Add support for 'checkstyle' output (#209)

* Add support for 'checkstyle' output

* improve code comments

* remove severity translation

* use xml encoder

* use xml encoder

* update checkstyle usage to show exact xml output

* use assert.PanicsWithError

docs/snippets/woke.md

@@ -27,7 +27,7 @@ woke [globs ...] [flags]
       --exit-1-on-failure       Exit with exit code 1 on failures
   -h, --help                    help for woke
       --no-ignore               Ignored files in .gitignore, .ignore, .wokeignore, .git/info/exclude, and inline ignores are processed
-  -o, --output string           Output type [text,simple,github-actions,json,sonarqube] (default "text")
+  -o, --output string           Output type [text,simple,github-actions,json,sonarqube,checkstyle] (default "text")
       --stdin                   Read from stdin
 ```
 

docs/usage.md

@@ -63,7 +63,7 @@ This option may not be used at the same time as [File Globs](#file-globs)
 
 ## Outputs
 
-Options for output include text (default), simple, json, github-actions, or sonarqube format.
+Options for output include text (default), simple, json, github-actions, sonarqube, or checkstyle format.
 The following fields are supported, depending on format:
 
 | Field        | Description                                       |
@@ -216,6 +216,24 @@ Format used to populate results into the popular [SonarQube](https://www.sonarqu
 !!! note
     `<sonarqubeseverity>` is mapped from severity, such that an error in `woke` is translated to a `MAJOR`, warning to a `MINOR`, and info to `INFO`
 
+### Checkstyle
+
+!!! example ""
+    `woke -o checkstyle`
+
+Format used to populate results into the [Checkstyle](https://checkstyle.org/) XML format.
+
+#### Structure
+
+```xml
+<?xml version="1.0" encoding="UTF-8"?>
+<checkstyle version="5.0">
+  <file name="filepath">
+    <error column="startcol" line="lineno" message="description" severity="severity" source="woke"></error>
+  </file>
+</checkstyle>
+```
+
 ## Exit Code
 
 By default, `woke` will exit with a successful exit code when there are any rule failures.

pkg/printer/checkstyle.go

@@ -0,0 +1,83 @@
+package printer
+
+import (
+	"encoding/xml"
+	"fmt"
+	"io"
+
+	"github.com/get-woke/woke/pkg/result"
+)
+
+// Checkstyle is a Checkstyle printer meant for use by a Checkstyle annotation
+type Checkstyle struct {
+	writer  io.Writer
+	encoder *xml.Encoder
+}
+
+// NewCheckstyle returns a new Checkstyle printer
+func NewCheckstyle(w io.Writer) *Checkstyle {
+	return &Checkstyle{
+		writer:  w,
+		encoder: xml.NewEncoder(w),
+	}
+}
+
+type File struct {
+	XMLName xml.Name `xml:"file"`
+	Name    string   `xml:"name,attr"`
+	Errors  []Error  `xml:"error"`
+}
+type Error struct {
+	XMLName  xml.Name `xml:"error"`
+	Column   int      `xml:"column,attr"`
+	Line     int      `xml:"line,attr"`
+	Message  string   `xml:"message,attr"`
+	Severity string   `xml:"severity,attr"`
+	Source   string   `xml:"source,attr"`
+}
+
+func (p *Checkstyle) PrintSuccessExitMessage() bool {
+	return true
+}
+
+// Print prints in the format for Checkstyle.
+// https://github.com/checkstyle/checkstyle
+func (p *Checkstyle) Print(fs *result.FileResults) error {
+	var f File
+	f.Name = fs.Filename
+	for _, r := range fs.Results {
+		f.Errors = append(f.Errors, Error{
+			Column:   r.GetStartPosition().Column,
+			Line:     r.GetStartPosition().Line,
+			Message:  r.Reason(),
+			Severity: r.GetSeverity().String(),
+			Source:   "woke",
+		})
