Adds new rule empty-block (#14)

* Adds rule superfluous-else (an extension of indent-error-flow)

* initial (non functional) version

* empty-block working version

* adds tests for empty-block rule

* Adds empty-block to the rules table

* code clean-up

README.md

@@ -196,6 +196,7 @@ List of all available rules. The rules ported from `golint` are left unchanged a
 | `cyclomatic`          |  int   | Sets restriction for maximum Cyclomatic complexity.              |    no    |  no   |
 | `max-public-structs`  |  int   | The maximum number of public structs in a file.                  |    no    |  no   |
 | `file-header`         | string | Header which each file should have.                              |    no    |  no   |
+| `empty-block`         |  n/a   | Warns on empty code blocks                                       |    no    |  no   |
 | `superfluous-else`    |  n/a   | Prevents redundant else statements (extends `indent-error-flow`) |    no    |  no   |
 
 ## Available Formatters

config.go

@@ -47,6 +47,7 @@ var allRules = append([]lint.Rule{
 	&rule.ArgumentsLimitRule{},
 	&rule.CyclomaticRule{},
 	&rule.FileHeaderRule{},
+	&rule.EmptyBlockRule{},
 }, defaultRules...)
 
 var allFormatters = []lint.Formatter{

fixtures/empty-block.go

@@ -0,0 +1,33 @@
+// Test of empty-blocks.
+
+package fixtures
+
+func f(x int) bool { // MATCH /this block is empty, you can remove it/
+
+}
+
+func g(f func() bool) string {
+	{ // MATCH /this block is empty, you can remove it/
+	}
+
+	if ok := f(); ok { // MATCH /this block is empty, you can remove it/
+		// only a comment
+	} else {
+		println("it's NOT empty!")
+	}
+
+	if ok := f(); ok {
+		println("it's NOT empty!")
+	} else { // MATCH /this block is empty, you can remove it/
+
+	}
+
+	for i := 0; i < 10; i++ { // MATCH /this block is empty, you can remove it/
+
+	}
+
+	for { // MATCH /this block is empty, you can remove it/
+
+	}
+
+}

rule/empty-block.go

@@ -0,0 +1,52 @@
+package rule
+
+import (
+	"go/ast"
+
+	"github.com/mgechev/revive/lint"
+)
+
+// EmptyBlockRule lints given else constructs.
+type EmptyBlockRule struct{}
+
+// Apply applies the rule to given file.
+func (r *EmptyBlockRule) Apply(file *lint.File, arguments lint.Arguments) []lint.Failure {
+	var failures []lint.Failure
+
+	onFailure := func(failure lint.Failure) {
+		failures = append(failures, failure)
+	}
+
+	w := lintEmptyBlock{make(map[*ast.IfStmt]bool), onFailure}
+	ast.Walk(w, file.AST)
+	return failures
+}
+
+// Name returns the rule name.
+func (r *EmptyBlockRule) Name() string {
+	return "empty-block"
+}
+
+type lintEmptyBlock struct {
+	ignore    map[*ast.IfStmt]bool
+	onFailure func(lint.Failure)
+}
+
+func (w lintEmptyBlock) Visit(node ast.Node) ast.Visitor {
+	block, ok := node.(*ast.BlockStmt)
+	if !ok {
+		return w
+	}
+
+	if len(block.List) == 0 {
+		w.onFailure(lint.Failure{
+			Confidence: 1,
+			Node:       block,
+			Category:   "logic",
+			URL:        "#empty-block",
+			Failure:    "this block is empty, you can remove it",
+		})
+	}
+
+	return w
+}

test/empty-block_test.go

@@ -0,0 +1,12 @@
+package test
+
+import (
+	"testing"
+
+	"github.com/mgechev/revive/rule"
+)
+
+// TestEmptyBlock rule.
+func TestEmptyBlock(t *testing.T) {
+	testRule(t, "empty-block", &rule.EmptyBlockRule{})
+}

untyped.toml

@@ -12,3 +12,4 @@
 [rule.range]
 [rule.receiver-naming]
 [rule.indent-error-flow]
+[rule.empty-block]