feat: configuration file of rules (#91)

fixes #82

This PR adds a few things:
- A severity of issues and rules (info, warning and error)
- Parsing of a configuration file to add new rules, update severity of
rules or remove default rules
- Appropriated documentation for configuration file and the new system
when creating a rule
- A flag to init an empty configuration file

This refactor a lot of code so I am really open to any criticism as I
don't believe it is the best way to implement these features.
I also added a data field in the rules to be used later on.

README.md

@@ -62,6 +62,34 @@ To check the current directory, run:
 tlin .
 ```
 
+## Configuration
+
+tlin supports a configuration file (`.tlin.yaml`) to customize its behavior. You can generate a default configuration file by running:
+
+```bash
+tlin -init
+```
+
+This command will create a `.tlin.yaml` file in the current directory with the following content:
+
+```yaml
+# .tlin.yaml
+name: tlin
+rules:
+```
+
+You can customize the configuration file to enable or disable specific lint rules, set cyclomatic complexity thresholds, and more.
+
+```yaml	
+# .tlin.yaml
+name: tlin
+rules:
+  useless-break:
+    severity: WARNING
+  deprecated-function:
+    severity: OFF
+```
+
 ## Adding Gno-Specific Lint Rules
 
 Our linter allows addition of custom lint rules beyond the default golangci-lint rules. To add a new lint rule, follow these steps:
@@ -91,7 +119,7 @@ Our linter allows addition of custom lint rules beyond the default golangci-lint
    }
    ```
 
-   b. Register your new rule in the `registerDefaultRules` method of the `Engine` struct in `internal/engine.go`:
+   b. Register your new rule in the `registerAllRules` and maybe `registerDefaultRules` method of the `Engine` struct in `internal/engine.go`:
 
    ```go
    func (e *Engine) registerDefaultRules() {
@@ -103,6 +131,16 @@ Our linter allows addition of custom lint rules beyond the default golangci-lint
    }
    ```
 
+   ```go
+   func (e *Engine) registerAllRules() {
+       e.rules = append(e.rules,
+           &GolangciLintRule{},
+           // ...
+           &NewRule{}, // Add your new rule here
+       )
+   }
+   ```
+
 5. (Optional) If your rule requires special formatting, create a new formatter in the `formatter` package:
 
    a. Create a new file (e.g., `formatter/new_rule.go`).
@@ -157,6 +195,8 @@ tlin supports several flags to customize its behavior:
 - `-confidence <float>`: Set confidence threshold for auto-fixing (0.0 to 1.0, default: 0.75)
 - `-o <path>`: Write output to a file instead of stdout
 - `-json-output`: Output results in JSON format
+- `-init`: Initialize a new tlin configuration file in the current directory
+- `-c <path>`: Specify a custom configuration file
 
 ## Contributing
 

cmd/tlin/main.go

@@ -20,6 +20,7 @@ import (
 	tt "github.com/gnolang/tlin/internal/types"
 	"github.com/gnolang/tlin/lint"
 	"go.uber.org/zap"
+	"gopkg.in/yaml.v3"
 )
 
 const (
@@ -31,6 +32,7 @@ type Config struct {
 	IgnoreRules          string
 	FuncName             string
 	Output               string
+	ConfigurationPath    string
 	Paths                []string
 	Timeout              time.Duration
 	CyclomaticThreshold  int
@@ -40,6 +42,7 @@ type Config struct {
 	AutoFix              bool
 	DryRun               bool
 	JsonOutput           bool
+	Init                 bool
 }
 
 func main() {
@@ -51,7 +54,16 @@ func main() {
 	ctx, cancel := context.WithTimeout(context.Background(), config.Timeout)
 	defer cancel()
 
-	engine, err := lint.New(".", nil)
+	if config.Init {
