Notice Me is a static analysis tool for Go programs that can identify unused
values, typically function call results. This is similar to the errcheck
tool, but instead of checking for unused results of type error, it checks
for unused results of whatever types you specify. There's also some overlap
with the unusedresult example analysis pass.
To build, run go build in cmd/noticeme. The noticeme tool should work
with any reasonably-recent version of Go. It relies on the golang.org/x/tools
package, but shouldn't care about the specific version.
To check the package in the current directory for any and all unused
values of type error:
noticeme -types error .
Note that this will be pickier than other utilities -- for instance,
fmt.Printf returns an error which is almost never checked. There's no
hooks for disabling these warnings case-by-case right now. To specify
additional types, use a comma-separated list. So for instance, the motive
for developing this involved the usage of *Container objects in our
Roaring bitmap implementation:
noticeme -types "*roaring.Container" .
Type names are checked with full import path qualifiers, package qualifiers only, and unqualified. Note that these qualifiers are applied to all the types in a line at once, so a type like this won't work:
map[package.Foo]github.com/user/repo.Bar
The design here is to assume that the type of an expression which exists as a standalone "expression statement" has not been "used". If you assign a value, or use it in another expression, then it's being used. You may be able to bypass this analysis. However, it does handle fairly arbitrary expressions, not just direct function or method calls.
There is no guessing about pointers and non-pointers; if you specify a
type of foo as important, functions returning *foo are not special, and
vise versa.
Nested types are not recognized, but tuples (such as functions with multiple return values) are handled.