internal/core/runtime: consistently follow CUE_DEBUG env var flags

The previous behavior followed the env var CUE_DEBUG if using
the cmd/cue tool, but explicitly ignored the same env var
if using the Go API via cuecontext.New.

We have been moving towards consistent behavior where users of
cuecontext.New see the same behavior in regards to following defaults
and environment variables; for example, https://cuelang.org/cl/1202685
taught cuecontext.New to obey the env var CUE_EXPERIMENT=evalv3.

Do the same for CUE_DEBUG, which now follows the environment variable
by default for both cmd/cue and cuecontext.New. Go API users can use
the cuecontext.CUE_DEBUG option to override any flags set by
the environment, or they can change the environment via os.Setenv.

This fixes CUE_DEBUG=sortfields so that it is obeyed by the Go API
just as it already was for cmd/cue.

Signed-off-by: Daniel Martí <[email protected]>
Change-Id: I18f5aadf1efce859f14d12c81ccbf3f17dd6949b
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1205202
Reviewed-by: Matthew Sackman <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>
Unity-Result: CUE porcuepine <[email protected]>

Author: mvdan

cmd/cue/cmd/root.go

@@ -35,7 +35,6 @@ import (
 	"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"
 	"cuelang.org/go/internal/filetypes"
@@ -105,9 +104,6 @@ func mkRunE(c *Command, f runFunction) func(*cobra.Command, []string) error {
 		if err := cueexperiment.Init(); err != nil {
 			return err
 		}
-		if err := cuedebug.Init(); err != nil {
-			return err
-		}
 		var opts []cuecontext.Option
 		if wasmInterp != nil {
 			opts = append(opts, cuecontext.Interpreter(wasmInterp))
@@ -138,10 +134,6 @@ func mkRunE(c *Command, f runFunction) func(*cobra.Command, []string) error {
 			const dev = internal.DevVersion
 			(*cueruntime.Runtime)(c.ctx).SetVersion(internal.EvaluatorVersion(dev))
 		}
-		// Note that, while some debugging flags like "strict" or "sharing"
-		// are only used by evalv3, some others like "sortfields" are used by all versions.
-		(*cueruntime.Runtime)(c.ctx).SetDebugOptions(&cuedebug.Flags)
-
 		err = f(c, args)
 
 		// TODO(mvdan): support -memprofilerate like `go help testflag`.

cmd/cue/cmd/testdata/script/sortfields.txtar

@@ -26,10 +26,9 @@ exec cue export input.cue
 cmp stdout export.stdout
 
 # Also ensure that it's wired up for the Go API.
-# TODO: it is not, currently.
 stdin input.cue
 exec cuectx_export
-cmp stdout export-unsorted.stdout
+cmp stdout export.stdout
 
 -- input.cue --
 c: true

cue/cuecontext/cuecontext.go

@@ -31,20 +31,15 @@ type Option struct {
 	apply func(r *runtime.Runtime)
 }
 
-// defaultFlags defines the debug flags that are set by default.
-var defaultFlags cuedebug.Config
-
-func init() {
-	if err := envflag.Parse(&defaultFlags, ""); err != nil {
-		panic(err)
-	}
-}
-
-// New creates a new Context.
+// New creates a new [*cue.Context].
+//
+// The environment variables CUE_EXPERIMENT and CUE_DEBUG are followed to configure
+// the evaluator, just like the cue tool documents via [cue help environment].
+// You can override these settings via options like [EvaluatorVersion] and [CUE_DEBUG].
+//
+// [cue help environment]: https://cuelang.org/docs/reference/command/cue-help-environment/
 func New(options ...Option) *cue.Context {
 	r := runtime.New()
-	// Ensure default behavior if the flags are not set explicitly.
-	r.SetDebugOptions(&defaultFlags)
 	for _, o := range options {
 		o.apply(r)
 	}

internal/core/runtime/runtime.go

@@ -57,8 +57,8 @@ func (r *Runtime) BuildData(b *build.Instance) (x interface{}, ok bool) {
 	return x, ok
 }
 
-// New is short for [NewWithSettings] while obeying `CUE_EXPERIMENT=evalv3`
-// for the evaluator version and using zero [cuedebug] flags.
+// New creates a new Runtime obeying the CUE_EXPERIMENT and CUE_DEBUG flags set
+// via environment variables.
 func New() *Runtime {
 	r := &Runtime{}
 	r.Init()
@@ -69,9 +69,11 @@ func New() *Runtime {
 // debug flags. The builtins registered with RegisterBuiltin are available for
 // evaluation.
 func NewWithSettings(v internal.EvaluatorVersion, flags cuedebug.Config) *Runtime {
-	r := &Runtime{flags: flags}
-	r.Init()
+	r := New()
+	// Override the evaluator version and debug flags derived from env vars
+	// with the explicit arguments given to us here.
 	r.version = v
+	r.SetDebugOptions(&flags)
 	return r
 }
 
@@ -119,4 +121,10 @@ func (r *Runtime) Init() {
 		r.version = internal.DefaultVersion
 	}
 	r.topoSort = cueexperiment.Flags.TopoSort
+
+	// By default we follow the environment's CUE_DEBUG settings,
+	// which can be overriden via [Runtime.SetDebugOptions],
+	// such as with the API option [cuelang.org/go/cue/cuecontext.CUE_DEBUG].
+	cuedebug.Init()
+	r.SetDebugOptions(&cuedebug.Flags)
 }