The number of tools for statically checking Go source for errors and warnings is impressive.
This is a tool that concurrently runs a whole bunch of those linters and normalises their output to a standard format:
<file>:<line>:[<column>]: <message> (<linter>)
eg.
stutter.go:9::warning: unused global variable unusedGlobal (varcheck)
stutter.go:12:6:warning: exported type MyStruct should have comment or be unexported (golint)
It is intended for use with editor/IDE integration.
- SublimeLinter plugin.
- vim-go with the
:GoMetaLintercommand. - syntastic (vim)
let g:syntastic_go_checkers = ['gometalinter'] - Atom linter plugin.
- Emacs Flycheck checker.
- go vet - Reports potential errors that otherwise compile.
- go vet --shadow - Reports variables that may have been unintentionally shadowed.
- gotype - Syntactic and semantic analysis similar to the Go compiler.
- deadcode - Finds unused code.
- gocyclo - Computes the cyclomatic complexity of functions.
- golint - Google's (mostly stylistic) linter.
- varcheck - Find unused global variables and constants.
- structcheck - Find unused struct fields.
- aligncheck - Warn about un-optimally aligned structures.
- errcheck - Check that error return values are used.
- dupl - Reports potentially duplicated code.
- ineffassign - Detect when assignments to existing variables are not used.
- interfacer - Suggest narrower interfaces that can be used.
Disabled by default (enable with --enable=<linter>):
- testify - Show location of failed testify assertions (disabled by default).
- test - Show location of test failures from the stdlib testing module (disabled by default).
- gofmt -s - Checks if the code is properly formatted and could not be further simplified.
- goimports - Checks missing or unreferenced package imports.
Additional linters can be added through the command line with --linter=NAME:COMMAND:PATTERN (see below).
Install gometalinter:
$ go get github.com/alecthomas/gometalinter
Install all known linters:
$ gometalinter --install --update
Installing:
structcheck
aligncheck
deadcode
gocyclo
ineffassign
dupl
golint
gotype
goimports
errcheck
varcheck
interfacer
Run it:
$ cd example
$ gometalinter ./...
stutter.go:13::warning: unused struct field MyStruct.Unused (structcheck)
stutter.go:9::warning: unused global variable unusedGlobal (varcheck)
stutter.go:12:6:warning: exported type MyStruct should have comment or be unexported (golint)
stutter.go:16:6:warning: exported type PublicUndocumented should have comment or be unexported (golint)
stutter.go:8:1:warning: unusedGlobal is unused (deadcode)
stutter.go:12:1:warning: MyStruct is unused (deadcode)
stutter.go:16:1:warning: PublicUndocumented is unused (deadcode)
stutter.go:20:1:warning: duplicateDefer is unused (deadcode)
stutter.go:21:15:warning: error return value not checked (defer a.Close()) (errcheck)
stutter.go:22:15:warning: error return value not checked (defer a.Close()) (errcheck)
stutter.go:27:6:warning: error return value not checked (doit() // test for errcheck) (errcheck)
stutter.go:29::error: unreachable code (vet)
stutter.go:26::error: missing argument for Printf("%d"): format reads arg 1, have only 0 args (vet)
Gometalinter also supports the commonly seen <path>/... recursive path
format. Note that this can be very slow, and you may need to increase the linter --deadline to allow linters to complete.
gometalinter sets two bits of the exit status to indicate different issues:
| Bit | Meaning |
|---|---|
| 0 | A linter generated an issue. |
| 1 | An underlying error occurred; eg. a linter failed to execute. In this situation a warning will also be displayed. |
eg. linter only = 1, underlying only = 2, linter + underlying = 3
gometalinter has no specific support for vendor paths, however if the
underlying tools support it then it should Just Work™. Ensure that all
of the linters are up to date and built with Go 1.5
(gometalinter --install --update --force) then run
GO15VENDOREXPERIMENT=1 gometalinter .. That should be it.
I forked gocyclo because the upstream behaviour is to recursively check all
subdirectories even when just a single directory is specified. This made it
unusably slow when vendoring. The recursive behaviour can be achieved with
gometalinter by explicitly specifying <path>/.... There is a
pull request open.
That's more of a statement than a question, but okay.
Sometimes gometalinter will not report issues that you think it should. There are three things to try in that case:
go get -u github.com/alecthomas/gometalinter
gometalinter --install --update
If you're lucky, this will fix the problem.
If that doesn't help, the problem may be elsewhere (in no particular order):
- Upstream linter has changed its output or semantics.
- gometalinter is not invoking the tool correctly.
- gometalinter regular expression matches are not correct for a linter.
- Linter is exceeding the deadline.
To find out what's going on run in debug mode:
gometalinter --debug
This will show all output from the linters and should indicate why it is failing.
Failing all else, if the problem looks like a bug please file an issue and
include the output of gometalinter --debug.
$ gometalinter --help
usage: gometalinter [<flags>] [<path>...]
Aggregate and normalise the output of a whole bunch of Go linters.
