// UsesImport reports whether a given import is used.
func UsesImport(f *ast.File, path string) (used bool) {
spec := importSpec(f, path)
if spec == nil {
return
}
name := spec.Name.String()
switch name {
case "<nil>":
// If the package name is not explicitly specified,
// make an educated guess. This is not guaranteed to be correct.
lastSlash := strings.LastIndex(path, "/")
if lastSlash == -1 {
name = path
} else {
name = path[lastSlash+1:]
}
case "_", ".":
// Not sure if this import is used - err on the side of caution.
return true
}
ast.Walk(visitFn(func(n ast.Node) {
sel, ok := n.(*ast.SelectorExpr)
if ok && isTopName(sel.X, name) {
used = true
}
}), f)
return
}
// idents is an iterator that returns all idents in f via the result channel.
func idents(f *ast.File) <-chan *ast.Ident {
v := make(visitor)
go func() {
ast.Walk(v, f)
close(v)
}()
return v
}
func simplify(f *ast.File) {
var s simplifier
// determine if f contains dot imports
for _, imp := range f.Imports {
if imp.Name != nil && imp.Name.Name == "." {
s.hasDotImport = true
break
}
}
// remove empty declarations such as "const ()", etc
removeEmptyDeclGroups(f)
ast.Walk(&s, f)
}
func fixImports(fset *token.FileSet, f *ast.File, filename string) (added []string, err error) {
// refs are a set of possible package references currently unsatisfied by imports.
// first key: either base package (e.g. "fmt") or renamed package
// second key: referenced package symbol (e.g. "Println")
refs := make(map[string]map[string]bool)
// decls are the current package imports. key is base package or renamed package.
decls := make(map[string]*ast.ImportSpec)
// collect potential uses of packages.
var visitor visitFn
visitor = visitFn(func(node ast.Node) ast.Visitor {
if node == nil {
return visitor
}
switch v := node.(type) {
case *ast.ImportSpec:
if v.Name != nil {
decls[v.Name.Name] = v
} else {
local := importPathToName(strings.Trim(v.Path.Value, `\"`))
decls[local] = v
}
case *ast.SelectorExpr:
xident, ok := v.X.(*ast.Ident)
if !ok {
break
}
if xident.Obj != nil {
// if the parser can resolve it, it's not a package ref
break
}
pkgName := xident.Name
if refs[pkgName] == nil {
refs[pkgName] = make(map[string]bool)
}
if decls[pkgName] == nil {
refs[pkgName][v.Sel.Name] = true
}
}
return visitor
})
ast.Walk(visitor, f)
// Nil out any unused ImportSpecs, to be removed in following passes
unusedImport := map[string]string{}
for pkg, is := range decls {
if refs[pkg] == nil && pkg != "_" && pkg != "." {
name := ""
if is.Name != nil {
name = is.Name.Name
}
unusedImport[strings.Trim(is.Path.Value, `"`)] = name
}
}
for ipath, name := range unusedImport {
if ipath == "C" {
// Don't remove cgo stuff.
continue
}
astutil.DeleteNamedImport(fset, f, name, ipath)
}
// Search for imports matching potential package references.
searches := 0
type result struct {
ipath string
name string
err error
}
results := make(chan result)
for pkgName, symbols := range refs {
if len(symbols) == 0 {
continue // skip over packages already imported
}
go func(pkgName string, symbols map[string]bool) {
ipath, rename, err := findImport(pkgName, symbols, filename)
r := result{ipath: ipath, err: err}
if rename {
r.name = pkgName
}
results <- r
}(pkgName, symbols)
searches++
}
for i := 0; i < searches; i++ {
result := <-results
if result.err != nil {
return nil, result.err
}
if result.ipath != "" {
if result.name != "" {
astutil.AddNamedImport(fset, f, result.name, result.ipath)
} else {
astutil.AddImport(fset, f, result.ipath)
}
added = append(added, result.ipath)
}
}
return added, nil
}
func (s *simplifier) Visit(node ast.Node) ast.Visitor {
switch n := node.(type) {
case *ast.CompositeLit:
// array, slice, and map composite literals may be simplified
outer := n
var eltType ast.Expr
switch typ := outer.Type.(type) {
case *ast.ArrayType:
eltType = typ.Elt
case *ast.MapType:
eltType = typ.Value
}
if eltType != nil {
typ := reflect.ValueOf(eltType)
for i, x := range outer.Elts {
px := &outer.Elts[i]
// look at value of indexed/named elements
if t, ok := x.(*ast.KeyValueExpr); ok {
x = t.Value
px = &t.Value
}
ast.Walk(s, x) // simplify x
// if the element is a composite literal and its literal type
// matches the outer literal's element type exactly, the inner
// literal type may be omitted
if inner, ok := x.(*ast.CompositeLit); ok {
if match(nil, typ, reflect.ValueOf(inner.Type)) {
inner.Type = nil
}
}
// if the outer literal's element type is a pointer type *T
// and the element is & of a composite literal of type T,
// the inner &T may be omitted.
