feat(engine): Add language-agnostic formatting engine with Go adapter

1 files changed, 308 insertions, 0 deletions

diff --git a/parity_test.go b/parity_test.go
new file mode 100644
index 0000000..af747f8
--- /dev/null
+++ b/parity_test.go
@@ -0,0 +1,308 @@
+package main
+
+import (
+	"github.com/Fuwn/iku/engine"
+	"testing"
+)
+
+type parityInput struct {
+	name   string
+	source string
+}
+
+var parityInputs = []parityInput{
+	{
+		name: "extra blank lines collapsed",
+		source: `package main
+
+func main() {
+	x := 1
+
+
+	y := 2
+}
+`,
+	},
+	{
+		name: "scoped statements",
+		source: `package main
+
+func main() {
+	x := 1
+	if x > 0 {
+		y := 2
+	}
+	z := 3
+}
+`,
+	},
+	{
+		name: "nested scopes",
+		source: `package main
+
+func main() {
+	if true {
+		x := 1
+		if false {
+			y := 2
+		}
+		z := 3
+	}
+}
+`,
+	},
+	{
+		name: "for loop",
+		source: `package main
+
+func main() {
+	x := 1
+	for i := 0; i < 10; i++ {
+		y := i
+	}
+	z := 2
+}
+`,
+	},
+	{
+		name: "switch statement",
+		source: `package main
+
+func main() {
+	x := 1
+	switch x {
+	case 1:
+		y := 2
+	}
+	z := 3
+}
+`,
+	},
+	{
+		name: "multiple functions",
+		source: `package main
+
+func foo() {
+	x := 1
+}
+
+
+func bar() {
+	y := 2
+}
+`,
+	},
+	{
+		name: "type struct before var",
+		source: `package main
+
+type Foo struct {
+	X int
+}
+var x = 1
+`,
+	},
+	{
+		name: "different statement types",
+		source: `package main
+
+func main() {
+	x := 1
+	y := 2
+	var a = 3
+	defer cleanup()
+	defer cleanup2()
+	go worker()
+	return
+}
+`,
+	},
+	{
+		name: "consecutive ifs",
+		source: `package main
+
+func main() {
+	if err != nil {
+		return
+	}
+	if x > 0 {
+		y = 1
+	}
+}
+`,
+	},
+	{
+		name: "case clause with scoped statement",
+		source: `package main
+
+func main() {
+	switch x {
+	case 1:
+		foo()
+		if err != nil {
+			return
+		}
+	}
+}
+`,
+	},
+	{
+		name: "defer inline func",
+		source: `package main
+
+func main() {
+	defer func() { _ = file.Close() }()
+	fileInfo, err := file.Stat()
+}
+`,
+	},
+	{
+		name: "case clause assignments only",
+		source: `package main
+
+func main() {
+	switch x {
+	case "user":
+		roleStyle = UserStyle
+		contentStyle = ContentStyle
+		prefix = "You"
+	case "assistant":
+		roleStyle = AssistantStyle
+	}
+}
+`,
+	},
+	{
+		name:   "raw string literal",
+		source: "package main\n\nvar x = `\nline 1\n\nline 2\n`\nvar y = 1\n",
+	},
+	{
+		name: "mixed top-level declarations",
+		source: `package main
+
+import "fmt"
+
+const x = 1
+
+var y = 2
+
+type Z struct{}
+
+func main() {
+	fmt.Println(x, y)
+}
+`,
+	},
+	{
+		name: "empty function body",
+		source: `package main
+
+func main() {
+}
+`,
+	},
+	{
+		name: "comment before scoped statement",
+		source: `package main
+
+func main() {
+	x := 1
+	// this is a comment
+	if x > 0 {
+		y := 2
+	}
+}
+`,
+	},
+	{
+		name: "multiple blank lines between functions",
+		source: `package main
+
+func a() {}
+
+
+
+func b() {}
+
+
+
+
+func c() {}
+`,
+	},
+	{
+		name: "select statement",
+		source: `package main
+
+func main() {
+	x := 1
+	select {
+	case <-ch:
+		y := 2
+	}
+	z := 3
+}
+`,
+	},
+	{
+		name: "range loop",
+		source: `package main
+
+func main() {
+	items := []int{1, 2, 3}
+	for _, item := range items {
+		_ = item
+	}
+	done := true
+}
+`,
+	},
+	{
+		name: "interface declaration",
+		source: `package main
+
+type Reader interface {
+	Read(p []byte) (n int, err error)
+}
+var x = 1
+`,
+	},
+}
+
+func TestEngineParityWithFormatter(t *testing.T) {
+	for _, commentMode := range []CommentMode{CommentsFollow, CommentsPrecede, CommentsStandalone} {
+		for _, input := range parityInputs {
+			name := input.name
+
+			switch commentMode {
+			case CommentsPrecede:
+				name += "/precede"
+			case CommentsStandalone:
+				name += "/standalone"
+			}
+
+			t.Run(name, func(t *testing.T) {
+				formatter := &Formatter{CommentMode: commentMode}
+				oldResult, err := formatter.Format([]byte(input.source))
+
+				if err != nil {
+					t.Fatalf("old formatter error: %v", err)
+				}
+
+				adapter := &GoAdapter{}
+				_, events, err := adapter.Analyze([]byte(input.source))
+
+				if err != nil {
+					t.Fatalf("adapter error: %v", err)
+				}
+
+				formattingEngine := &engine.Engine{CommentMode: MapCommentMode(commentMode)}
+				newResult := formattingEngine.FormatToString(events)
+
+				if string(oldResult) != newResult {
+					t.Errorf("parity mismatch\nold:\n%s\nnew:\n%s", oldResult, newResult)
+				}
+			})
+		}
+	}
+}