adds [allowRegex] parameter for unused-parameter and `unused-receiv…

…er` rules (#858)

RULES_DESCRIPTIONS.md

@@ -735,13 +735,36 @@ _Configuration_: N/A
 
 _Description_: This rule warns on unused parameters. Functions or methods with unused parameters can be a symptom of an unfinished refactoring or a bug.
 
-_Configuration_: N/A
+_Configuration_: Supports arguments with single of `map[string]any` with option `allowRegex` to provide additional to `_` mask to allowed unused parameter names, for example:
+
+```toml
+[rule.unused-parameter]
+ Arguments = [ { allowRegex = "^_" } ]
+```
+
+allows any names started with `_`, not just `_` itself:
+
+```go
+func SomeFunc(_someObj *MyStruct) {} // matches rule
+```
 
 ## unused-receiver
 
 _Description_: This rule warns on unused method receivers. Methods with unused receivers can be a symptom of an unfinished refactoring or a bug.
 
-_Configuration_: N/A
+_Configuration_: Supports arguments with single of `map[string]any` with option `allowRegex` to provide additional to `_` mask to allowed unused receiver names, for example:
+
+```toml
+[rule.unused-receiver]
+ Arguments = [ { allowRegex = "^_" } ]
+```
+
+allows any names started with `_`, not just `_` itself:
+
+```go
+func (_my *MyStruct) SomeMethod() {} // matches rule
+```
+
 
 ## use-any
 

rule/unused-param.go

@@ -3,22 +3,72 @@ package rule
 import (
  "fmt"
  "go/ast"
+ "regexp"
+ "sync"
 
  "github.com/mgechev/revive/lint"
 )
 
 // UnusedParamRule lints unused params in functions.
-type UnusedParamRule struct{}
+type UnusedParamRule struct {
+ configured bool
+ // regex to check if some name is valid for unused parameter, "^_$" by default
+ allowRegex *regexp.Regexp
+ failureMsg string
+ sync.Mutex
+}
+
+func (r *UnusedParamRule) configure(args lint.Arguments) {
+ r.Lock()
+ defer r.Unlock()
+
+ if r.configured {
+ return
+ }
+ r.configured = true
+
+ // while by default args is an array, i think it's good to provide structures inside it by default, not arrays or primitives
+ // it's more compatible to JSON nature of configurations
+ var allowedRegexStr string
+ if len(args) == 0 {
+ allowedRegexStr = "^_$"
+ r.failureMsg = "parameter '%s' seems to be unused, consider removing or renaming it as _"
+ } else {
+ // Arguments = [{}]
+ options := args[0].(map[string]interface{})
+ // Arguments = [{allowedRegex="^_"}]
+
+ if allowedRegexParam, ok := options["allowRegex"]; ok {
+ allowedRegexStr, ok = allowedRegexParam.(string)
+ if !ok {
+ panic(fmt.Errorf("error configuring %s rule: allowedRegex is not string but [%T]", r.Name(), allowedRegexParam))
+ }
+ }
+ }
+ var err error
+ r.allowRegex, err = regexp.Compile(allowedRegexStr)
+ if err != nil {
+ panic(fmt.Errorf("error configuring %s rule: allowedRegex is not valid regex [%s]: %v", r.Name(), allowedRegexStr, err))
+ }
+
+ if r.failureMsg == "" {
+ r.failureMsg = "parameter '%s' seems to be unused, consider removing or renaming it to match " + r.allowRegex.String()
+ }
+}
 
 // Apply applies the rule to given file.
-func (*UnusedParamRule) Apply(file *lint.File, _ lint.Arguments) []lint.Failure {
+func (r *UnusedParamRule) Apply(file *lint.File, args lint.Arguments) []lint.Failure {
+ r.configure(args)
  var failures []lint.Failure
 
  onFailure := func(failure lint.Failure) {
  failures = append(failures, failure)
  }
-
- w := lintUnusedParamRule{onFailure: onFailure}
+ w := lintUnusedParamRule{
+ onFailure: onFailure,
+ allowRegex: r.allowRegex,
+ failureMsg: r.failureMsg,
+ }
 
  ast.Walk(w, file.AST)
 
@@ -31,7 +81,9 @@ func (*UnusedParamRule) Name() string {
 }
 
 type lintUnusedParamRule struct {
- onFailure func(lint.Failure)
+ onFailure func(lint.Failure)
+ allowRegex *regexp.Regexp
+ failureMsg string
 }
 
 func (w lintUnusedParamRule) Visit(node ast.Node) ast.Visitor {
@@ -65,12 +117,15 @@ func (w lintUnusedParamRule) Visit(node ast.Node) ast.Visitor {
 
  for _, p := range n.Type.Params.List {
  for _, n := range p.Names {
+ if w.allowRegex.FindStringIndex(n.Name) != nil {
+ continue
+ }
  if params[n.Obj] {
  w.onFailure(lint.Failure{
  Confidence: 1,
  Node: n,
  Category: "bad practice",
- Failure: fmt.Sprintf("parameter '%s' seems to be unused, consider removing or renaming it as _", n.Name),
+ Failure: fmt.Sprintf(w.failureMsg, n.Name),
  })
  }
  }

rule/unused-receiver.go

@@ -3,22 +3,72 @@ package rule
 import (
  "fmt"
  "go/ast"
+ "regexp"
+ "sync"
 
  "github.com/mgechev/revive/lint"
 )
 
