cue/load: remove import comment parsing

Import comments were introduced in Go 1.4 (see background document [1])
but as far as I am aware, have never been used or supported in CUE: they
were only useful in Go before the `go.mod` file made it possible to
declare a module name, and CUE has had `module.cue` files for a long
time. In any case, CUE generally uses attributes for this kind of thing
rather than comments.

So remove the import comment parsing and deprecate the
`cue/build.Instance.ImportComment` field.

Also in passing remove the unused `fsPath` type.

[1] https://docs.google.com/document/d/1jVFkZTcYbNLaTxXD9OcGfn7vYv5hWtPx9--lTx1gPMs/edit

Signed-off-by: Roger Peppe <[email protected]>
Change-Id: I48aefec1a37c73c5f6ddef50367799d9cff276eb
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1197524
TryBot-Result: CUEcueckoo <[email protected]>
Reviewed-by: Paul Jolly <[email protected]>
Unity-Result: CUE porcuepine <[email protected]>

Author: rogpeppe

cmd/cue/cmd/testdata/script/load_underscore.txtar

@@ -8,7 +8,7 @@ cmp stderr want-stderr
 ! exec cue export other.example/m:_
 cmp stderr want-stderr-2
 -- want-stderr --
-test.example/foo/foo@v0: import failed: cannot find package "other.example/m": _ is not a valid import path qualifier in "other.example/m:_":
+test.example/foo/foo@v0: import failed: _ is not a valid import path qualifier in "other.example/m:_":
     ./foo/foo.cue:8:8
 -- want-stderr-2 --
 invalid import path qualifier _ in "other.example/m:_"

cue/build/instance.go

@@ -93,6 +93,8 @@ type Instance struct {
 	// NOTICE: the below tags may change in the future.
 
 	// ImportComment is the path in the import comment on the package statement.
+	//
+	// Deprecated: CUE has never needed or supported import comments.
 	ImportComment string `api:"alpha"`
 
 	// AllTags are the build tags that can influence file selection in this

cue/load/config.go

@@ -309,8 +309,6 @@ func (c *Config) stdin() io.Reader {
 
 type importPath string
 
-type fsPath string
-
 func addImportQualifier(pkg importPath, name string) (importPath, error) {
 	if name == "" {
 		return pkg, nil

cue/load/import.go

@@ -162,7 +162,7 @@ func (l *loader) importPkg(pos token.Pos, p *build.Instance) []*build.Instance {
 						ExcludeReason: errors.Newf(token.NoPos, "unknown filetype"),
 					})
 				} else {
-					fp.add(dir, file, importComment)
+					fp.add(dir, file, 0)
 				}
 			}
 			if p.PkgName == "" || !inModule || l.cfg.isModRoot(dir) || dir == d[0] {
@@ -377,7 +377,7 @@ func (l *loader) newInstance(pos token.Pos, p importPath) *build.Instance {
 	i.PkgName = parts.Qualifier
 	if i.PkgName == "" {
 		i.Err = errors.Append(i.Err, l.errPkgf([]token.Pos{pos}, "cannot determine package name for %q; set it explicitly with ':'", p))
-	} else if i.PkgName == "" {
+	} else if i.PkgName == "_" {
 		i.Err = errors.Append(i.Err, l.errPkgf([]token.Pos{pos}, "_ is not a valid import path qualifier in %q", p))
 	}
 	i.DisplayPath = string(p)

cue/load/loader_common.go

@@ -15,16 +15,13 @@
 package load
 
 import (
-	"bytes"
 	"cmp"
 	pathpkg "path"
 	"path/filepath"
 	"slices"
 	"sort"
 	"strconv"
 	"strings"
-	"unicode"
-	"unicode/utf8"
 
 	"cuelang.org/go/cue/build"
 	"cuelang.org/go/cue/errors"
@@ -36,13 +33,7 @@ import (
 type importMode uint
 
 const (
-	// If importComment is set, parse import comments on package statements.
-	// Import returns an error if it finds a comment it cannot understand
-	// or finds conflicting comments in multiple source files.
-	// See golang.org/s/go14customimport for more information.
-	importComment importMode = 1 << iota
-
-	allowAnonymous
+	allowAnonymous = 1 << iota
 	allowExcludedFiles
 )
 
