[dot-imports] support allow list of packages (#939)

Add the ability to allow list of packages to be dot imported.

Add a new don-imports configuration:
* `allowedPackages`: (string) comma-separated list of allowed dot import packages

Example:

```toml
[rule.dot-imports]
  arguments = [{ allowedPackages = "github.com/onsi/ginkgo/v2,github.com/onsi/gomega" }]
```

RULES_DESCRIPTIONS.md

@@ -282,7 +282,17 @@ _Description_: Importing with `.` makes the programs much harder to understand b
 
 More information [here](https://github.com/golang/go/wiki/CodeReviewComments#import-dot)
 
-_Configuration_: N/A
+_Configuration_:
+
+* `allowedPackages`: (list of strings) comma-separated list of allowed dot import packages
+
+Example:
+
+```toml
+[rule.dot-imports]
+  arguments = [{ allowedPackages = ["github.com/onsi/ginkgo/v2","github.com/onsi/gomega"] }]
+```
+
 
 ## duplicated-imports
 

rule/dot-imports.go

@@ -1,16 +1,23 @@
 package rule
 
 import (
+	"fmt"
 	"go/ast"
+	"sync"
 
 	"github.com/mgechev/revive/lint"
 )
 
 // DotImportsRule lints given else constructs.
-type DotImportsRule struct{}
+type DotImportsRule struct {
+	sync.Mutex
+	allowedPackages allowPackages
+}
 
 // Apply applies the rule to given file.
-func (*DotImportsRule) Apply(file *lint.File, _ lint.Arguments) []lint.Failure {
+func (r *DotImportsRule) Apply(file *lint.File, arguments lint.Arguments) []lint.Failure {
+	r.configure(arguments)
+
 	var failures []lint.Failure
 
 	fileAst := file.AST
@@ -20,6 +27,7 @@ func (*DotImportsRule) Apply(file *lint.File, _ lint.Arguments) []lint.Failure {
 		onFailure: func(failure lint.Failure) {
 			failures = append(failures, failure)
 		},
+		allowPackages: r.allowedPackages,
 	}
 
 	ast.Walk(walker, fileAst)
@@ -32,15 +40,49 @@ func (*DotImportsRule) Name() string {
 	return "dot-imports"
 }
 
+func (r *DotImportsRule) configure(arguments lint.Arguments) {
+	r.Lock()
+	defer r.Unlock()
+
+	if r.allowedPackages != nil {
+		return
+	}
+
+	r.allowedPackages = make(allowPackages)
+	if len(arguments) == 0 {
+		return
+	}
+
+	args, ok := arguments[0].(map[string]any)
+	if !ok {
+		panic(fmt.Sprintf("Invalid argument to the dot-imports rule. Expecting a k,v map, got %T", arguments[0]))
+	}
+
+	if allowedPkgArg, ok := args["allowedPackages"]; ok {
+		if pkgs, ok := allowedPkgArg.([]any); ok {
+			for _, p := range pkgs {
+				if pkg, ok := p.(string); ok {
+					r.allowedPackages.add(pkg)
+				} else {
+					panic(fmt.Sprintf("Invalid argument to the dot-imports rule, string expected. Got '%v' (%T)", p, p))
+				}
+			}
+		} else {
+			panic(fmt.Sprintf("Invalid argument to the dot-imports rule, []string expected. Got '%v' (%T)", allowedPkgArg, allowedPkgArg))
+		}
+	}
+}
+
 type lintImports struct {
-	file      *lint.File
+	file          *lint.File
-	fileAst   *ast.File
+	fileAst       *ast.File
-	onFailure func(lint.Failure)
+	onFailure     func(lint.Failure)
+	allowPackages allowPackages
 }
 
 func (w lintImports) Visit(_ ast.Node) ast.Visitor {
 	for _, is := range w.fileAst.Imports {
-		if is.Name != nil && is.Name.Name == "." {
+		if is.Name != nil && is.Name.Name == "." && !w.allowPackages.isAllowedPackage(is.Path.Value) {
 			w.onFailure(lint.Failure{
 				Confidence: 1,
 				Failure:    "should not use dot imports",
@@ -51,3 +93,14 @@ func (w lintImports) Visit(_ ast.Node) ast.Visitor {
 	}
 	return nil
 }
+
+type allowPackages map[string]struct{}
+
+func (ap allowPackages) add(pkg string) {
+	ap[fmt.Sprintf(`"%s"`, pkg)] = struct{}{} // import path strings are with double quotes
+}
+
+func (ap allowPackages) isAllowedPackage(pkg string) bool {
+	_, allowed := ap[pkg]
+	return allowed
+}

test/dot_imports_test.go

@@ -0,0 +1,18 @@
+package test
+
+import (
+	"testing"
+
+	"github.com/mgechev/revive/lint"
+	"github.com/mgechev/revive/rule"
+)
+
+func TestDotImports(t *testing.T) {
+	args := []any{map[string]any{
+		"allowedPackages": []any{"errors", "context", "github.com/BurntSushi/toml"},
+	}}
+
+	testRule(t, "import-dot", &rule.DotImportsRule{}, &lint.RuleConfig{
+		Arguments: args,
+	})
+}

testdata/import-dot.go

@@ -0,0 +1,22 @@
+// Test that dot imports are flagged.
+
+package fixtures
+
+import (
+	. "context" // in allowedPackages (standard library => just the name without full path)
+	. "errors"  // in allowedPackages (standard library => just the name without full path)
+	. "fmt"     // MATCH /should not use dot imports/
+	"math/rand"
+	tmplt "text/template"
+
+	. "github.com/BurntSushi/toml" // in allowedPackages (not in the standard library)
+)
+
+var _ Stringer // from "fmt"
+var _ = New("fake error")
+var _ = Background()
+
+var _ = Position{} // check a package not in the standard library
+
+var _ = rand.Rand{}      // check non-alias package
+var _ = tmplt.Template{} // check alias package