+	}
+	return p.encoder.Encode(f)
+}
+
+func (p *Checkstyle) Start() {
+	fmt.Fprint(p.writer, xml.Header)
+	p.encoder.Indent("", "  ")
+	if err := p.encoder.EncodeToken(xml.StartElement{
+		Name: xml.Name{Local: "checkstyle"},
+		Attr: []xml.Attr{
+			{Name: xml.Name{Local: "version"}, Value: "5.0"},
+		},
+	}); err != nil {
+		panic(err)
+	}
+	if err := p.encoder.Flush(); err != nil {
+		panic(err)
+	}
+}
+
+func (p *Checkstyle) End() {
+	if err := p.encoder.EncodeToken(xml.EndElement{Name: xml.Name{Local: "checkstyle"}}); err != nil {
+		panic(err)
+	}
+	if err := p.encoder.Flush(); err != nil {
+		panic(err)
+	}
+}

pkg/printer/checkstyle_test.go

@@ -0,0 +1,65 @@
+package printer
+
+import (
+	"bytes"
+	"go/token"
+	"testing"
+
+	"github.com/get-woke/woke/pkg/result"
+	"github.com/get-woke/woke/pkg/rule"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestFormatResultForCheckstyle(t *testing.T) {
+	testResults := result.FileResults{
+		Filename: "my/file",
+		Results: []result.Result{
+			result.LineResult{
+				Rule:    &rule.TestRule,
+				Finding: "whitelist",
+				StartPosition: &token.Position{
+					Filename: "my/file",
+					Offset:   0,
+					Line:     5,
+					Column:   3,
+				},
+				EndPosition: &token.Position{
+					Filename: "my/file",
+					Offset:   0,
+					Line:     5,
+					Column:   12,
+				},
+			},
+		},
+	}
+	buf := new(bytes.Buffer)
+	p := NewCheckstyle(buf)
+	p.Start()
+	p.Print(&testResults)
+	p.End()
+	expected := `<?xml version="1.0" encoding="UTF-8"?>
+<checkstyle version="5.0">
+  <file name="my/file">
+    <error column="3" line="5" message="` + "`" + `whitelist` + "`" + ` may be insensitive, use ` + "`" + `allowlist` + "`" + ` instead" severity="warning" source="woke"></error>
+  </file>
+</checkstyle>`
+	assert.Equal(t, expected, buf.String())
+}
+
+func TestCheckstyle_Start(t *testing.T) {
+	buf := new(bytes.Buffer)
+	p := NewCheckstyle(buf)
+	p.Start()
+	got := buf.String()
+
+	expected := `<?xml version="1.0" encoding="UTF-8"?>
+<checkstyle version="5.0">`
+	assert.Equal(t, expected, got)
+}
+
+func TestCheckstyle_End(t *testing.T) {
+	buf := new(bytes.Buffer)
+	p := NewCheckstyle(buf)
+	assert.PanicsWithError(t, "xml: end tag </checkstyle> without start tag", func() { p.End() })
+}

pkg/printer/printer.go

@@ -34,6 +34,10 @@ const (
 	// OutFormatSonarQube is an output format supported by SonarQube
 	// https://docs.sonarqube.org/latest/analysis/generic-issue/
 	OutFormatSonarQube = "sonarqube"
+
+	// OutFormatCheckstyle outputs in checkstyle format.
+	// https://github.com/checkstyle/checkstyle
+	OutFormatCheckstyle = "checkstyle"
 )
 
 // OutFormats are all the available output formats. The first one should be the default
@@ -43,6 +47,7 @@ var OutFormats = []string{
 	OutFormatGitHubActions,
 	OutFormatJSON,
 	OutFormatSonarQube,
+	OutFormatCheckstyle,
 }
 
 // OutFormatsString is all OutFormats, as a comma-separated string
@@ -62,6 +67,8 @@ func NewPrinter(f string, w io.Writer) (Printer, error) {
 		p = NewJSON(w)
 	case OutFormatSonarQube:
 		p = NewSonarQube(w)
+	case OutFormatCheckstyle:
+		p = NewCheckstyle(w)
 	default:
 		return p, fmt.Errorf("%s is not a valid printer type", f)
 	}

pkg/printer/printer_test.go

@@ -17,6 +17,7 @@ func TestCreatePrinter(t *testing.T) {
 		{OutFormatGitHubActions, &GitHubActions{}},
 		{OutFormatJSON, &JSON{}},
 		{OutFormatSonarQube, &SonarQube{}},
+		{OutFormatCheckstyle, &Checkstyle{}},
 	}
 
 	for _, test := range tests {