Added hardcoded weaver module version.

> Module Version

We want a `weaver version` command that prints out the weaver module
version the `weaver` binary was built with, or failing that, the commit
at which the binary was built. Unfortunately, both of these things are
hard.

There is currently no nice way to automatically get the version of the
main module in a go program [1]. There is a way to get the git commit
using `debug.ReadBuildInfo()` [2], but when `go install`ing a binary,
the version control information is stripped.

Browsing existing open source projects, it seems the standard practice
is to hard code the module version in the code. This PR does that and
updates the `weaver version` command to use it:

```
$ weaver version
weaver v0.17.0 linux/amd64
```

> Other Versions

The weaver repo has two other versioned APIs: the deployer API version
and the codegen version. Currently, the deployer API version is the
latest module version where the deployer API changed (and the same for
the codegen version).

We discussed offline the idea of replacing the three versions (module,
deployer API, codegen) with just the module version. Then, we could
write additional code to check version compatibility. Is codegen v0.17.3
incompatible with v0.12.0, for example?

When trying to implement this, however, I ran into some problems. For
example, let's say a deployer is at version v0.10.0 and tries to deploy
an app at version v0.12.0. Is deployer API version v0.12.0 compatible
with version v0.10.0? Well, the deployer was written before v0.12.0 was
even created, so it doesn't have a good way to know.

The codegen version is also tricky because it relies on some compiler
tricks to prevent an app from compiling if it has code generated with a
stale version of `weaver generate`. I'm not sure how to implement these
tricks without hardcoding a codegen version.

Because of these challenges, I decided to stick with our current
approach to versioning, for now at least. To clean things up a bit
though, I moved all versioning related code to `runtime/version.go`. I
also moved some code to the `bin` package because it felt more
appropriate there.

[1]: golang/go#29228
[2]: https://pkg.go.dev/runtime/debug#ReadBuildInfo

cmd/weaver/main.go

@@ -25,6 +25,7 @@ import (
 	"os/exec"
 	"strings"
 
+	itool "github.com/ServiceWeaver/weaver/internal/tool"
 	"github.com/ServiceWeaver/weaver/internal/tool/callgraph"
 	"github.com/ServiceWeaver/weaver/internal/tool/generate"
 	"github.com/ServiceWeaver/weaver/internal/tool/multi"
@@ -84,11 +85,12 @@ func main() {
 		return
 
 	case "version":
-		cmd := tool.VersionCmd("weaver")
+		cmd := itool.VersionCmd("weaver")
 		if err := cmd.Fn(context.Background(), flag.Args()[1:]); err != nil {
 			fmt.Fprintln(os.Stderr, err)
 			os.Exit(1)
 		}
+		return
 
 	case "callgraph":
 		const usage = `Generate component callgraphs.

