golangci: support running errcheck with all its options

Follow golangci/golangci-lint#223, I've added the option to run the errcheck
linter with all its options. Also, kept backwards compatibility in order to
do the transition in the golangci-lint package gradually.

Author: a8m

golangci/golangci.go

@@ -7,15 +7,59 @@ import (
 	"golang.org/x/tools/go/loader"
 )
 
+var dotStar = regexp.MustCompile(".*")
+
 type Issue errcheck.UncheckedError
 
 func Run(program *loader.Program, checkBlank, checkAsserts bool) ([]Issue, error) {
+	return RunWithConfig(program, &Config{
+		Blank:   checkBlank,
+		Asserts: checkAsserts,
+	})
+}
+
+// Config is a copy of the `errcheck.Checker` with exported `Exclude` field.
+type Config struct {
+	// ignore is a map of package names to regular expressions. Identifiers from a package are
+	// checked against its regular expressions and if any of the expressions match the call
+	// is not checked.
+	Ignore map[string]*regexp.Regexp
+
+	// If blank is true then assignments to the blank identifier are also considered to be
+	// ignored errors.
+	Blank bool
+
+	// If asserts is true then ignored type assertion results are also checked
+	Asserts bool
+
+	// build tags
+	Tags []string
+
+	Verbose bool
+
+	// If true, checking of _test.go files is disabled
+	WithoutTests bool
+
+	// Excluded functions.
+	Exclude map[string]bool
+}
+
+// RunWithConfig runs the `errchecker` linter with all its options.
+func RunWithConfig(program *loader.Program, c *Config) ([]Issue, error) {
 	checker := errcheck.NewChecker()
-	checker.Blank = checkBlank
-	checker.Asserts = checkAsserts
+	checker.Tags = c.Tags
+	checker.Blank = c.Blank
+	checker.Asserts = c.Asserts
+	checker.Verbose = c.Verbose
+	checker.WithoutTests = c.WithoutTests
+
+	checker.SetExclude(c.Exclude)
 
 	checker.Ignore = map[string]*regexp.Regexp{
-		"fmt": regexp.MustCompile(".*"),
+		"fmt": dotStar,
+	}
+	for pkg, re := range c.Ignore {
+		checker.Ignore[pkg] = re
 	}
 
 	if err := checker.CheckProgram(program); err != nil {