feat: expand value-only field assignments to key-value

Signed-off-by: Ilya Lesikov <ilya@lesikov.com>

Author: ilya-lesikov

.gitignore

@@ -1,2 +1,13 @@
+# remove this block when fixed: https://github.com/anthropics/claude-code/issues/17087
+/.bash_profile
+/.bashrc
+/.gitconfig
+/.gitmodules
+/.mcp.json
+/.profile
+/.ripgreprc
+/.zprofile
+/.zshrc
+
 /bin/
 /.task/

README.md

@@ -276,6 +276,18 @@ cfg := &Config{Name: "app", Timeout: 30, debug: true}
 
 </details>
 
+**Positional literals** are automatically converted to keyed literals:
+
+```go
+// Before — positional
+p := Person{"John", 30}
+
+// After — converted to keyed, then sorted
+p := Person{Age: 30, Name: "John"}
+```
+
+This conversion only applies to structs defined in the same file. External struct literals are left unchanged.
+
 ---
 
 ### Functions

pkg/formatter/file.go

@@ -55,9 +55,11 @@ func FormatFile(filePath string, opts Options) error {
 		return nil
 	}
 
-	structDefs := collectStructDefinitions(f)
+	originalFieldOrder := collectOriginalFieldOrder(f)
+	convertPositionalToKeyed(f, originalFieldOrder)
 	reorderStructFields(f)
-	reorderStructLiterals(f, structDefs)
+	sortedFieldOrder := collectStructDefinitions(f)
+	reorderStructLiterals(f, sortedFieldOrder)
 	f.Decls = reorderDeclarations(f)
 	normalizeSpacing(f)
 	expandOneLineFunctions(f)

pkg/formatter/structs.go

@@ -37,6 +37,29 @@ func collectStructDefinitions(f *dst.File) map[string][]string {
 	return structDefs
 }
 
+// collectOriginalFieldOrder collects the original (unsorted) field order for each struct.
+// This is needed for converting positional literals to keyed literals.
+func collectOriginalFieldOrder(f *dst.File) map[string][]string {
+	structDefs := make(map[string][]string)
+
+	dst.Inspect(f, func(n dst.Node) bool {
+		ts, ok := n.(*dst.TypeSpec)
+		if !ok {
+			return true
+		}
+		st, ok := ts.Type.(*dst.StructType)
+		if !ok {
+			return true
+		}
+
+		structDefs[ts.Name.Name] = getFieldNamesFromStructType(st)
+
+		return true
+	})
+
+	return structDefs
+}
+
 func reorderFields(st *dst.StructType) {
 	if st.Fields == nil || len(st.Fields.List) == 0 {
 		return
@@ -191,3 +214,95 @@ func reorderCompositeLitFields(cl *dst.CompositeLit, fieldOrder []string) {
 
 	cl.Elts = newElts
 }
+
+func isPositionalLiteral(cl *dst.CompositeLit) bool {
+	if len(cl.Elts) == 0 {
+		return false
+	}
+
+	for _, elt := range cl.Elts {
+		if _, ok := elt.(*dst.KeyValueExpr); ok {
+			return false
+		}
+	}
+
+	return true
+}
+
+func getFieldNamesFromStructType(st *dst.StructType) []string {
+	if st == nil || st.Fields == nil {
+		return nil
+	}
+
+	var names []string
+	for _, field := range st.Fields.List {
+		if len(field.Names) == 0 {
+			// Embedded field - use type name
+			names = append(names, getFieldTypeName(field))
+		} else {
+			// Named field(s)
+			for _, name := range field.Names {
+				names = append(names, name.Name)
+			}
+		}
+	}
+
+	return names
+}
+
+func convertToKeyedLiteral(cl *dst.CompositeLit, fieldNames []string) {
+	if len(fieldNames) == 0 || len(cl.Elts) == 0 {
+		return
+	}
+
+	newElts := make([]dst.Expr, 0, len(cl.Elts))
+	for i, elt := range cl.Elts {
+		if i >= len(fieldNames) {
+			break
+		}
+
+		kv := &dst.KeyValueExpr{
+			Key:   dst.NewIdent(fieldNames[i]),
+			Value: elt,
+		}
+		newElts = append(newElts, kv)
+	}
+
+	cl.Elts = newElts
+}
+
+func convertPositionalToKeyed(f *dst.File, structDefs map[string][]string) {
+	dst.Inspect(f, func(n dst.Node) bool {
+		cl, ok := n.(*dst.CompositeLit)
+		if !ok {
+			return true
+		}
+
+		if !isPositionalLiteral(cl) {
+			return true
+		}
+
+		// Handle anonymous struct type
+		if st, ok := cl.Type.(*dst.StructType); ok {
+			fieldNames := getFieldNamesFromStructType(st)
+			convertToKeyedLiteral(cl, fieldNames)
+			return true
+		}
+
+		// Handle named struct type
+		typeName := extractTypeName(cl.Type)
+		if typeName == "" {
+			return true
+		}
+
+		fieldNames, exists := structDefs[typeName]
+		if !exists {
+			// Type not in this file - leave untouched
+			return true
+		}
+
+		convertToKeyedLiteral(cl, fieldNames)
+
+		return true
+	})
+}