+		err := initConfigurationFile(config.ConfigurationPath)
+		if err != nil {
+			logger.Error("Error initializing config file", zap.Error(err))
+			os.Exit(1)
+		}
+		return
+	}
+
+	engine, err := lint.New(".", nil, config.ConfigurationPath)
 	if err != nil {
 		logger.Fatal("Failed to initialize lint engine", zap.Error(err))
 	}
@@ -97,6 +109,8 @@ func parseFlags(args []string) Config {
 	flagSet.BoolVar(&config.DryRun, "dry-run", false, "Run in dry-run mode (show fixes without applying them)")
 	flagSet.BoolVar(&config.JsonOutput, "json", false, "Output issues in JSON format")
 	flagSet.Float64Var(&config.ConfidenceThreshold, "confidence", defaultConfidenceThreshold, "Confidence threshold for auto-fixing (0.0 to 1.0)")
+	flagSet.BoolVar(&config.Init, "init", false, "Initialize a new linter configuration file")
+	flagSet.StringVar(&config.ConfigurationPath, "c", ".tlin.yaml", "Path to the linter configuration file")
 
 	err := flagSet.Parse(args)
 	if err != nil {
@@ -105,7 +119,7 @@ func parseFlags(args []string) Config {
 	}
 
 	config.Paths = flagSet.Args()
-	if len(config.Paths) == 0 {
+	if !config.Init && len(config.Paths) == 0 {
 		fmt.Println("error: Please provide file or directory paths")
 		os.Exit(1)
 	}
@@ -212,6 +226,36 @@ func runAutoFix(ctx context.Context, logger *zap.Logger, engine lint.LintEngine,
 	}
 }
 
+func initConfigurationFile(configurationPath string) error {
+	if configurationPath == "" {
+		configurationPath = ".tlin.yaml"
+	}
+
+	// Create a yaml file with rules
+	config := lint.Config{
+		Name:  "tlin",
+		Rules: map[string]tt.ConfigRule{},
+	}
+	d, err := yaml.Marshal(config)
+	if err != nil {
+		return err
+	}
+
+	f, err := os.Create(configurationPath)
+	if err != nil {
+		return err
+	}
+
+	defer f.Close()
+
+	_, err = f.Write(d)
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
 func printIssues(logger *zap.Logger, issues []tt.Issue, isJson bool, jsonOutput string) {
 	issuesByFile := make(map[string][]tt.Issue)
 	for _, issue := range issues {

cmd/tlin/main_test.go

@@ -14,31 +14,33 @@ import (
 	"testing"
 	"time"
 
-	"github.com/gnolang/tlin/internal/types"
+	tt "github.com/gnolang/tlin/internal/types"
+	"github.com/gnolang/tlin/lint"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/mock"
 	"go.uber.org/zap"
+	"gopkg.in/yaml.v3"
 )
 
 type mockLintEngine struct {
 	mock.Mock
 }
 
-func (m *mockLintEngine) Run(filePath string) ([]types.Issue, error) {
+func (m *mockLintEngine) Run(filePath string) ([]tt.Issue, error) {
 	args := m.Called(filePath)
-	return args.Get(0).([]types.Issue), args.Error(1)
+	return args.Get(0).([]tt.Issue), args.Error(1)
 }
 
-func (m *mockLintEngine) RunSource(source []byte) ([]types.Issue, error) {
+func (m *mockLintEngine) RunSource(source []byte) ([]tt.Issue, error) {
 	args := m.Called(source)
-	return args.Get(0).([]types.Issue), args.Error(1)
+	return args.Get(0).([]tt.Issue), args.Error(1)
 }
 
 func (m *mockLintEngine) IgnoreRule(rule string) {
 	m.Called(rule)
 }
 
-func setupMockEngine(expectedIssues []types.Issue, filePath string) *mockLintEngine {
+func setupMockEngine(expectedIssues []tt.Issue, filePath string) *mockLintEngine {
 	mockEngine := new(mockLintEngine)
 	mockEngine.On("Run", filePath).Return(expectedIssues, nil)
 	return mockEngine
@@ -58,6 +60,7 @@ func TestParseFlags(t *testing.T) {
 				AutoFix:             true,
 				Paths:               []string{"file.go"},
 				ConfidenceThreshold: defaultConfidenceThreshold,
+				ConfigurationPath:   ".tlin.yaml",
 			},
 		},
 		{
@@ -68,6 +71,7 @@ func TestParseFlags(t *testing.T) {
 				DryRun:              true,
