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package stylecheck // import "honnef.co/go/tools/stylecheck"
import (
"fmt"
"go/ast"
"go/constant"
"go/token"
"go/types"
"strconv"
"strings"
"unicode"
"unicode/utf8"
"honnef.co/go/tools/config"
"honnef.co/go/tools/internal/passes/buildssa"
. "honnef.co/go/tools/lint/lintdsl"
"honnef.co/go/tools/ssa"
"golang.org/x/tools/go/analysis"
"golang.org/x/tools/go/analysis/passes/inspect"
"golang.org/x/tools/go/ast/inspector"
"golang.org/x/tools/go/types/typeutil"
)
func CheckPackageComment(pass *analysis.Pass) (interface{}, error) {
// - At least one file in a non-main package should have a package comment
//
// - The comment should be of the form
// "Package x ...". This has a slight potential for false
// positives, as multiple files can have package comments, in
// which case they get appended. But that doesn't happen a lot in
// the real world.
if pass.Pkg.Name() == "main" {
return nil, nil
}
hasDocs := false
for _, f := range pass.Files {
if IsInTest(pass, f) {
continue
}
if f.Doc != nil && len(f.Doc.List) > 0 {
hasDocs = true
prefix := "Package " + f.Name.Name + " "
if !strings.HasPrefix(strings.TrimSpace(f.Doc.Text()), prefix) {
ReportNodef(pass, f.Doc, `package comment should be of the form "%s..."`, prefix)
}
f.Doc.Text()
}
}
if !hasDocs {
for _, f := range pass.Files {
if IsInTest(pass, f) {
continue
}
ReportNodef(pass, f, "at least one file in a package should have a package comment")
}
}
return nil, nil
}
func CheckDotImports(pass *analysis.Pass) (interface{}, error) {
for _, f := range pass.Files {
imports:
for _, imp := range f.Imports {
path := imp.Path.Value
path = path[1 : len(path)-1]
for _, w := range config.For(pass).DotImportWhitelist {
if w == path {
continue imports
}
}
if imp.Name != nil && imp.Name.Name == "." && !IsInTest(pass, f) {
ReportNodefFG(pass, imp, "should not use dot imports")
}
}
}
return nil, nil
}
func CheckBlankImports(pass *analysis.Pass) (interface{}, error) {
fset := pass.Fset
for _, f := range pass.Files {
if IsInMain(pass, f) || IsInTest(pass, f) {
continue
}
// Collect imports of the form `import _ "foo"`, i.e. with no
// parentheses, as their comment will be associated with the
// (paren-free) GenDecl, not the import spec itself.
//
// We don't directly process the GenDecl so that we can
// correctly handle the following:
//
// import _ "foo"
// import _ "bar"
//
// where only the first import should get flagged.
skip := map[ast.Spec]bool{}
ast.Inspect(f, func(node ast.Node) bool {
switch node := node.(type) {
case *ast.File:
return true
case *ast.GenDecl:
if node.Tok != token.IMPORT {
return false
}
if node.Lparen == token.NoPos && node.Doc != nil {
skip[node.Specs[0]] = true
}
return false
}
return false
})
for i, imp := range f.Imports {
pos := fset.Position(imp.Pos())
if !IsBlank(imp.Name) {
continue
}
// Only flag the first blank import in a group of imports,
// or don't flag any of them, if the first one is
// commented
if i > 0 {
prev := f.Imports[i-1]
prevPos := fset.Position(prev.Pos())
if pos.Line-1 == prevPos.Line && IsBlank(prev.Name) {
continue
}
}
if imp.Doc == nil && imp.Comment == nil && !skip[imp] {
ReportNodef(pass, imp, "a blank import should be only in a main or test package, or have a comment justifying it")
}
}
}
return nil, nil
}
func CheckIncDec(pass *analysis.Pass) (interface{}, error) {
// TODO(dh): this can be noisy for function bodies that look like this:
// x += 3
// ...
// x += 2
// ...
