internal/core: don't resolve values into anonymous packages

Non-CUE files are equivalent to a CUE file without a package
clause or an anonyous package clause (package _).

Identifier resolution should only happend across files of the
same package.

This can be a breaking change and we should probably introduce
this in its separate release, maybe even minor release (say v0.4).

Fixes #736

Change-Id: I28a0eb8618c2527b66c953c03e4bad695188654e
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/8925
Reviewed-by: Marcel van Lohuizen <[email protected]>
Reviewed-by: CUE cueckoo <[email protected]>

cmd/cue/cmd/testdata/script/eval_resolve.txt

@@ -0,0 +1,80 @@
+# Issue #736
+#
+# references should never resolve to files of an
+# anonymous package (no package or package _).
+
+! cue eval data.yaml check.cue
+cmp stderr out-stderr
+
+! cue eval none.cue check.cue
+cmp stderr out-stderr
+
+! cue eval anon.cue check.cue
+cmp stderr out-stderr
+
+# TODO: allow this for now. Files without a package clause should not resolve
+# across other files.
+cue eval package.cue check.cue
+
+-- data.yaml --
+nodes:
+- name: foo
+  childs:
+  - bar
+  - baz
+
+- name: bar
+  parent: foo
+
+- name: baz
+  parent: foo
+
+-- none.cue --
+nodes: [{
+    name: "foo"
+    childs: ["bar", "baz"]
+}, {
+    name:   "bar"
+    parent: "foo"
+}, {
+    name:   "baz"
+    parent: "foo"
+}]
+
+-- anon.cue --
+// This is an explicitly declared anonymous package.
+package _
+
+nodes: [{
+    name: "foo"
+    childs: ["bar", "baz"]
+}, {
+    name:   "bar"
+    parent: "foo"
+}, {
+    name:   "baz"
+    parent: "foo"
+}]
+
+-- package.cue --
+package list
+
+nodes: [{
+    name: "foo"
+    childs: ["bar", "baz"]
+}, {
+    name:   "bar"
+    parent: "foo"
+}, {
+    name:   "baz"
+    parent: "foo"
+}]
+
+-- check.cue --
+import "list"
+
+#map: {for n in nodes {"\(n.name)": n}}
+
+-- out-stderr --
+#map: reference "nodes" not found:
+    ./check.cue:3:17

cue/testdata/definitions/files.txtar

@@ -3,6 +3,8 @@
 // fields of another.
 
 -- in.cue --
+package foo
+
 #theme: {
 	color:   string
 	ctermbg: string
@@ -20,6 +22,8 @@ light: #theme & {
 }
 
 -- box.cue --
+package foo
+
 #Config & {
 	console: dark
 }

internal/core/compile/compile.go

@@ -235,9 +235,18 @@ func (c *compiler) popScope() {
 func (c *compiler) compileFiles(a []*ast.File) *adt.Vertex { // Or value?
 	c.fileScope = map[adt.Feature]bool{}
 
-	// Populate file scope to handle unresolved references. Note that we do
-	// not allow aliases to be resolved across file boundaries.
+	// TODO(resolve): this is also done in the runtime package, do we need both?
+
+	// Populate file scope to handle unresolved references.
+	// Excluded from cross-file resolution are:
+	// - import specs
+	// - aliases
+	// - anything in an anonymous file
+	//
 	for _, f := range a {
+		if p := internal.GetPackageInfo(f); p.IsAnonymous() {
+			continue
+		}
 		for _, d := range f.Decls {
 			if f, ok := d.(*ast.Field); ok {
 				if id, ok := f.Label.(*ast.Ident); ok {

internal/core/runtime/resolve.go

@@ -21,16 +21,21 @@ import (
 	"cuelang.org/go/cue/ast"
 	"cuelang.org/go/cue/build"
 	"cuelang.org/go/cue/errors"
+	"cuelang.org/go/internal"
 )
 
+// TODO(resolve): this is also done in compile, do we need both?
 func (r *Runtime) ResolveFiles(p *build.Instance) (errs errors.Error) {
 	idx := r.index
 
 	// Link top-level declarations. As top-level entries get unified, an entry
 	// may be linked to any top-level entry of any of the files.
 	allFields := map[string]ast.Node{}
-	for _, file := range p.Files {
-		for _, d := range file.Decls {
+	for _, f := range p.Files {
+		if p := internal.GetPackageInfo(f); p.IsAnonymous() {
+			continue
+		}
+		for _, d := range f.Decls {
 			if f, ok := d.(*ast.Field); ok && f.Value != nil {
 				if ident, ok := f.Label.(*ast.Ident); ok {
 					allFields[ident.Name] = f.Value
@@ -39,6 +44,9 @@ func (r *Runtime) ResolveFiles(p *build.Instance) (errs errors.Error) {
 		}
 	}
 	for _, f := range p.Files {
+		if p := internal.GetPackageInfo(f); p.IsAnonymous() {
+			continue
+		}
 		err := resolveFile(idx, f, p, allFields)
 		errs = errors.Append(errs, err)
 	}

internal/internal.go

@@ -109,6 +109,11 @@ type PkgInfo struct {
 	Name    string
 }
 
+// IsAnonymous reports whether the package is anonymous.
+func (p *PkgInfo) IsAnonymous() bool {
+	return p.Name == "" || p.Name == "_"
+}
+
 func GetPackageInfo(f *ast.File) PkgInfo {
 	for i, d := range f.Decls {
 		switch x := d.(type) {