 				Paths:               []string{"file.go"},
 				ConfidenceThreshold: defaultConfidenceThreshold,
+				ConfigurationPath:   ".tlin.yaml",
 			},
 		},
 		{
@@ -77,6 +81,7 @@ func TestParseFlags(t *testing.T) {
 				AutoFix:             true,
 				Paths:               []string{"file.go"},
 				ConfidenceThreshold: 0.9,
+				ConfigurationPath:   ".tlin.yaml",
 			},
 		},
 		{
@@ -86,6 +91,7 @@ func TestParseFlags(t *testing.T) {
 				Paths:               []string{"file.go"},
 				JsonOutput:          true,
 				ConfidenceThreshold: defaultConfidenceThreshold,
+				ConfigurationPath:   ".tlin.yaml",
 			},
 		},
 		{
@@ -95,6 +101,16 @@ func TestParseFlags(t *testing.T) {
 				Paths:               []string{"file.go"},
 				Output:              "output.svg",
 				ConfidenceThreshold: defaultConfidenceThreshold,
+				ConfigurationPath:   ".tlin.yaml",
+			},
+		},
+		{
+			name: "Configuration File",
+			args: []string{"-c", "config.yaml", "file.go"},
+			expected: Config{
+				Paths:               []string{"file.go"},
+				ConfidenceThreshold: defaultConfidenceThreshold,
+				ConfigurationPath:   "config.yaml",
 			},
 		},
 	}
@@ -111,6 +127,7 @@ func TestParseFlags(t *testing.T) {
 			assert.Equal(t, tt.expected.Paths, config.Paths)
 			assert.Equal(t, tt.expected.JsonOutput, config.JsonOutput)
 			assert.Equal(t, tt.expected.Output, config.Output)
+			assert.Equal(t, tt.expected.ConfigurationPath, config.ConfigurationPath)
 		})
 	}
 }
@@ -136,6 +153,33 @@ func TestRunWithTimeout(t *testing.T) {
 	}
 }
 
+func TestInitConfigurationFile(t *testing.T) {
+	t.Parallel()
+	tempDir, err := os.MkdirTemp("", "init-test")
+	assert.NoError(t, err)
+	defer os.RemoveAll(tempDir)
+
+	configPath := filepath.Join(tempDir, ".tlin.yaml")
+
+	err = initConfigurationFile(configPath)
+	assert.NoError(t, err)
+
+	_, err = os.Stat(configPath)
+	assert.NoError(t, err)
+
+	content, err := os.ReadFile(configPath)
+	assert.NoError(t, err)
+
+	expectedConfig := lint.Config{
+		Name:  "tlin",
+		Rules: map[string]tt.ConfigRule{},
+	}
+	config := &lint.Config{}
+	yaml.Unmarshal(content, config)
+
+	assert.Equal(t, expectedConfig, *config)
+}
+
 func TestRunCFGAnalysis(t *testing.T) {
 	t.Parallel()
 	logger, _ := zap.NewProduction()
@@ -208,7 +252,7 @@ func TestRunAutoFix(t *testing.T) {
 	err = os.WriteFile(testFile, []byte(sliceRangeIssueExample), 0o644)
 	assert.NoError(t, err)
 
-	expectedIssues := []types.Issue{
+	expectedIssues := []tt.Issue{
 		{
 			Rule:       "simplify-slice-range",
 			Filename:   testFile,
@@ -267,7 +311,7 @@ func TestRunJsonOutput(t *testing.T) {
 			content, err := os.ReadFile(jsonOutput)
 			assert.NoError(t, err)
 
-			var actualContent map[string][]types.Issue
+			var actualContent map[string][]tt.Issue
 			err = json.Unmarshal(content, &actualContent)
 			assert.NoError(t, err)
 
@@ -284,6 +328,7 @@ func TestRunJsonOutput(t *testing.T) {
 				assert.Equal(t, 5, issue.Start.Column)
 				assert.Equal(t, 5, issue.End.Line)
 				assert.Equal(t, 24, issue.End.Column)
+				assert.Equal(t, tt.SeverityError, issue.Severity)
 			}
 
 			return
@@ -302,7 +347,7 @@ func TestRunJsonOutput(t *testing.T) {
 	err = os.WriteFile(testFile, []byte(sliceRangeIssueExample), 0o644)
 	assert.NoError(t, err)
 
-	expectedIssues := []types.Issue{
+	expectedIssues := []tt.Issue{
 		{
 			Rule:       "simplify-slice-range",
 			Filename:   testFile,

formatter/builder.go

@@ -120,22 +120,15 @@ func NewIssueFormatterBuilder(issue tt.Issue, snippet *internal.SourceCode) *Iss
 	}
 }
 
-// headerType represents the type of header to be added to the formatted issue.
