internal/cueversion: split language and module versions

This means that the CUE logic will not predicate language semantics on a
relatively volatile build-info-derived version.

Instead the semantics are predicated on a simple compiled-in string and
the original logic is used for version information that's displayed as
part of the `cue version` command and forms part of the User-Agent HTTP
header.

We also fix the module version logic so that it works when CUE is used
as a dependency as well as a main module.

Note that writing a local regression test for this is hard, as
dependency modules only have versions as provided by a proxy, and deps
replaced by a directory don't have module versions.

Fixes #3061

Signed-off-by: Roger Peppe <rogpeppe@gmail.com>
Change-Id: I55bc931590974a5a50b0d82d78cba0a64efbd0f6
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1194044
Unity-Result: CUE porcuepine <cue.porcuepine@gmail.com>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>

cmd/cue/cmd/modinit.go

@@ -25,6 +25,7 @@ import (
 	"golang.org/x/mod/semver"
 
 	"cuelang.org/go/internal/cueexperiment"
+	"cuelang.org/go/internal/cueversion"
 	"cuelang.org/go/mod/modfile"
 	"cuelang.org/go/mod/module"
 )
@@ -95,14 +96,8 @@ func runModInit(cmd *Command, args []string) (err error) {
 			return err
 		}
 	}
-	vers := versionForModFile()
-	if vers == "" {
-		// Shouldn't happen because we should use the
-		// fallback version if we can't the version otherwise.
-		return fmt.Errorf("cannot determine language version for module")
-	}
 	mf.Language = &modfile.Language{
-		Version: vers,
+		Version: cueversion.LanguageVersion(),
 	}
 
 	err = os.Mkdir(mod, 0755)
@@ -129,7 +124,7 @@ func runModInit(cmd *Command, args []string) (err error) {
 }
 
 func versionForModFile() string {
-	version := cueVersion()
+	version := cueversion.LanguageVersion()
 	earliestPossibleVersion := modfile.EarliestClosedSchemaVersion()
 	if semver.Compare(version, earliestPossibleVersion) < 0 {
 		// The reported version is earlier than it should be,

cmd/cue/cmd/modtidy.go

@@ -22,6 +22,7 @@ import (
 
 	"github.com/spf13/cobra"
 
+	"cuelang.org/go/internal/cueversion"
 	"cuelang.org/go/internal/mod/modload"
 )
 
@@ -71,7 +72,7 @@ func runModTidy(cmd *Command, args []string) error {
 	if flagCheck.Bool(cmd) {
 		return modload.CheckTidy(ctx, os.DirFS(modRoot), ".", reg)
 	}
-	mf, err := modload.Tidy(ctx, os.DirFS(modRoot), ".", reg, versionForModFile())
+	mf, err := modload.Tidy(ctx, os.DirFS(modRoot), ".", reg, cueversion.LanguageVersion())
 	if err != nil {
 		return err
 	}

cmd/cue/cmd/script_test.go

@@ -46,6 +46,7 @@ import (
 	"cuelang.org/go/cue/errors"
 	"cuelang.org/go/cue/parser"
 	"cuelang.org/go/internal/cuetest"
+	"cuelang.org/go/internal/cueversion"
 	"cuelang.org/go/internal/registrytest"
 )
 
@@ -232,6 +233,7 @@ func TestScript(t *testing.T) {
 			e.Vars = append(e.Vars,
 				"GOPROXY="+srv.URL,
 				"GONOSUMDB=*", // GOPROXY is a private proxy
+				"CUE_LANGUAGE_VERSION="+cueversion.LanguageVersion(),
 			)
 			entries, err := os.ReadDir(e.WorkDir)
 			if err != nil {

cmd/cue/cmd/testdata/script/modinit_majorversion.txtar

@@ -1,4 +1,5 @@
-env CUE_VERSION_OVERRIDE=v0.8.100
+env-fill want-module.cue
+env-fill want-module-experiment.cue
 
