go/build: report positions for go:embed directives

For #43469
For #43632

Change-Id: I9ac2da690344935da0e1dbe00b134dfcee65ec8a
Reviewed-on: https://go-review.googlesource.com/c/go/+/283636
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Jay Conrod <jayconrod@google.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

3 files changed, 133 insertions, 66 deletions

diff --git a/src/go/build/build.go b/src/go/build/build.go
index 82e481bdc2..72311c7d2c 100644
--- a/src/go/build/build.go
+++ b/src/go/build/build.go
@@ -449,9 +449,12 @@ type Package struct {
 	//	//go:embed a* b.c
 	// then the list will contain those two strings as separate entries.
 	// (See package embed for more details about //go:embed.)
-	EmbedPatterns      []string // patterns from GoFiles, CgoFiles
-	TestEmbedPatterns  []string // patterns from TestGoFiles
-	XTestEmbedPatterns []string // patterns from XTestGoFiles
+	EmbedPatterns        []string                    // patterns from GoFiles, CgoFiles
+	EmbedPatternPos      map[string][]token.Position // line information for EmbedPatterns
+	TestEmbedPatterns    []string                    // patterns from TestGoFiles
+	TestEmbedPatternPos  map[string][]token.Position // line information for TestEmbedPatterns
+	XTestEmbedPatterns   []string                    // patterns from XTestGoFiles
+	XTestEmbedPatternPos map[string][]token.Position // line information for XTestEmbedPatternPos
 }
 
 // IsCommand reports whether the package is considered a
@@ -794,10 +797,12 @@ Found:
 	var badGoError error
 	var Sfiles []string // files with ".S"(capital S)/.sx(capital s equivalent for case insensitive filesystems)
 	var firstFile, firstCommentFile string
-	var embeds, testEmbeds, xTestEmbeds []string
-	imported := make(map[string][]token.Position)
-	testImported := make(map[string][]token.Position)
-	xTestImported := make(map[string][]token.Position)
+	embedPos := make(map[string][]token.Position)
+	testEmbedPos := make(map[string][]token.Position)
+	xTestEmbedPos := make(map[string][]token.Position)
+	importPos := make(map[string][]token.Position)
+	testImportPos := make(map[string][]token.Position)
+	xTestImportPos := make(map[string][]token.Position)
 	allTags := make(map[string]bool)
 	fset := token.NewFileSet()
 	for _, d := range dirs {
@@ -920,31 +925,31 @@ Found:
 			}
 		}
 
-		var fileList, embedList *[]string
-		var importMap map[string][]token.Position
+		var fileList *[]string
+		var importMap, embedMap map[string][]token.Position
 		switch {
 		case isCgo:
 			allTags["cgo"] = true
 			if ctxt.CgoEnabled {
 				fileList = &p.CgoFiles
-				importMap = imported
-				embedList = &embeds
+				importMap = importPos
+				embedMap = embedPos
 			} else {
-				// Ignore imports from cgo files if cgo is disabled.
+				// Ignore imports and embeds from cgo files if cgo is disabled.
 				fileList = &p.IgnoredGoFiles
 			}
 		case isXTest:
 			fileList = &p.XTestGoFiles
-			importMap = xTestImported
-			embedList = &xTestEmbeds
+			importMap = xTestImportPos
+			embedMap = xTestEmbedPos
 		case isTest:
 			fileList = &p.TestGoFiles
-			importMap = testImported
-			embedList = &testEmbeds
+			importMap = testImportPos
+			embedMap = testEmbedPos
 		default:
 			fileList = &p.GoFiles
-			importMap = imported
-			embedList = &embeds
+			importMap = importPos
+			embedMap = embedPos
 		}
 		*fileList = append(*fileList, name)
 		if importMap != nil {
@@ -952,8 +957,10 @@ Found:
 				importMap[imp.path] = append(importMap[imp.path], fset.Position(imp.pos))
 			}
 		}
-		if embedList != nil {
-			*embedList = append(*embedList, info.embeds...)
+		if embedMap != nil {
+			for _, emb := range info.embeds {
+				embedMap[emb.pattern] = append(embedMap[emb.pattern], emb.pos)
+			}
 		}
 	}
 