// x += 1
fn := func(node ast.Node) {
assign := node.(*ast.AssignStmt)
if assign.Tok != token.ADD_ASSIGN && assign.Tok != token.SUB_ASSIGN {
return
}
if (len(assign.Lhs) != 1 || len(assign.Rhs) != 1) ||
!IsIntLiteral(assign.Rhs[0], "1") {
return
}
suffix := ""
switch assign.Tok {
case token.ADD_ASSIGN:
suffix = "++"
case token.SUB_ASSIGN:
suffix = "--"
}
ReportNodef(pass, assign, "should replace %s with %s%s", Render(pass, assign), Render(pass, assign.Lhs[0]), suffix)
}
pass.ResultOf[inspect.Analyzer].(*inspector.Inspector).Preorder([]ast.Node{(*ast.AssignStmt)(nil)}, fn)
return nil, nil
}
func CheckErrorReturn(pass *analysis.Pass) (interface{}, error) {
fnLoop:
for _, fn := range pass.ResultOf[buildssa.Analyzer].(*buildssa.SSA).SrcFuncs {
sig := fn.Type().(*types.Signature)
rets := sig.Results()
if rets == nil || rets.Len() < 2 {
continue
}
if rets.At(rets.Len()-1).Type() == types.Universe.Lookup("error").Type() {
// Last return type is error. If the function also returns
// errors in other positions, that's fine.
continue
}
for i := rets.Len() - 2; i >= 0; i-- {
if rets.At(i).Type() == types.Universe.Lookup("error").Type() {
pass.Reportf(rets.At(i).Pos(), "error should be returned as the last argument")
continue fnLoop
}
}
}
return nil, nil
}
// CheckUnexportedReturn checks that exported functions on exported
// types do not return unexported types.
func CheckUnexportedReturn(pass *analysis.Pass) (interface{}, error) {
for _, fn := range pass.ResultOf[buildssa.Analyzer].(*buildssa.SSA).SrcFuncs {
if fn.Synthetic != "" || fn.Parent() != nil {
continue
}
if !ast.IsExported(fn.Name()) || IsInMain(pass, fn) || IsInTest(pass, fn) {
continue
}
sig := fn.Type().(*types.Signature)
if sig.Recv() != nil && !ast.IsExported(Dereference(sig.Recv().Type()).(*types.Named).Obj().Name()) {
continue
}
res := sig.Results()
for i := 0; i < res.Len(); i++ {
if named, ok := DereferenceR(res.At(i).Type()).(*types.Named); ok &&
!ast.IsExported(named.Obj().Name()) &&
named != types.Universe.Lookup("error").Type() {
pass.Reportf(fn.Pos(), "should not return unexported type")
}
}
}
return nil, nil
}
func CheckReceiverNames(pass *analysis.Pass) (interface{}, error) {
ssapkg := pass.ResultOf[buildssa.Analyzer].(*buildssa.SSA).Pkg
for _, m := range ssapkg.Members {
if T, ok := m.Object().(*types.TypeName); ok && !T.IsAlias() {
ms := typeutil.IntuitiveMethodSet(T.Type(), nil)
for _, sel := range ms {
fn := sel.Obj().(*types.Func)
recv := fn.Type().(*types.Signature).Recv()
if Dereference(recv.Type()) != T.Type() {
// skip embedded methods
continue
}
if recv.Name() == "self" || recv.Name() == "this" {
ReportfFG(pass, recv.Pos(), `receiver name should be a reflection of its identity; don't use generic names such as "this" or "self"`)
}
if recv.Name() == "_" {
ReportfFG(pass, recv.Pos(), "receiver name should not be an underscore, omit the name if it is unused")
}
}
}
}
return nil, nil
}
func CheckReceiverNamesIdentical(pass *analysis.Pass) (interface{}, error) {
ssapkg := pass.ResultOf[buildssa.Analyzer].(*buildssa.SSA).Pkg
for _, m := range ssapkg.Members {
names := map[string]int{}
var firstFn *types.Func
if T, ok := m.Object().(*types.TypeName); ok && !T.IsAlias() {
ms := typeutil.IntuitiveMethodSet(T.Type(), nil)
for _, sel := range ms {