 # Without the experiment, the major version is allowed,
 # even though it's not particularly useful.
@@ -19,10 +20,10 @@ exists cue.mod/pkg
 -- want-module.cue --
 module: "foo.com/bar@v1"
 language: {
-	version: "v0.8.100"
+	version: "$CUE_LANGUAGE_VERSION"
 }
 -- want-module-experiment.cue --
 module: "foo.com/bar@v1"
 language: {
-	version: "v0.8.100"
+	version: "$CUE_LANGUAGE_VERSION"
 }

cmd/cue/cmd/testdata/script/modinit_noargs.txtar

@@ -1,13 +1,13 @@
 # TODO we might want to deprecate or remove the ability to create
 # module file with an empty module directive.
-env CUE_VERSION_OVERRIDE=v0.8.100
 exec cue mod init
+env-fill want-module.cue
 cmp cue.mod/module.cue want-module.cue
 exists cue.mod/usr
 exists cue.mod/pkg
 
 -- want-module.cue --
 module: ""
 language: {
-	version: "v0.8.100"
+	version: "$CUE_LANGUAGE_VERSION"
 }

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

@@ -1,4 +1,5 @@
-env CUE_VERSION_OVERRIDE=v0.8.0
+env-fill want-module.cue
+env-fill want-module-experiment.cue
 
 # Without the experiment, we use the module path as-is.
 exec cue mod init foo.com/bar
@@ -17,10 +18,10 @@ exists cue.mod/pkg
 -- want-module.cue --
 module: "foo.com/bar"
 language: {
-	version: "v0.8.0"
+	version: "$CUE_LANGUAGE_VERSION"
 }
 -- want-module-experiment.cue --
 module: "foo.com/bar@v0"
 language: {
-	version: "v0.8.0"
+	version: "$CUE_LANGUAGE_VERSION"
 }

cmd/cue/cmd/testdata/script/modinit_without_version.txtar

@@ -1,8 +1,7 @@
-# Check that cue mod init uses the latest schema
-# version when it lacks any version information at all.
-# A zero pseudo-version is one such case, as there are no semver numbers.
+# Check that cue mod init is independent of the module version.
 env CUE_EXPERIMENT=modules
 env CUE_VERSION_OVERRIDE=v0.0.0-00010101000000-000000000000
+env-fill want-module
 exec cue mod init foo.example
 cmp cue.mod/module.cue want-module
 
@@ -15,5 +14,5 @@ cmp cue.mod/module.cue want-module
 -- want-module --
 module: "foo.example@v0"
 language: {
-	version: "v0.9.0-alpha.0"
+	version: "$CUE_LANGUAGE_VERSION"
 }

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

@@ -1,6 +1,7 @@
 # Test that we can use the --source flag to cue mod init.
 
-env CUE_VERSION_OVERRIDE=v0.9.0-alpha.2
+env-fill $WORK/want-module.cue-0
+env-fill $WORK/want-module.cue-1
 
 mkdir $WORK/test0
 cd $WORK/test0
@@ -20,15 +21,15 @@ cmp stderr $WORK/want-stderr
 -- want-module.cue-0 --
 module: "test.example"
 language: {
-	version: "v0.9.0-alpha.2"
+	version: "$CUE_LANGUAGE_VERSION"
 }
 source: {
 	kind: "self"
 }
 -- want-module.cue-1 --
 module: "test.example"
 language: {
-	version: "v0.9.0-alpha.2"
+	version: "$CUE_LANGUAGE_VERSION"
 }
 source: {
 	kind: "git"

cmd/cue/cmd/testdata/script/modtidy_logging.txtar

@@ -3,7 +3,7 @@ env CUE_DEBUG=http
 # Smoke test that the logging looks reasonable. The actual log messages
 # are tested more fully in the httplog package itself.
 exec cue mod tidy
-stderr '{"time":".*","level":"INFO","msg":"http client->","info":{"id":[0-9]+,"method":"GET","url":"http://[^/]+/v2/example.com/tags/list\?n=\d+","contentLength":0,"header":{"User-Agent":\["Cue/.* \(cmd/cue\) Go/[^ ]+ \(.*\)"\]}}}'
+stderr '{"time":".*","level":"INFO","msg":"http client->","info":{"id":[0-9]+,"method":"GET","url":"http://[^/]+/v2/example.com/tags/list\?n=\d+","contentLength":0,"header":{"User-Agent":\["Cue/[^ ]+ \(cmd/cue; .*\) Go/[^ ]+ \(.*\)"\]}}}'
 
 # Check that the resulting module evaluates as expected.
 exec cue export .

cmd/cue/cmd/testdata/script/version.txtar

@@ -1,14 +1,15 @@
 # Version output without VCS information.
 exec cue version
-stdout -count=1 '^cue version v0.[1-9]'
+stdout -count=1 '^cue version .+'
 stdout -count=1 '^go version (devel )?go1.'
 
