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errcheck.go
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errcheck.go
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// Package errcheck is the library used to implement the errcheck command-line tool.
//
// Note: The API of this package has not been finalized and may change at any point.
package errcheck
import (
"bufio"
"errors"
"fmt"
"go/ast"
"go/build"
"go/token"
"go/types"
"os"
"regexp"
"sort"
"strings"
"sync"
"golang.org/x/tools/go/loader"
)
var errorType *types.Interface
func init() {
errorType = types.Universe.Lookup("error").Type().Underlying().(*types.Interface)
}
var (
// ErrNoGoFiles is returned when CheckPackage is run on a package with no Go source files
ErrNoGoFiles = errors.New("package contains no go source files")
)
// UncheckedError indicates the position of an unchecked error return.
type UncheckedError struct {
Pos token.Position
Line string
}
// UncheckedErrors is returned from the CheckPackage function if the package contains
// any unchecked errors.
// Errors should be appended using the Append method, which is safe to use concurrently.
type UncheckedErrors struct {
mu sync.Mutex
// Errors is a list of all the unchecked errors in the package.
// Printing an error reports its position within the file and the contents of the line.
Errors []UncheckedError
}
func (e *UncheckedErrors) Append(errors ...UncheckedError) {
e.mu.Lock()
defer e.mu.Unlock()
e.Errors = append(e.Errors, errors...)
}
func (e *UncheckedErrors) Error() string {
return fmt.Sprintf("%d unchecked errors", len(e.Errors))
}
// Len is the number of elements in the collection.
func (e *UncheckedErrors) Len() int { return len(e.Errors) }
// Swap swaps the elements with indexes i and j.
func (e *UncheckedErrors) Swap(i, j int) { e.Errors[i], e.Errors[j] = e.Errors[j], e.Errors[i] }
type byName struct{ *UncheckedErrors }
// Less reports whether the element with index i should sort before the element with index j.
func (e byName) Less(i, j int) bool {
ei, ej := e.Errors[i], e.Errors[j]
pi, pj := ei.Pos, ej.Pos
if pi.Filename != pj.Filename {
return pi.Filename < pj.Filename
}
if pi.Line != pj.Line {
return pi.Line < pj.Line
}
if pi.Column != pj.Column {
return pi.Column < pj.Column
}
return ei.Line < ej.Line
}
type Checker struct {
// ignore is a map of package names to regular expressions. Identifiers from a package are
// checked against its regular expressions and if any of the expressions match the call
// is not checked.
Ignore map[string]*regexp.Regexp
// If blank is true then assignments to the blank identifier are also considered to be
// ignored errors.
Blank bool
// If asserts is true then ignored type assertion results are also checked
Asserts bool
// build tags
Tags []string
Verbose bool
// If true, checking of of _test.go files is disabled
WithoutTests bool
exclude map[string]bool
}
func NewChecker() *Checker {
c := Checker{}
c.SetExclude(map[string]bool{})
return &c
}
func (c *Checker) SetExclude(l map[string]bool) {
// Default exclude for stdlib functions
c.exclude = map[string]bool{
"math/rand.Read": true,
"(*math/rand.Rand).Read": true,
"(*bytes.Buffer).Write": true,
"(*bytes.Buffer).WriteByte": true,
"(*bytes.Buffer).WriteRune": true,
"(*bytes.Buffer).WriteString": true,
}
for k := range l {
c.exclude[k] = true
}
}
func (c *Checker) logf(msg string, args ...interface{}) {
if c.Verbose {
fmt.Fprintf(os.Stderr, msg+"\n", args...)
}
}
func (c *Checker) load(paths ...string) (*loader.Program, error) {
ctx := build.Default
for _, tag := range c.Tags {
ctx.BuildTags = append(ctx.BuildTags, tag)
}
loadcfg := loader.Config{
Build: &ctx,
}
rest, err := loadcfg.FromArgs(paths, !c.WithoutTests)
if err != nil {
return nil, fmt.Errorf("could not parse arguments: %s", err)
}
if len(rest) > 0 {
return nil, fmt.Errorf("unhandled extra arguments: %v", rest)
}
return loadcfg.Load()
}
// CheckPackages checks packages for errors.
func (c *Checker) CheckPackages(paths ...string) error {
program, err := c.load(paths...)
