr: + if isAcceptableCast(pass, e) { + return true + } t := pass.TypesInfo.TypeOf(e) return !isDuration(t) case *ast.SelectorExpr: diff --git a/testdata/src/a/a.go b/testdata/src/a/a.go index d8cf13b..2bc13d4 100644 --- a/testdata/src/a/a.go +++ b/testdata/src/a/a.go @@ -74,6 +74,8 @@ func validCases() { _ = time.Second * b.SomeInt _ = time.Duration(intArr[0]) * time.Second + + _ = time.Duration(y) * 24 * time.Hour } func invalidCases() {