x/tools/go/packages: add Embed support

Add EmbedFiles and EmbedPatterns to the exported set of information in
the Package struct. Available on Go 1.16+, everywhere that go:embed is
available.

Fixes golang/go#50720

Change-Id: Ie84402ace1151fedaaa2a81c881d0e3d1e3ed9a7
Reviewed-on: https://go-review.googlesource.com/c/tools/+/379974
Reviewed-by: Michael Matloob <matloob@golang.org>
Trust: Michael Matloob <matloob@golang.org>
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
gopls-CI: kokoro <noreply+kokoro@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

go/packages/golist.go

@@ -393,6 +393,8 @@ type jsonPackage struct {
 	CompiledGoFiles   []string
 	IgnoredGoFiles    []string
 	IgnoredOtherFiles []string
+	EmbedPatterns     []string
+	EmbedFiles        []string
 	CFiles            []string
 	CgoFiles          []string
 	CXXFiles          []string
@@ -565,6 +567,8 @@ func (state *golistState) createDriverResponse(words ...string) (*driverResponse
 			GoFiles:         absJoin(p.Dir, p.GoFiles, p.CgoFiles),
 			CompiledGoFiles: absJoin(p.Dir, p.CompiledGoFiles),
 			OtherFiles:      absJoin(p.Dir, otherFiles(p)...),
+			EmbedFiles:      absJoin(p.Dir, p.EmbedFiles),
+			EmbedPatterns:   absJoin(p.Dir, p.EmbedPatterns),
 			IgnoredFiles:    absJoin(p.Dir, p.IgnoredGoFiles, p.IgnoredOtherFiles),
 			forTest:         p.ForTest,
 			depsErrors:      p.DepsErrors,

go/packages/packages.go

@@ -80,6 +80,12 @@ const (
 
 	// NeedModule adds Module.
 	NeedModule
+
+	// NeedEmbedFiles adds EmbedFiles.
+	NeedEmbedFiles
+
+	// NeedEmbedPatterns adds EmbedPatterns.
+	NeedEmbedPatterns
 )
 
 const (
@@ -296,6 +302,14 @@ type Package struct {
 	// including assembly, C, C++, Fortran, Objective-C, SWIG, and so on.
 	OtherFiles []string
 
+	// EmbedFiles lists the absolute file paths of the package's files
+	// embedded with go:embed.
+	EmbedFiles []string
+
+	// EmbedPatterns lists the absolute file patterns of the package's
+	// files embedded with go:embed.
+	EmbedPatterns []string
+
 	// IgnoredFiles lists source files that are not part of the package
 	// using the current build configuration but that might be part of
 	// the package using other build configurations.
@@ -431,6 +445,8 @@ type flatPackage struct {
 	GoFiles         []string          `json:",omitempty"`
 	CompiledGoFiles []string          `json:",omitempty"`
 	OtherFiles      []string          `json:",omitempty"`
+	EmbedFiles      []string          `json:",omitempty"`
+	EmbedPatterns   []string          `json:",omitempty"`
 	IgnoredFiles    []string          `json:",omitempty"`
 	ExportFile      string            `json:",omitempty"`
 	Imports         map[string]string `json:",omitempty"`
@@ -454,6 +470,8 @@ func (p *Package) MarshalJSON() ([]byte, error) {
 		GoFiles:         p.GoFiles,
 		CompiledGoFiles: p.CompiledGoFiles,
 		OtherFiles:      p.OtherFiles,
+		EmbedFiles:      p.EmbedFiles,
+		EmbedPatterns:   p.EmbedPatterns,
 		IgnoredFiles:    p.IgnoredFiles,
 		ExportFile:      p.ExportFile,
 	}
@@ -481,6 +499,8 @@ func (p *Package) UnmarshalJSON(b []byte) error {
 		GoFiles:         flat.GoFiles,
 		CompiledGoFiles: flat.CompiledGoFiles,
 		OtherFiles:      flat.OtherFiles,
+		EmbedFiles:      flat.EmbedFiles,
+		EmbedPatterns:   flat.EmbedPatterns,
 		ExportFile:      flat.ExportFile,
 	}
 	if len(flat.Imports) > 0 {
@@ -752,6 +772,12 @@ func (ld *loader) refine(roots []string, list ...*Package) ([]*Package, error) {
 			ld.pkgs[i].OtherFiles = nil
 			ld.pkgs[i].IgnoredFiles = nil
 		}
+		if ld.requestedMode&NeedEmbedFiles == 0 {
+			ld.pkgs[i].EmbedFiles = nil
+		}
+		if ld.requestedMode&NeedEmbedPatterns == 0 {
+			ld.pkgs[i].EmbedPatterns = nil
+		}
 		if ld.requestedMode&NeedCompiledGoFiles == 0 {
 			ld.pkgs[i].CompiledGoFiles = nil
 		}