@@ -962,13 +969,13 @@ Found:
 	}
 	sort.Strings(p.AllTags)
 
-	p.EmbedPatterns = uniq(embeds)
-	p.TestEmbedPatterns = uniq(testEmbeds)
-	p.XTestEmbedPatterns = uniq(xTestEmbeds)
+	p.EmbedPatterns, p.EmbedPatternPos = cleanDecls(embedPos)
+	p.TestEmbedPatterns, p.TestEmbedPatternPos = cleanDecls(testEmbedPos)
+	p.XTestEmbedPatterns, p.XTestEmbedPatternPos = cleanDecls(xTestEmbedPos)
 
-	p.Imports, p.ImportPos = cleanImports(imported)
-	p.TestImports, p.TestImportPos = cleanImports(testImported)
-	p.XTestImports, p.XTestImportPos = cleanImports(xTestImported)
+	p.Imports, p.ImportPos = cleanDecls(importPos)
+	p.TestImports, p.TestImportPos = cleanDecls(testImportPos)
+	p.XTestImports, p.XTestImportPos = cleanDecls(xTestImportPos)
 
 	// add the .S/.sx files only if we are using cgo
 	// (which means gcc will compile them).
@@ -1340,7 +1347,7 @@ type fileInfo struct {
 	parsed   *ast.File
 	parseErr error
 	imports  []fileImport
-	embeds   []string
+	embeds   []fileEmbed
 	embedErr error
 }
 
@@ -1350,6 +1357,11 @@ type fileImport struct {
 	doc  *ast.CommentGroup
 }
 
+type fileEmbed struct {
+	pattern string
+	pos     token.Position
+}
+
 // matchFile determines whether the file with the given name in the given directory
 // should be included in the package being constructed.
 // If the file should be included, matchFile returns a non-nil *fileInfo (and a nil error).
@@ -1424,7 +1436,7 @@ func (ctxt *Context) matchFile(dir, name string, allTags map[string]bool, binary
 	return info, nil
 }
 
-func cleanImports(m map[string][]token.Position) ([]string, map[string][]token.Position) {
+func cleanDecls(m map[string][]token.Position) ([]string, map[string][]token.Position) {
 	all := make([]string, 0, len(m))
 	for path := range m {
 		all = append(all, path)
diff --git a/src/go/build/read.go b/src/go/build/read.go
index 6da921d471..aa7c6ee59e 100644
--- a/src/go/build/read.go
+++ b/src/go/build/read.go
@@ -10,6 +10,7 @@ import (
 	"fmt"
 	"go/ast"
 	"go/parser"
+	"go/token"
 	"io"
 	"strconv"
 	"strings"
@@ -24,6 +25,18 @@ type importReader struct {
 	err  error
 	eof  bool
 	nerr int
+	pos  token.Position
+}
+
+func newImportReader(name string, r io.Reader) *importReader {
+	return &importReader{
+		b: bufio.NewReader(r),
+		pos: token.Position{
+			Filename: name,
+			Line:     1,
+			Column:   1,
+		},
+	}
 }
 
 func isIdent(c byte) bool {
@@ -66,22 +79,32 @@ func (r *importReader) readByte() byte {
 // readByteNoBuf is like readByte but doesn't buffer the byte.
 // It exhausts r.buf before reading from r.b.
 func (r *importReader) readByteNoBuf() byte {
+	var c byte
+	var err error
 	if len(r.buf) > 0 {
-		c := r.buf[0]
+		c = r.buf[0]
 		r.buf = r.buf[1:]
-		return c
-	}
-	c, err := r.b.ReadByte()
-	if err == nil && c == 0 {
-		err = errNUL
+	} else {
+		c, err = r.b.ReadByte()
+		if err == nil && c == 0 {
+			err = errNUL
+		}
 	}
+
 	if err != nil {
 		if err == io.EOF {
 			r.eof = true
 		} else if r.err == nil {
 			r.err = err
 		}
-		c = 0
+		return 0
+	}
+	r.pos.Offset++
+	if c == '\n' {
+		r.pos.Line++
+		r.pos.Column = 1
+	} else {
+		r.pos.Column++
 	}
 	return c
 }
@@ -323,7 +346,7 @@ func (r *importReader) readImport() {
 // readComments is like io.ReadAll, except that it only reads the leading
 // block of comments in the file.
 func readComments(f io.Reader) ([]byte, error) {
-	r := &importReader{b: bufio.NewReader(f)}
+	r := newImportReader("", f)
 	r.peekByte(true)
 	if r.err == nil && !r.eof {
 		// Didn't reach EOF, so must have found a non-space byte. Remove it.
@@ -340,7 +363,7 @@ func readComments(f io.Reader) ([]byte, error) {
 // It only returns an error if there are problems reading the file,
 // not for syntax errors in the file itself.
 func readGoInfo(f io.Reader, info *fileInfo) error {
-	r := &importReader{b: bufio.NewReader(f)}
+	r := newImportReader(info.name, f)
 
