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convert.go
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convert.go
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package gadget
import (
"fmt"
"go/ast"
"go/token"
"strconv"
)
func convertTypeSpec(spec ast.Expr) (Type, error) {
switch t := spec.(type) {
case *ast.Ident:
return Ident(t.Name), nil
case *ast.SelectorExpr:
ident, ok := t.X.(*ast.Ident)
if !ok {
return nil, fmt.Errorf("expected selector expression to start with identifier")
}
return Selector{
Left: Ident(ident.Name),
Right: Ident(t.Sel.Name),
}, nil
case *ast.StarExpr:
elem, err := convertTypeSpec(t.X)
if err != nil {
return nil, fmt.Errorf("failed to convert pointer: %w", err)
}
return Pointer{
Elem: elem,
}, nil
case *ast.ArrayType:
elem, err := convertTypeSpec(t.Elt)
if err != nil {
return nil, fmt.Errorf("failed to convert array element: %w", err)
}
if t.Len == nil {
return Slice{Elem: elem}, nil
}
size, err := asIntLiteral(t.Len)
if err != nil {
return nil, fmt.Errorf("failed to convert array size: %w", err)
}
return Array{Elem: elem, Size: size}, nil
case *ast.MapType:
key, err := convertTypeSpec(t.Key)
if err != nil {
return nil, fmt.Errorf("failed to convert map key: %w", err)
}
val, err := convertTypeSpec(t.Value)
if err != nil {
return nil, fmt.Errorf("failed to convert map value: %w", err)
}
return Map{Key: key, Value: val}, nil
case *ast.ChanType:
elem, err := convertTypeSpec(t.Value)
if err != nil {
return nil, fmt.Errorf("failed to convert channel element: %w", err)
}
dir := BOTH
if t.Dir == ast.RECV {
dir = RECV
}
if t.Dir == ast.SEND {
dir = SEND
}
return Chan{
Dir: dir,
Elem: elem,
}, nil
case *ast.StructType:
var s Struct
for fieldNum, field := range t.Fields.List {
if field.Names == nil {
t, err := convertTypeSpec(field.Type)
if err != nil {
return nil, fmt.Errorf("failed to convert struct field %d: %w", fieldNum+1, err)
}
var tag string
if field.Tag != nil {
tag, err = asStringLiteral(field.Tag)
if err != nil {
return nil, fmt.Errorf("failed to convert tag for struct field %d: %w", fieldNum+1, err)
}
}
s.Fields = append(s.Fields, StructField{
Type: t,
Tag: tag,
})
continue
}
for _, name := range field.Names {
t, err := convertTypeSpec(field.Type)
if err != nil {
return nil, fmt.Errorf("failed to convert struct field %s: %w", name.Name, err)
}
var tag string
if field.Tag != nil {
tag, err = asStringLiteral(field.Tag)
if err != nil {
return nil, fmt.Errorf("failed to convert tag for struct field %s: %w", name.Name, err)
}
}
s.Fields = append(s.Fields, StructField{
Name: name.Name,
Type: t,
Tag: tag,
})
}
}
return s, nil
case *ast.FuncType:
var params []FuncParam
if t.Params != nil {
for fieldNum, field := range t.Params.List {
if field.Names == nil {
t, err := convertTypeSpec(field.Type)
if err != nil {
return nil, fmt.Errorf("failed to convert function parameter %d: %w", fieldNum+1, err)
}
params = append(params, FuncParam{
Type: t,
})
continue
}
for _, name := range field.Names {
t, err := convertTypeSpec(field.Type)
if err != nil {
return nil, fmt.Errorf("failed to convert function parameter %s: %w", name.Name, err)
}
params = append(params, FuncParam{
Name: name.Name,
Type: t,
})
}
}
}
var results []FuncResult
if t.Results != nil {
for fieldNum, field := range t.Results.List {
if field.Names == nil {
t, err := convertTypeSpec(field.Type)
if err != nil {
return nil, fmt.Errorf("failed to convert function return value %d: %w", fieldNum+1, err)
}
results = append(results, FuncResult{
Type: t,
})
continue
}
for _, name := range field.Names {
t, err := convertTypeSpec(field.Type)
if err != nil {
return nil, fmt.Errorf("failed to convert function return value %s: %w", name.Name, err)
}
results = append(results, FuncResult{
Name: name.Name,
Type: t,
})
}
}
}
return Func{
Params: params,
Results: results,
}, nil
case *ast.InterfaceType:
var i Interface
if t.Methods != nil {
for _, field := range t.Methods.List {
for _, name := range field.Names {
t, err := convertTypeSpec(field.Type)
if err != nil {
return nil, fmt.Errorf("failed to convert function parameter %s: %w", name.Name, err)
}
f, ok := t.(Func)
if !ok {
return nil, fmt.Errorf("interface method %s was somehow not a function type: %w", name.Name, err)
}
i.Methods = append(i.Methods, InterfaceMethod{
Name: name.Name,
Type: f,
})
}
}
}
return i, nil
}
return nil, fmt.Errorf("unknown kind of type spec %#v", spec)
}
func asIntLiteral(expr ast.Expr) (int, error) {
t, ok := expr.(*ast.BasicLit)
if !ok {
return 0, fmt.Errorf("expression is not a basic literal")
}
if t.Kind != token.INT {
return 0, fmt.Errorf("expression is not a basic literal integer")
}
return strconv.Atoi(t.Value)
}
func asStringLiteral(expr ast.Expr) (string, error) {
t, ok := expr.(*ast.BasicLit)
if !ok {
return "", fmt.Errorf("expression is not a basic literal")
}
if t.Kind != token.STRING {
return "", fmt.Errorf("expression is not a basic literal string")
}
return strconv.Unquote(t.Value)
}
type funcVisitor func(ast.Node) ast.Visitor
func (f funcVisitor) Visit(node ast.Node) ast.Visitor {
return f(node)
}
func findTypeAlias(fileSet *ast.File, pos token.Pos) (Type, error) {
done := false
var typ ast.Expr
var err error
var search funcVisitor
search = funcVisitor(func(node ast.Node) ast.Visitor {
if done {
return nil
}
if node == nil {
return search
}
if node.Pos() > pos {
done = true
switch concrete := node.(type) {
case *ast.Ident:
typ = concrete
return nil
case *ast.SelectorExpr:
typ = concrete
return nil
default:
err = fmt.Errorf("type alias is not an identifier or selector")
return nil
}
}
return search
})
ast.Walk(search, fileSet)
if err != nil {
return nil, fmt.Errorf("failed to find alias: %w", err)
}
if typ == nil {
return nil, fmt.Errorf("failed to find alias")
}
converted, err := convertTypeSpec(typ)
if err != nil {
return nil, fmt.Errorf("failed to convert identifier in alias: %w", err)
}
return converted, nil
}