Add errchkjson linter (#2362)

.golangci.example.yml

@@ -137,6 +137,24 @@ linters-settings:
       - io.Copy(*bytes.Buffer)
       - io.Copy(os.Stdout)
 
+  errchkjson:
+    # with check-error-free-encoding set to true, errchkjson does warn about errors
+    # from json encoding functions that are safe to be ignored,
+    # because they are not possible to happen (default false)
+    #
+    # if check-error-free-encoding is set to true and errcheck linter is enabled,
+    # it is recommended to add the following exceptions to prevent from false positives:
+    #
+    #     linters-settings:
+    #       errcheck:
+    #         exclude-functions:
+    #           - encoding/json.Marshal
+    #           - encoding/json.MarshalIndent
+    #           - (*encoding/json.Encoder).Encode
+    check-error-free-encoding: false
+    # if report-no-exported is true, encoding a struct without exported fields is reported as issue (default false)
+    report-no-exported: false
+
   errorlint:
     # Check whether fmt.Errorf uses the %w verb for formatting errors. See the readme for caveats
     errorf: true

go.mod

@@ -16,6 +16,7 @@ require (
 	github.com/blizzy78/varnamelen v0.5.0
 	github.com/bombsimon/wsl/v3 v3.3.0
 	github.com/breml/bidichk v0.2.1
+	github.com/breml/errchkjson v0.2.0
 	github.com/butuzov/ireturn v0.1.1
 	github.com/charithe/durationcheck v0.0.9
 	github.com/daixiang0/gci v0.2.9

pkg/config/linters_settings.go

@@ -89,6 +89,7 @@ type LintersSettings struct {
 	Dogsled          DogsledSettings
 	Dupl             DuplSettings
 	Errcheck         ErrcheckSettings
+	ErrChkJSON       ErrChkJSONSettings
 	ErrorLint        ErrorLintSettings
 	Exhaustive       ExhaustiveSettings
 	ExhaustiveStruct ExhaustiveStructSettings
@@ -165,6 +166,11 @@ type Cyclop struct {
 	SkipTests      bool    `mapstructure:"skip-tests"`
 }
 
+type ErrChkJSONSettings struct {
+	CheckErrorFreeEncoding bool `mapstructure:"check-error-free-encoding"`
+	ReportNoExported       bool `mapstructure:"report-no-exported"`
+}
+
 type DepGuardSettings struct {
 	ListType                 string `mapstructure:"list-type"`
 	Packages                 []string

pkg/golinters/errchkjson.go

@@ -0,0 +1,33 @@
+package golinters
+
+import (
+	"github.com/breml/errchkjson"
+	"golang.org/x/tools/go/analysis"
+
+	"github.com/golangci/golangci-lint/pkg/config"
+	"github.com/golangci/golangci-lint/pkg/golinters/goanalysis"
+)
+
+func NewErrChkJSONFuncName(cfg *config.ErrChkJSONSettings) *goanalysis.Linter {
+	a := errchkjson.NewAnalyzer()
+
+	cfgMap := map[string]map[string]interface{}{}
+	cfgMap[a.Name] = map[string]interface{}{
+		"omit-safe": true,
+	}
+	if cfg != nil {
+		cfgMap[a.Name] = map[string]interface{}{
+			"omit-safe":          !cfg.CheckErrorFreeEncoding,
+			"report-no-exported": cfg.ReportNoExported,
+		}
+	}
+
+	return goanalysis.NewLinter(
+		"errchkjson",
+		"Checks types passed to the json encoding functions. "+
+			"Reports unsupported types and optionally reports occations, "+
+			"where the check for the returned error can be omitted.",
+		[]*analysis.Analyzer{a},
+		cfgMap,
+	).WithLoadMode(goanalysis.LoadModeTypesInfo)
+}

pkg/lint/lintersdb/manager.go

@@ -102,6 +102,7 @@ func enableLinterConfigs(lcs []*linter.Config, isEnabled func(lc *linter.Config)
 func (m Manager) GetAllSupportedLinterConfigs() []*linter.Config {
 	var bidichkCfg *config.BiDiChkSettings
 	var cyclopCfg *config.Cyclop
+	var errchkjsonCfg *config.ErrChkJSONSettings
 	var errorlintCfg *config.ErrorLintSettings
 	var exhaustiveCfg *config.ExhaustiveSettings
 	var exhaustiveStructCfg *config.ExhaustiveStructSettings
@@ -129,6 +130,7 @@ func (m Manager) GetAllSupportedLinterConfigs() []*linter.Config {
 	if m.cfg != nil {
 		bidichkCfg = &m.cfg.LintersSettings.BiDiChk
 		cyclopCfg = &m.cfg.LintersSettings.Cyclop
+		errchkjsonCfg = &m.cfg.LintersSettings.ErrChkJSON
 		errorlintCfg = &m.cfg.LintersSettings.ErrorLint
 		exhaustiveCfg = &m.cfg.LintersSettings.Exhaustive
 		exhaustiveStructCfg = &m.cfg.LintersSettings.ExhaustiveStruct
@@ -548,6 +550,11 @@ func (m Manager) GetAllSupportedLinterConfigs() []*linter.Config {
 			WithSince("1.43.0").
 			WithPresets(linter.PresetBugs).
 			WithURL("https://github.com/breml/bidichk"),
+		linter.NewConfig(golinters.NewErrChkJSONFuncName(errchkjsonCfg)).
+			WithSince("1.44.0").
+			WithPresets(linter.PresetBugs).
+			WithLoadForGoAnalysis().
+			WithURL("https://github.com/breml/errchkjson"),
 
 		// nolintlint must be last because it looks at the results of all the previous linters for unused nolint directives
 		linter.NewConfig(golinters.NewNoLintLint()).

test/testdata/configs/errchkjson.yml

@@ -0,0 +1,2 @@
+issues:
+  max-issues-per-linter: 100

test/testdata/configs/errchkjson_check_error_free_encoding.yml

@@ -0,0 +1,5 @@
+issues:
+  max-issues-per-linter: 100
+linters-settings:
+  errchkjson:
+    check-error-free-encoding: true

test/testdata/configs/errchkjson_no_exported.yml

@@ -0,0 +1,3 @@
+linters-settings:
+  errchkjson:
+    report-no-exported: true