go/packages/packages_test.go

@@ -1077,6 +1077,10 @@ func testAbsoluteFilenames(t *testing.T, exporter packagestest.Exporter) {
 			"e/e2.go":         `package main; import _ "golang.org/fake/c"`,
 			"f/f.go":          `package f`,
 			"f/f.s":           ``,
+			"g/g.go":          `package g; import _ "embed";` + "\n//go:embed g2.txt\n" + `var s string`,
+			"g/g2.txt":        "hello",
+			"h/h.go":          `package g; import _ "embed";` + "\n//go:embed a*.txt\n" + `var s string`,
+			"h/aa.txt":        "hello",
 		}}})
 	defer exported.Cleanup()
 	exported.Config.Dir = filepath.Dir(filepath.Dir(exported.File("golang.org/fake", "a/a.go")))
@@ -1103,6 +1107,8 @@ func testAbsoluteFilenames(t *testing.T, exporter packagestest.Exporter) {
 		{"golang.org/fake/subdir/e", "d.go"},
 		{"golang.org/fake/e", "e.go e2.go"},
 		{"golang.org/fake/f", "f.go f.s"},
+		{"golang.org/fake/g", "g.go g2.txt"},
+		{"golang.org/fake/h", "h.go aa.txt"},
 		// Relative paths
 		{"./a", "a.go"},
 		{"./b/vendor/a", "a.go"},
@@ -1112,8 +1118,10 @@ func testAbsoluteFilenames(t *testing.T, exporter packagestest.Exporter) {
 		{"./subdir/e", "d.go"},
 		{"./e", "e.go e2.go"},
 		{"./f", "f.go f.s"},
+		{"./g", "g.go g2.txt"},
+		{"./h", "h.go aa.txt"},
 	} {
-		exported.Config.Mode = packages.LoadFiles
+		exported.Config.Mode = packages.LoadFiles | packages.NeedEmbedFiles
 		pkgs, err := packages.Load(exported.Config, test.pattern)
 		if err != nil {
 			t.Errorf("pattern %s: %v", test.pattern, err)
@@ -1133,6 +1141,9 @@ func testAbsoluteFilenames(t *testing.T, exporter packagestest.Exporter) {
 			for _, filename := range pkg.OtherFiles {
 				checkFile(filename)
 			}
+			for _, filename := range pkg.EmbedFiles {
+				checkFile(filename)
+			}
 			for _, filename := range pkg.IgnoredFiles {
 				checkFile(filename)
 			}
@@ -2707,7 +2718,7 @@ func errorMessages(errors []packages.Error) []string {
 }
 
 func srcs(p *packages.Package) []string {
-	return cleanPaths(append(p.GoFiles[:len(p.GoFiles):len(p.GoFiles)], p.OtherFiles...))
+	return cleanPaths(append(append(p.GoFiles[:len(p.GoFiles):len(p.GoFiles)], p.OtherFiles...), p.EmbedFiles...))
 }
 
 // cleanPaths attempts to reduce path names to stable forms