internal/cueexperiment: flip modules experiment flag default

This change enables the modules experiment by default.
This will cause CUE code to fail if there is no language
version in the module.cue file, amongst other things.

The experiment can be disabled by setting

        CUE_EXPERIMENT=modules=0

Many of the unit tests need to be changed in order to
add the now-mandatory language.version field.

Some error messages have now changed.

Some logic in the `cue fmt` command that relies on seeing
a `load.PackageError` required the respective code inside
`cue/load` to produce that error, which also changes some
error messages.

The `cue mod fix` command is now available to make it
it more straightforward to migrate.

The module path in encoding/gocode/testdata/cue.mod/module.cue
has been  changed to match the modules-enabled default,
otherwise the generation code fails with an error about a mismatched
module path.

Fixes #3127.

Signed-off-by: Roger Peppe <rogpeppe@gmail.com>
Change-Id: I7c384c785eac6203966460703283ecfa2d9f0447
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1194664
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>

cmd/cue/cmd/script_test.go

@@ -239,7 +239,10 @@ func TestScript(t *testing.T) {
 			if err != nil {
 				return fmt.Errorf("cannot read workdir: %v", err)
 			}
-			hasRegistry := false
+			// As modules are enabled by default, we always want a cache directory.
+			// Since os.UserCacheDir relies on OS-specific env vars that we don't set,
+			// explicitly set up the cache directory somewhere predictable.
+			e.Vars = append(e.Vars, "CUE_CACHE_DIR="+filepath.Join(e.WorkDir, ".tmp/cache"))
 			for _, entry := range entries {
 				if !entry.IsDir() {
 					continue
@@ -250,7 +253,6 @@ func TestScript(t *testing.T) {
 				}
 				// There's a _registry directory. Start a fake registry server to serve
 				// the modules in it.
-				hasRegistry = true
 				registryDir := filepath.Join(e.WorkDir, entry.Name())
 				prefix := ""
 				if data, err := os.ReadFile(filepath.Join(e.WorkDir, "_registry"+regID+"_prefix")); err == nil {
@@ -268,18 +270,9 @@ func TestScript(t *testing.T) {
 					// This enables some tests to construct their own malformed
 					// CUE_REGISTRY values that still refer to the test registry.
 					"DEBUG_REGISTRY"+regID+"_HOST="+reg.Host(),
-					// Some tests execute cue commands that need to write cache files.
-					// Since os.UserCacheDir relies on OS-specific env vars that we don't set,
-					// explicitly set up the cache directory somewhere predictable.
-					"CUE_CACHE_DIR="+filepath.Join(e.WorkDir, ".tmp/cache"),
 				)
 				e.Defer(reg.Close)
 			}
-			if hasRegistry {
-				e.Vars = append(e.Vars,
-					"CUE_EXPERIMENT=modules",
-				)
-			}
 			return nil
 		},
 		Condition: cuetest.Condition,

cmd/cue/cmd/testdata/script/cmd_filetypes.txtar

@@ -29,10 +29,10 @@ exec cue export ./somepkg/
 cmp stdout export.golden
 # TODO(mvdan): we should support loading packages from absolute directories.
 ! exec cue export ${WORK}${/}somepkg
-[!windows] stderr 'cannot find package ".*somepkg"'
+[!windows] stderr 'no location found for package ".*somepkg"'
 [windows] stderr 'no encoding specified for file ".*somepkg.*"'
 ! exec cue export ${WORK}${/}somepkg${/}
-[!windows] stderr 'cannot find package ".*somepkg"'
+[!windows] stderr 'no dependency found for package ".*somepkg"'
 [windows] stderr 'no encoding specified for file ".*somepkg.*"'
 
 # Now do some of the same filename tests, but for a file without any extension.
@@ -57,7 +57,7 @@ stderr 'standard library import path "somefile" cannot be imported as a CUE pack
 stderr 'cannot find package "\./somefile"'
 # TODO(mvdan): we probably should not behave differently on Windows.
 ! exec cue export ${WORK}${/}somefile
-[!windows] stderr 'cannot find package ".*somefile"'
+[!windows] stderr 'no location found for package ".*somefile"'
 [windows] stderr 'no encoding specified for file ".*somefile"'
 