Default linters:
gofmt
gofmt -l -s ./*.go
:^(?P<path>[^\n]+)$
gotype (golang.org/x/tools/cmd/gotype)
gotype -e {tests=-a} .
:PATH:LINE:COL:MESSAGE
goimports (golang.org/x/tools/cmd/goimports)
goimports -l ./*.go
:^(?P<path>[^\n]+)$
testify
go test
:Location:\s+(?P<path>[^:]+):(?P<line>\d+)$\s+Error:\s+(?P<message>[^\n]+)
test
go test
:^--- FAIL: .*$\s+(?P<path>[^:]+):(?P<line>\d+): (?P<message>.*)$
dupl (github.com/mibk/dupl)
dupl -plumbing -threshold {duplthreshold} ./*.go
:^(?P<path>[^\s][^:]+?\.go):(?P<line>\d+)-\d+:\s*(?P<message>.*)$
golint (github.com/golang/lint/golint)
golint -min_confidence {min_confidence} .
:PATH:LINE:COL:MESSAGE
structcheck (github.com/opennota/check/cmd/structcheck)
structcheck {tests=-t} .
:^(?:[^:]+: )?(?P<path>[^:]+):(?P<line>\d+):(?P<col>\d+):\s*(?P<message>.+)$
aligncheck (github.com/opennota/check/cmd/aligncheck)
aligncheck .
:^(?:[^:]+: )?(?P<path>[^:]+):(?P<line>\d+):(?P<col>\d+):\s*(?P<message>.+)$
gocyclo (github.com/alecthomas/gocyclo)
gocyclo -over {mincyclo} .
:^(?P<cyclo>\d+)\s+\S+\s(?P<function>\S+)\s+(?P<path>[^:]+):(?P<line>\d+):(\d+)$
vet
go tool vet ./*.go
:PATH:LINE:MESSAGE
errcheck (github.com/alecthomas/errcheck)
errcheck .
:^(?P<path>[^:]+):(?P<line>\d+):(?P<col>\d+)\t(?P<message>.*)$
ineffassign (github.com/gordonklaus/ineffassign)
ineffassign -n .
:PATH:LINE:COL:MESSAGE
vetshadow
go tool vet --shadow ./*.go
:PATH:LINE:MESSAGE
varcheck (github.com/opennota/check/cmd/varcheck)
varcheck .
:^(?:[^:]+: )?(?P<path>[^:]+):(?P<line>\d+):(?P<col>\d+):\s*(?P<message>\w+)$
deadcode (github.com/tsenart/deadcode)
deadcode .
:^deadcode: (?P<path>[^:]+):(?P<line>\d+):(?P<col>\d+):\s*(?P<message>.*)$
interfacer (github.com/mvdan/interfacer/cmd/interfacer)
interfacer ./
:PATH:LINE:MESSAGE
Severity override map (default is "warning"):
gotype -> error
test -> error
testify -> error
vet -> error
Flags:
--help Show context-sensitive help (also try --help-long
and --help-man).
--fast Only run fast linters.
-i, --install Attempt to install all known linters.
-u, --update Pass -u to go tool when installing.
-f, --force Pass -f to go tool when installing.
-d, --debug Display messages for failed linters, etc.
-j, --concurrency=16 Number of concurrent linters to run.
-e, --exclude=REGEXP Exclude messages matching these regular expressions.
--cyclo-over=10 Report functions with cyclomatic complexity over N
(using gocyclo).
--min-confidence=.80 Minimum confidence interval to pass to golint
--dupl-threshold=50 Minimum token sequence as a clone for dupl.
--sort=none Sort output by any of none, path, line, column,
severity, message, linter.
-t, --tests Include test files for linters that support this
option
--deadline=5s Cancel linters if they have not completed within
this duration.
--errors Only show errors.
--json Generate structured JSON rather than standard
line-based output.
-D, --disable=LINTER List of linters to disable (testify,test).
-E, --enable=LINTER Enable previously disabled linters.
--linter=NAME:COMMAND:PATTERN
Specify a linter.
--message-overrides=LINTER:MESSAGE
Override message from linter. {message} will be
expanded to the original message.
--severity=LINTER:SEVERITY
Map of linter severities.
--disable-all Disable all linters.
Args:
[<path>] Directory to lint. Defaults to ".". <path>/... will recurse.
Additional linters can be configured via the command line:
$ gometalinter --linter='vet:go tool vet -printfuncs=Infof,Debugf,Warningf,Errorf {paths}:PATH:LINE:MESSAGE' .
stutter.go:21:15:warning: error return value not checked (defer a.Close()) (errcheck)
stutter.go:22:15:warning: error return value not checked (defer a.Close()) (errcheck)
stutter.go:27:6:warning: error return value not checked (doit() // test for errcheck) (errcheck)
stutter.go:9::warning: unused global variable unusedGlobal (varcheck)
stutter.go:13::warning: unused struct field MyStruct.Unused (structcheck)
stutter.go:12:6:warning: exported type MyStruct should have comment or be unexported (golint)
stutter.go:16:6:warning: exported type PublicUndocumented should have comment or be unexported (deadcode)