Support relative pkg paths with go modules

There is no public API for finding and reading the go.mod file, so copy some internals
from go to locate and read the package line from the go.mod file

testjson/pkgpathprefix.go

@@ -0,0 +1,126 @@
+package testjson
+
+import (
+	"bytes"
+	"go/build"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strconv"
+	"strings"
+)
+
+func relativePackagePath(pkgpath string) string {
+	if pkgpath == pkgPathPrefix {
+		return "."
+	}
+	return strings.TrimPrefix(pkgpath, pkgPathPrefix+"/")
+}
+
+func getPkgPathPrefix() string {
+	cwd, _ := os.Getwd()
+	if isGoModuleEnabled() {
+		prefix := getPkgPathPrefixFromGoModule(cwd)
+		if prefix != "" {
+			return prefix
+		}
+	}
+	return getPkgPathPrefixGoPath(cwd)
+}
+
+func isGoModuleEnabled() bool {
+	version := runtime.Version()
+	if strings.HasPrefix(version, "go1.10") {
+		return false
+	}
+	// Go modules may not be enabled if env var is unset, or set to auto, however
+	// we can always fall back to using GOPATH as the prefix if a go.mod is not
+	// found.
+	return os.Getenv("GO111MODULE") != "off"
+}
+
+// TODO: might not work on windows
+func getPkgPathPrefixGoPath(cwd string) string {
+	gopaths := strings.Split(build.Default.GOPATH, string(filepath.ListSeparator))
+	for _, gopath := range gopaths {
+		gosrcpath := gopath + "/src/"
+		if strings.HasPrefix(cwd, gosrcpath) {
+			return strings.TrimPrefix(cwd, gosrcpath)
+		}
+	}
+	return ""
+}
+
+func getPkgPathPrefixFromGoModule(cwd string) string {
+	filename := goModuleFilePath(cwd)
+	if filename == "" {
+		return ""
+	}
+	raw, err := ioutil.ReadFile(filename)
+	if err != nil {
+		// TODO: log.Warn
+		return ""
+	}
+	return pkgPathFromGoModuleFile(raw)
+}
+
+var (
+	slashSlash = []byte("//")
+	moduleStr  = []byte("module")
+)
+
+// Copy of ModulePath from golang.org/src/cmd/go/internal/modfile/read.go
+func pkgPathFromGoModuleFile(mod []byte) string {
+	for len(mod) > 0 {
+		line := mod
+		mod = nil
+		if i := bytes.IndexByte(line, '\n'); i >= 0 {
+			line, mod = line[:i], line[i+1:]
+		}
+		if i := bytes.Index(line, slashSlash); i >= 0 {
+			line = line[:i]
+		}
+		line = bytes.TrimSpace(line)
+		if !bytes.HasPrefix(line, moduleStr) {
+			continue
+		}
+		line = line[len(moduleStr):]
+		n := len(line)
+		line = bytes.TrimSpace(line)
+		if len(line) == n || len(line) == 0 {
+			continue
+		}
+
+		if line[0] == '"' || line[0] == '`' {
+			p, err := strconv.Unquote(string(line))
+			if err != nil {
+				return "" // malformed quoted string or multi-line module path
+			}
+			return p
+		}
+
+		return string(line)
+	}
+	return "" // missing module path
+}
+
+// A rough re-implementation of FindModuleRoot from
+// golang.org/src/cmd/go/internal/modload/init.go
+func goModuleFilePath(cwd string) string {
+	dir := filepath.Clean(cwd)
+
+	for {
+		path := filepath.Join(dir, "go.mod")
+		if _, err := os.Stat(path); err == nil {
+			return path
+		}
+		parent := filepath.Dir(dir)
+		if parent == dir {
+			return ""
+		}
+		dir = parent
+	}
+}
+
+var pkgPathPrefix = getPkgPathPrefix()

testjson/pkgpathprefix_test.go

@@ -0,0 +1,29 @@
+package testjson
+
+import (
+	"testing"
+
+	"gotest.tools/assert"
+	"gotest.tools/skip"
+)
+
+func TestRelativePackagePath(t *testing.T) {
+	prefix := "gotest.tools/gotestsum/testjson"
+	defer patchPkgPathPrefix(prefix)()
+	relPath := relativePackagePath(prefix + "/extra/relpath")
+	assert.Equal(t, relPath, "extra/relpath")
+
+	relPath = relativePackagePath(prefix)
+	assert.Equal(t, relPath, ".")
+}
+
+func TestGetPkgPathPrefix(t *testing.T) {
+	t.Run("with go path", func(t *testing.T) {
+		skip.If(t, isGoModuleEnabled())
+		assert.Equal(t, getPkgPathPrefix(), "gotest.tools/gotestsum/testjson")
+	})
+	t.Run("with go modules", func(t *testing.T) {
+		skip.If(t, !isGoModuleEnabled())
+		assert.Equal(t, getPkgPathPrefix(), "gotest.tools/gotestsum")
+	})
+}

testjson/printer.go

@@ -2,9 +2,6 @@ package testjson
 
 import (
 	"fmt"
-	"go/build"
-	"os"
-	"path/filepath"
 	"strings"
 
 	"github.com/fatih/color"
@@ -157,28 +154,6 @@ func colorEvent(event TestEvent) func(format string, a ...interface{}) string {
 	return color.WhiteString
 }
 
-func relativePackagePath(pkgpath string) string {
-	if pkgpath == pkgPathPrefix {
-		return "."
-	}
-	return strings.TrimPrefix(pkgpath, pkgPathPrefix+"/")
-}
-
-// TODO: might not work on windows
-func getPkgPathPrefix() string {
-	cwd, _ := os.Getwd()
-	gopaths := strings.Split(build.Default.GOPATH, string(filepath.ListSeparator))
-	for _, gopath := range gopaths {
-		gosrcpath := gopath + "/src/"
-		if strings.HasPrefix(cwd, gosrcpath) {
-			return strings.TrimPrefix(cwd, gosrcpath)
-		}
-	}
-	return ""
-}
-
-var pkgPathPrefix = getPkgPathPrefix()
-
 // NewEventFormatter returns a formatter for printing events.
 func NewEventFormatter(format string) EventFormatter {
 	switch format {

testjson/printer_test.go

@@ -54,20 +54,6 @@ func patchPkgPathPrefix(val string) func() {
 	return func() { pkgPathPrefix = oldVal }
 }
 
-func TestRelativePackagePath(t *testing.T) {
-	relPath := relativePackagePath(
-		"gotest.tools/gotestsum/testjson/extra/relpath")
-	assert.Equal(t, relPath, "extra/relpath")
-
-	relPath = relativePackagePath(
-		"gotest.tools/gotestsum/testjson")
-	assert.Equal(t, relPath, ".")
-}
-
-func TestGetPkgPathPrefix(t *testing.T) {
-	assert.Equal(t, pkgPathPrefix, "gotest.tools/gotestsum/testjson")
-}
-
 func TestScanTestOutputWithShortVerboseFormat(t *testing.T) {
 	defer patchPkgPathPrefix("github.com/gotestyourself/gotestyourself")()