add a go_test directive to enable generating go_test targets per _test.go file

README.rst

@@ -735,6 +735,15 @@ The following directives are recognized:
 | ``proto_library`` rules. If there are any pre-generated Go files, they will be treated as  |
 | regular Go files.                                                                          |
 +---------------------------------------------------+----------------------------------------+
+| :direc:`# gazelle:go_test mode`                   | ``default``                            |
++---------------------------------------------------+----------------------------------------+
+| Tells Gazelle how to generate rules for _test.go files. Valid values are:                  |
+|                                                                                            |
+| * ``default``: One ``go_test`` rule will be generated whose ``srcs`` includes              |
+|   all ``_test.go`` files in the directory.                                                 |
+| * ``file``: A distinct ``go_test`` rule will be generated for each ``_test.go`` file in the|
+|   package directory.                                                                       |
++---------------------------------------------------+----------------------------------------+
 | :direc:`# gazelle:go_grpc_compilers`              | ``@io_bazel_rules_go//proto:go_grpc``  |
 +---------------------------------------------------+----------------------------------------+
 | The protocol buffers compiler(s) to use for building go bindings for gRPC.                 |

language/go/config.go

@@ -19,7 +19,6 @@ import (
 	"errors"
 	"flag"
 	"fmt"
-	"github.com/bazelbuild/bazel-gazelle/internal/module"
 	"go/build"
 	"io/ioutil"
 	"log"
@@ -30,6 +29,8 @@ import (
 	"strconv"
 	"strings"
 
+	"github.com/bazelbuild/bazel-gazelle/internal/module"
+
 	"github.com/bazelbuild/bazel-gazelle/config"
 	gzflag "github.com/bazelbuild/bazel-gazelle/flag"
 	"github.com/bazelbuild/bazel-gazelle/internal/version"
@@ -126,18 +127,55 @@ type goConfig struct {
 	// in internal packages.
 	submodules []moduleRepo
 
+	// testMode determines how go_test targets are generated.
+	testMode testMode
+
 	// buildDirectives, buildExternalAttr, buildExtraArgsAttr,
 	// buildFileGenerationAttr, buildFileNamesAttr, buildFileProtoModeAttr and
 	// buildTagsAttr are attributes for go_repository rules, set on the command
 	// line.
 	buildDirectivesAttr, buildExternalAttr, buildExtraArgsAttr, buildFileGenerationAttr, buildFileNamesAttr, buildFileProtoModeAttr, buildTagsAttr string
 }
 
+// testMode determines how go_test rules are generated.
+type testMode int
+
+const (
+	// defaultTestMode generates a go_test for the primary package in a directory.
+	defaultTestMode = iota
+
+	// fileTestMode generates a go_test for each Go test file.
+	fileTestMode
+)
+
 var (
 	defaultGoProtoCompilers = []string{"@io_bazel_rules_go//proto:go_proto"}
 	defaultGoGrpcCompilers  = []string{"@io_bazel_rules_go//proto:go_grpc"}
 )
 
+func (m testMode) String() string {
+	switch m {
+	case defaultTestMode:
+		return "default"
+	case fileTestMode:
+		return "file"
+	default:
+		log.Panicf("unknown mode %d", m)
+		return ""
+	}
+}
+
+func testModeFromString(s string) (testMode, error) {
+	switch s {
+	case "default":
+		return defaultTestMode, nil
+	case "file":
+		return fileTestMode, nil
+	default:
+		return 0, fmt.Errorf("unrecognized go_test mode: %q", s)
+	}
+}
+
 func newGoConfig() *goConfig {
 	gc := &goConfig{
 		goProtoCompilers: defaultGoProtoCompilers,
@@ -351,6 +389,7 @@ func (*goLang) KnownDirectives() []string {
 		"go_naming_convention",
 		"go_naming_convention_external",
 		"go_proto_compilers",
+		"go_test",
 		"go_visibility",
 		"importmap_prefix",
 		"prefix",
@@ -592,6 +631,14 @@ Update io_bazel_rules_go to a newer version in your WORKSPACE file.`
 					gc.goProtoCompilers = splitValue(d.Value)
 				}
 
