Exclude generated code from coverage

README.md

@@ -20,6 +20,13 @@ error rather than a panic.
 ### Notest comments
 Blocks or files with a `// notest` comment are excluded.
 
+### Generated code
+Generated code files, that contain the respective comment line that is
+specified by the [Go Team](https://github.com/golang/go/issues/41196) in
+[`go generate`](https://golang.org/s/generatedcode).
+
+This exclude is disabled by default. Use flag `-g` to enable this behavior.
+
 ### Blocks returning a error tested to be non-nil
 We only exclude blocks where the error being returned has been tested to be 
 non-nil, so:
@@ -114,6 +121,11 @@ courtney -t="-count=2" -t="-parallel=4"
 
 All the output from the `go test -v` command is shown.
 
+### Exclude generated code: -g
+`Exclude generated code from coverage`
+
+All generated code is excluded from coverage.
+
 # Output
 Courtney will fail if the tests fail. If the tests succeed, it will create or
 overwrite a `coverage.out` file in the current directory.

courtney.go

@@ -27,19 +27,21 @@ func main() {
 	argsFlag := new(argsValue)
 	flag.Var(argsFlag, "t", "Argument to pass to the 'go test' command. Can be used more than once.")
 	loadFlag := flag.String("l", "", "Load coverage file(s) instead of running 'go test'")
+	excludeGeneratedCodeFlag := flag.Bool("g", false, "Exclude generated code from coverage")
 
 	flag.Parse()
 
 	setup := &shared.Setup{
-		Env:      env,
-		Paths:    patsy.NewCache(env),
-		Enforce:  *enforceFlag,
-		Verbose:  *verboseFlag,
-		Short:    *shortFlag,
-		Timeout:  *timeoutFlag,
-		Output:   *outputFlag,
-		TestArgs: argsFlag.args,
-		Load:     *loadFlag,
+		Env:                  env,
+		Paths:                patsy.NewCache(env),
+		Enforce:              *enforceFlag,
+		Verbose:              *verboseFlag,
+		Short:                *shortFlag,
+		Timeout:              *timeoutFlag,
+		Output:               *outputFlag,
+		TestArgs:             argsFlag.args,
+		Load:                 *loadFlag,
+		ExcludeGeneratedCode: *excludeGeneratedCodeFlag,
 	}
 	if err := Run(setup); err != nil {
 		fmt.Printf("%+v", err)

scanner/generated.go

@@ -0,0 +1,36 @@
+// Copyright (c) 2013 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 or at
+// https://developers.google.com/open-source/licenses/bsd.
+
+// Taken from https://github.com/golang/lint/blob/85993ffd0a6cd043291f3f63d45d656d97b165bd/lint.go
+
+// Once https://github.com/golang/go/issues/28089 is implemented (proposal is accepted),
+// this can be replaced with the official implementation.
+
+package scanner
+
+import (
+	"bufio"
+	"bytes"
+)
+
+var (
+	genHdr = []byte("// Code generated ")
+	genFtr = []byte(" DO NOT EDIT.")
+)
+
+// isGenerated reports whether the source file is generated code
+// according the rules from https://golang.org/s/generatedcode.
+//
+func isGenerated(src []byte) bool {
+	sc := bufio.NewScanner(bytes.NewReader(src))
+	for sc.Scan() {
+		b := sc.Bytes()
+		if bytes.HasPrefix(b, genHdr) && bytes.HasSuffix(b, genFtr) && len(b) >= len(genHdr)+len(genFtr) {
+			return true
+		}
+	}
+	return false
+}