pkg/formatter/testdata/expected.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"fmt"
+	"os"
 	"strings"
 )
 
@@ -212,19 +213,80 @@ func newMyPrivateType() *myPrivateType {
 	}
 }
 
+// Test: positional literals should be converted to keyed
+type PositionalTest struct {
+	Age  int
+	City string
+	Name string
+}
+
+// Test: embedded fields in positional literal
+type WithEmbedded struct {
+	PositionalTest
+
+	Extra string
+}
+
 func HelperUpper() {}
 
 func ProcessDataPublic(data string) string {
 	return strings.ToLower(data)
 }
 
+// Test: anonymous struct with positional literal
+func createAnonymous() interface{} {
+	return struct {
+		A string
+		B int
+	}{B: 42, A: "hello"}
+}
+
+// Test: empty literal - no change
+func createEmpty() *PositionalTest {
+	return &PositionalTest{}
+}
+
+// Test: external struct literal should NOT be touched
+func createExternal() *os.File {
+	// This uses positional but type is external - leave untouched
+	// (os.File doesn't actually support this, so use a keyed example)
+	return nil
+}
+
+// Test: already keyed literal - no change
+func createKeyed() *PositionalTest {
+	return &PositionalTest{
+		Age: 35, City: "Boston", Name: "Alice",
+	}
+}
+
 // Test: struct literal field reordering
 func createMixed() *Mixed {
 	return &Mixed{
 		Address: "addr", Name: "test", age: 25, count: 1,
 	}
 }
 
+func createPositional() *PositionalTest {
+	return &PositionalTest{
+		Age: 30, City: "NYC", Name: "John",
+	}
+}
+
+func createPositionalPartial() *PositionalTest {
+	return &PositionalTest{
+		Age: 25, Name: "Jane",
+	}
+}
+
+func createWithEmbedded() *WithEmbedded {
+	return &WithEmbedded{
+		PositionalTest: PositionalTest{
+			Age: 40, City: "LA", Name: "Bob",
+		}, Extra: "extra",
+	}
+}
+
 // Test: blank line before comments
 func functionWithComment() {
 	x := 1

pkg/formatter/testdata/input.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"fmt"
+	"os"
 	"strings"
 )
 
@@ -287,3 +288,53 @@ type myPrivateType struct {
 func newMyPrivateType() *myPrivateType {
 	return &myPrivateType{value: 1}
 }
+
+// Test: positional literals should be converted to keyed
+type PositionalTest struct {
+	Name string
+	Age  int
+	City string
+}
+
+func createPositional() *PositionalTest {
+	return &PositionalTest{"John", 30, "NYC"}
+}
+
+func createPositionalPartial() *PositionalTest {
+	return &PositionalTest{"Jane", 25}
+}
+
+// Test: anonymous struct with positional literal
+func createAnonymous() interface{} {
+	return struct {
+		B int
+		A string
+	}{42, "hello"}
+}
+
+// Test: embedded fields in positional literal
+type WithEmbedded struct {
+	PositionalTest
+	Extra string
+}
+
+func createWithEmbedded() *WithEmbedded {
+	return &WithEmbedded{PositionalTest{"Bob", 40, "LA"}, "extra"}
+}
+
+// Test: external struct literal should NOT be touched
+func createExternal() *os.File {
+	// This uses positional but type is external - leave untouched
+	// (os.File doesn't actually support this, so use a keyed example)
+	return nil
+}
+
+// Test: already keyed literal - no change
+func createKeyed() *PositionalTest {
+	return &PositionalTest{Name: "Alice", Age: 35, City: "Boston"}
+}
+
+// Test: empty literal - no change
+func createEmpty() *PositionalTest {
+	return &PositionalTest{}
+}