+			case "go_test":
+				mode, err := testModeFromString(d.Value)
+				if err != nil {
+					log.Print(err)
+					continue
+				}
+				gc.testMode = mode
+
 			case "go_visibility":
 				gc.goVisibility = append(gc.goVisibility, strings.TrimSpace(d.Value))
 

language/go/generate.go

@@ -282,9 +282,8 @@ func (gl *goLang) GenerateRules(args language.GenerateArgs) language.GenerateRes
 			g.maybePublishToolLib(r, pkg)
 			rules = append(rules, r)
 		}
-		rules = append(rules,
-			g.generateBin(pkg, libName),
-			g.generateTest(pkg, libName))
+		rules = append(rules, g.generateBin(pkg, libName))
+		rules = append(rules, g.generateTests(pkg, libName)...)
 	}
 
 	for _, r := range rules {
@@ -517,22 +516,48 @@ func (g *generator) generateBin(pkg *goPackage, library string) *rule.Rule {
 	return goBinary
 }
 
-func (g *generator) generateTest(pkg *goPackage, library string) *rule.Rule {
+func (g *generator) generateTests(pkg *goPackage, library string) []*rule.Rule {
 	gc := getGoConfig(g.c)
-	name := testNameByConvention(gc.goNamingConvention, pkg.importPath)
-	goTest := rule.NewRule("go_test", name)
-	if !pkg.test.sources.hasGo() {
-		return goTest // empty
-	}
-	var embed string
-	if pkg.test.hasInternalTest {
-		embed = library
+	tests := pkg.tests
+	if len(tests) == 0 && gc.testMode == defaultTestMode {
+		tests = []goTarget{goTarget{}}
+	}
+	var name func(goTarget) string
+	switch gc.testMode {
+	case defaultTestMode:
+		name = func(goTarget) string {
+			return testNameByConvention(gc.goNamingConvention, pkg.importPath)
+		}
+	case fileTestMode:
+		name = func(test goTarget) string {
+			if test.sources.hasGo() {
+				if srcs := test.sources.buildFlat(); len(srcs) == 1 {
+					return testNameFromSingleSource(srcs[0])
+				}
+			}
+			return testNameByConvention(gc.goNamingConvention, pkg.importPath)
+		}
 	}
-	g.setCommonAttrs(goTest, pkg.rel, nil, pkg.test, embed)
-	if pkg.hasTestdata {
-		goTest.SetAttr("data", rule.GlobValue{Patterns: []string{"testdata/**"}})
+	var res []*rule.Rule
+	for i, test := range tests {
+		goTest := rule.NewRule("go_test", name(test))
+		hasGo := test.sources.hasGo()
+		if hasGo || i == 0 {
+			res = append(res, goTest)
+			if !hasGo {
+				continue
+			}
+		}
+		var embed string
+		if test.hasInternalTest {
+			embed = library
+		}
+		g.setCommonAttrs(goTest, pkg.rel, nil, test, embed)
+		if pkg.hasTestdata {
+			goTest.SetAttr("data", rule.GlobValue{Patterns: []string{"testdata/**"}})
+		}
 	}
-	return goTest
+	return res
 }
 
 // maybePublishToolLib makes the given go_library rule public if needed for nogo.

language/go/package.go

@@ -32,11 +32,12 @@ import (
 // goPackage contains metadata for a set of .go and .proto files that can be
 // used to generate Go rules.
 type goPackage struct {
-	name, dir, rel        string
-	library, binary, test goTarget
-	proto                 protoTarget
-	hasTestdata           bool
-	importPath            string
+	name, dir, rel  string
+	library, binary goTarget
+	tests           []goTarget
+	proto           protoTarget
+	hasTestdata     bool
+	importPath      string
 }
 
 // goTarget contains information used to generate an individual Go rule
@@ -107,9 +108,16 @@ func (pkg *goPackage) addFile(c *config.Config, er *embedResolver, info fileInfo
 		if info.isCgo {
 			return fmt.Errorf("%s: use of cgo in test not supported", info.path)
 		}
-		pkg.test.addFile(c, er, info)
+		if getGoConfig(c).testMode == fileTestMode || len(pkg.tests) == 0 {
+			pkg.tests = append(pkg.tests, goTarget{})
+		}
+		// Add the the file to the most recently added test target (in fileTestMode)
+		// or the only test target (in defaultMode).
+		// In both cases, this will be the last element in the slice.
+		test := &pkg.tests[len(pkg.tests)-1]
+		test.addFile(c, er, info)
 		if !info.isExternalTest {
-			pkg.test.hasInternalTest = true
+			test.hasInternalTest = true
 		}
 	default:
 		pkg.library.addFile(c, er, info)
@@ -136,8 +144,11 @@ func (pkg *goPackage) firstGoFile() string {
 	goSrcs := []platformStringsBuilder{
 		pkg.library.sources,
 		pkg.binary.sources,
-		pkg.test.sources,
 	}
+	for _, test := range pkg.tests {
+		goSrcs = append(goSrcs, test.sources)
+	}
+
 	for _, sb := range goSrcs {
 		if sb.strs != nil {
 			for s := range sb.strs {
@@ -151,7 +162,15 @@ func (pkg *goPackage) firstGoFile() string {
 }
 
