cmd/vet: add a check for tests with malformed names

According to golang.org/pkg/testing the first character after Test has
to be non-lowercase. Functions that don't conform to this are not
considered tests and are not loaded which can cause surprises.

This change adds a check to warn about Test-like functions in a _test
file that are not actually run by go test.

Moved over from https://go-review.googlesource.com/#/c/19466/

Change-Id: I2f89676058b27a0e35f721bdabc9fa8a9d34430d
Reviewed-on: https://go-review.googlesource.com/19724Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Rob Pike <r@golang.org>

src/cmd/vet/doc.go

@@ -85,12 +85,12 @@ Flag: -copylocks
 
 Locks that are erroneously passed by value.
 
-Documentation examples
+Tests, benchmarks and documentation examples
 
-Flag: -example
+Flag: -tests
 
-Mistakes involving example tests, including examples with incorrect names or
-function signatures, or that document identifiers not in the package.
+Mistakes involving tests including functions with incorrect names or signatures
+and example tests that document identifiers not in the package.
 
 Methods
 

src/cmd/vet/testdata/examples_test.go → src/cmd/vet/testdata/tests_test.go

-// Test of examples.
-
 package testdata
 
+import (
+	"testing"
+)
+
 // Buf is a ...
 type Buf []byte
 
@@ -46,3 +48,27 @@ func ExamplePuffer() // ERROR "ExamplePuffer refers to unknown identifier: Puffe
 func ExamplePuffer_Append() // ERROR "ExamplePuffer_Append refers to unknown identifier: Puffer"
 
 func ExamplePuffer_suffix() // ERROR "ExamplePuffer_suffix refers to unknown identifier: Puffer"
+
+func nonTest() {} // OK because it doesn't start with "Test".
+
+func (Buf) TesthasReceiver() {} // OK because it has a receiver.
+
+func TestOKSuffix(*testing.T) {} // OK because first char after "Test" is Uppercase.
+
+func TestÜnicodeWorks(*testing.T) {} // OK because the first char after "Test" is Uppercase.
+
+func TestbadSuffix(*testing.T) {} // ERROR "first letter after 'Test' must not be lowercase"
+
+func TestemptyImportBadSuffix(*T) {} // ERROR "first letter after 'Test' must not be lowercase"
+
+func Test(*testing.T) {} // OK "Test" on its own is considered a test.
+
+func Testify() {} // OK because it takes no parameters.
+
+func TesttooManyParams(*testing.T, string) {} // OK because it takes too many parameters.
+
+func TesttooManyNames(a, b *testing.T) {} // OK because it takes too many names.
+
+func TestnoTParam(string) {} // OK because it doesn't take a *testing.T
+
+func BenchmarkbadSuffix(*testing.B) {} // ERROR "first letter after 'Benchmark' must not be lowercase"

src/cmd/vet/example.go → src/cmd/vet/tests.go

@@ -13,9 +13,9 @@ import (
 )
 
 func init() {
-	register("example",
-		"check for common mistaken usages of documentation examples",
-		checkExample,
+	register("tests",
+		"check for common mistaken usages of tests/documentation examples",
+		checkTestFunctions,
 		funcDecl)
 }
 
@@ -24,32 +24,47 @@ func isExampleSuffix(s string) bool {
 	return size > 0 && unicode.IsLower(r)
 }
 