if err != nil {
return fmt.Errorf("could not type check: %s", err)
}
var wg sync.WaitGroup
u := &UncheckedErrors{}
for _, pkgInfo := range program.InitialPackages() {
if pkgInfo.Pkg.Path() == "unsafe" { // not a real package
continue
}
wg.Add(1)
go func(pkgInfo *loader.PackageInfo) {
defer wg.Done()
c.logf("Checking %s", pkgInfo.Pkg.Path())
v := &visitor{
prog: program,
pkg: pkgInfo,
ignore: c.Ignore,
blank: c.Blank,
asserts: c.Asserts,
lines: make(map[string][]string),
exclude: c.exclude,
errors: []UncheckedError{},
}
for _, astFile := range v.pkg.Files {
ast.Walk(v, astFile)
}
u.Append(v.errors...)
}(pkgInfo)
}
wg.Wait()
if u.Len() > 0 {
sort.Sort(byName{u})
return u
}
return nil
}
// visitor implements the errcheck algorithm
type visitor struct {
prog *loader.Program
pkg *loader.PackageInfo
ignore map[string]*regexp.Regexp
blank bool
asserts bool
lines map[string][]string
exclude map[string]bool
errors []UncheckedError
}
func (v *visitor) excludeCall(call *ast.CallExpr) bool {
sel, ok := call.Fun.(*ast.SelectorExpr)
if !ok {
return false
}
fn, ok := v.pkg.ObjectOf(sel.Sel).(*types.Func)
if !ok {
// Shouldn't happen, but be paranoid
return false
}
// The name is fully qualified by the import path, possible type,
// function/method name and pointer receiver.
//
// TODO(dh): vendored packages will have /vendor/ in their name,
// thus not matching vendored standard library packages. If we
// want to support vendored stdlib packages, we need to implement
// FullName with our own logic.
name := fn.FullName()
return v.exclude[name]
}
func (v *visitor) ignoreCall(call *ast.CallExpr) bool {
if v.excludeCall(call) {
return true
}
// Try to get an identifier.
// Currently only supports simple expressions:
// 1. f()
// 2. x.y.f()
var id *ast.Ident
switch exp := call.Fun.(type) {
case (*ast.Ident):
id = exp
case (*ast.SelectorExpr):
id = exp.Sel
default:
// eg: *ast.SliceExpr, *ast.IndexExpr
}
if id == nil {
return false
}
// If we got an identifier for the function, see if it is ignored
if re, ok := v.ignore[""]; ok && re.MatchString(id.Name) {
return true
}
if obj := v.pkg.Uses[id]; obj != nil {
if pkg := obj.Pkg(); pkg != nil {
if re, ok := v.ignore[pkg.Path()]; ok {
return re.MatchString(id.Name)
}
// if current package being considered is vendored, check to see if it should be ignored based
// on the unvendored path.
if nonVendoredPkg, ok := nonVendoredPkgPath(pkg.Path()); ok {
if re, ok := v.ignore[nonVendoredPkg]; ok {
return re.MatchString(id.Name)
}
}
}
}
return false
}
// nonVendoredPkgPath returns the unvendored version of the provided package path (or returns the provided path if it
// does not represent a vendored path). The second return value is true if the provided package was vendored, false
// otherwise.
func nonVendoredPkgPath(pkgPath string) (string, bool) {
lastVendorIndex := strings.LastIndex(pkgPath, "/vendor/")
if lastVendorIndex == -1 {
return pkgPath, false
}
return pkgPath[lastVendorIndex+len("/vendor/"):], true
}
// errorsByArg returns a slice s such that
// len(s) == number of return types of call
// s[i] == true iff return type at position i from left is an error type
func (v *visitor) errorsByArg(call *ast.CallExpr) []bool {
switch t := v.pkg.Types[call].Type.(type) {
case *types.Named:
// Single return
return []bool{isErrorType(t)}
case *types.Pointer:
// Single return via pointer
return []bool{isErrorType(t)}
case *types.Tuple:
// Multiple returns
s := make([]bool, t.Len())
for i := 0; i < t.Len(); i++ {
switch et := t.At(i).Type().(type) {
case *types.Named:
// Single return
s[i] = isErrorType(et)
case *types.Pointer:
// Single return via pointer
s[i] = isErrorType(et)
default:
s[i] = false
}
}
return s
}
return []bool{false}
}
func (v *visitor) callReturnsError(call *ast.CallExpr) bool {
if v.isRecover(call) {
return true
}
for _, isError := range v.errorsByArg(call) {
if isError {
return true
}
}
return false
}
// isRecover returns true if the given CallExpr is a call to the built-in recover() function.