 -- cue.mod/module.cue --

cmd/cue/cmd/testdata/script/issue174.txtar

@@ -1,8 +1,7 @@
 ! exec cue export ./issue174
 cmp stderr expect-stderr
 -- expect-stderr --
-build constraints exclude all CUE files in ./issue174:
-    issue174/issue174.cue: no package name
+cannot enumerate all module imports: invalid import path "'foo'" in issue174/issue174.cue
 -- cue.mod/module.cue --
 module: "mod.test"
 language: version: "v0.9.0"

cmd/cue/cmd/testdata/script/modinit_nomajorversion.txtar

@@ -2,6 +2,7 @@ env-fill want-module.cue
 env-fill want-module-experiment.cue
 
 # Without the experiment, we use the module path as-is.
+env CUE_EXPERIMENT=modules=false
 exec cue mod init foo.com/bar
 cmp cue.mod/module.cue want-module.cue
 exists cue.mod/usr

cmd/cue/cmd/testdata/script/modinit_withsource.txtar

@@ -19,15 +19,15 @@ cd $WORK/test2
 cmp stderr $WORK/want-stderr
 
 -- want-module.cue-0 --
-module: "test.example"
+module: "test.example@v0"
 language: {
 	version: "$CUE_LANGUAGE_VERSION"
 }
 source: {
 	kind: "self"
 }
 -- want-module.cue-1 --
-module: "test.example"
+module: "test.example@v0"
 language: {
 	version: "$CUE_LANGUAGE_VERSION"
 }

cmd/cue/cmd/testdata/script/modpublish_registry_not_enabled.txtar

@@ -1,3 +1,4 @@
+env CUE_EXPERIMENT=modules=false
 ! exec cue mod publish v1.0.0
 cmp stderr want-stderr
 -- want-stderr --

cmd/cue/cmd/testdata/script/modtidy_default_modules_mode.txtar

@@ -0,0 +1,5 @@
+# Check that modules are enabled by default.
+exec cue mod tidy
+-- cue.mod/module.cue --
+module: "test.example"
+language: version: "v0.9.0"

cmd/cue/cmd/testdata/script/modtidy_registry_not_enabled.txtar

@@ -1,3 +1,5 @@
+env CUE_EXPERIMENT=modules=0
+
 ! exec cue mod tidy
 cmp stderr want-stderr
 -- want-stderr --

cmd/cue/cmd/testdata/script/registry_experiment_not_set.txtar → cmd/cue/cmd/testdata/script/registry_modules_disabled.txtar

@@ -1,7 +1,7 @@
-# When CUE_EXPERIMENT is empty, the CUE_REGISTRY
+# When CUE_EXPERIMENT is disabled, the CUE_REGISTRY
 # variable is ignored, as are the new fields in module.cue
 
-env CUE_EXPERIMENT=
+env CUE_EXPERIMENT=modules=false
 exec cue export .
 cmp stdout expect-stdout
 

cmd/cue/cmd/testdata/script/registry_no_experiment_warning.txtar → cmd/cue/cmd/testdata/script/registry_modules_disabled_warning.txtar

@@ -1,4 +1,4 @@
-env CUE_EXPERIMENT=
+env CUE_EXPERIMENT=modules=false
 env CUE_REGISTRY=ignored.example.com
 exec cue export .
 cmp stdout expect-stdout

cue/interpreter/wasm/exe_test.go

@@ -50,6 +50,7 @@ func TestExe(t *testing.T) {
 		RequireUniqueNames:  true,
 		Setup: func(e *testscript.Env) error {
 			copyWasmFiles(t, e.WorkDir, wasmFiles)
+			e.Vars = append(e.Vars, "CUE_CACHE_DIR="+filepath.Join(e.WorkDir, ".tmp/cache"))
 			return nil
 		},
 		Condition: cuetest.Condition,

