Add gocognit linter (#756)

* Add gocognit linter

* Remove gocognit to the golangci config

* Make changes on README.md

* Remove gocognit from megacheck benchtest

* Remove command line flags

* Comply with new style

Author: uudashr

.golangci.example.yml

@@ -116,6 +116,9 @@ linters-settings:
   gocyclo:
     # minimal code complexity to report, 30 by default (but we recommend 10-20)
     min-complexity: 10
+  gocognit:
+    # minimal code complexity to report, 30 by default (but we recommend 10-20)
+    min-complexity: 10
   maligned:
     # print struct with more effective memory layout or not, false by default
     suggest-new: true

README.md

@@ -201,6 +201,7 @@ dupl: Tool for code clone detection [fast: true, auto-fix: false]
 funlen: Tool for detection of long functions [fast: true, auto-fix: false]
 gochecknoglobals: Checks that no globals are present in Go code [fast: true, auto-fix: false]
 gochecknoinits: Checks that no init functions are present in Go code [fast: true, auto-fix: false]
+gocognit: Computes and checks the cognitive complexity of functions [fast: true, auto-fix: false]
 goconst: Finds repeated strings that could be replaced by a constant [fast: true, auto-fix: false]
 gocritic: The most opinionated Go source code linter [fast: true, auto-fix: false]
 gocyclo: Computes and checks the cyclomatic complexity of functions [fast: true, auto-fix: false]
@@ -449,6 +450,7 @@ golangci-lint help linters
 - [dupl](https://github.com/mibk/dupl) - Tool for code clone detection
 - [goconst](https://github.com/jgautheron/goconst) - Finds repeated strings that could be replaced by a constant
 - [gocyclo](https://github.com/alecthomas/gocyclo) - Computes and checks the cyclomatic complexity of functions
+- [gocognit](https://github.com/uudashr/gocognit) - Computes and checks the cognitive complexity of functions
 - [gofmt](https://golang.org/cmd/gofmt/) - Gofmt checks whether code was gofmt-ed. By default this tool runs with -s option to check for code simplification
 - [goimports](https://godoc.org/golang.org/x/tools/cmd/goimports) - Goimports does everything that gofmt does. Additionally it checks unused imports
 - [maligned](https://github.com/mdempsky/maligned) - Tool to detect Go structs that would take less memory if their fields were sorted
@@ -703,6 +705,9 @@ linters-settings:
   gocyclo:
     # minimal code complexity to report, 30 by default (but we recommend 10-20)
     min-complexity: 10
+  gocognit:
+    # minimal code complexity to report, 30 by default (but we recommend 10-20)
+    min-complexity: 10
   maligned:
     # print struct with more effective memory layout or not, false by default
     suggest-new: true
@@ -1108,6 +1113,7 @@ Thanks to developers and authors of used linters:
 - [jgautheron](https://github.com/jgautheron)
 - [remyoudompheng](https://github.com/remyoudompheng)
 - [alecthomas](https://github.com/alecthomas)
+- [uudashr](https://github.com/uudashr)
 - [OpenPeeDeeP](https://github.com/OpenPeeDeeP)
 - [client9](https://github.com/client9)
 - [walle](https://github.com/walle)

go.mod

@@ -37,6 +37,7 @@ require (
 	github.com/timakin/bodyclose v0.0.0-20190930140734-f7f2e9bca95e
 	github.com/ultraware/funlen v0.0.2
 	github.com/ultraware/whitespace v0.0.3
+	github.com/uudashr/gocognit v0.0.0-20190926065955-1655d0de0517
 	github.com/valyala/quicktemplate v1.2.0
 	golang.org/x/tools v0.0.0-20190912215617-3720d1ec3678
 	gopkg.in/yaml.v2 v2.2.2

go.sum

@@ -234,6 +234,8 @@ github.com/ultraware/funlen v0.0.2 h1:Av96YVBwwNSe4MLR7iI/BIa3VyI7/djnto/pK3Uxbd
 github.com/ultraware/funlen v0.0.2/go.mod h1:Dp4UiAus7Wdb9KUZsYWZEWiRzGuM2kXM1lPbfaF6xhA=
 github.com/ultraware/whitespace v0.0.3 h1:S5BCRRB5sttNy0bSOhbpw+0mb+cHiCmWfrvxpEzuUk0=
 github.com/ultraware/whitespace v0.0.3/go.mod h1:aVMh/gQve5Maj9hQ/hg+F75lr/X5A89uZnzAmWSineA=
+github.com/uudashr/gocognit v0.0.0-20190926065955-1655d0de0517 h1:ChMKTho2hWKpks/nD/FL2KqM1wuVt62oJeiE8+eFpGs=
+github.com/uudashr/gocognit v0.0.0-20190926065955-1655d0de0517/go.mod h1:j44Ayx2KW4+oB6SWMv8KsmHzZrOInQav7D3cQMJ5JUM=
 github.com/valyala/bytebufferpool v1.0.0 h1:GqA5TC/0021Y/b9FG4Oi9Mr3q7XYx6KllzawFIhcdPw=
 github.com/valyala/bytebufferpool v1.0.0/go.mod h1:6bBcMArwyJ5K/AmCkWv1jt77kVWyCJ6HpOuEn7z0Csc=
 github.com/valyala/fasthttp v1.2.0/go.mod h1:4vX61m6KN+xDduDNwXrhIAVZaZaZiQ1luJk8LWSxF3s=