 // UnusedReceiverRule lints unused params in functions.
-type UnusedReceiverRule struct{}
+type UnusedReceiverRule struct {
+ configured bool
+ // regex to check if some name is valid for unused parameter, "^_$" by default
+ allowRegex *regexp.Regexp
+ failureMsg string
+ sync.Mutex
+}
+
+func (r *UnusedReceiverRule) configure(args lint.Arguments) {
+ r.Lock()
+ defer r.Unlock()
+
+ if r.configured {
+ return
+ }
+ r.configured = true
+
+ // while by default args is an array, i think it's good to provide structures inside it by default, not arrays or primitives
+ // it's more compatible to JSON nature of configurations
+ var allowedRegexStr string
+ if len(args) == 0 {
+ allowedRegexStr = "^_$"
+ r.failureMsg = "method receiver '%s' is not referenced in method's body, consider removing or renaming it as _"
+ } else {
+ // Arguments = [{}]
+ options := args[0].(map[string]interface{})
+ // Arguments = [{allowedRegex="^_"}]
+
+ if allowedRegexParam, ok := options["allowRegex"]; ok {
+ allowedRegexStr, ok = allowedRegexParam.(string)
+ if !ok {
+ panic(fmt.Errorf("error configuring [unused-receiver] rule: allowedRegex is not string but [%T]", allowedRegexParam))
+ }
+ }
+ }
+ var err error
+ r.allowRegex, err = regexp.Compile(allowedRegexStr)
+ if err != nil {
+ panic(fmt.Errorf("error configuring [unused-receiver] rule: allowedRegex is not valid regex [%s]: %v", allowedRegexStr, err))
+ }
+ if r.failureMsg == "" {
+ r.failureMsg = "method receiver '%s' is not referenced in method's body, consider removing or renaming it to match " + r.allowRegex.String()
+ }
+}
 
 // Apply applies the rule to given file.
-func (*UnusedReceiverRule) Apply(file *lint.File, _ lint.Arguments) []lint.Failure {
+func (r *UnusedReceiverRule) Apply(file *lint.File, args lint.Arguments) []lint.Failure {
+ r.configure(args)
  var failures []lint.Failure
 
  onFailure := func(failure lint.Failure) {
  failures = append(failures, failure)
  }
 
- w := lintUnusedReceiverRule{onFailure: onFailure}
+ w := lintUnusedReceiverRule{
+ onFailure: onFailure,
+ allowRegex: r.allowRegex,
+ failureMsg: r.failureMsg,
+ }
 
  ast.Walk(w, file.AST)
 
@@ -31,7 +81,9 @@ func (*UnusedReceiverRule) Name() string {
 }
 
 type lintUnusedReceiverRule struct {
- onFailure func(lint.Failure)
+ onFailure func(lint.Failure)
+ allowRegex *regexp.Regexp
+ failureMsg string
 }
 
 func (w lintUnusedReceiverRule) Visit(node ast.Node) ast.Visitor {
@@ -51,6 +103,10 @@ func (w lintUnusedReceiverRule) Visit(node ast.Node) ast.Visitor {
  return nil // the receiver is already named _
  }
 
+ if w.allowRegex != nil && w.allowRegex.FindStringIndex(recID.Name) != nil {
+ return nil
+ }
+
  // inspect the func body looking for references to the receiver id
  fselect := func(n ast.Node) bool {
  ident, isAnID := n.(*ast.Ident)
@@ -67,7 +123,7 @@ func (w lintUnusedReceiverRule) Visit(node ast.Node) ast.Visitor {
  Confidence: 1,
  Node: recID,
  Category: "bad practice",
- Failure: fmt.Sprintf("method receiver '%s' is not referenced in method's body, consider removing or renaming it as _", recID.Name),
+ Failure: fmt.Sprintf(w.failureMsg, recID.Name),
  })
 
  return nil // full method body already inspected

test/unused-param_test.go

@@ -3,11 +3,15 @@ package test
 import (
  "testing"
 
+ "github.com/mgechev/revive/lint"
  "github.com/mgechev/revive/rule"
 )
 
 func TestUnusedParam(t *testing.T) {
  testRule(t, "unused-param", &rule.UnusedParamRule{})
+ testRule(t, "unused-param-custom-regex", &rule.UnusedParamRule{}, &lint.RuleConfig{Arguments: []interface{}{
+ map[string]interface{}{"allowRegex": "^xxx"},
+ }})
 }
 
 func BenchmarkUnusedParam(b *testing.B) {

test/unused-receiver_test.go

@@ -3,9 +3,13 @@ package test
 import (
  "testing"
 
+ "github.com/mgechev/revive/lint"
  "github.com/mgechev/revive/rule"
 )
 
 func TestUnusedReceiver(t *testing.T) {
  testRule(t, "unused-receiver", &rule.UnusedReceiverRule{})
+ testRule(t, "unused-receiver-custom-regex", &rule.UnusedReceiverRule{}, &lint.RuleConfig{Arguments: []interface{}{
+ map[string]interface{}{"allowRegex": "^xxx"},
+ }})
 }

testdata/unused-param-custom-regex.go

@@ -0,0 +1,12 @@
+package fixtures
+
+// all will ok with xxxParam if Arguments = [{allowRegex="^xxx"}]
+
+func f0(xxxParam int) {}
+
+// still works with _
+
+func f1(_ int) {}
+
+func f2(yyyParam int) { // MATCH /parameter 'yyyParam' seems to be unused, consider removing or renaming it to match ^xxx/
+}

testdata/unused-receiver-custom-regex.go

@@ -0,0 +1,12 @@
+package fixtures
+
+// all will ok with xxxParam if Arguments = [{allowRegex="^xxx"}]
+
+func (xxxParam *SomeObj) f0() {}
+
+// still works with _
+
+func (_ *SomeObj) f1() {}
+
+func (yyyParam *SomeObj) f2() { // MATCH /method receiver 'yyyParam' is not referenced in method's body, consider removing or renaming it to match ^xxx/
+}