errcheck: add an option to remove default exclusions (golangci#2607)

Author: ldez

.golangci.example.yml

@@ -204,6 +204,11 @@ linters-settings:
     # see https://github.com/kisielk/errcheck#the-deprecated-method for details
     ignore: fmt:.*,io/ioutil:^Read.*
 
+    # To disable the errcheck built-in exclude list.
+    # See `-excludeonly` option in https://github.com/kisielk/errcheck#excluding-functions for details.
+    # Default: false
+    disable-default-exclusions: true
+
     # DEPRECATED use exclude-functions instead.
     #
     # Path to a file containing a list of functions to exclude from checking.

pkg/config/linters_settings.go

@@ -215,10 +215,11 @@ type DuplSettings struct {
 }
 
 type ErrcheckSettings struct {
-	CheckTypeAssertions bool     `mapstructure:"check-type-assertions"`
-	CheckAssignToBlank  bool     `mapstructure:"check-blank"`
-	Ignore              string   `mapstructure:"ignore"`
-	ExcludeFunctions    []string `mapstructure:"exclude-functions"`
+	DisableDefaultExclusions bool     `mapstructure:"disable-default-exclusions"`
+	CheckTypeAssertions      bool     `mapstructure:"check-type-assertions"`
+	CheckAssignToBlank       bool     `mapstructure:"check-blank"`
+	Ignore                   string   `mapstructure:"ignore"`
+	ExcludeFunctions         []string `mapstructure:"exclude-functions"`
 
 	// Deprecated: use ExcludeFunctions instead
 	Exclude string `mapstructure:"exclude"`

pkg/golinters/errcheck.go

@@ -140,10 +140,13 @@ func getChecker(errCfg *config.ErrcheckSettings) (*errcheck.Checker, error) {
 			BlankAssignments:       !errCfg.CheckAssignToBlank,
 			TypeAssertions:         !errCfg.CheckTypeAssertions,
 			SymbolRegexpsByPackage: map[string]*regexp.Regexp{},
-			Symbols:                append([]string{}, errcheck.DefaultExcludedSymbols...),
 		},
 	}
 
+	if !errCfg.DisableDefaultExclusions {
+		checker.Exclusions.Symbols = append(checker.Exclusions.Symbols, errcheck.DefaultExcludedSymbols...)
+	}
+
 	for pkg, re := range ignoreConfig {
 		checker.Exclusions.SymbolRegexpsByPackage[pkg] = re
 	}