 func (pkg *goPackage) haveCgo() bool {
-	return pkg.library.cgo || pkg.binary.cgo || pkg.test.cgo
+	if pkg.library.cgo || pkg.binary.cgo {
+		return true
+	}
+	for _, t := range pkg.tests {
+		if t.cgo {
+			return true
+		}
+	}
+	return false
 }
 
 func (pkg *goPackage) inferImportPath(c *config.Config) error {
@@ -217,6 +236,22 @@ func testNameByConvention(nc namingConvention, imp string) string {
 	return libName + "_test"
 }
 
+// testNameFromSingleSource returns a suitable name for a go_test using the
+// single Go source file name.
+func testNameFromSingleSource(src string) string {
+	if i := strings.LastIndexByte(src, '.'); i >= 0 {
+		src = src[0:i]
+	}
+	libName := libNameFromImportPath(src)
+	if libName == "" {
+		return ""
+	}
+	if strings.HasSuffix(libName, "_test") {
+		return libName
+	}
+	return libName + "_test"
+}
+
 // binName returns a suitable name for a go_binary.
 func binName(rel, prefix, repoRoot string) string {
 	return pathtools.RelBaseName(rel, prefix, repoRoot)

language/go/testdata/tests_per_file/BUILD.old

@@ -0,0 +1 @@
+# gazelle:go_test file

language/go/testdata/tests_per_file/BUILD.want

@@ -0,0 +1,35 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
+
+go_library(
+    name = "tests_per_file",
+    srcs = ["lib.go"],
+    _gazelle_imports = [],
+    importpath = "example.com/repo/tests_per_file",
+    visibility = ["//visibility:public"],
+)
+
+go_test(
+    name = "bar_test",
+    srcs = ["bar_test.go"],
+    _gazelle_imports = ["testing"],
+    embed = [":tests_per_file"],
+)
+
+go_test(
+    name = "external_test",
+    srcs = ["external_test.go"],
+    _gazelle_imports = [
+        "example.com/repo/tests_per_file",
+        "testing",
+    ],
+)
+
+go_test(
+    name = "foo_test",
+    srcs = ["foo_test.go"],
+    _gazelle_imports = [
+        "github.com/bazelbuild/bazel-gazelle/testtools",
+        "testing",
+    ],
+    embed = [":tests_per_file"],
+)

language/go/testdata/tests_per_file/bar_test.go

@@ -0,0 +1,5 @@
+package tests_per_file
+
+import "testing"
+
+func TestStuff(t *testing.T) {}

language/go/testdata/tests_per_file/external_test.go

@@ -0,0 +1,11 @@
+package tests_per_file_test
+
+import (
+	"testing"
+
+	"example.com/repo/tests_per_file"
+)
+
+func TestStuff(t *testing.T) {
+	var _ tests_per_file.Type
+}

language/go/testdata/tests_per_file/foo_test.go

@@ -0,0 +1,11 @@
+package tests_per_file
+
+import (
+	"testing"
+
+	"github.com/bazelbuild/bazel-gazelle/testtools"
+)
+
+type fileSpec testtools.FileSpec
+
+func TestStuff(t *testing.T) {}

language/go/testdata/tests_per_file/lib.go

@@ -0,0 +1,3 @@
+package tests_per_file
+
+type Type int

language/go/testdata/tests_per_file_from_default/BUILD.old

@@ -0,0 +1,29 @@
+# gazelle:go_test file
+load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
+
+go_library(
+    name = "tests_per_file_from_default",
+    srcs = ["lib.go"],
+    _gazelle_imports = [],
+    importpath = "example.com/repo/tests_per_file_from_default",
+    visibility = ["//visibility:public"],
+)
+
+go_test(
+    name = "test_per_file_from_default_test",
+    srcs = [
+        "bar_test.go",
+        "foo_test.go",
+    ],
+    _gazelle_imports = ["testing"],
+    embed = [":tests_per_file_from_default"],
+)
+
+go_test(
+    name = "external_test",
+    srcs = ["external_test.go"],
+    _gazelle_imports = [
+        "example.com/repo/tests_per_file_from_default",
+        "testing",
+    ],
+)