Add rules

defaultrule/blank-imports.go

@@ -0,0 +1,74 @@
+package defaultrule
+
+import (
+	"go/ast"
+
+	"github.com/mgechev/revive/file"
+	"github.com/mgechev/revive/rule"
+)
+
+// BlankImportsRule lints given else constructs.
+type BlankImportsRule struct{}
+
+// Apply applies the rule to given file.
+func (r *BlankImportsRule) Apply(file *file.File, arguments rule.Arguments) []rule.Failure {
+	var failures []rule.Failure
+
+	fileAst := file.GetAST()
+	walker := lintBlankImports{
+		file:    file,
+		fileAst: fileAst,
+		onFailure: func(failure rule.Failure) {
+			failures = append(failures, failure)
+		},
+	}
+
+	ast.Walk(walker, fileAst)
+
+	return failures
+}
+
+// Name returns the rule name.
+func (r *BlankImportsRule) Name() string {
+	return "argument-limit"
+}
+
+type lintBlankImports struct {
+	fileAst   *ast.File
+	file      *file.File
+	onFailure func(rule.Failure)
+}
+
+func (w lintBlankImports) Visit(n ast.Node) ast.Visitor {
+	// In package main and in tests, we don't complain about blank imports.
+	if w.fileAst.Name.Name == "main" || isTest(w.file) {
+		return nil
+	}
+
+	// The first element of each contiguous group of blank imports should have
+	// an explanatory comment of some kind.
+	for i, imp := range w.fileAst.Imports {
+		pos := w.file.ToPosition(imp.Pos())
+
+		if !isBlank(imp.Name) {
+			continue // Ignore non-blank imports.
+		}
+		if i > 0 {
+			prev := w.fileAst.Imports[i-1]
+			prevPos := w.file.ToPosition(prev.Pos())
+			if isBlank(prev.Name) && prevPos.Line+1 == pos.Line {
+				continue // A subsequent blank in a group.
+			}
+		}
+
+		// This is the first blank import of a group.
+		if imp.Doc == nil && imp.Comment == nil {
+			w.onFailure(rule.Failure{
+				Node:       imp,
+				Failure:    "a blank import should be only in a main or test package, or have a comment justifying it",
+				Confidence: 1,
+			})
+		}
+	}
+	return nil
+}

defaultrule/blank-imports_test.go

@@ -0,0 +1,46 @@
+package defaultrule
+
+import (
+	"testing"
+
+	"github.com/mgechev/revive/rule"
+	"github.com/mgechev/revive/testutil"
+)
+
+func TestBlankImports(t *testing.T) {
+	t.Parallel()
+
+	program := `
+	package foo
+	
+	import (
+		"fmt"
+	
+		/* MATCH /blank import/ */ [@f1]_ "os"[/@f1]
+	
+		/* MATCH /blank import/ */ [@f2]_ "net/http"[/@f2]
+		_ "path"
+	)
+	     
+	`
+	testutil.AssertFailures(t, program, &BlankImportsRule{}, rule.Arguments{})
+}
+
+func TestBlankImports_ShouldSkipMain(t *testing.T) {
+	t.Parallel()
+
+	program := `
+	package main
+	
+	import (
+		"fmt"
+	
+		/* MATCH /blank import/ */ _ "os"
+	
+		/* MATCH /blank import/ */ _ "net/http"
+		_ "path"
+	)
+	     
+	`
+	testutil.AssertSuccess(t, program, &BlankImportsRule{}, rule.Arguments{})
+}

defaultrule/utils.go

@@ -1,13 +1,18 @@
 package defaultrule
 
 import (
+	"go/ast"
 	"strings"
 
 	"github.com/mgechev/revive/file"
 )
 
+const styleGuideBase = "https://golang.org/wiki/CodeReviewComments"
+
+// isBlank returns whether id is the blank identifier "_".
+// If id == nil, the answer is false.
+func isBlank(id *ast.Ident) bool { return id != nil && id.Name == "_" }
+
 func isTest(f *file.File) bool {
 	return strings.HasSuffix(f.Name, "_test.go")
 }
-
-const styleGuideBase = "https://golang.org/wiki/CodeReviewComments"