 	r.readKeyword("package")
 	r.readIdent()
@@ -428,6 +451,7 @@ func readGoInfo(f io.Reader, info *fileInfo) error {
 		var line []byte
 		for first := true; r.findEmbed(first); first = false {
 			line = line[:0]
+			pos := r.pos
 			for {
 				c := r.readByteNoBuf()
 				if c == '\n' || r.err != nil || r.eof {
@@ -438,9 +462,9 @@ func readGoInfo(f io.Reader, info *fileInfo) error {
 			// Add args if line is well-formed.
 			// Ignore badly-formed lines - the compiler will report them when it finds them,
 			// and we can pretend they are not there to help go list succeed with what it knows.
-			args, err := parseGoEmbed(string(line))
+			embs, err := parseGoEmbed(string(line), pos)
 			if err == nil {
-				info.embeds = append(info.embeds, args...)
+				info.embeds = append(info.embeds, embs...)
 			}
 		}
 	}
@@ -450,11 +474,23 @@ func readGoInfo(f io.Reader, info *fileInfo) error {
 
 // parseGoEmbed parses the text following "//go:embed" to extract the glob patterns.
 // It accepts unquoted space-separated patterns as well as double-quoted and back-quoted Go strings.
-// There is a copy of this code in cmd/compile/internal/gc/noder.go as well.
-func parseGoEmbed(args string) ([]string, error) {
-	var list []string
-	for args = strings.TrimSpace(args); args != ""; args = strings.TrimSpace(args) {
+// This is based on a similar function in cmd/compile/internal/gc/noder.go;
+// this version calculates position information as well.
+func parseGoEmbed(args string, pos token.Position) ([]fileEmbed, error) {
+	trimBytes := func(n int) {
+		pos.Offset += n
+		pos.Column += utf8.RuneCountInString(args[:n])
+		args = args[n:]
+	}
+	trimSpace := func() {
+		trim := strings.TrimLeftFunc(args, unicode.IsSpace)
+		trimBytes(len(args) - len(trim))
+	}
+
+	var list []fileEmbed
+	for trimSpace(); args != ""; trimSpace() {
 		var path string
+		pathPos := pos
 	Switch:
 		switch args[0] {
 		default:
@@ -466,7 +502,7 @@ func parseGoEmbed(args string) ([]string, error) {
 				}
 			}
 			path = args[:i]
-			args = args[i:]
+			trimBytes(i)
 
 		case '`':
 			i := strings.Index(args[1:], "`")
@@ -474,7 +510,7 @@ func parseGoEmbed(args string) ([]string, error) {
 				return nil, fmt.Errorf("invalid quoted string in //go:embed: %s", args)
 			}
 			path = args[1 : 1+i]
-			args = args[1+i+1:]
+			trimBytes(1 + i + 1)
 
 		case '"':
 			i := 1
@@ -489,7 +525,7 @@ func parseGoEmbed(args string) ([]string, error) {
 						return nil, fmt.Errorf("invalid quoted string in //go:embed: %s", args[:i+1])
 					}
 					path = q
-					args = args[i+1:]
+					trimBytes(i + 1)
 					break Switch
 				}
 			}
@@ -504,7 +540,7 @@ func parseGoEmbed(args string) ([]string, error) {
 				return nil, fmt.Errorf("invalid quoted string in //go:embed: %s", args)
 			}
 		}
-		list = append(list, path)
+		list = append(list, fileEmbed{path, pathPos})
 	}
 	return list, nil
 }
diff --git a/src/go/build/read_test.go b/src/go/build/read_test.go
index 36c773ecea..32e6bae008 100644
--- a/src/go/build/read_test.go
+++ b/src/go/build/read_test.go
@@ -5,9 +5,9 @@
 package build
 