func (v *visitor) isRecover(call *ast.CallExpr) bool {
if fun, ok := call.Fun.(*ast.Ident); ok {
if _, ok := v.pkg.Uses[fun].(*types.Builtin); ok {
return fun.Name == "recover"
}
}
return false
}
func (v *visitor) addErrorAtPosition(position token.Pos) {
pos := v.prog.Fset.Position(position)
lines, ok := v.lines[pos.Filename]
if !ok {
lines = readfile(pos.Filename)
v.lines[pos.Filename] = lines
}
line := "??"
if pos.Line-1 < len(lines) {
line = strings.TrimSpace(lines[pos.Line-1])
}
v.errors = append(v.errors, UncheckedError{pos, line})
}
func readfile(filename string) []string {
var f, err = os.Open(filename)
if err != nil {
return nil
}
var lines []string
var scanner = bufio.NewScanner(f)
for scanner.Scan() {
lines = append(lines, scanner.Text())
}
return lines
}
func (v *visitor) Visit(node ast.Node) ast.Visitor {
switch stmt := node.(type) {
case *ast.ExprStmt:
if call, ok := stmt.X.(*ast.CallExpr); ok {
if !v.ignoreCall(call) && v.callReturnsError(call) {
v.addErrorAtPosition(call.Lparen)
}
}
case *ast.GoStmt:
if !v.ignoreCall(stmt.Call) && v.callReturnsError(stmt.Call) {
v.addErrorAtPosition(stmt.Call.Lparen)
}
case *ast.DeferStmt:
if !v.ignoreCall(stmt.Call) && v.callReturnsError(stmt.Call) {
v.addErrorAtPosition(stmt.Call.Lparen)
}
case *ast.AssignStmt:
if len(stmt.Rhs) == 1 {
// single value on rhs; check against lhs identifiers
if call, ok := stmt.Rhs[0].(*ast.CallExpr); ok {
if !v.blank {
break
}
if v.ignoreCall(call) {
break
}
isError := v.errorsByArg(call)
for i := 0; i < len(stmt.Lhs); i++ {
if id, ok := stmt.Lhs[i].(*ast.Ident); ok {
// We shortcut calls to recover() because errorsByArg can't
// check its return types for errors since it returns interface{}.
if id.Name == "_" && (v.isRecover(call) || isError[i]) {
v.addErrorAtPosition(id.NamePos)
}
}
}
} else if assert, ok := stmt.Rhs[0].(*ast.TypeAssertExpr); ok {
if !v.asserts {
break
}
if assert.Type == nil {
// type switch
break
}
if len(stmt.Lhs) < 2 {
// assertion result not read
v.addErrorAtPosition(stmt.Rhs[0].Pos())
} else if id, ok := stmt.Lhs[1].(*ast.Ident); ok && v.blank && id.Name == "_" {
// assertion result ignored
v.addErrorAtPosition(id.NamePos)
}
}
} else {
// multiple value on rhs; in this case a call can't return
// multiple values. Assume len(stmt.Lhs) == len(stmt.Rhs)
for i := 0; i < len(stmt.Lhs); i++ {
if id, ok := stmt.Lhs[i].(*ast.Ident); ok {
if call, ok := stmt.Rhs[i].(*ast.CallExpr); ok {
if !v.blank {
continue
}
if v.ignoreCall(call) {
continue
}
if id.Name == "_" && v.callReturnsError(call) {
v.addErrorAtPosition(id.NamePos)
}
} else if assert, ok := stmt.Rhs[i].(*ast.TypeAssertExpr); ok {
if !v.asserts {
continue
}
if assert.Type == nil {
// Shouldn't happen anyway, no multi assignment in type switches
continue
}
v.addErrorAtPosition(id.NamePos)
}
}
}
}
default:
}
return v
}
func isErrorType(t types.Type) bool {
return types.Implements(t, errorType)
}