cue/load/loader_test.go

@@ -77,8 +77,14 @@ func TestLoad(t *testing.T) {
 		name: "BadModuleFile",
 		cfg:  badModCfg,
 		args: []string{"."},
-		want: `err:    module: cannot use value 123 (type int) as string:
+		want: `err:    module: 2 errors in empty disjunction:
+module: conflicting values 123 and "" (mismatched types int and string):
     $CWD/testdata/badmod/cue.mod/module.cue:2:9
+    cuelang.org/go/mod/modfile/schema.cue:56:22
+module: conflicting values 123 and string (mismatched types int and string):
+    $CWD/testdata/badmod/cue.mod/module.cue:2:9
+    cuelang.org/go/mod/modfile/schema.cue:56:12
+    cuelang.org/go/mod/modfile/schema.cue:101:12
 path:   ""
 module: ""
 root:   ""
@@ -91,30 +97,30 @@ display:""`,
 		// package of this directory.
 		cfg:  dirCfg,
 		args: nil,
-		want: `err:    import failed: cannot find package "mod.test/test/sub":
-    $CWD/testdata/testmod/test.cue:3:8
-path:   mod.test/test@v0
+		want: `path:   mod.test/test@v0
 module: mod.test/test@v0
 root:   $CWD/testdata/testmod
 dir:    $CWD/testdata/testmod
 display:.
 files:
-    $CWD/testdata/testmod/test.cue`}, {
+    $CWD/testdata/testmod/test.cue
+imports:
+    mod.test/test/sub: $CWD/testdata/testmod/sub/sub.cue`}, {
 		name: "DefaultPackageWithExplicitDotArgument",
 		// Even though the directory is called testdata, the last path in
 		// the module is test. So "package test" is correctly the default
 		// package of this directory.
 		cfg:  dirCfg,
 		args: []string{"."},
-		want: `err:    import failed: cannot find package "mod.test/test/sub":
-    $CWD/testdata/testmod/test.cue:3:8
-path:   mod.test/test@v0
+		want: `path:   mod.test/test@v0
 module: mod.test/test@v0
 root:   $CWD/testdata/testmod
 dir:    $CWD/testdata/testmod
 display:.
 files:
-    $CWD/testdata/testmod/test.cue`}, {
+    $CWD/testdata/testmod/test.cue
+imports:
+    mod.test/test/sub: $CWD/testdata/testmod/sub/sub.cue`}, {
 		name: "RelativeImportPathWildcard",
 		cfg:  dirCfg,
 		args: []string{"./other/..."},
@@ -150,36 +156,41 @@ files:
 		name: "RelativePathSuccess",
 		cfg:  dirCfg,
 		args: []string{"./hello"},
-		want: `err:    import failed: cannot find package "mod.test/test/sub":
-    $CWD/testdata/testmod/test.cue:3:8
-path:   mod.test/test/hello@v0:test
+		want: `path:   mod.test/test/hello@v0:test
 module: mod.test/test@v0
 root:   $CWD/testdata/testmod
 dir:    $CWD/testdata/testmod/hello
 display:./hello
 files:
     $CWD/testdata/testmod/test.cue
-    $CWD/testdata/testmod/hello/test.cue`}, {
+    $CWD/testdata/testmod/hello/test.cue
+imports:
+    mod.test/test/sub: $CWD/testdata/testmod/sub/sub.cue`}, {
 		name: "ExplicitPackageIdentifier",
 		cfg:  dirCfg,
 		args: []string{"mod.test/test/hello:test"},
-		want: `err:    cannot find package "mod.test/test/hello:test"
-path:   mod.test/test/hello:test
+		want: `path:   mod.test/test/hello:test
 module: mod.test/test@v0
 root:   $CWD/testdata/testmod
-dir:    $CWD/testdata/testmod/cue.mod/gen/mod.test/test/hello
-display:mod.test/test/hello:test`,
-	}, {
+dir:    $CWD/testdata/testmod/hello
+display:mod.test/test/hello:test
+files:
+    $CWD/testdata/testmod/test.cue
+    $CWD/testdata/testmod/hello/test.cue
+imports:
+    mod.test/test/sub: $CWD/testdata/testmod/sub/sub.cue`}, {
 		name: "NoPackageName",
 		cfg:  dirCfg,
 		args: []string{"mod.test/test/hello:nonexist"},
-		want: `err:    cannot find package "mod.test/test/hello:nonexist"
+		want: `err:    build constraints exclude all CUE files in mod.test/test/hello:nonexist:
+    anon.cue: no package name
+    test.cue: package is test, want nonexist
+    hello/test.cue: package is test, want nonexist
 path:   mod.test/test/hello:nonexist
 module: mod.test/test@v0
 root:   $CWD/testdata/testmod
-dir:    $CWD/testdata/testmod/cue.mod/gen/mod.test/test/hello
-display:mod.test/test/hello:nonexist`,
-	}, {
+dir:    $CWD/testdata/testmod/hello
+display:mod.test/test/hello:nonexist`}, {
 		name: "ExplicitNonPackageFiles",
 		cfg:  dirCfg,
 		args: []string{"./anon.cue", "./other/anon.cue"},
@@ -190,7 +201,8 @@ dir:    $CWD/testdata/testmod
 display:command-line-arguments
 files:
     $CWD/testdata/testmod/anon.cue
-    $CWD/testdata/testmod/other/anon.cue`}, {
+    $CWD/testdata/testmod/other/anon.cue`,
+	}, {
 		name: "AbsoluteFileIsNormalized", // TODO(rogpeppe) what is this actually testing?
 		cfg:  dirCfg,
 		// Absolute file is normalized.
@@ -215,11 +227,11 @@ files:
 		name: "BadIdentifier",
 		cfg:  dirCfg,
 		args: []string{"foo.com/bad-identifier"},
-		want: `err:    implied package identifier "bad-identifier" from import path "foo.com/bad-identifier" is not valid
+		want: `err:    cannot find package "foo.com/bad-identifier": cannot find module providing package foo.com/bad-identifier
 path:   foo.com/bad-identifier
 module: mod.test/test@v0
 root:   $CWD/testdata/testmod
-dir:    $CWD/testdata/testmod/cue.mod/gen/foo.com/bad-identifier
+dir:    ""
 display:foo.com/bad-identifier`,
 	}, {
 		name: "NonexistentStdlibImport",

