internal/core/runtime: decouple cue API from Runtime

The main goal here is to decouple the caching, and
that to the cue.Runtime. That will ultimately make it
easier to not cache Instances, which can hog memory
allocation.

Change-Id: I0cf9678b867e6afd18d1e5abb6961702e37170c9
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/8222
Reviewed-by: CUE cueckoo <cueckoo@gmail.com>
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>

cue/build.go

@@ -193,33 +193,27 @@ func (r *Runtime) FromExpr(expr ast.Expr) (*Instance, error) {
 	})
 }
 
-type importIndex map[*build.Instance]*Instance
-
 // index maps conversions from label names to internal codes.
 //
 // All instances belonging to the same package should share this index.
 type index struct {
 	*runtime.Runtime
-	loaded importIndex
+	loaded map[*build.Instance]*Instance
 }
 
 // NewRuntime creates a *runtime.Runtime with builtins preloaded.
 func NewRuntime() *runtime.Runtime {
-	r := runtime.New()
-	i := &index{
-		Runtime: r,
-		loaded:  importIndex{},
-	}
-	r.Data = i
-	return r
+	i := newIndex()
+	i.Runtime.Data = i
+	return i.Runtime
 }
 
 // newIndex creates a new index.
 func newIndex() *index {
 	r := runtime.New()
 	i := &index{
 		Runtime: r,
-		loaded:  importIndex{},
+		loaded:  map[*build.Instance]*Instance{},
 	}
 	r.Data = i
 	return i
@@ -230,6 +224,6 @@ func isBuiltin(s string) bool {
 }
 
 func (idx *index) loadInstance(p *build.Instance) *Instance {
-	idx.Runtime.Build(p)
-	return idx.getImportFromBuild(p)
+	v, _ := idx.Runtime.Build(p)
+	return idx.getImportFromBuild(p, v)
 }

cue/instance.go

@@ -59,18 +59,13 @@ func (x *index) addInst(p *Instance) *Instance {
 	return p
 }
 
-func (x *index) getImportFromBuild(p *build.Instance) *Instance {
+func (x *index) getImportFromBuild(p *build.Instance, v *adt.Vertex) *Instance {
 	inst := x.loaded[p]
 
 	if inst != nil {
 		return inst
 	}
 
-	v := x.GetNodeFromInstance(p)
-	if v == nil {
-		return nil
-	}
-
 	inst = &Instance{
 		ImportPath:  p.ImportPath,
 		Dir:         p.Dir,
@@ -95,7 +90,7 @@ func (x *index) getImportFromNode(v *adt.Vertex) *Instance {
 		return nil
 	}
 
-	return x.getImportFromBuild(p)
+	return x.getImportFromBuild(p, v)
 }
 
 func (x *index) getImportFromPath(id string) *Instance {

cue/types.go

@@ -1857,7 +1857,7 @@ func (v Value) instance() *Instance {
 	if v.v == nil {
 		return nil
 	}
-	return v.ctx().getImportFromNode(v.v)
+	return v.idx.getImportFromNode(v.v)
 }
 
 // Reference returns the instance and path referred to by this value such that

internal/core/runtime/build.go

@@ -28,7 +28,7 @@ import (
 // Build builds b and all its transitive dependencies, insofar they have not
 // been build yet.
 func (x *Runtime) Build(b *build.Instance) (v *adt.Vertex, errs errors.Error) {
-	if v := x.GetNodeFromInstance(b); v != nil {
+	if v := x.getNodeFromInstance(b); v != nil {
 		return v, b.Err
 	}
 	// TODO: clear cache of old implementation.

internal/core/runtime/imports.go

@@ -95,7 +95,7 @@ func (r *Runtime) GetInstanceFromNode(key *adt.Vertex) *build.Instance {
 	return r.index.imports[key]
 }
 
-func (r *Runtime) GetNodeFromInstance(key *build.Instance) *adt.Vertex {
+func (r *Runtime) getNodeFromInstance(key *build.Instance) *adt.Vertex {
 	return r.index.importsByBuild[key]
 }