-// checkExample walks the documentation example functions checking for common
-// mistakes of misnamed functions, failure to map functions to existing
-// identifiers, etc.
-func checkExample(f *File, node ast.Node) {
-	if !strings.HasSuffix(f.name, "_test.go") {
-		return
+func isTestSuffix(name string) bool {
+	if len(name) == 0 {
+		// "Test" is ok.
+		return true
 	}
-	var (
-		pkg     = f.pkg
-		pkgName = pkg.typesPkg.Name()
-		scopes  = []*types.Scope{pkg.typesPkg.Scope()}
-		lookup  = func(name string) types.Object {
+	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(name string, scopes []*types.Scope) types.Object {
 	for _, scope := range scopes {
 		if o := scope.Lookup(name); o != nil {
 			return o
 		}
 	}
 	return nil
-		}
-	)
-	if strings.HasSuffix(pkgName, "_test") {
-		// Treat 'package foo_test' as an alias for 'package foo'.
-		var (
-			basePkg = strings.TrimSuffix(pkgName, "_test")
-			pkg     = f.pkg
-		)
+}
+
+func extendedScope(pkg *Package) []*types.Scope {
+	scopes := []*types.Scope{pkg.typesPkg.Scope()}
+
+	pkgName := pkg.typesPkg.Name()
+	if strings.HasPrefix(pkgName, "_test") {
+		basePkg := strings.TrimSuffix(pkgName, "_test")
 		for _, p := range pkg.typesPkg.Imports() {
 			if p.Name() == basePkg {
 				scopes = append(scopes, p.Scope())
@@ -57,40 +72,35 @@ func checkExample(f *File, node ast.Node) {
 			}
 		}
 	}
-	fn, ok := node.(*ast.FuncDecl)
-	if !ok {
-		// Ignore non-functions.
-		return
-	}
-	var (
-		fnName = fn.Name.Name
-		report = func(format string, args ...interface{}) { f.Badf(node.Pos(), format, args...) }
-	)
-	if fn.Recv != nil || !strings.HasPrefix(fnName, "Example") {
-		// Ignore methods and types not named "Example".
-		return
-	}
+	return scopes
+}
+
+func checkExample(fn *ast.FuncDecl, pkg *Package, report reporter) {
+	fnName := fn.Name.Name
 	if params := fn.Type.Params; len(params.List) != 0 {
 		report("%s should be niladic", fnName)
 	}
 	if results := fn.Type.Results; results != nil && len(results.List) != 0 {
 		report("%s should return nothing", fnName)
 	}
-	if fnName == "Example" {
-		// Nothing more to do.
-		return
-	}
+
 	if filesRun && !includesNonTest {
 		// The coherence checks between a test and the package it tests
 		// will report false positives if no non-test files have
 		// been provided.
 		return
 	}
+
+	if fnName == "Example" {
+		// Nothing more to do.
+		return
+	}
+
 	var (
 		exName = strings.TrimPrefix(fnName, "Example")
 		elems  = strings.SplitN(exName, "_", 3)
 		ident  = elems[0]
-		obj    = lookup(ident)
+		obj    = lookup(ident, extendedScope(pkg))
 	)
 	if ident != "" && obj == nil {
 		// Check ExampleFoo and ExampleBadFoo.
@@ -98,11 +108,11 @@ func checkExample(f *File, node ast.Node) {
 		// Abort since obj is absent and no subsequent checks can be performed.
 		return
 	}
-	if elemCnt := strings.Count(exName, "_"); elemCnt == 0 {
+	if len(elems) < 2 {
 		// Nothing more to do.
 		return
 	}
-	mmbr := elems[1]
+
 	if ident == "" {
 		// Check Example_suffix and Example_BadSuffix.
 		if residual := strings.TrimPrefix(exName, "_"); !isExampleSuffix(residual) {
@@ -110,6 +120,8 @@ func checkExample(f *File, node ast.Node) {
 		}
 		return
 	}
+
+	mmbr := elems[1]
 	if !isExampleSuffix(mmbr) {
 		// Check ExampleFoo_Method and ExampleFoo_BadMethod.
 		if obj, _, _ := types.LookupFieldOrMethod(obj.Type(), true, obj.Pkg(), mmbr); obj == nil {
@@ -120,5 +132,51 @@ func checkExample(f *File, node ast.Node) {
 		// Check ExampleFoo_Method_suffix and ExampleFoo_Method_Badsuffix.
 		report("%s has malformed example suffix: %s", fnName, elems[2])
 	}
+}
+
+func checkTest(fn *ast.FuncDecl, prefix string, report reporter) {
+	// 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):]) {
+		report("%s has malformed name: first letter after '%s' must not be lowercase", fn.Name.Name, prefix)
+	}
+}
+
+type reporter func(format string, args ...interface{})
+
+// checkTestFunctions walks Test, Benchmark and Example functions checking
+// malformed names, wrong signatures and examples documenting inexistent
+// identifiers.
+func checkTestFunctions(f *File, node ast.Node) {
+	if !strings.HasSuffix(f.name, "_test.go") {
+		return
+	}
+
+	fn, ok := node.(*ast.FuncDecl)
+	if !ok || fn.Recv != nil {
+		// Ignore non-functions or functions with receivers.
 		return
+	}
+
+	report := func(format string, args ...interface{}) { f.Badf(node.Pos(), format, args...) }
+
+	switch {
+	case strings.HasPrefix(fn.Name.Name, "Example"):
+		checkExample(fn, f.pkg, report)
+	case strings.HasPrefix(fn.Name.Name, "Test"):
+		checkTest(fn, "Test", report)
+	case strings.HasPrefix(fn.Name.Name, "Benchmark"):
+		checkTest(fn, "Benchmark", report)
+	}
 }