 # Version output with VCS information.
 env CUE_VERSION_TEST_CFG='[{"Key":"vcs","Value":"git"},{"Key":"vcs.revision","Value":"47b7032385cb490fab7d47b89fca36835cf13d39"},{"Key":"vcs.time","Value":"2022-05-10T04:58:46Z"},{"Key":"vcs.modified","Value":"true"}]'
 exec cue version
-stdout -count=1 '^cue version v0.[1-9]'
+stdout -count=1 '^cue version .+'
 stdout -count=1 '^go version (devel )?go1.'
 stdout -count=1 'vcs git'
 stdout -count=1 'vcs\.revision 47b7032385cb490fab7d47b89fca36835cf13d39'
 stdout -count=1 'vcs\.time 2022-05-10T04:58:46Z'
 stdout -count=1 'vcs\.modified true'
+stdout -count=1 'cue\.lang\.version '${CUE_LANGUAGE_VERSION@R}'$'

cmd/cue/cmd/version.go

@@ -56,8 +56,12 @@ func runVersion(cmd *Command, args []string) error {
 		// shouldn't happen
 		return errors.New("unknown error reading build-info")
 	}
-	fmt.Fprintf(w, "cue version %s\n\n", cueVersion())
+	fmt.Fprintf(w, "cue version %s\n\n", moduleVersion())
 	fmt.Fprintf(w, "go version %s\n", runtime.Version())
+	bi.Settings = append(bi.Settings, debug.BuildSetting{
+		Key:   "cue.lang.version",
+		Value: cueversion.LanguageVersion(),
+	})
 	for _, s := range bi.Settings {
 		if s.Value == "" {
 			// skip empty build settings
@@ -68,16 +72,17 @@ func runVersion(cmd *Command, args []string) error {
 		//   veryverylong.key value
 		//          short.key some-other-value
 		//
-		// Empirically, 16 is enough; the longest key seen is "vcs.revision".
+		// Empirically, 16 is enough; the longest key seen outside our own "cue.lang.version"
+		// is "vcs.revision".
 		fmt.Fprintf(w, "%16s %s\n", s.Key, s.Value)
 	}
 	return nil
 }
 
-// cueVersion returns the version of the CUE module as much
+// moduleVersion returns the version of the main module as much
 // as can reasonably be determined. If no version can be
 // determined, it returns the empty string.
-func cueVersion() string {
+func moduleVersion() string {
 	if testing.Testing() {
 		if v := os.Getenv("CUE_VERSION_OVERRIDE"); v != "" {
 			return v
@@ -87,7 +92,7 @@ func cueVersion() string {
 		// The global version variable has been configured via ldflags.
 		return v
 	}
-	return cueversion.Version()
+	return cueversion.ModuleVersion()
 }
 
 func readBuildInfo() (*debug.BuildInfo, bool) {

internal/cueversion/version.go

@@ -10,42 +10,61 @@ import (
 	"sync"
 )
 
-// fallbackVersion is used when there isn't a recorded main module version,
-// for example when building via `go install ./cmd/cue`.
-// It should reflect the last release in the current branch.
-//
-// TODO: remove once Go stamps local builds with a main module version
-// derived from the local VCS information per https://go.dev/issue/50603.
-const fallbackVersion = "v0.9.0-alpha.3"
-
-// Version returns the version of the cuelang.org/go module as best as can
-// reasonably be determined. The result is always a valid Go semver version.
-func Version() string {
-	return versionOnce()
+// LanguageVersion returns the CUE language version.
+// This determines the latest version of CUE that
+// is accepted by the module.
+func LanguageVersion() string {
+	return "v0.9.0"
+}
+
+// ModuleVersion returns the version of the cuelang.org/go module as best as can
+// reasonably be determined. This is provided for informational
+// and debugging purposes and should not be used to predicate
+// version-specific behavior.
+func ModuleVersion() string {
+	return moduleVersionOnce()
 }
 