if ptr, ok := eltType.(*ast.StarExpr); ok {
if addr, ok := x.(*ast.UnaryExpr); ok && addr.Op == token.AND {
if inner, ok := addr.X.(*ast.CompositeLit); ok {
if match(nil, reflect.ValueOf(ptr.X), reflect.ValueOf(inner.Type)) {
inner.Type = nil // drop T
*px = inner // drop &
}
}
}
}
}
// node was simplified - stop walk (there are no subnodes to simplify)
return nil
}
case *ast.SliceExpr:
// a slice expression of the form: s[a:len(s)]
// can be simplified to: s[a:]
// if s is "simple enough" (for now we only accept identifiers)
if n.Max != nil || s.hasDotImport {
// - 3-index slices always require the 2nd and 3rd index
// - if dot imports are present, we cannot be certain that an
// unresolved "len" identifier refers to the predefined len()
break
}
if s, _ := n.X.(*ast.Ident); s != nil && s.Obj != nil {
// the array/slice object is a single, resolved identifier
if call, _ := n.High.(*ast.CallExpr); call != nil && len(call.Args) == 1 && !call.Ellipsis.IsValid() {
// the high expression is a function call with a single argument
if fun, _ := call.Fun.(*ast.Ident); fun != nil && fun.Name == "len" && fun.Obj == nil {
// the function called is "len" and it is not locally defined; and
// because we don't have dot imports, it must be the predefined len()
if arg, _ := call.Args[0].(*ast.Ident); arg != nil && arg.Obj == s.Obj {
// the len argument is the array/slice object
n.High = nil
}
}
}
}
// Note: We could also simplify slice expressions of the form s[0:b] to s[:b]
// but we leave them as is since sometimes we want to be very explicit
// about the lower bound.
// An example where the 0 helps:
// x, y, z := b[0:2], b[2:4], b[4:6]
// An example where it does not:
// x, y := b[:n], b[n:]
case *ast.RangeStmt:
// - a range of the form: for x, _ = range v {...}
// can be simplified to: for x = range v {...}
// - a range of the form: for _ = range v {...}
// can be simplified to: for range v {...}
if isBlank(n.Value) {
n.Value = nil
}
if isBlank(n.Key) && n.Value == nil {
n.Key = nil
}
}
return s
}
func fileWithAnnotationComments(file *ast.File, fset, oldFset *token.FileSet, src []byte) ([]byte, *ast.File, error) {
// TODO: So this is an extremely hacky way of doing this. We're going to
// add the comments directly to the source comments, as text, and then
// we're going to re-parse it. This is because I tried manipulating the
// AST, adding the commments there an shifting the nodes' positions, but
// doing that right is very very convoluted; you need to be tracking all
// the time where you are, where you _were_, figure out where's a line
// break, etc. So, well, this will do for now.
var err error
var dstChunks [][]byte
var lastChunkEnd int
skipNextSpec := false
addDoc := func(node ast.Node, name *ast.Ident, typ ast.Expr) {
if typ == nil {
return
}
if name != nil && len(name.Name) > 0 {
c := name.Name[0]
if !(c >= 'A' && c <= 'Z') {
return
}
}
buf := &bytes.Buffer{}
err = printer.Fprint(buf, token.NewFileSet(), typ)
if err != nil {
return
}
pos := int(node.Pos()) - oldFset.File(file.Pos()).Base()
var space []byte
for i := pos - 1; i >= 0 && (src[i] == ' ' || src[i] == '\t'); i-- {
space = append([]byte{src[i]}, space...)
}
text := append([]byte("// For SGo: "+buf.String()+"\n"), space...)
dstChunks = append(dstChunks, src[lastChunkEnd:pos], text)
lastChunkEnd = pos
}
var visitor visitorFunc
visitor = visitorFunc(func(node ast.Node) (w ast.Visitor) {
var typ ast.Expr
var name *ast.Ident
switch node := node.(type) {
case *ast.FuncDecl:
typ = node.Type
name = node.Name
case *ast.GenDecl:
if node.Lparen != 0 || node.Tok == token.IMPORT || node.Tok == token.CONST {
return visitor
}
switch spec := node.Specs[0].(type) {
case *ast.TypeSpec:
skipNextSpec = true
typ = spec.Type
name = spec.Name
case *ast.ValueSpec:
skipNextSpec = true
typ = spec.Type
if len(spec.Names.List) > 0 {
name = spec.Names.List[0]
}
}
switch typ.(type) {
case *ast.InterfaceType, *ast.StructType:
return visitor
}
case *ast.InterfaceType:
for i := 0; i < len(node.Methods.List); i++ {
item := node.Methods.List[i]
if len(item.Names) > 0 {
name = item.Names[0]
}
addDoc(item, name, item.Type)
}
return visitor
case *ast.StructType:
for i := 0; i < len(node.Fields.List); i++ {
item := node.Fields.List[i]
if len(item.Names) > 0 {
name = item.Names[0]
}
addDoc(item, name, item.Type)
}
return visitor
case *ast.TypeSpec:
if skipNextSpec {
skipNextSpec = false
return visitor
}
typ = node.Type
name = node.Name
case *ast.ValueSpec:
if skipNextSpec {
skipNextSpec = false
return visitor
}
typ = node.Type
if len(node.Names.List) > 0 {
name = node.Names.List[0]
}
default:
return visitor
}
addDoc(node, name, typ)
return visitor
})
ast.Walk(visitor, file)
if err != nil {
return nil, nil, err
}
dst := append(
[]byte("// Autogenerated by SGo revision: "+SGoRevision+"\n// DO NOT EDIT!\n\n"),
bytes.Join(append(dstChunks, src[lastChunkEnd:]), nil)...)
dstFile, err := parser.ParseFile(fset, file.Name.Name, dst, parser.ParseComments)
return dst, dstFile, err
}