encoding/gocode/testdata/cue.mod/module.cue

@@ -1,2 +1,2 @@
-module: "cuelang.org/go/encoding/gocode/testdata"
+module: "cuelang.org/go/encoding/gocode/testdata@v0"
 language: version: "v0.9.0"

encoding/gocode/testdata/gen.go

@@ -45,7 +45,7 @@ func main() {
 		inst := cue.Build(load.Instances([]string{pkg}, &load.Config{
 			Dir:        dir,
 			ModuleRoot: dir,
-			Module:     "cuelang.org/go/encoding/gocode/testdata",
+			Module:     "cuelang.org/go/encoding/gocode/testdata@v0",
 		}))[0]
 		if err := inst.Err; err != nil {
 			log.Fatal(err)

internal/cueexperiment/exp.go

@@ -9,7 +9,7 @@ import (
 // Flags holds the set of CUE_EXPERIMENT flags. It is initialized
 // by Init.
 var Flags struct {
-	Modules bool
+	Modules bool `envflag:"default:true"`
 
 	// YAMLV3Decoder swaps the old internal/third_party/yaml decoder with the new
 	// decoder implemented in internal/encoding/yaml on top of yaml.v3.

internal/cueexperiment/exp_test.go

@@ -13,7 +13,7 @@ func TestInit(t *testing.T) {
 	t.Setenv("CUE_EXPERIMENT", "")
 	err := initAlways()
 	qt.Assert(t, qt.IsNil(err))
-	qt.Assert(t, qt.IsFalse(Flags.Modules))
+	qt.Assert(t, qt.IsTrue(Flags.Modules))
 	qt.Assert(t, qt.IsTrue(Flags.YAMLV3Decoder))
 
 	// Check that we can enable all experiments.