pkg/config/config.go

@@ -138,6 +138,9 @@ type LintersSettings struct {
 	Gocyclo struct {
 		MinComplexity int `mapstructure:"min-complexity"`
 	}
+	Gocognit struct {
+		MinComplexity int `mapstructure:"min-complexity"`
+	}
 	Varcheck struct {
 		CheckExportedFields bool `mapstructure:"exported-fields"`
 	}

pkg/golinters/gocognit.go

@@ -0,0 +1,69 @@
+// nolint:dupl
+package golinters
+
+import (
+	"fmt"
+	"sort"
+	"sync"
+
+	"github.com/uudashr/gocognit"
+	"golang.org/x/tools/go/analysis"
+
+	"github.com/golangci/golangci-lint/pkg/golinters/goanalysis"
+	"github.com/golangci/golangci-lint/pkg/lint/linter"
+	"github.com/golangci/golangci-lint/pkg/result"
+)
+
+const gocognitName = "gocognit"
+
+func NewGocognit() *goanalysis.Linter {
+	var mu sync.Mutex
+	var resIssues []result.Issue
+
+	analyzer := &analysis.Analyzer{
+		Name: goanalysis.TheOnlyAnalyzerName,
+		Doc:  goanalysis.TheOnlyanalyzerDoc,
+	}
+	return goanalysis.NewLinter(
+		gocognitName,
+		"Computes and checks the cognitive complexity of functions",
+		[]*analysis.Analyzer{analyzer},
+		nil,
+	).WithContextSetter(func(lintCtx *linter.Context) {
+		analyzer.Run = func(pass *analysis.Pass) (interface{}, error) {
+			var stats []gocognit.Stat
+			for _, f := range pass.Files {
+				stats = gocognit.ComplexityStats(f, pass.Fset, stats)
+			}
+			if len(stats) == 0 {
+				return nil, nil
+			}
+
+			sort.Slice(stats, func(i, j int) bool {
+				return stats[i].Complexity > stats[j].Complexity
+			})
+
+			res := make([]result.Issue, 0, len(stats))
+			for _, s := range stats {
+				if s.Complexity <= lintCtx.Settings().Gocognit.MinComplexity {
+					break // Break as the stats is already sorted from greatest to least
+				}
+
+				res = append(res, result.Issue{
+					Pos: s.Pos,
+					Text: fmt.Sprintf("cognitive complexity %d of func %s is high (> %d)",
+						s.Complexity, formatCode(s.FuncName, lintCtx.Cfg), lintCtx.Settings().Gocognit.MinComplexity),
+					FromLinter: gocognitName,
+				})
+			}
+
+			mu.Lock()
+			resIssues = append(resIssues, res...)
+			mu.Unlock()
+
+			return nil, nil
+		}
+	}).WithIssuesReporter(func(*linter.Context) []result.Issue {
+		return resIssues
+	}).WithLoadMode(goanalysis.LoadModeSyntax)
+}

pkg/golinters/gocyclo.go

@@ -1,3 +1,4 @@
+// nolint:dupl
 package golinters
 
 import (

pkg/lint/lintersdb/manager.go

@@ -137,6 +137,9 @@ func (m Manager) GetAllSupportedLinterConfigs() []*linter.Config {
 		linter.NewConfig(golinters.NewGocyclo()).
 			WithPresets(linter.PresetComplexity).
 			WithURL("https://github.com/alecthomas/gocyclo"),
+		linter.NewConfig(golinters.NewGocognit()).
+			WithPresets(linter.PresetComplexity).
+			WithURL("https://github.com/uudashr/gocognit"),
 		linter.NewConfig(golinters.NewTypecheck()).
 			WithLoadForGoAnalysis().
 			WithPresets(linter.PresetBugs).

test/testdata/gocognit.go

@@ -0,0 +1,23 @@
+//args: -Egocognit
+//config: linters-settings.gocognit.min-complexity=2
+package testdata
+
+func GocognitGetWords(number int) string { // ERROR "cognitive complexity 4 of func .* is high .*"
+	if number == 1 { // +1
+		return "one"
+	} else if number == 2 { // +1
+		return "a couple"
+	} else if number == 3 { // +1
+		return "a few"
+	} else { // +1
+		return "lots"
+	}
+} // total complexity = 4
+
+func GoCognitFact(n int) int { // ERROR "cognitive complexity 3 of func .* is high .*"
+	if n <= 1 { // +1
+		return 1
+	} else { // +1
+		return n + GoCognitFact(n-1) // +1
+	}
+} // total complexity = 3