ci(lint): enable nolintlint and remove redundant comments

[alexandear]

This PR enables nolintlint linter to check //nolint comments. Also, removes redundant //nolint: directives.

[bboreham]

Can you explain a little bit more background why we want this linter and why the comments are redundant, please?

[alexandear]

@bboreham yeah.

nolintlint is a Go static analysis tool to find ill-formed or insufficiently explained //nolint directives. In other words, it allows us to search for mistakenly added //nolint comments.

When I enabled nolintlint and run golangci-lint I got the following lint issues:

❯ ./bin/golangci-lint run
cmd/prometheus/main.go:15:1: directive `// nolint:revive // Many unsued function arguments in this file by design.` should be written without leading space as `//nolint:revive // Many unsued function arguments in this file by design.` (nolintlint)
// nolint:revive // Many unsued function arguments in this file by design.
^
cmd/promtool/backfill_test.go:47:113: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
func queryAllSeries(t testing.TB, q storage.Querier, expectedMinTime, expectedMaxTime int64) []backfillSample { // nolint:revive
                                                                                                                ^
cmd/promtool/main.go:414:1: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
// nolint:revive
^
cmd/promtool/rules_test.go:38:145: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
func (mockAPI mockQueryRangeAPI) QueryRange(_ context.Context, query string, r v1.Range, opts ...v1.Option) (model.Value, v1.Warnings, error) { // nolint:revive
                                                                                                                                                ^
discovery/kubernetes/endpoints.go:14:1: directive `// nolint:revive // Many legitimately empty blocks in this file.` should be written without leading space as `//nolint:revive // Many legitimately empty blocks in this file.` (nolintlint)
// nolint:revive // Many legitimately empty blocks in this file.
^
discovery/kubernetes/endpointslice.go:193:28: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
                for e.process(ctx, ch) { // nolint:revive
                                         ^
discovery/kubernetes/ingress.go:91:28: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
                for i.process(ctx, ch) { // nolint:revive
                                         ^
discovery/kubernetes/node.go:99:28: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
                for n.process(ctx, ch) { // nolint:revive
                                         ^
discovery/kubernetes/pod.go:134:28: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
                for p.process(ctx, ch) { // nolint:revive
                                         ^
discovery/kubernetes/service.go:94:28: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
                for s.process(ctx, ch) { // nolint:revive
                                         ^
discovery/zookeeper/zookeeper.go:196:27: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
                        for range pathUpdate { // nolint:revive
                                               ^
promql/engine.go:2019:49: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
                for drop = 0; floats[drop].T < mint; drop++ { // nolint:revive
                                                              ^
promql/engine.go:2041:53: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
                for drop = 0; histograms[drop].T < mint; drop++ { // nolint:revive
                                                                  ^
promql/engine_test.go:1659:2: directive `//nolint:govet` is unused for linter "govet" (nolintlint)
        //nolint:govet
        ^
promql/functions.go:14:1: directive `// nolint:revive // Many unsued function arguments in this file by design.` should be written without leading space as `//nolint:revive // Many unsued function arguments in this file by design.` (nolintlint)
// nolint:revive // Many unsued function arguments in this file by design.
^
promql/parser/ast.go:58:2: directive `// nolint:unused` should be written without leading space as `//nolint:unused` (nolintlint)
        // nolint:unused
        ^
promql/parser/lex.go:14:1: directive `// nolint:revive // Many legitimately empty blocks in this file.` should be written without leading space as `//nolint:revive // Many legitimately empty blocks in this file.` (nolintlint)
// nolint:revive // Many legitimately empty blocks in this file.
^
promql/parser/parse.go:75:1: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
// nolint:revive
^
promql/parser/parse.go:663:94: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
                        for r.Start = n.LHS.PositionRange().End; isSpace(rune(p.lex.input[r.Start])); r.Start++ { // nolint:revive
                                                                                                                  ^
promql/parser/parse.go:665:94: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
                        for r.End = n.RHS.PositionRange().Start - 1; isSpace(rune(p.lex.input[r.End])); r.End-- { // nolint:revive
                                                                                                                  ^
promql/parser/parse_test.go:4039:2: directive `//nolint:govet` is unused for linter "govet" (nolintlint)
        //nolint:govet
        ^
scrape/target.go:148:2: directive `//nolint: errcheck` is unused for linter "errcheck" (nolintlint)
        //nolint: errcheck
        ^
scrape/target.go:150:2: directive `//nolint: errcheck` is unused for linter "errcheck" (nolintlint)
        //nolint: errcheck
        ^
storage/buffer_test.go:214:38: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
        for it.Next() != chunkenc.ValNone { // nolint:revive
                                            ^
storage/memoized_iterator_test.go:115:38: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