@@ -99,11 +90,10 @@ func (s *importStack) Copy() []string {
 }
 
 type fileProcessor struct {
-	firstFile        string
-	firstCommentFile string
-	imported         map[string][]token.Pos
-	ignoreOther      bool // ignore files from other packages
-	allPackages      bool
+	firstFile   string
+	imported    map[string][]token.Pos
+	ignoreOther bool // ignore files from other packages
+	allPackages bool
 
 	c      *fileProcessorConfig
 	tagger *tagger
@@ -283,21 +273,6 @@ func (fp *fileProcessor) add(root string, file *build.File, mode importMode) (ad
 	isTest := strings.HasSuffix(base, "_test"+cueSuffix)
 	isTool := strings.HasSuffix(base, "_tool"+cueSuffix)
 
-	if mode&importComment != 0 {
-		qcom, line := findImportComment(data)
-		if line != 0 {
-			com, err := strconv.Unquote(qcom)
-			if err != nil {
-				badFile(errors.Newf(pos, "%s:%d: cannot parse import comment", fullPath, line))
-			} else if p.ImportComment == "" {
-				p.ImportComment = com
-				fp.firstCommentFile = base
-			} else if p.ImportComment != com {
-				badFile(errors.Newf(pos, "found import comments %q (%s) and %q (%s) in %s", p.ImportComment, fp.firstCommentFile, com, base, p.Dir))
-			}
-		}
-	}
-
 	for _, spec := range pf.Imports {
 		quoted := spec.Path.Value
 		path, err := strconv.Unquote(quoted)
@@ -334,95 +309,6 @@ func (fp *fileProcessor) add(root string, file *build.File, mode importMode) (ad
 	return true
 }
 
-func findImportComment(data []byte) (s string, line int) {
-	// expect keyword package
-	word, data := parseWord(data)
-	if string(word) != "package" {
-		return "", 0
-	}
-
-	// expect package name
-	_, data = parseWord(data)
-
-	// now ready for import comment, a // comment
-	// beginning and ending on the current line.
-	for len(data) > 0 && (data[0] == ' ' || data[0] == '\t' || data[0] == '\r') {
-		data = data[1:]
-	}
-
-	var comment []byte
-	switch {
-	case bytes.HasPrefix(data, slashSlash):
-		i := bytes.Index(data, newline)
-		if i < 0 {
-			i = len(data)
-		}
-		comment = data[2:i]
-	}
-	comment = bytes.TrimSpace(comment)
-
-	// split comment into `import`, `"pkg"`
-	word, arg := parseWord(comment)
-	if string(word) != "import" {
-		return "", 0
-	}
-
-	line = 1 + bytes.Count(data[:cap(data)-cap(arg)], newline)
-	return strings.TrimSpace(string(arg)), line
-}
-
-var (
-	slashSlash = []byte("//")
-	newline    = []byte("\n")
-)
-
-// skipSpaceOrComment returns data with any leading spaces or comments removed.
-func skipSpaceOrComment(data []byte) []byte {
-	for len(data) > 0 {
-		switch data[0] {
-		case ' ', '\t', '\r', '\n':
-			data = data[1:]
-			continue
-		case '/':
-			if bytes.HasPrefix(data, slashSlash) {
-				i := bytes.Index(data, newline)
-				if i < 0 {
-					return nil
-				}
-				data = data[i+1:]
-				continue
-			}
-		}
-		break
-	}
-	return data
-}
-
-// parseWord skips any leading spaces or comments in data
-// and then parses the beginning of data as an identifier or keyword,
-// returning that word and what remains after the word.
-func parseWord(data []byte) (word, rest []byte) {
-	data = skipSpaceOrComment(data)
-
-	// Parse past leading word characters.
-	rest = data
-	for {
-		r, size := utf8.DecodeRune(rest)
-		if unicode.IsLetter(r) || '0' <= r && r <= '9' || r == '_' {
-			rest = rest[size:]
-			continue
-		}
-		break
-	}
-
-	word = data[:len(data)-len(rest)]
-	if len(word) == 0 {
-		return nil, nil
-	}
-
-	return word, rest
-}
-
 func cleanImports(m map[string][]token.Pos) ([]string, map[string][]token.Pos) {
 	all := make([]string, 0, len(m))
 	for path := range m {