-var versionOnce = sync.OnceValue(func() string {
+const cueModule = "cuelang.org/go"
+
+var moduleVersionOnce = sync.OnceValue(func() string {
 	bi, ok := debug.ReadBuildInfo()
 	if !ok {
-		return fallbackVersion
+		// This might happen if the binary was not built with module support
+		// or with an alternative toolchain.
+		return "(no-build-info)"
 	}
-	switch bi.Main.Version {
-	case "": // missing version
-	case "(devel)": // local build
-	case "v0.0.0-00010101000000-000000000000": // build via a directory replace directive
-	default:
-		return bi.Main.Version
+	cueMod := findCUEModule(bi)
+	if cueMod == nil {
+		// Could happen if someone has forked CUE under a different
+		// module name; it also happens when running the cue tests.
+		return "(no-cue-module)"
 	}
-	return fallbackVersion
+	return cueMod.Version
 })
 
+func findCUEModule(bi *debug.BuildInfo) *debug.Module {
+	if bi.Main.Path == cueModule {
+		return &bi.Main
+	}
+	for _, m := range bi.Deps {
+		if m.Replace != nil && m.Replace.Path == cueModule {
+			return m.Replace
+		}
+		if m.Path == cueModule {
+			return m
+		}
+	}
+	return nil
+}
+
 // UserAgent returns a string suitable for adding as the User-Agent
 // header in an HTTP agent. The clientType argument specifies
 // how CUE is being used: if this is empty it defaults to "cuelang.org/go".
 //
 // Example:
 //
-//	Cue/v0.8.0 (cuelang.org/go) Go/go1.22.0 (linux/amd64)
+//	Cue/v0.8.0 (cuelang.org/go; vxXXX) Go/go1.22.0 (linux/amd64)
 func UserAgent(clientType string) string {
 	if clientType == "" {
 		clientType = "cuelang.org/go"
@@ -55,5 +74,6 @@ func UserAgent(clientType string) string {
 	// As the runtime version won't contain underscores itself, this
 	// is reversible.
 	goVersion := strings.ReplaceAll(runtime.Version(), " ", "_")
-	return fmt.Sprintf("Cue/%s (%s) Go/%s (%s/%s)", Version(), clientType, goVersion, runtime.GOOS, runtime.GOARCH)
+
+	return fmt.Sprintf("Cue/%s (%s; lang %s) Go/%s (%s/%s)", ModuleVersion(), clientType, LanguageVersion(), goVersion, runtime.GOOS, runtime.GOARCH)
 }

internal/cueversion/version_test.go

@@ -7,24 +7,23 @@ import (
 	"testing"
 
 	"github.com/go-quicktest/qt"
-	"golang.org/x/mod/semver"
 )
 
-func TestVersion(t *testing.T) {
+func TestModuleVersion(t *testing.T) {
 	// This is just a smoke test to make sure that things
 	// are wired up OK. It would be possible to unit
 	// test the logic inside Version, but it's simple
 	// enough that that would amount to creating invariants
 	// that just match the code, not providing any more
 	// assurance of correctness.
-	vers := Version()
-	qt.Assert(t, qt.Satisfies(vers, semver.IsValid))
+	vers := ModuleVersion()
+	qt.Assert(t, qt.Not(qt.Equals(vers, "")))
 }
 
 func TestUserAgent(t *testing.T) {
 	agent := UserAgent("custom")
 	qt.Assert(t, qt.Matches(agent,
-		`Cue/v[^ ]+ \(custom\) Go/[^ ]+ \([^/]+/[^/]+\)`,
+		`Cue/[^ ]+ \(custom; lang v[^)]+\) Go/[^ ]+ \([^/]+/[^/]+\)`,
 	))
 }
 
@@ -41,5 +40,5 @@ func TestTransport(t *testing.T) {
 	defer resp.Body.Close()
 	data, err := io.ReadAll(resp.Body)
 	qt.Assert(t, qt.IsNil(err))
-	qt.Assert(t, qt.Matches(string(data), `Cue/v[^ ]+ \(foo\) Go/[^ ]+ \([^/]+/[^/]+\)`))
+	qt.Assert(t, qt.Matches(string(data), `Cue/[^ ]+ \(foo; lang v[^)]+\) Go/[^ ]+ \([^/]+/[^/]+\)`))
 }