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// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package tests defines an Analyzer that checks for common mistaken
// usages of tests and examples.
package tests
import (
"go/ast"
"go/types"
"strings"
"unicode"
"unicode/utf8"
"golang.org/x/tools/go/analysis"
)
const Doc = `check for common mistaken usages of tests and examples
The tests checker walks Test, Benchmark and Example functions checking
malformed names, wrong signatures and examples documenting non-existent
identifiers.
Please see the documentation for package testing in golang.org/pkg/testing
for the conventions that are enforced for Tests, Benchmarks, and Examples.`
var Analyzer = &analysis.Analyzer{
Name: "tests",
Doc: Doc,
Run: run,
}
func run(pass *analysis.Pass) (interface{}, error) {
for _, f := range pass.Files {
if !strings.HasSuffix(pass.Fset.File(f.Pos()).Name(), "_test.go") {
continue
}
for _, decl := range f.Decls {
fn, ok := decl.(*ast.FuncDecl)
if !ok || fn.Recv != nil {
// Ignore non-functions or functions with receivers.
continue
}
switch {
case strings.HasPrefix(fn.Name.Name, "Example"):
checkExample(pass, fn)
case strings.HasPrefix(fn.Name.Name, "Test"):
checkTest(pass, fn, "Test")
case strings.HasPrefix(fn.Name.Name, "Benchmark"):
checkTest(pass, fn, "Benchmark")
}
}
}
return nil, nil
}
func isExampleSuffix(s string) bool {
r, size := utf8.DecodeRuneInString(s)
return size > 0 && unicode.IsLower(r)
}
func isTestSuffix(name string) bool {
if len(name) == 0 {
// "Test" is ok.
return true
}
r, _ := utf8.DecodeRuneInString(name)
return !unicode.IsLower(r)
}
func isTestParam(typ ast.Expr, wantType string) bool {
ptr, ok := typ.(*ast.StarExpr)
if !ok {
// Not a pointer.
return false
}
// No easy way of making sure it's a *testing.T or *testing.B:
// ensure the name of the type matches.
if name, ok := ptr.X.(*ast.Ident); ok {
return name.Name == wantType
}
if sel, ok := ptr.X.(*ast.SelectorExpr); ok {
return sel.Sel.Name == wantType
}
return false
}
func lookup(pkg *types.Package, name string) []types.Object {
if o := pkg.Scope().Lookup(name); o != nil {
return []types.Object{o}
}
var ret []types.Object
// Search through the imports to see if any of them define name.
// It's hard to tell in general which package is being tested, so
// for the purposes of the analysis, allow the object to appear
// in any of the imports. This guarantees there are no false positives
// because the example needs to use the object so it must be defined
// in the package or one if its imports. On the other hand, false
// negatives are possible, but should be rare.
for _, imp := range pkg.Imports() {
if obj := imp.Scope().Lookup(name); obj != nil {
ret = append(ret, obj)
}
}
return ret
}
func checkExample(pass *analysis.Pass, fn *ast.FuncDecl) {
fnName := fn.Name.Name
if params := fn.Type.Params; len(params.List) != 0 {
pass.Reportf(fn.Pos(), "%s should be niladic", fnName)
}
if results := fn.Type.Results; results != nil && len(results.List) != 0 {
pass.Reportf(fn.Pos(), "%s should return nothing", fnName)
}
if fnName == "Example" {
// Nothing more to do.
return
}
var (
exName = strings.TrimPrefix(fnName, "Example")
elems = strings.SplitN(exName, "_", 3)
ident = elems[0]
objs = lookup(pass.Pkg, ident)
)
if ident != "" && len(objs) == 0 {
// Check ExampleFoo and ExampleBadFoo.
pass.Reportf(fn.Pos(), "%s refers to unknown identifier: %s", fnName, ident)
// Abort since obj is absent and no subsequent checks can be performed.
return
}
if len(elems) < 2 {
// Nothing more to do.
return
}
if ident == "" {
// Check Example_suffix and Example_BadSuffix.
if residual := strings.TrimPrefix(exName, "_"); !isExampleSuffix(residual) {
pass.Reportf(fn.Pos(), "%s has malformed example suffix: %s", fnName, residual)
}
return
}
mmbr := elems[1]
if !isExampleSuffix(mmbr) {
// Check ExampleFoo_Method and ExampleFoo_BadMethod.
found := false
// Check if Foo.Method exists in this package or its imports.
for _, obj := range objs {
if obj, _, _ := types.LookupFieldOrMethod(obj.Type(), true, obj.Pkg(), mmbr); obj != nil {
found = true
break
}
}
if !found {
pass.Reportf(fn.Pos(), "%s refers to unknown field or method: %s.%s", fnName, ident, mmbr)
}
}
if len(elems) == 3 && !isExampleSuffix(elems[2]) {
// Check ExampleFoo_Method_suffix and ExampleFoo_Method_Badsuffix.
pass.Reportf(fn.Pos(), "%s has malformed example suffix: %s", fnName, elems[2])
}
}
func checkTest(pass *analysis.Pass, fn *ast.FuncDecl, prefix string) {
// Want functions with 0 results and 1 parameter.
if fn.Type.Results != nil && len(fn.Type.Results.List) > 0 ||
fn.Type.Params == nil ||
len(fn.Type.Params.List) != 1 ||
len(fn.Type.Params.List[0].Names) > 1 {
return
}
// The param must look like a *testing.T or *testing.B.
if !isTestParam(fn.Type.Params.List[0].Type, prefix[:1]) {
return
}
if !isTestSuffix(fn.Name.Name[len(prefix):]) {
pass.Reportf(fn.Pos(), "%s has malformed name: first letter after '%s' must not be lowercase", fn.Name.Name, prefix)
}
}
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