354 lines
8.9 KiB
Text
354 lines
8.9 KiB
Text
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Статический Анализ Go Кода
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Короткий Фёдор
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* Работа с Go кодом в stdlib
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import (
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"go/types"
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"go/constant"
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"go/parser"
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"go/ast"
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"go/scanner"
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"go/token"
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"golang.org/x/tools/go/loader"
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)
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- `go/token` - определяет токены
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- `go/scanner` - разбивает файл с исходным кодом на токены
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- `go/ast` - определяет типы, из которых состоит AST
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- `go/parser` - рекурсивный парсер, строящий AST
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- `go/constant` - представление констант и операции над ними
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- `go/types` - реализует type-checker.
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* Type Checker
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Три процесса:
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1. Для каждого *имени* определяет *объявление*. (identifier resolution)
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var x int // declaration
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func F() {
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_ = x // name
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}
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2. Для каждого *выражения* определяет *тип*. (type deduction)
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time.Now().String()
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// time.Now() -> *time.Time
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// time.Now().String() -> string
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3. Для каждого *константного*выражения* определяет *значение*. (constant evaluation)
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const x = 1 + 2
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* Type Checker Fun Facts
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- Сonst evaluation depends on type deduction
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const x = unsafe.Sizeof(int(0))
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- Type deduction depends on const evalutation
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var y = [2+3]int{}
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- Identifier resolution depends on type deduction
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type T struct{ k int }
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var _ = T{k: 0}
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type T [10]int
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const k = 1
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var _ = T{k: 0}
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* Example
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.code pkginfo/main.go /const/,/END/
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* Run Example
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$ ./pkginfo
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Package "cmd/hello"
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Name: main
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Imports: [package fmt ("fmt")]
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Scope: package "cmd/hello" scope 0x820533590 {
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. func cmd/hello.main()
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}
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* Objects
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*Identifier*resolution* строит отображение из *имени* (`*ast.Ident`) в `Object` (например `var`, `const` или `func`).
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type Object interface {
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Name() string // package-local object name
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Exported() bool // reports whether the name starts with a capital letter
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Type() Type // object type
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Pos() token.Pos // position of object identifier in declaration
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Parent() *Scope // scope in which this object is declared
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Pkg() *Package // nil for objects in the Universe scope and labels
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Id() string // object id (see Ids section below)
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}
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* Objects
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Object = *Func // function, concrete method, or abstract method
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| *Var // variable, parameter, result, or struct field
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| *Const // constant
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| *TypeName // type name
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| *Label // statement label
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| *PkgName // package name, e.g. json after import "encoding/json"
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| *Builtin // predeclared function such as append or len
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| *Nil // predeclared nil
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Некоторые типы имеют дополнительные методы
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func (*Func) Scope() *Scope
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func (*Var) Anonymous() bool
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func (*Var) IsField() bool
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func (*Const) Val() constant.Value
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func (*TypeName) IsAlias() bool
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func (*PkgName) Imported() *Package
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* Identifier Resolution
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type Info struct {
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Defs map[*ast.Ident]Object
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Uses map[*ast.Ident]Object
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Implicits map[ast.Node]Object
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Selections map[*ast.SelectorExpr]*Selection
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Scopes map[ast.Node]*Scope
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...
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}
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Пример:
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var x int // def of x, use of int
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fmt.Println(x) // uses of fmt, Println, and x
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type T struct{U} // def of T, use of U (type), def of U (field)
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* Types
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type Type interface {
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Underlying() Type
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}
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Реализации Type
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Type = *Basic
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| *Pointer
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| *Array
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| *Slice
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| *Map
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| *Chan
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| *Struct
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| *Tuple
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| *Signature
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| *Named
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| *Interface
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* Struct types
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Описание структуры.
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type Struct struct{ ... }
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func (*Struct) NumFields() int
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func (*Struct) Field(i int) *Var
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func (*Struct) Tag(i int) string
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* Named Types
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type Celsius float64
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Идентификатор `Celsius` определяет объект `*TypeName`.
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`*TypeName` ссылается на `*Named` тип.
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type Named struct{ ... }
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func (*Named) NumMethods() int
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func (*Named) Method(i int) *Func
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func (*Named) Obj() *TypeName
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func (*Named) Underlying() Type
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`Underlying()` возвращает `int` в обоих случаях.
