cmd/cue/cmd: expose evalv3 experiment

Right now this is only done through a global variable
for the cue command line. It is not possible to set this
through the API.

Note: do not close this issue until we allow exposing the
experiment everywhere in the API.

Issue #2886

Signed-off-by: Marcel van Lohuizen <[email protected]>
Change-Id: I445485d905a21831ae1395a9d3dc78c19365a11f

cmd/cue/cmd/root.go

@@ -28,7 +28,9 @@ import (
 	"cuelang.org/go/cue/cuecontext"
 	"cuelang.org/go/cue/errors"
 	"cuelang.org/go/cue/stats"
+	"cuelang.org/go/internal"
 	"cuelang.org/go/internal/core/adt"
+	cueruntime "cuelang.org/go/internal/core/runtime"
 	"cuelang.org/go/internal/cuedebug"
 	"cuelang.org/go/internal/cueexperiment"
 	"cuelang.org/go/internal/encoding"
@@ -96,6 +98,13 @@ func mkRunE(c *Command, f runFunction) func(*cobra.Command, []string) error {
 		// We don't want that work to count towards $CUE_STATS.
 		adt.ResetStats()
 
+		// TODO: do not rely on a global variable here, as this API is also used
+		// in a non-tooling context.
+		if cueexperiment.Flags.EvalV3 {
+			const dev = internal.DevVersion
+			(*cueruntime.Runtime)(c.ctx).SetVersion(internal.EvaluatorVersion(dev))
+		}
+
 		err := f(c, args)
 
 		if statsEnc != nil {

cmd/cue/cmd/testdata/script/cmd_textproto.txtar

@@ -7,6 +7,13 @@ cmp stdout out/foo.textproto
 ! exec cue eval -d '#X' schema.cue foo.textproto -l c
 cmp stderr out/stderr3
 
+# This asserts the compatibility of Vertex.MatchAndInsert, which is only used
+# outside of the core evaluator.
+env CUE_EXPERIMENT=evalv3
+
+exec cue eval topschema.cue foo.textproto
+cmp stdout out/topfoo.textproto
+
 -- topschema.cue --
 a: int
 b: [...int]

cmd/cue/cmd/testdata/script/dev.txtar

@@ -0,0 +1,13 @@
+env CUE_EXPERIMENT=evalv3
+exec cue eval
+cmp stdout out
+
+-- test.cue --
+package foo
+
+// This only works in the new evaluator as of this writing.
+y: 1 | {y: 1}
+y
+
+-- out --
+y: 1

cue/context.go

@@ -250,6 +250,12 @@ func (c *Context) CompileBytes(b []byte, options ...BuildOption) Value {
 
 func (c *Context) make(v *adt.Vertex) Value {
 	opCtx := newContext(c.runtime())
+	// TODO: this is currently needed to ensure that node is properly recognized
+	// as evaluated. Not dereferencing nodes, however, will have the benefit of
+	// retaining more information. Remove the indirection when the code will be
+	// able to properly handle this.
+	v.Finalize(opCtx)
+	v = v.Indirect()
 	x := newValueRoot(c.runtime(), opCtx, v)
 	adt.AddStats(opCtx)
 	return x

internal/core/runtime/runtime.go

@@ -60,6 +60,12 @@ func NewVersioned(v internal.EvaluatorVersion) *Runtime {
 	return r
 }
 
+// SetVersion sets the version to use for the Runtime. This should only be set
+// before first use.
+func (r *Runtime) SetVersion(v internal.EvaluatorVersion) {
+	r.version = v
+}
+
 // IsInitialized reports whether the runtime has been initialized.
 func (r *Runtime) IsInitialized() bool {
 	return r.index != nil

internal/cueexperiment/exp.go

@@ -10,6 +10,7 @@ import (
 // by Init.
 var Flags struct {
 	Modules bool
+	EvalV3  bool
 }
 
 // Init initializes Flags. Note: this isn't named "init" because we