-// The header can be either a warning or an error.
-type headerType int
-
-const (
-	warningHeader headerType = iota
-	errorHeader
-)
-
-func (b *IssueFormatterBuilder) AddHeader(kind headerType) *IssueFormatterBuilder {
+func (b *IssueFormatterBuilder) AddHeader() *IssueFormatterBuilder {
 	// add header type and rule name
-	switch kind {
-	case errorHeader:
+	switch b.issue.Severity {
+	case tt.SeverityError:
 		b.result.WriteString(errorStyle.Sprint("error: "))
-	case warningHeader:
+	case tt.SeverityWarning:
 		b.result.WriteString(warningStyle.Sprint("warning: "))
+	case tt.SeverityInfo:
+		b.result.WriteString(messageStyle.Sprint("info: "))
 	}
 
 	b.result.WriteString(ruleStyle.Sprintln(b.issue.Rule))

formatter/cyclomatic_complexity.go

@@ -13,7 +13,7 @@ type CyclomaticComplexityFormatter struct{}
 func (f *CyclomaticComplexityFormatter) Format(issue tt.Issue, snippet *internal.SourceCode) string {
 	builder := NewIssueFormatterBuilder(issue, snippet)
 	return builder.
-		AddHeader(warningHeader).
+		AddHeader().
 		AddCodeSnippet().
 		AddComplexityInfo().
 		AddSuggestion().

formatter/defers.go

@@ -10,7 +10,7 @@ type DefersFormatter struct{}
 func (f *DefersFormatter) Format(issue tt.Issue, snippet *internal.SourceCode) string {
 	builder := NewIssueFormatterBuilder(issue, snippet)
 	return builder.
-		AddHeader(errorHeader).
+		AddHeader().
 		AddCodeSnippet().
 		AddUnderlineAndMessage().
 		AddNote().

formatter/deprecated.go

@@ -10,7 +10,7 @@ type DeprecatedFuncFormatter struct{}
 func (f *DeprecatedFuncFormatter) Format(issue tt.Issue, snippet *internal.SourceCode) string {
 	builder := NewIssueFormatterBuilder(issue, snippet)
 	return builder.
-		AddHeader(errorHeader).
+		AddHeader().
 		AddCodeSnippet().
 		AddUnderlineAndMessage().
 		AddNote().

formatter/early_return.go

@@ -10,7 +10,7 @@ type EarlyReturnOpportunityFormatter struct{}
 func (f *EarlyReturnOpportunityFormatter) Format(issue tt.Issue, snippet *internal.SourceCode) string {
 	builder := NewIssueFormatterBuilder(issue, snippet)
 	return builder.
-		AddHeader(warningHeader).
+		AddHeader().
 		AddCodeSnippet().
 		AddUnderlineAndMessage().
 		AddSuggestion().