cue/load: prepare for files package refactor

Currently when files are specified on the command line,
they're considered after all packages have been evaluated
with respect to modules. We need to change that so that
we consider imports from files before creating the loader,
which requires factoring the `cueFilesPackage` method
out from `loader`.

This change makes some preparations for that by:
- parsing file arguments before invoking `loadPackages`
- passing the `filesMode` boolean as an argument rather
than indirectly in `Config`, where it doesn't really feel
like it belongs anyway, as `Config` isn't really the right
place for values that change over time.

For #3144
For #3147

Signed-off-by: Roger Peppe <rogpeppe@gmail.com>
Change-Id: If6c342757e97a3752edb3fefea64ad4bdfdbe23f
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1194761
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>

cue/load/config.go

@@ -243,10 +243,6 @@ type Config struct {
 	// a package.
 	Tools bool
 
-	// filesMode indicates that files are specified
-	// explicitly on the command line.
-	filesMode bool
-
 	// If DataFiles is set, the loader includes entries for directories that
 	// have no CUE files, but have recognized data files that could be converted
 	// to CUE.

cue/load/instances.go

@@ -62,6 +62,10 @@ func Instances(args []string, c *Config) []*build.Instance {
 	}
 	pkgArgs := args[:i]
 	otherArgs := args[i:]
+	otherFiles, err := filetypes.ParseArgs(otherArgs)
+	if err != nil {
+		return []*build.Instance{c.newErrInstance(err)}
+	}
 
 	// Pass all arguments that look like packages to loadPackages
 	// so that they'll be available when looking up the packages
@@ -95,12 +99,8 @@ func Instances(args []string, c *Config) []*build.Instance {
 		}
 	}
 
-	if len(otherArgs) > 0 {
-		files, err := filetypes.ParseArgs(otherArgs)
-		if err != nil {
-			return []*build.Instance{c.newErrInstance(err)}
-		}
-		a = append(a, l.cueFilesPackage(files))
+	if len(otherFiles) > 0 {
+		a = append(a, l.cueFilesPackage(otherFiles))
 	}
 
 	for _, p := range a {

cue/load/loader.go

@@ -94,39 +94,38 @@ func (l *loader) errPkgf(importPos []token.Pos, format string, args ...interface
 // cueFilesPackage creates a package for building a collection of CUE files
 // (typically named on the command line).
 func (l *loader) cueFilesPackage(files []*build.File) *build.Instance {
-	cfg := l.cfg
-	cfg.filesMode = true
+
 	// ModInit() // TODO: support modules
-	pkg := l.cfg.Context.NewInstance(cfg.Dir, l.loadFunc)
+	pkg := l.cfg.Context.NewInstance(l.cfg.Dir, l.loadFunc)
 
 	for _, bf := range files {
 		f := bf.Filename
 		if f == "-" {
 			continue
 		}
 		if !filepath.IsAbs(f) {
-			f = filepath.Join(cfg.Dir, f)
+			f = filepath.Join(l.cfg.Dir, f)
 		}
-		fi, err := cfg.fileSystem.stat(f)
+		fi, err := l.cfg.fileSystem.stat(f)
 		if err != nil {
-			return cfg.newErrInstance(errors.Wrapf(err, token.NoPos, "could not find file %v", f))
+			return l.cfg.newErrInstance(errors.Wrapf(err, token.NoPos, "could not find file %v", f))
 		}
 		if fi.IsDir() {
-			return cfg.newErrInstance(errors.Newf(token.NoPos, "file is a directory %v", f))
+			return l.cfg.newErrInstance(errors.Newf(token.NoPos, "file is a directory %v", f))
 		}
 	}
 
-	fp := newFileProcessor(cfg, pkg, l.tagger)
+	fp := newFileProcessor(l.cfg, pkg, l.tagger)
 	if l.cfg.Package == "*" {
 		fp.allPackages = true
 		pkg.PkgName = "_"
 	}
 	for _, file := range files {
-		fp.add(cfg.Dir, file, allowAnonymous)
+		fp.add(l.cfg.Dir, file, allowAnonymous|allowExcludedFiles)
 	}
 
 	// TODO: ModImportFromFiles(files)
-	pkg.Dir = cfg.Dir
+	pkg.Dir = l.cfg.Dir
 	rewriteFiles(pkg, pkg.Dir, true)
 	for _, err := range errors.Errors(fp.finalize(pkg)) { // ImportDir(&ctxt, dir, 0)
 		var x *NoFilesError
@@ -142,7 +141,7 @@ func (l *loader) cueFilesPackage(files []*build.File) *build.Instance {
 	// }
 
 	pkg.User = true
-	l.addFiles(cfg.Dir, pkg)
+	l.addFiles(l.cfg.Dir, pkg)
 
 	l.stk.Push("user")
 	_ = pkg.Complete()

cue/load/loader_common.go

@@ -45,6 +45,7 @@ const (
 	importComment importMode = 1 << iota
 
 	allowAnonymous
+	allowExcludedFiles
 )
 
 func rewriteFiles(p *build.Instance, root string, isLocal bool) {
@@ -184,7 +185,7 @@ func (fp *fileProcessor) add(root string, file *build.File, mode importMode) (ad
 		return true
 	}
 
-	match, data, err := matchFile(fp.c, file, true, fp.allTags)
+	match, data, err := matchFile(fp.c, file, true, fp.allTags, mode)
 	switch {
 	case match:
 

cue/load/match.go

@@ -49,7 +49,7 @@ func (e excludeError) Is(err error) bool { return err == errExclude }
 // considers text until the first non-comment.
 // If allTags is non-nil, matchFile records any encountered build tag
 // by setting allTags[tag] = true.
-func matchFile(cfg *Config, file *build.File, returnImports bool, allTags map[string]bool) (match bool, data []byte, err errors.Error) {
+func matchFile(cfg *Config, file *build.File, returnImports bool, allTags map[string]bool, mode importMode) (match bool, data []byte, err errors.Error) {
 	if fi := cfg.fileSystem.getOverlay(file.Filename); fi != nil {
 		if fi.file != nil {
 			file.Source = fi.file
@@ -73,7 +73,7 @@ func matchFile(cfg *Config, file *build.File, returnImports bool, allTags map[st
 	}
 
 	name := filepath.Base(file.Filename)
-	if !cfg.filesMode {
+	if (mode & allowExcludedFiles) == 0 {
 		for _, prefix := range []string{".", "_"} {
 			if strings.HasPrefix(name, prefix) {
 				return false, nil, &excludeError{