cue/load: simplify registry example

CUE_EXPERIMENT=modules has been on by default for many months now,
and we will not revert that change at this point,
so it doesn't make any sense for the examples and tests to still
reach into the ./internal/cueexperiment package to set it to true.

Particularly since that confuses users reading the example,
as well as showing them internal APIs that they cannot use themselves.

While here, tweak the docs for Config.Registry a bit
to link the reader directly to the documentation for $CUE_REGISTRY.

Signed-off-by: Daniel Martí <[email protected]>
Change-Id: I114cf047153cde3f00f0d18ddb96c6e92bbb9282
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1202597
TryBot-Result: CUEcueckoo <[email protected]>
Unity-Result: CUE porcuepine <[email protected]>
Reviewed-by: Roger Peppe <[email protected]>

cue/load/config.go

@@ -285,10 +285,12 @@ type Config struct {
 	// Registry is used to fetch CUE module dependencies.
 	//
 	// When nil, [modconfig.NewRegistry] will be used to create a
-	// registry instance using the usual cmd/cue conventions for
-	// environment variables (but see the Env field below).
+	// registry instance using the variables set in [Config.Env]
+	// as documented in `[cue help registryconfig]`.
 	//
 	// THIS IS EXPERIMENTAL. API MIGHT CHANGE.
+	//
+	// [cue help registryconfig]: https://cuelang.org/docs/reference/command/cue-help-registryconfig/
 	Registry modconfig.Registry
 
 	// Env provides environment variables for use in the configuration.

cue/load/example_test.go

@@ -24,7 +24,6 @@ import (
 	"cuelang.org/go/cue"
 	"cuelang.org/go/cue/cuecontext"
 	"cuelang.org/go/cue/load"
-	"cuelang.org/go/internal/cueexperiment"
 	"cuelang.org/go/internal/registrytest"
 )
 
@@ -90,8 +89,9 @@ func Example() {
 
 func Example_externalModules() {
 	// setUpModulesExample starts a temporary in-memory registry,
-	// populates it with an example module, and sets CUE_REGISTRY
-	// to refer to it
+	// populates it with an example module, and sets CUE_REGISTRY to refer to it.
+	// Users can leave [load.Config.Env] empty to use the default registry,
+	// or set one globally with os.Setenv("CUE_REGISTRY", "registry.myorg.com").
 	env, cleanup := setUpModulesExample()
 	defer cleanup()
 
@@ -139,21 +139,12 @@ value: "world"
 	if err != nil {
 		panic(err)
 	}
-	cleanups := []func(){registry.Close}
 	env = append(env, "CUE_REGISTRY="+registry.Host()+"+insecure")
+	// We also set up a temporary cache directory to fetch and extract modules into.
 	dir, err := os.MkdirTemp("", "")
 	if err != nil {
 		panic(err)
 	}
 	env = append(env, "CUE_CACHE_DIR="+dir)
-	oldModulesExperiment := cueexperiment.Flags.Modules
-	cueexperiment.Flags.Modules = true
-	cleanups = append(cleanups, func() {
-		cueexperiment.Flags.Modules = oldModulesExperiment
-	})
-	return env, func() {
-		for i := len(cleanups) - 1; i >= 0; i-- {
-			cleanups[i]()
-		}
-	}
+	return env, registry.Close
 }

cue/load/loader_test.go

@@ -36,9 +36,8 @@ import (
 )
 
 func init() {
-	// Ignore the value of CUE_EXPERIMENT for the purposes
-	// of these tests, which we want to test both with the experiment
-	// enabled and disabled.
+	// Ignore the value of CUE_EXPERIMENT for the purposes of these tests,
+	// as we want them to start off with the default experiment values.
 	os.Setenv("CUE_EXPERIMENT", "")
 
 	// Once we've called cueexperiment.Init, cueexperiment.Vars

cue/load/module_test.go

@@ -14,17 +14,14 @@ import (
 	"cuelang.org/go/cue/cuecontext"
 	"cuelang.org/go/cue/errors"
 	"cuelang.org/go/cue/load"
-	"cuelang.org/go/internal/cueexperiment"
 	"cuelang.org/go/internal/cuetxtar"
 	"cuelang.org/go/internal/registrytest"
 	"cuelang.org/go/mod/modcache"
 )
 
 func TestModuleLoadWithInvalidRegistryConfig(t *testing.T) {
-	// When the modules experiment is enabled and there's an invalid
-	// registry configuration, we shouldn't get an error unless the
-	// module actually tries to use a registry.
-	qt.Patch(t, &cueexperiment.Flags.Modules, true)
+	// When there's an invalid registry configuration,
+	// we shouldn't get an error unless the module actually tries to use a registry.
 	t.Setenv("CUE_REGISTRY", "invalid}host:")
 	cacheDir := t.TempDir()
 	t.Setenv("CUE_CACHE_DIR", cacheDir)
@@ -94,7 +91,6 @@ func TestModuleFetch(t *testing.T) {
 		// The fetched files are read-only, so testing fails when trying
 		// to remove them.
 		defer modcache.RemoveAll(tmpDir)
-		qt.Patch(t, &cueexperiment.Flags.Modules, true)
 		ctx := cuecontext.New()
 		insts := t.RawInstances()
 		if len(insts) != 1 {