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Staticcheck is go vet on steroids, applying a ton of static analysis checks you might be used to from tools like ReSharper for C#.

This project is supported by patrons on Patreon. If you, too, would like to support the project's development, consider becoming a patron.

Installation

Staticcheck requires Go 1.6 or later.

go get honnef.co/go/staticcheck/cmd/staticcheck

Usage

Invoke staticcheck with one or more filenames, a directory, or a package named by its import path. Staticcheck uses the same import path syntax as the go command and therefore also supports relative import paths like ./.... Additionally the ... wildcard can be used as suffix on relative and absolute file paths to recurse into them.

The output of this tool is a list of suggestions in Vim quickfix format, which is accepted by lots of different editors.

Purpose

The main purpose of staticcheck is editor integration, or workflow integration in general. For example, by running staticcheck when saving a file, one can quickly catch simple bugs without having to run the whole test suite or the program itself.

The tool shouldn't report any errors unless there are legitimate bugs - or very dubious constructs - in the code.

It is similar in nature to go vet, but has more checks that catch bugs that would also be caught easily at runtime, to reduce the number of edit, compile and debug cycles.

Checks

The following things are currently checked by staticcheck:

Check Description
SA1??? Various misuses of the standard library
SA1000 Invalid regular expression
SA1001 Invalid template
SA1002 Invalid format in time.Parse
SA1003 Unsupported argument to functions in encoding/binary
SA1004 Suspiciously small untyped constant in time.Sleep
SA1005 Invalid first argument to exec.Command
SA1006 Printf with dynamic first argument and no further arguments
SA1007 Invalid URL in net/url.Parse
SA1008 Non-canonical key in http.Header map
SA1010 (*regexp.Regexp).FindAll called with n == 0, which will always return zero results
SA1011 Various methods in the strings package expect valid UTF-8, but invalid input is provided
SA1012 A nil context.Context is being passed to a function, consider using context.TODO instead
SA1013 io.Seeker.Seek is being called with the whence constant as the first argument, but it should be the second
SA1014 Non-pointer value passed to Unmarshal or Decode
SA1015 Using time.Tick in a way that will leak. Consider using time.NewTicker, and only use time.Tick in tests, commands and endless functions
SA1016 Trapping a signal that cannot be trapped
SA1017 Channels used with signal.Notify should be buffered
SA1018 strings.Replace called with n == 0, which does nothing
SA1019 Using a deprecated function, variable, constant or field
SA1020 Using an invalid host:port pair with a net.Listen-related function
SA1021 Using bytes.Equal to compare two net.IP
SA2??? Concurrency issues
SA2000 sync.WaitGroup.Add called inside the goroutine, leading to a race condition
SA2001 Empty critical section, did you mean to defer the unlock?
SA2002 Called testing.T.FailNow or SkipNow in a goroutine, which isn't allowed
SA2003 Deferred Lock right after locking, likely meant to defer Unlock instead
SA3??? Testing issues
SA3000 TestMain doesn't call os.Exit, hiding test failures
SA3001 Assigning to b.N in benchmarks distorts the results
SA4??? Code that isn't really doing anything
SA4000 Boolean expression has identical expressions on both sides
SA4001 &*x gets simplified to x, it does not copy x
SA4002 Comparing strings with known different sizes has predictable results
SA4003 Comparing unsigned values against negative values is pointless
SA4004 The loop exits unconditionally after one iteration
SA4005 Field assignment that will never be observed. Did you mean to use a pointer receiver?
SA4006 A value assigned to a variable is never read before being overwritten. Forgotten error check or dead code?
SA4008 The variable in the loop condition never changes, are you incrementing the wrong variable?
SA4009 A function argument is overwritten before its first use
SA4010 The result of append will never be observed anywhere
SA4011 Break statement with no effect. Did you mean to break out of an outer loop?
SA4012 Comparing a value against NaN even though no value is equal to NaN
SA4013 Negating a boolean twice (!!b) is the same as writing b. This is either redundant, or a typo.
SA4014 An if/else if chain has repeated conditions and no side-effects; if the condition didn't match the first time, it won't match the second time, either
SA4015 Calling functions like math.Ceil on floats converted from integers doesn't do anything useful
SA4016 Certain bitwise operations, such as x ^ 0, do not do anything useful
SA4017 A pure function's return value is discarded, making the call pointless
SA5??? Correctness issues
SA5000 Assignment to nil map
SA5001 Defering Close before checking for a possible error
SA5002 The empty for loop (for {}) spins and can block the scheduler
SA5003 Defers in infinite loops will never execute
SA5004 for { select { ... with an empty default branch spins
SA5005 The finalizer references the finalized object, preventing garbage collection
SA5006 Slice index out of bounds
SA5007 Infinite recursive call
SA9??? Dubious code constructs that have a high probability of being wrong
SA9000 Storing non-pointer values in sync.Pool allocates memory
SA9001 defers in for range loops may not run when you expect them to
SA9002 Using a non-octal os.FileMode that looks like it was meant to be in octal.

Ignoring checks

staticcheck allows disabling some or all checks for certain files. The -ignore flag takes a whitespace-separated list of glob:check1,check2,... pairs. glob is a glob pattern matching files in packages, and check1,check2,... are checks named by their IDs.

For example, to ignore assignment to nil maps in all test files in the os/exec package, you would write -ignore "os/exec/*_test.go:SA5000"

Additionally, the check IDs support globbing, too. Using a pattern such as os/exec/*.gen.go:* would disable all checks in all auto-generated files in the os/exec package.

Any whitespace can be used to separate rules, including newlines. This allows for a setup like the following:

$ cat stdlib.ignore
sync/*_test.go:SA2001
testing/benchmark.go:SA3001
runtime/string_test.go:SA4007
runtime/proc_test.go:SA5004
runtime/lfstack_test.go:SA4010
runtime/append_test.go:SA4010
errors/errors_test.go:SA4000
reflect/all_test.go:SA4000

$ staticcheck -ignore "$(cat stdlib.ignore)" std