fn := sel.Obj().(*types.Func)
recv := fn.Type().(*types.Signature).Recv()
if Dereference(recv.Type()) != T.Type() {
// skip embedded methods
continue
}
if firstFn == nil {
firstFn = fn
}
if recv.Name() != "" && recv.Name() != "_" {
names[recv.Name()]++
}
}
}
if len(names) > 1 {
var seen []string
for name, count := range names {
seen = append(seen, fmt.Sprintf("%dx %q", count, name))
}
pass.Reportf(firstFn.Pos(), "methods on the same type should have the same receiver name (seen %s)", strings.Join(seen, ", "))
}
}
return nil, nil
}
func CheckContextFirstArg(pass *analysis.Pass) (interface{}, error) {
// TODO(dh): this check doesn't apply to test helpers. Example from the stdlib:
// func helperCommandContext(t *testing.T, ctx context.Context, s ...string) (cmd *exec.Cmd) {
fnLoop:
for _, fn := range pass.ResultOf[buildssa.Analyzer].(*buildssa.SSA).SrcFuncs {
if fn.Synthetic != "" || fn.Parent() != nil {
continue
}
params := fn.Signature.Params()
if params.Len() < 2 {
continue
}
if types.TypeString(params.At(0).Type(), nil) == "context.Context" {
continue
}
for i := 1; i < params.Len(); i++ {
param := params.At(i)
if types.TypeString(param.Type(), nil) == "context.Context" {
pass.Reportf(param.Pos(), "context.Context should be the first argument of a function")
continue fnLoop
}
}
}
return nil, nil
}
func CheckErrorStrings(pass *analysis.Pass) (interface{}, error) {
objNames := map[*ssa.Package]map[string]bool{}
ssapkg := pass.ResultOf[buildssa.Analyzer].(*buildssa.SSA).Pkg
objNames[ssapkg] = map[string]bool{}
for _, m := range ssapkg.Members {
if typ, ok := m.(*ssa.Type); ok {
objNames[ssapkg][typ.Name()] = true
}
}
for _, fn := range pass.ResultOf[buildssa.Analyzer].(*buildssa.SSA).SrcFuncs {
objNames[fn.Package()][fn.Name()] = true
}
for _, fn := range pass.ResultOf[buildssa.Analyzer].(*buildssa.SSA).SrcFuncs {
if IsInTest(pass, fn) {
// We don't care about malformed error messages in tests;
// they're usually for direct human consumption, not part
// of an API
continue
}
for _, block := range fn.Blocks {
instrLoop:
for _, ins := range block.Instrs {
call, ok := ins.(*ssa.Call)
if !ok {
continue
}
if !IsCallTo(call.Common(), "errors.New") && !IsCallTo(call.Common(), "fmt.Errorf") {
continue
}
k, ok := call.Common().Args[0].(*ssa.Const)
if !ok {
continue
}
s := constant.StringVal(k.Value)
if len(s) == 0 {
continue
}
switch s[len(s)-1] {
case '.', ':', '!', '\n':
pass.Reportf(call.Pos(), "error strings should not end with punctuation or a newline")
}
idx := strings.IndexByte(s, ' ')
if idx == -1 {
// single word error message, probably not a real
// error but something used in tests or during
// debugging
continue
}
word := s[:idx]
first, n := utf8.DecodeRuneInString(word)
if !unicode.IsUpper(first) {
continue
}
for _, c := range word[n:] {
if unicode.IsUpper(c) {
// Word is probably an initialism or
// multi-word function name
continue instrLoop
}
}
word = strings.TrimRightFunc(word, func(r rune) bool { return unicode.IsPunct(r) })
if objNames[fn.Package()][word] {
// Word is probably the name of a function or type in this package
continue
}
// First word in error starts with a capital
// letter, and the word doesn't contain any other
// capitals, making it unlikely to be an
// initialism or multi-word function name.
