Add errorformat printer

This is only slightly different than `simple`. The only difference is it supports errorformating and can be used by reviewdog to signify errors vs warnings.
* https://vim-jp.org/vimdoc-en/quickfix.html#error-file-format
* https://github.com/reviewdog/reviewdog#input-format

pkg/printer/errorformat.go

@@ -0,0 +1,37 @@
+package printer
+
+import (
+	"fmt"
+
+	"github.com/get-woke/woke/pkg/result"
+)
+
+// ErrorFormat is a ErrorFormat printer meant to be read by errorformat
+// https://vim-jp.org/vimdoc-en/quickfix.html#error-file-format
+type ErrorFormat struct {
+	format string
+}
+
+// NewErrorFormat returns a new ErrorFormat printer
+func NewErrorFormat() *ErrorFormat {
+	return &ErrorFormat{
+		format: "%s:%d:%d [%c] %s",
+	}
+}
+
+// Print prints in the format 'filename:line:column: [s] message'
+// where `s` is the first character of Severity
+// The formatting is meant to line up with errorformat
+// "%f:%l:%c [%t] %m"
+// https://vim-jp.org/vimdoc-en/quickfix.html#error-file-format
+func (e *ErrorFormat) Print(fs *result.FileResults) error {
+	for _, r := range fs.Results {
+		fmt.Printf(e.format+"\n",
+			r.StartPosition.Filename,
+			r.StartPosition.Line,
+			r.StartPosition.Column,
+			r.Rule.Severity.String()[0],
+			r.Reason())
+	}
+	return nil
+}

pkg/printer/errorformat_test.go

@@ -0,0 +1,18 @@
+package printer
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestErrorformat_Print(t *testing.T) {
+	p := NewErrorFormat()
+	res := generateFileResult()
+	got := captureOutput(func() {
+		assert.NoError(t, p.Print(res))
+	})
+	expected := fmt.Sprintf("foo.txt:1:6 [w] %s\n", res.Results[0].Reason())
+	assert.Equal(t, expected, got)
+}

pkg/printer/printer.go

@@ -18,12 +18,14 @@ const (
 	OutFormatText          = "text"
 	OutFormatSimple        = "simple"
 	OutFormatGitHubActions = "github-actions"
+	OutFormatErrorformat   = "efm"
 )
 
 var OutFormats = []string{
 	OutFormatText,
 	OutFormatSimple,
 	OutFormatGitHubActions,
+	OutFormatErrorformat,
 }
 
 var OutFormatsString = strings.Join(OutFormats, ",")
@@ -37,6 +39,8 @@ func NewPrinter(f string) (Printer, error) {
 		p = NewSimple()
 	case OutFormatGitHubActions:
 		p = NewGitHubActions()
+	case OutFormatErrorformat:
+		p = NewErrorFormat()
 	default:
 		return p, fmt.Errorf("%s is not a valid printer type", f)
 	}

pkg/printer/simple.go

@@ -2,41 +2,32 @@ package printer
 
 import (
 	"fmt"
-	"go/token"
 
 	"github.com/get-woke/woke/pkg/result"
 )
 
 // Simple is a simple printer meant for a machine to read
-type Simple struct{}
+type Simple struct {
+	format string
+}
 
 // NewSimple returns a new simple printer
 func NewSimple() *Simple {
-	return &Simple{}
+	return &Simple{
+		format: "%s:%d:%d: [%s] %s",
+	}
 }
 
 // Print prints in the format 'filename:line:column: message'
 // based on golint's output: https://github.com/golang/lint/blob/738671d3881b9731cc63024d5d88cf28db875626/golint/golint.go#L121
-func (p *Simple) Print(fs *result.FileResults) error {
+func (s *Simple) Print(fs *result.FileResults) error {
 	for _, r := range fs.Results {
-		fmt.Printf("%v: [%s] %s\n",
-			positionString(r.StartPosition),
+		fmt.Printf(s.format+"\n",
+			r.StartPosition.Filename,
+			r.StartPosition.Line,
+			r.StartPosition.Column,
 			r.Rule.Severity,
 			r.Reason())
 	}
 	return nil
 }
-
-// positionString is similar to Position.String, but includes the Column
-// even if the column is 0
-func positionString(pos *token.Position) string {
-	s := pos.Filename
-	if pos.IsValid() {
-		if s != "" {
-			s += ":"
-		}
-		s += fmt.Sprintf("%d", pos.Line)
-		s += fmt.Sprintf(":%d", pos.Column)
-	}
-	return s
-}

pkg/printer/simple_test.go

@@ -2,41 +2,11 @@ package printer
 
 import (
 	"fmt"
-	"go/token"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
 )
 
-func TestSimple_positionString(t *testing.T) {
-	tests := []struct {
-		pos      token.Position
-		expected string
-	}{
-		{
-			token.Position{Filename: "my/file", Offset: 0, Line: 10, Column: 4},
-			"my/file:10:4",
-		},
-		{
-			token.Position{Filename: "my/file", Offset: 0, Line: 1, Column: 0},
-			"my/file:1:0",
-		},
-		{
-			token.Position{Filename: "my/file", Offset: 0, Line: 0, Column: 4},
-			"my/file",
-		},
-		{
-			token.Position{Filename: "", Offset: 0, Line: 5, Column: 32},
-			"5:32",
-		},
-	}
-
-	for _, test := range tests {
-		p := positionString(&test.pos)
-		assert.Equal(t, test.expected, p)
-	}
-}
-
 func TestSimple_Print(t *testing.T) {
 	p := NewSimple()
 	res := generateFileResult()