Upgrade golangci-lint to v1.56.2; fix gocritic issues

[alexandear]

The PR upgrades golangci-lint version to the latest v1.56.2), enables a lot of gocritic's checks and fixes up issues.

Explanation of some gocritic's fixes

• in idiomatic Go, we should use len(v) =! 0 instead of string(v) != "" when v is []byte. See https://dmitri.shuralyov.com/idiomatic-go#empty-string-check;
• we should use v != "" instead of len(v) != when v is string;
• we can compare byte slices with bytes.Equal instead of converting them to string;
• rw.Write([]byte(str),... can be rewritten to rw.WriteString(str,....

The full log of running golangci-lint

❯ golangci-lint run
prefork/prefork.go:155:14: evalOrder: may want to evaluate cmd.Start() before the return statement (gocritic)
        return cmd, cmd.Start()
                    ^
bytesconv.go:38:6: emptyStringTest: replace `len(sub) > 0` with `sub != ""` (gocritic)
                if len(sub) > 0 {
                   ^
fs.go:471:5: emptyStringTest: replace `len(fs.CompressedFileSuffix) > 0` with `fs.CompressedFileSuffix != ""` (gocritic)
        if len(fs.CompressedFileSuffix) > 0 {
           ^
fs.go:105:23: emptyStringTest: replace `len(path) > 0` with `path != ""` (gocritic)
                hasTrailingSlash := len(path) > 0 && (path[len(path)-1] == '/' || path[len(path)-1] == '\\')
                                    ^
fs.go:445:6: emptyStringTest: replace `len(root) > 0` with `root != ""` (gocritic)
        for len(root) > 0 && root[len(root)-1] == os.PathSeparator {
            ^
http.go:1253:7: emptyStringTest: replace `len(req.multipartFormBoundary) > 0` with `req.multipartFormBoundary != ""` (gocritic)
                        if len(req.multipartFormBoundary) > 0 && len(req.Header.peek(strContentEncoding)) == 0 {
                           ^
http.go:1332:7: emptyStringTest: replace `len(req.multipartFormBoundary) > 0` with `req.multipartFormBoundary != ""` (gocritic)
                        if len(req.multipartFormBoundary) > 0 && len(req.Header.peek(strContentEncoding)) == 0 {
                           ^
args_test.go:452:5: stringXbytes: suggestion: len(a.Peek("foo0")) != 0 (gocritic)
        if string(a.Peek("foo0")) != "" {
           ^
args_test.go:446:6: stringXbytes: suggestion: len(a.Peek(k)) != 0 (gocritic)
                if string(a.Peek(k)) != "" {
                   ^
args_test.go:477:6: stringXbytes: suggestion: len(a.Peek(k)) != 0 (gocritic)
                if string(a.Peek(k)) != "" {
                   ^
brotli_test.go:124:5: stringXbytes: suggestion: len(ce) != 0 (gocritic)
        if string(ce) != "" {
           ^
client_test.go:459:25: regexpSimplify: can re-write `^127\.0\.0\.1:[0-9]{4,5}$` as `^127\.0\.0\.1:\d{4,5}$` (gocritic)
        if !regexp.MustCompile(`^127\.0\.0\.1:[0-9]{4,5}$`).MatchString(res.LocalAddr().String()) {
                               ^
client_test.go:2326:7: stringXbytes: can simplify `[]byte(r.s[r.n:])` to `r.s[r.n:]` (gocritic)
        n := copy(p, []byte(r.s[r.n:]))
             ^
fs_fs_test.go:257:5: stringXbytes: suggestion: len(ce) != 0 (gocritic)
        if string(ce) != "" {
           ^
fs_test.go:655:5: stringXbytes: suggestion: len(ce) != 0 (gocritic)
        if string(ce) != "" {
           ^
fuzz_test.go:47:3: assignOp: replace `max = max % (10 * 1024)` with `max %= (10 * 1024)` (gocritic)
                max = max % (10 * 1024)
                ^
fuzz_test.go:62:3: assignOp: replace `max = max % (10 * 1024)` with `max %= (10 * 1024)` (gocritic)
                max = max % (10 * 1024)
                ^
header_test.go:170:5: stringXbytes: suggestion: !bytes.Equal(h.ContentType(), h1.ContentType()) (gocritic)
        if string(h.ContentType()) != string(h1.ContentType()) {
           ^
header_test.go:225:5: stringXbytes: suggestion: !bytes.Equal(h.Host(), h1.Host()) (gocritic)
        if string(h.Host()) != string(h1.Host()) {
           ^
header_test.go:690:5: stringXbytes: suggestion: !bytes.Equal(hv, defaultContentType) (gocritic)
        if string(hv) != string(defaultContentType) {
           ^
header_test.go:2124:5: stringXbytes: suggestion: !bytes.Equal(m, m1) (gocritic)
        if string(m) != string(m1) {
           ^
header_test.go:344:6: stringXbytes: suggestion: len(h.Host()) != 0 (gocritic)
                if string(h.Host()) != "" {
                   ^
header_test.go:1522:5: stringXbytes: suggestion: len(h1.contentType) != 0 (gocritic)
        if string(h1.contentType) != "" {
           ^
http_test.go:1326:5: stringXbytes: suggestion: !bytes.Equal(formData, r.Body()) (gocritic)
        if string(formData) != string(r.Body()) {
           ^
http_test.go:1213:5: stringXbytes: suggestion: !bytes.Equal(r.Body(), body) (gocritic)
        if string(r.Body()) != string(body) {
           ^
server_test.go:2015:5: stringXbytes: suggestion: len(ce) != 0 (gocritic)
        if string(ce) != "" {
           ^
server_test.go:2113:5: stringXbytes: suggestion: len(ce) != 0 (gocritic)
        if string(ce) != "" {
           ^
server_test.go:2117:5: stringXbytes: suggestion: len(vary) != 0 (gocritic)
        if string(vary) != "" {
           ^
fasthttpadaptor/adaptor_test.go:163:18: preferStringWriter: rw.WriteString("bar") should be preferred to the rw.Write([]byte("bar")) (gocritic)
                                if _, err := rw.Write([]byte("bar")); err != nil {
                                             ^

[erikdubbelboer]

Thanks!