//
// It could still be a proper noun, though.
pass.Reportf(call.Pos(), "error strings should not be capitalized")
}
}
}
return nil, nil
}
func CheckTimeNames(pass *analysis.Pass) (interface{}, error) {
suffixes := []string{
"Sec", "Secs", "Seconds",
"Msec", "Msecs",
"Milli", "Millis", "Milliseconds",
"Usec", "Usecs", "Microseconds",
"MS", "Ms",
}
fn := func(T types.Type, names []*ast.Ident) {
if !IsType(T, "time.Duration") && !IsType(T, "*time.Duration") {
return
}
for _, name := range names {
for _, suffix := range suffixes {
if strings.HasSuffix(name.Name, suffix) {
ReportNodef(pass, name, "var %s is of type %v; don't use unit-specific suffix %q", name.Name, T, suffix)
break
}
}
}
}
for _, f := range pass.Files {
ast.Inspect(f, func(node ast.Node) bool {
switch node := node.(type) {
case *ast.ValueSpec:
T := pass.TypesInfo.TypeOf(node.Type)
fn(T, node.Names)
case *ast.FieldList:
for _, field := range node.List {
T := pass.TypesInfo.TypeOf(field.Type)
fn(T, field.Names)
}
}
return true
})
}
return nil, nil
}
func CheckErrorVarNames(pass *analysis.Pass) (interface{}, error) {
for _, f := range pass.Files {
for _, decl := range f.Decls {
gen, ok := decl.(*ast.GenDecl)
if !ok || gen.Tok != token.VAR {
continue
}
for _, spec := range gen.Specs {
spec := spec.(*ast.ValueSpec)
if len(spec.Names) != len(spec.Values) {
continue
}
for i, name := range spec.Names {
val := spec.Values[i]
if !IsCallToAST(pass, val, "errors.New") && !IsCallToAST(pass, val, "fmt.Errorf") {
continue
}
prefix := "err"
if name.IsExported() {
prefix = "Err"
}
if !strings.HasPrefix(name.Name, prefix) {
ReportNodef(pass, name, "error var %s should have name of the form %sFoo", name.Name, prefix)
}
}
}
}
}
return nil, nil
}
var httpStatusCodes = map[int]string{
100: "StatusContinue",
101: "StatusSwitchingProtocols",
102: "StatusProcessing",
200: "StatusOK",
201: "StatusCreated",
202: "StatusAccepted",
203: "StatusNonAuthoritativeInfo",
204: "StatusNoContent",
205: "StatusResetContent",
206: "StatusPartialContent",
207: "StatusMultiStatus",
208: "StatusAlreadyReported",
226: "StatusIMUsed",
300: "StatusMultipleChoices",
301: "StatusMovedPermanently",
302: "StatusFound",
303: "StatusSeeOther",
304: "StatusNotModified",
305: "StatusUseProxy",
307: "StatusTemporaryRedirect",
308: "StatusPermanentRedirect",
400: "StatusBadRequest",
401: "StatusUnauthorized",
402: "StatusPaymentRequired",
403: "StatusForbidden",
404: "StatusNotFound",
405: "StatusMethodNotAllowed",
406: "StatusNotAcceptable",
407: "StatusProxyAuthRequired",
408: "StatusRequestTimeout",
409: "StatusConflict",
410: "StatusGone",
411: "StatusLengthRequired",
412: "StatusPreconditionFailed",
413: "StatusRequestEntityTooLarge",
414: "StatusRequestURITooLong",
415: "StatusUnsupportedMediaType",
416: "StatusRequestedRangeNotSatisfiable",
417: "StatusExpectationFailed",
418: "StatusTeapot",
422: "StatusUnprocessableEntity",
423: "StatusLocked",
424: "StatusFailedDependency",
426: "StatusUpgradeRequired",
428: "StatusPreconditionRequired",
429: "StatusTooManyRequests",
