A better go code formatter, and now make fmt can run in Windows (#17684)

* go build / format tools
* re-format imports

build/codeformat/formatimports_test.go

@@ -0,0 +1,125 @@
+// Copyright 2021 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package codeformat
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestFormatImportsSimple(t *testing.T) {
+	formatted, err := formatGoImports([]byte(`
+package codeformat
+
+import (
+	"github.com/stretchr/testify/assert"
+	"testing"
+)
+`))
+
+	expected := `
+package codeformat
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+`
+
+	assert.NoError(t, err)
+	assert.Equal(t, expected, string(formatted))
+}
+
+func TestFormatImportsGroup(t *testing.T) {
+	// gofmt/goimports won't group the packages, for example, they produce such code:
+	//     "bytes"
+	//     "image"
+	//        (a blank line)
+	//     "fmt"
+	//     "image/color/palette"
+	// our formatter does better, and these packages are grouped into one.
+
+	formatted, err := formatGoImports([]byte(`
+package test
+
+import (
+	"bytes"
+	"fmt"
+	"image"
+	"image/color/palette"
+
+	_ "image/gif"  // for processing gif images
+	_ "image/jpeg" // for processing jpeg images
+	_ "image/png"  // for processing png images
+
+	"code.gitea.io/other/package"
+
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/util"
+
+  "xorm.io/the/package"
+
+	"github.com/issue9/identicon"
+	"github.com/nfnt/resize"
+	"github.com/oliamb/cutter"
+)
+`))
+
+	expected := `
+package test
+
+import (
+	"bytes"
+	"fmt"
+	"image"
+	"image/color/palette"
+
+	_ "image/gif"  // for processing gif images
+	_ "image/jpeg" // for processing jpeg images
+	_ "image/png"  // for processing png images
+
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/modules/util"
+
+	"code.gitea.io/other/package"
+	"github.com/issue9/identicon"
+	"github.com/nfnt/resize"
+	"github.com/oliamb/cutter"
+	"xorm.io/the/package"
+)
+`
+
+	assert.NoError(t, err)
+	assert.Equal(t, expected, string(formatted))
+}
+
+func TestFormatImportsInvalidComment(t *testing.T) {
+	// why we shouldn't write comments between imports: it breaks the grouping of imports
+	// for example:
+	//    "pkg1"
+	//    "pkg2"
+	//    // a comment
+	//    "pkgA"
+	//    "pkgB"
+	// the comment splits the packages into two groups, pkg1/2 are sorted separately, pkgA/B are sorted separately
+	// we don't want such code, so the code should be:
+	//    "pkg1"
+	//    "pkg2"
+	//    "pkgA" // a comment
+	//    "pkgB"
+
+	_, err := formatGoImports([]byte(`
+package test
+
+import (
+  "image/jpeg"
+	// for processing gif images
+	"image/gif"
+)
+`))
+	assert.ErrorIs(t, err, errInvalidCommentBetweenImports)
+}