adds blacklist to unhandled-error (#128)

* adds blacklist for unhandled-error

* uses ignoreList in place of blackList

rule/unhandled-error.go

@@ -11,12 +11,26 @@ import (
 // UnhandledErrorRule lints given else constructs.
 type UnhandledErrorRule struct{}
 
+type ignoreListType map[string]struct{}
+
 // Apply applies the rule to given file.
-func (r *UnhandledErrorRule) Apply(file *lint.File, _ lint.Arguments) []lint.Failure {
+func (r *UnhandledErrorRule) Apply(file *lint.File, args lint.Arguments) []lint.Failure {
 	var failures []lint.Failure
 
+	ignoreList := make(ignoreListType, len(args))
+
+	for _, arg := range args {
+		argStr, ok := arg.(string)
+		if !ok {
+			panic(fmt.Sprintf("Invalid argument to the unhandled-error rule. Expecting a string, got %T", arg))
+		}
+
+		ignoreList[argStr] = struct{}{}
+	}
+
 	walker := &lintUnhandledErrors{
-		pkg: file.Pkg,
+		ignoreList: ignoreList,
+		pkg:        file.Pkg,
 		onFailure: func(failure lint.Failure) {
 			failures = append(failures, failure)
 		},
@@ -34,8 +48,9 @@ func (r *UnhandledErrorRule) Name() string {
 }
 
 type lintUnhandledErrors struct {
-	pkg       *lint.Package
-	onFailure func(lint.Failure)
+	ignoreList ignoreListType
+	pkg        *lint.Package
+	onFailure  func(lint.Failure)
 }
 
 // Visit looks for statements that are function calls.
@@ -75,11 +90,16 @@ func (w *lintUnhandledErrors) Visit(node ast.Node) ast.Visitor {
 }
 
 func (w *lintUnhandledErrors) addFailure(n *ast.CallExpr) {
+	funcName := gofmt(n.Fun)
+	if _, mustIgnore := w.ignoreList[funcName]; mustIgnore {
+		return
+	}
+
 	w.onFailure(lint.Failure{
 		Category:   "bad practice",
 		Confidence: 1,
 		Node:       n,
-		Failure:    fmt.Sprintf("Unhandled error in call to function %v", gofmt(n.Fun)),
+		Failure:    fmt.Sprintf("Unhandled error in call to function %v", funcName),
 	})
 }