431: "StatusRequestHeaderFieldsTooLarge",
451: "StatusUnavailableForLegalReasons",
500: "StatusInternalServerError",
501: "StatusNotImplemented",
502: "StatusBadGateway",
503: "StatusServiceUnavailable",
504: "StatusGatewayTimeout",
505: "StatusHTTPVersionNotSupported",
506: "StatusVariantAlsoNegotiates",
507: "StatusInsufficientStorage",
508: "StatusLoopDetected",
510: "StatusNotExtended",
511: "StatusNetworkAuthenticationRequired",
}
func CheckHTTPStatusCodes(pass *analysis.Pass) (interface{}, error) {
whitelist := map[string]bool{}
for _, code := range config.For(pass).HTTPStatusCodeWhitelist {
whitelist[code] = true
}
fn := func(node ast.Node) bool {
if node == nil {
return true
}
call, ok := node.(*ast.CallExpr)
if !ok {
return true
}
var arg int
switch CallNameAST(pass, call) {
case "net/http.Error":
arg = 2
case "net/http.Redirect":
arg = 3
case "net/http.StatusText":
arg = 0
case "net/http.RedirectHandler":
arg = 1
default:
return true
}
lit, ok := call.Args[arg].(*ast.BasicLit)
if !ok {
return true
}
if whitelist[lit.Value] {
return true
}
n, err := strconv.Atoi(lit.Value)
if err != nil {
return true
}
s, ok := httpStatusCodes[n]
if !ok {
return true
}
ReportNodefFG(pass, lit, "should use constant http.%s instead of numeric literal %d", s, n)
return true
}
// OPT(dh): replace with inspector
for _, f := range pass.Files {
ast.Inspect(f, fn)
}
return nil, nil
}
func CheckDefaultCaseOrder(pass *analysis.Pass) (interface{}, error) {
fn := func(node ast.Node) {
stmt := node.(*ast.SwitchStmt)
list := stmt.Body.List
for i, c := range list {
if c.(*ast.CaseClause).List == nil && i != 0 && i != len(list)-1 {
ReportNodefFG(pass, c, "default case should be first or last in switch statement")
break
}
}
}
pass.ResultOf[inspect.Analyzer].(*inspector.Inspector).Preorder([]ast.Node{(*ast.SwitchStmt)(nil)}, fn)
return nil, nil
}
func CheckYodaConditions(pass *analysis.Pass) (interface{}, error) {
fn := func(node ast.Node) {
cond := node.(*ast.BinaryExpr)
if cond.Op != token.EQL && cond.Op != token.NEQ {
return
}
if _, ok := cond.X.(*ast.BasicLit); !ok {
return
}
if _, ok := cond.Y.(*ast.BasicLit); ok {
// Don't flag lit == lit conditions, just in case
return
}
ReportNodefFG(pass, cond, "don't use Yoda conditions")
}
pass.ResultOf[inspect.Analyzer].(*inspector.Inspector).Preorder([]ast.Node{(*ast.BinaryExpr)(nil)}, fn)
return nil, nil
}
func CheckInvisibleCharacters(pass *analysis.Pass) (interface{}, error) {
fn := func(node ast.Node) {
lit := node.(*ast.BasicLit)
if lit.Kind != token.STRING {
return
}
for _, r := range lit.Value {
if unicode.Is(unicode.Cf, r) {
ReportNodef(pass, lit, "string literal contains the Unicode format character %U, consider using the %q escape sequence", r, r)
} else if unicode.Is(unicode.Cc, r) && r != '\n' && r != '\t' && r != '\r' {
ReportNodef(pass, lit, "string literal contains the Unicode control character %U, consider using the %q escape sequence", r, r)
}
}
}
pass.ResultOf[inspect.Analyzer].(*inspector.Inspector).Preorder([]ast.Node{(*ast.BasicLit)(nil)}, fn)
return nil, nil
}