        for it.Next() != chunkenc.ValNone { // nolint:revive
                                            ^
storage/remote/azuread/azuread.go:50:29: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
type AzureADConfig struct { // nolint:revive
                            ^
template/template.go:184:32: directive `// nolint:staticcheck` should be written without leading space as `//nolint:staticcheck` (nolintlint)
                        "title":     strings.Title, // nolint:staticcheck
                                                    ^
tsdb/chunkenc/float_histogram.go:106:39: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
        for it.Next() == ValFloatHistogram { // nolint:revive
                                             ^
tsdb/chunkenc/float_histogram_test.go:160:40: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
        for itX.Next() == ValFloatHistogram { // nolint:revive
                                              ^
tsdb/chunkenc/histogram.go:117:34: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
        for it.Next() == ValHistogram { // nolint:revive
                                        ^
tsdb/chunkenc/histogram_test.go:165:35: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
        for itX.Next() == ValHistogram { // nolint:revive
                                         ^
tsdb/chunkenc/xor.go:102:29: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
        for it.Next() != ValNone { // nolint:revive
                                   ^
tsdb/errors/errors.go:28:43: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
func NewMulti(errs ...error) multiError { // nolint:revive
                                          ^
tsdb/head_test.go:14:1: directive `// nolint:revive // Many legitimately empty blocks in this file.` should be written without leading space as `//nolint:revive // Many legitimately empty blocks in this file.` (nolintlint)
// nolint:revive // Many legitimately empty blocks in this file.
^
tsdb/head_wal.go:14:1: directive `// nolint:revive // Many legitimately empty blocks in this file.` should be written without leading space as `//nolint:revive // Many legitimately empty blocks in this file.` (nolintlint)
// nolint:revive // Many legitimately empty blocks in this file.
^
tsdb/ooo_head_read.go:14:1: directive `// nolint:revive // Many unused function arguments in this file by design.` should be written without leading space as `//nolint:revive // Many unused function arguments in this file by design.` (nolintlint)
// nolint:revive // Many unused function arguments in this file by design.
^
tsdb/querier_bench_test.go:270:22: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
                                        for ss.Next() { // nolint:revive
                                                        ^
tsdb/querier_test.go:14:1: directive `// nolint:revive // Many unsued function arguments in this file by design.` should be written without leading space as `//nolint:revive // Many unsued function arguments in this file by design.` (nolintlint)
// nolint:revive // Many unsued function arguments in this file by design.
^
tsdb/wal.go:14:1: directive `// nolint:revive // Many unsued function arguments in this file by design.` should be written without leading space as `//nolint:revive // Many unsued function arguments in this file by design.` (nolintlint)
// nolint:revive // Many unsued function arguments in this file by design.
^
tsdb/wlog/reader_test.go:544:24: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
                        for reader.Next() { // nolint:revive
                                            ^
tsdb/wlog/wlog.go:974:1: directive `// nolint:revive // TODO: Consider exporting segmentBufReader` should be written without leading space as `//nolint:revive // TODO: Consider exporting segmentBufReader` (nolintlint)
// nolint:revive // TODO: Consider exporting segmentBufReader
^
tsdb/wlog/wlog.go:986:1: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
// nolint:revive
^
tsdb/wlog/wlog_test.go:167:20: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
                                for r.Next() { // nolint:revive
                                               ^
util/annotations/annotations.go:94:1: directive `//nolint:revive // Ignore ST1012` is unused for linter "revive" (nolintlint)
//nolint:revive // Ignore ST1012
^
util/runtime/statfs_default.go:75:2: directive `//nolint:unconvert // This ensure Type format on all Platforms` is unused for linter "unconvert" (nolintlint)
        //nolint:unconvert // This ensure Type format on all Platforms
        ^
util/treecache/treecache.go:119:30: directive `// nolint:revive` should be written without leading space as `//nolint:revive` (nolintlint)
                for range tc.head.events { // nolint:revive
                                           ^
util/zeropool/pool_test.go:152:17: directive `//nolint:staticcheck // This allocates.` is unused for linter "staticcheck" (nolintlint)
        pool.Put(item) //nolint:staticcheck // This allocates.
                       ^
util/zeropool/pool_test.go:158:18: directive `//nolint:staticcheck  // New pointer.` is unused for linter "staticcheck" (nolintlint)
                pool.Put(&buf) //nolint:staticcheck  // New pointer.
                               ^
web/api/v1/errors_test.go:14:1: directive `// nolint:revive // Many unsued function arguments in this file by design.` should be written without leading space as `//nolint:revive // Many unsued function arguments in this file by design.` (nolintlint)
// nolint:revive // Many unsued function arguments in this file by design.
^

I fixed all these issues in this PR and removed 19 unnecessary code lines.

[jesusvazquez]

This PR was reviewed during the Prometheus Bug Scrub event.

TIL about nolintlint and found it very cool 🎉

Thank you for the contribution.

[bboreham]

Sorry I'm still missing why it is OK to delete the comments as you did.
Maybe we don't run the revive linter any more?

[alexandear]

@bboreham you're right. There was a problem with revive's configuration. Fixed in #13068.