Errcheck not excluding functions as expected when used by Golangci-lint

[leosunmo]

I am having trouble getting Errcheck to not check methods that are supposedly excluded by default.
Specifically the Hash.Write method explicitly excluded here: https://github.com/kisielk/errcheck/blob/master/internal/errcheck/errcheck.go#L159

If I run Errcheck by itself it does not throw an error in this line, but with Golangci-lint it does, even if I add an explicit exclude file. I don't know what I'm missing here, so any suggestions or troubleshooting steps welcome!

Version:

$ golangci-lint --version
golangci-lint has version 1.17.1 built from 4ba2155 on 2019-06-10T09:06:49Z

Golangci-lint Config file:

$ cat golangci-lint.yaml
linters-settings:
  errcheck:
    # path to a file containing a list of functions to exclude from checking
    # see https://github.com/kisielk/errcheck#excluding-functions for details
    exclude: ./errcheck-exclude.txt

Errcheck exlude config:

$ cat errcheck-exclude.txt 
(hash.Hash).Write

Go version:
go version go1.12.5 linux/amd64

Golangci-lint output:

$ golangci-lint run -E golint -c golangci-lint.yaml -v
INFO [config_reader] Used config file golangci-lint.yaml 
INFO [lintersdb] Active 11 linters: [deadcode errcheck golint gosimple govet ineffassign staticcheck structcheck typecheck unused varcheck] 
INFO [lintersdb] Optimized sublinters [staticcheck gosimple unused] into metalinter megacheck 
INFO [loader] Go packages loading at mode load types and syntax took 1.538698963s 
INFO [loader] SSA repr building timing: packages building 25.196461ms, total 207.794664ms 
INFO [runner] worker.7 took 1.344549ms with stages: errcheck: 1.340164ms 
INFO [runner] worker.2 took 1.403045ms with stages: varcheck: 1.398897ms 
INFO [runner] worker.1 took 955ns                 
INFO [runner] worker.3 took 1.57871ms with stages: deadcode: 836.488µs, structcheck: 717.989µs, typecheck: 14.465µs 
main.go:362:9: Error return value of `h.Write` is not checked (errcheck)
        h.Write([]byte(key))
               ^
INFO [runner] worker.6 took 93.006833ms with stages: ineffassign: 93.000101ms 
INFO [runner] worker.8 took 372.121254ms with stages: govet: 372.110864ms 
INFO [runner] worker.5 took 433.001196ms with stages: golint: 432.992387ms 
INFO [runner] worker.4 took 1.578426975s with stages: megacheck: 1.578419329s 
INFO [runner] Workers idle times: #1: 1.576949046s, #2: 1.576962288s, #3: 1.576773932s, #5: 1.145364012s, #6: 1.48528822s, #7: 1.577010948s, #8: 1.206269976s 
INFO [runner] Issues before processing: 3, after processing: 1 
INFO [runner] processing took 999.692µs with stages: exclude: 461.177µs, autogenerated_exclude: 164.488µs, identifier_marker: 159.149µs, skip_dirs: 84.189µs, source_code: 58.289µs, nolint: 24.863µs, cgo: 15.244µs, path_prettifier: 13.987µs, max_same_issues: 5.004µs, path_shortener: 3.639µs, filename_unadjuster: 3.276µs, uniq_by_line: 1.788µs, max_from_linter: 1.678µs, diff: 943ns, max_per_file_from_linter: 932ns, skip_files: 553ns, exclude-rules: 493ns 
INFO File cache stats: 1 entries of total size 14.6KiB 
INFO Memory: 33 samples, avg is 629.1MB, max is 1081.6MB 
INFO Execution took 3.36854003s                   

[leosunmo]

I cloned Errcheck and commented out this line and it gives me the same error as golangci-lint does.

$ ~/go/bin/errcheck # Downloaded errcheck gives me no errors
$ ~/tmp/errcheck/errcheck # My modified errcheck
main.go:362:9:	h.Write([]byte(key)) # Same error golangci-lint throws.

Might be that golangci-lint just needs to upgrade its version of Errcheck.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[Zeplar]

I'm on golangci-lint v1.39.0 and this appears to still be a problem. As in the original post, errcheck alone respects the excludes file but golangci-lint does not.

[ldez]

@Zeplar could you provide an example? Thank you.

[na4ma4]

still an issue in v1.41.1, I didn't test pulling in an updated errcheck and rebuilding golangci-lint though.

linters-settings/errcheck/exclude and a file works, but using exclude-functions does not.

https://github.com/na4ma4/golangci-lint-errcheck-test

with .golangci.yml using:

linters:
  enable:
    - errcheck

issues:
  exclude-use-default: false

linters-settings:
  errcheck:
    # exclude: errcheck-exclude.txt
    exclude-functions:
    - (io.Closer).Close

golangci-lint still fails on resp.Body.Close() even though the exclude-functions covers (io.Closer).Close.

$ artifacts/bin/v1.41.1/golangci-lint run --sort-results --max-same-issues 0 --max-issues-per-linter 0  ./... | tee "artifacts/lint/golangci-lint"

cmd/errcheck-test/main.go:23:23: Error return value of `resp.Body.Close` is not checked (errcheck)
    defer resp.Body.Close()
                         ^

Using errcheck directly works as expected though.

$ cat "errcheck-exclude.txt"
(io.Closer).Close

$ artifacts/bin/errcheck -verbose ./...
checking github.com/na4ma4/golangci-lint-errcheck-test/cmd/errcheck-test
cmd/errcheck-test/main.go:23:23:	(io.Closer).Close	defer resp.Body.Close()

$ artifacts/bin/errcheck -verbose -exclude errcheck-exclude.txt ./...
checking github.com/na4ma4/golangci-lint-errcheck-test/cmd/errcheck-test

this is suppressed by the default exclude:

# EXC0001 errcheck: Almost all programs ignore errors on these functions and in most cases it's ok
- Error return value of .((os\.)?std(out|err)\..*|.*Close|.*Flush|os\.Remove(All)?|.*print(f|ln)?|os\.(Un)?Setenv). is not checked

[ldez]

exclude-functions options will be a part of the next release v1.42.0, it's not available in v1.41.1

[bunyk]

I seem to be doing something wrong. I created a folder with two files:

package okhandler

import "net/http"

func OkHandler(w http.ResponseWriter, r *http.Request) {
	w.WriteHeader(http.StatusOK)
	w.Write([]byte("OK"))
}

And .golangci.yml:

linters:
  enable:
    - errcheck
  errcheck:
    exclude-functions:
      - (http.ResponseWriter).Write

I run golangci-lint run okhandler.go and still get "Error return value of w.Write is not checked"

$ golangci-lint --version
golangci-lint has version v1.42.0 built from (unknown, mod sum: "h1:hqf1zo6zY3GKGjjBk3ttdH22tGwF6ZRpk6j6xyJmE8I=") on (unknown)

[ldez]

I found the root cause, it's a wrong configuration: you have to set the right package net/http instead of http:

linters:
  enable:
    - errcheck

linters-settings:
  errcheck:
    exclude-functions:
      - (net/http.ResponseWriter).Write