scanner/generated_test.go

@@ -0,0 +1,38 @@
+// Copyright (c) 2013 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 or at
+// https://developers.google.com/open-source/licenses/bsd.
+
+// Taken from https://github.com/golang/lint/blob/85993ffd0a6cd043291f3f63d45d656d97b165bd/lint_test.go
+
+package scanner
+
+import "testing"
+
+func TestIsGenerated(t *testing.T) {
+	tests := []struct {
+		source    string
+		generated bool
+	}{
+		{"// Code Generated by some tool. DO NOT EDIT.", false},
+		{"// Code generated by some tool. DO NOT EDIT.", true},
+		{"// Code generated by some tool. DO NOT EDIT", false},
+		{"// Code generated  DO NOT EDIT.", true},
+		{"// Code generated DO NOT EDIT.", false},
+		{"\t\t// Code generated by some tool. DO NOT EDIT.\npackage foo\n", false},
+		{"// Code generated by some tool. DO NOT EDIT.\npackage foo\n", true},
+		{"package foo\n// Code generated by some tool. DO NOT EDIT.\ntype foo int\n", true},
+		{"package foo\n // Code generated by some tool. DO NOT EDIT.\ntype foo int\n", false},
+		{"package foo\n// Code generated by some tool. DO NOT EDIT. \ntype foo int\n", false},
+		{"package foo\ntype foo int\n// Code generated by some tool. DO NOT EDIT.\n", true},
+		{"package foo\ntype foo int\n// Code generated by some tool. DO NOT EDIT.", true},
+	}
+
+	for i, test := range tests {
+		got := isGenerated([]byte(test.source))
+		if got != test.generated {
+			t.Errorf("test %d, isGenerated() = %v, want %v", i, got, test.generated)
+		}
+	}
+}

scanner/scanner.go

@@ -1,11 +1,13 @@
 package scanner
 
 import (
+	"bytes"
 	"fmt"
 	"go/ast"
 	"go/constant"
 	"go/token"
 	"go/types"
+	"os"
 
 	"github.com/dave/astrid"
 	"github.com/dave/brenda"
@@ -129,6 +131,22 @@ func (p *PackageMap) ScanPackage() error {
 			return errors.WithStack(err)
 		}
 	}
+
+	if p.setup.ExcludeGeneratedCode {
+		// Exclude complete files, if the code is generated.
+		for _, f := range p.pkg.GoFiles {
+			body, err := os.ReadFile(f)
+			if err != nil {
+				return errors.WithStack(err)
+			}
+			if !isGenerated(body) {
+				continue
+			}
+			for i := range bytes.Split(body, []byte("\n")) {
+				p.addExclude(f, i+1)
+			}
+		}
+	}
 	return nil
 }
 

scanner/scanner_test.go

@@ -686,6 +686,17 @@ func TestComments(t *testing.T) {
 	test(t, tests)
 }
 
+func TestGenerated(t *testing.T) {
+	tests := map[string]string{
+		"generated": `// Code generated by courtney. DO NOT EDIT.
+			package foo // *
+			func Baz() int { // *
+				return 0 // *
+			} // *`,
+	}
+	test(t, tests)
+}
+
 func test(t *testing.T, tests map[string]string) {
 	for name, source := range tests {
 		env := vos.Mock()
@@ -704,8 +715,9 @@ func test(t *testing.T, tests map[string]string) {
 
 		paths := patsy.NewCache(env)
 		setup := &shared.Setup{
-			Env:   env,
-			Paths: paths,
+			Env:                  env,
+			Paths:                paths,
+			ExcludeGeneratedCode: true,
 		}
 		if err := setup.Parse([]string{ppath}); err != nil {
 			t.Fatalf("Error parsing args in %s: %+v", name, err)
@@ -726,7 +738,8 @@ func test(t *testing.T, tests map[string]string) {
 		for i, line := range strings.Split(source, "\n") {
 			expected := strings.HasSuffix(line, "// *") ||
 				strings.HasSuffix(line, "//notest") ||
-				strings.HasSuffix(line, "// notest")
+				strings.HasSuffix(line, "// notest") ||
+				strings.HasSuffix(line, "// Code generated by courtney. DO NOT EDIT.")
 			if result[i+1] != expected {
 				t.Fatalf("Unexpected state in %s, line %d: %s\n", name, i, strconv.Quote(strings.Trim(line, "\t")))
 			}

shared/shared.go

@@ -10,16 +10,17 @@ import (
 // Setup holds globals, environment and command line flags for the courtney
 // command
 type Setup struct {
-	Env      vos.Env
-	Paths    *patsy.Cache
-	Enforce  bool
-	Verbose  bool
-	Short    bool
-	Timeout  string
-	Load     string
-	Output   string
-	TestArgs []string
-	Packages []PackageSpec
+	Env                  vos.Env
+	Paths                *patsy.Cache
+	Enforce              bool
+	Verbose              bool
+	Short                bool
+	Timeout              string
+	Load                 string
+	Output               string
+	TestArgs             []string
+	ExcludeGeneratedCode bool
+	Packages             []PackageSpec
 }
 
 // PackageSpec identifies a package by dir and path