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type T int
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type U T
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* TypeAndValue
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Для каждого вырашения выводится тип. Он доступен в `Types`.
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type Info struct {
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...
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Types map[ast.Expr]TypeAndValue
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}
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`TypeAndValue` описывает тип, и опциональное значение (для констант).
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type TypeAndValue struct {
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Type Type
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Value constant.Value // for constant expressions only
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...
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}
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func (TypeAndValue) IsVoid() bool // e.g. "main()"
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func (TypeAndValue) IsType() bool // e.g. "*os.File"
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func (TypeAndValue) IsBuiltin() bool // e.g. "len(x)"
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func (TypeAndValue) IsValue() bool // e.g. "*os.Stdout"
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func (TypeAndValue) IsNil() bool // e.g. "nil"
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func (TypeAndValue) Addressable() bool // e.g. "a[i]" but not "f()", "m[key]"
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func (TypeAndValue) Assignable() bool // e.g. "a[i]", "m[key]"
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func (TypeAndValue) HasOk() bool // e.g. "<-ch", "m[key]"
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* Пример
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// CheckNilFuncComparison reports unintended comparisons
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// of functions against nil, e.g., "if x.Method == nil {".
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func CheckNilFuncComparison(info *types.Info, n ast.Node) {
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e, ok := n.(*ast.BinaryExpr)
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if !ok {
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return // not a binary operation
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}
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if e.Op != token.EQL && e.Op != token.NEQ {
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return // not a comparison
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}
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// If this is a comparison against nil, find the other operand.
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var other ast.Expr
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if info.Types[e.X].IsNil() {
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other = e.Y
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} else if info.Types[e.Y].IsNil() {
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other = e.X
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} else {
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return // not a comparison against nil
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}
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...
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* Пример
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// CheckNilFuncComparison reports unintended comparisons
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// of functions against nil, e.g., "if x.Method == nil {".
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func CheckNilFuncComparison(info *types.Info, n ast.Node) {
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...
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// Find the object.
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var obj types.Object
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switch v := other.(type) {
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case *ast.Ident:
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obj = info.Uses[v]
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case *ast.SelectorExpr:
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obj = info.Uses[v.Sel]
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default:
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return // not an identifier or selection
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}
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if _, ok := obj.(*types.Func); !ok {
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return // not a function or method
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}
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fmt.Printf("%s: comparison of function %v %v nil is always %v\n",
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fset.Position(e.Pos()), obj.Name(), e.Op, e.Op == token.NEQ)
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}
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* Analysis
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package unusedresult
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var Analyzer = &analysis.Analyzer{
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Name: "unusedresult",
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Doc: "check for unused results of calls to some functions",
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Run: run,
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...
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}
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func run(pass *analysis.Pass) (interface{}, error) {
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...
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}
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Analysis реализует одну проверку.
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* Pass
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type Pass struct {
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Fset *token.FileSet
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Files []*ast.File
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OtherFiles []string
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IgnoredFiles []string
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Pkg *types.Package
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TypesInfo *types.Info
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ResultOf map[*Analyzer]interface{}
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Report func(Diagnostic)
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...
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}
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Pass - это запуск одного Analysis на одном пакете.
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* Standalone
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package main
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import (
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"golang.org/x/tools/go/analysis/passes/findcall"
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"golang.org/x/tools/go/analysis/singlechecker"
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)
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func main() { singlechecker.Main(findcall.Analyzer) }
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* Unitchecker
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package main
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import (
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"golang.org/x/tools/go/analysis/passes/findcall"
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"golang.org/x/tools/go/analysis/unitchecker"
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)
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func main() { unitchecker.Main(findcall.Analyzer) }
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Запуск через govet.
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$ go vet -vettool=$(which vet)
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* analysistest
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package jokelint
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import (
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"testing"
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"golang.org/x/tools/go/analysis/analysistest"
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)
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func Test(t *testing.T) {
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testdata := analysistest.TestData()
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analysistest.Run(t, testdata, Analyzer, "tests/...")
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}
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Тесты хранятся в testdata/.
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package test
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import "fmt"
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func F() {
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fmt.Println("lol no generics") // want `outdated joke`
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}
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* Пример
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.code jokelint/analysis.go /package/,/^}/
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* Пример
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.code jokelint/analysis.go /func run/,/^}/
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* Пример
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.code jokelint/analysis.go /func visitCall/,/^}/
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