 import (
+	"fmt"
 	"go/token"
 	"io"
-	"reflect"
 	"strings"
 	"testing"
 )
@@ -228,36 +228,45 @@ func TestReadFailuresIgnored(t *testing.T) {
 }
 
 var readEmbedTests = []struct {
-	in  string
-	out []string
+	in, out string
 }{
 	{
 		"package p\n",
-		nil,
+		"",
 	},
 	{
 		"package p\nimport \"embed\"\nvar i int\n//go:embed x y z\nvar files embed.FS",
-		[]string{"x", "y", "z"},
+		`test:4:12:x
+		 test:4:14:y
+		 test:4:16:z`,
 	},
 	{
 		"package p\nimport \"embed\"\nvar i int\n//go:embed x \"\\x79\" `z`\nvar files embed.FS",
-		[]string{"x", "y", "z"},
+		`test:4:12:x
+		 test:4:14:y
+		 test:4:21:z`,
 	},
 	{
 		"package p\nimport \"embed\"\nvar i int\n//go:embed x y\n//go:embed z\nvar files embed.FS",
-		[]string{"x", "y", "z"},
+		`test:4:12:x
+		 test:4:14:y
+		 test:5:12:z`,
 	},
 	{
 		"package p\nimport \"embed\"\nvar i int\n\t //go:embed x y\n\t //go:embed z\n\t var files embed.FS",
-		[]string{"x", "y", "z"},
+		`test:4:14:x
+		 test:4:16:y
+		 test:5:14:z`,
 	},
 	{
 		"package p\nimport \"embed\"\n//go:embed x y z\nvar files embed.FS",
-		[]string{"x", "y", "z"},
+		`test:3:12:x
+		 test:3:14:y
+		 test:3:16:z`,
 	},
 	{
 		"package p\nimport \"embed\"\nvar s = \"/*\"\n//go:embed x\nvar files embed.FS",
-		[]string{"x"},
+		`test:4:12:x`,
 	},
 	{
 		`package p
@@ -265,38 +274,48 @@ var readEmbedTests = []struct {
 		 var s = "\"\\\\"
 		 //go:embed x
 		 var files embed.FS`,
-		[]string{"x"},
+		`test:4:15:x`,
 	},
 	{
 		"package p\nimport \"embed\"\nvar s = `/*`\n//go:embed x\nvar files embed.FS",
-		[]string{"x"},
+		`test:4:12:x`,
 	},
 	{
 		"package p\nimport \"embed\"\nvar s = z/ *y\n//go:embed pointer\nvar pointer embed.FS",
-		[]string{"pointer"},
+		"test:4:12:pointer",
 	},
 	{
 		"package p\n//go:embed x y z\n", // no import, no scan
-		nil,
+		"",
 	},
 	{
 		"package p\n//go:embed x y z\nvar files embed.FS", // no import, no scan
-		nil,
+		"",
 	},
 }
 
 func TestReadEmbed(t *testing.T) {
 	fset := token.NewFileSet()
 	for i, tt := range readEmbedTests {
-		var info fileInfo
-		info.fset = fset
+		info := fileInfo{
+			name: "test",
+			fset: fset,
+		}
 		err := readGoInfo(strings.NewReader(tt.in), &info)
 		if err != nil {
 			t.Errorf("#%d: %v", i, err)
 			continue
 		}
-		if !reflect.DeepEqual(info.embeds, tt.out) {
-			t.Errorf("#%d: embeds=%v, want %v", i, info.embeds, tt.out)
+		b := &strings.Builder{}
+		sep := ""
+		for _, emb := range info.embeds {
+			fmt.Fprintf(b, "%s%v:%s", sep, emb.pos, emb.pattern)
+			sep = "\n"
+		}
+		got := b.String()
+		want := strings.Join(strings.Fields(tt.out), "\n")
+		if got != want {
+			t.Errorf("#%d: embeds:\n%s\nwant:\n%s", i, got, want)
 		}
 	}
 }