godeps.txt

@@ -59,6 +59,7 @@ github.com/ServiceWeaver/weaver/cmd/weaver
     errors
     flag
     fmt
+    github.com/ServiceWeaver/weaver/internal/tool
     github.com/ServiceWeaver/weaver/internal/tool/callgraph
     github.com/ServiceWeaver/weaver/internal/tool/generate
     github.com/ServiceWeaver/weaver/internal/tool/multi
@@ -517,6 +518,13 @@ github.com/ServiceWeaver/weaver/internal/status
     syscall
     text/template
     time
+github.com/ServiceWeaver/weaver/internal/tool
+    context
+    flag
+    fmt
+    github.com/ServiceWeaver/weaver/runtime/tool
+    github.com/ServiceWeaver/weaver/runtime/version
+    runtime
 github.com/ServiceWeaver/weaver/internal/tool/callgraph
     fmt
     github.com/ServiceWeaver/weaver/runtime/bin
@@ -550,6 +558,7 @@ github.com/ServiceWeaver/weaver/internal/tool/generate
     github.com/ServiceWeaver/weaver/internal/files
     github.com/ServiceWeaver/weaver/runtime/codegen
     github.com/ServiceWeaver/weaver/runtime/colors
+    github.com/ServiceWeaver/weaver/runtime/version
     go/ast
     go/format
     go/parser
@@ -589,6 +598,7 @@ github.com/ServiceWeaver/weaver/internal/tool/multi
     github.com/ServiceWeaver/weaver/internal/proxy
     github.com/ServiceWeaver/weaver/internal/routing
     github.com/ServiceWeaver/weaver/internal/status
+    github.com/ServiceWeaver/weaver/internal/tool
     github.com/ServiceWeaver/weaver/internal/tool/certs
     github.com/ServiceWeaver/weaver/internal/tool/config
     github.com/ServiceWeaver/weaver/runtime
@@ -629,6 +639,7 @@ github.com/ServiceWeaver/weaver/internal/tool/single
     fmt
     github.com/ServiceWeaver/weaver/internal/must
     github.com/ServiceWeaver/weaver/internal/status
+    github.com/ServiceWeaver/weaver/internal/tool
     github.com/ServiceWeaver/weaver/internal/tool/config
     github.com/ServiceWeaver/weaver/runtime
     github.com/ServiceWeaver/weaver/runtime/codegen
@@ -650,6 +661,7 @@ github.com/ServiceWeaver/weaver/internal/tool/ssh
     flag
     fmt
     github.com/ServiceWeaver/weaver/internal/status
+    github.com/ServiceWeaver/weaver/internal/tool
     github.com/ServiceWeaver/weaver/internal/tool/config
     github.com/ServiceWeaver/weaver/internal/tool/ssh/impl
     github.com/ServiceWeaver/weaver/runtime
@@ -743,7 +755,10 @@ github.com/ServiceWeaver/weaver/runtime/bin
     debug/pe
     fmt
     github.com/ServiceWeaver/weaver/runtime/codegen
+    github.com/ServiceWeaver/weaver/runtime/version
     os
+    regexp
+    strconv
 github.com/ServiceWeaver/weaver/runtime/bin/testprogram
     context
     github.com/ServiceWeaver/weaver
@@ -762,6 +777,7 @@ github.com/ServiceWeaver/weaver/runtime/codegen
     github.com/ServiceWeaver/weaver/metrics
     github.com/ServiceWeaver/weaver/runtime
     github.com/ServiceWeaver/weaver/runtime/protos
+    github.com/ServiceWeaver/weaver/runtime/version
     go.opentelemetry.io/otel/trace
     google.golang.org/protobuf/proto
     math
@@ -909,30 +925,17 @@ github.com/ServiceWeaver/weaver/runtime/tool
     errors
     flag
     fmt
-    github.com/ServiceWeaver/weaver/runtime/codegen
     github.com/ServiceWeaver/weaver/runtime/colors
     github.com/ServiceWeaver/weaver/runtime/logging
-    github.com/ServiceWeaver/weaver/runtime/version
     io
     os
     os/exec
-    runtime
-    runtime/debug
     sort
     strings
     text/template
     time
 github.com/ServiceWeaver/weaver/runtime/version
     fmt
-    github.com/ServiceWeaver/weaver/runtime/bin
-    regexp
-    strconv
-github.com/ServiceWeaver/weaver/runtime/version/testprogram
-    context
-    github.com/ServiceWeaver/weaver
-    github.com/ServiceWeaver/weaver/runtime/codegen
-    go.opentelemetry.io/otel/trace
-    reflect
 github.com/ServiceWeaver/weaver/weavertest
     context
     errors

internal/envelope/conn/envelope_conn.go

@@ -381,18 +381,13 @@ func verifyWeaveletInfo(wlet *protos.WeaveletInfo) error {
 // checkVersion checks that the deployer API version the deployer was built
 // with is compatible with the deployer API version the app was built with,
 // erroring out if they are not compatible.
-func checkVersion(appVersion *protos.SemVer) error {
-	if appVersion == nil {
+func checkVersion(v *protos.SemVer) error {
+	if v == nil {
 		return fmt.Errorf("version mismatch: nil app version")
 	}
-	if appVersion.Major != version.Major ||
-		appVersion.Minor != version.Minor ||
-		appVersion.Patch != version.Patch {
-		return fmt.Errorf(
-			"version mismatch: deployer version %d.%d.%d is incompatible with app version %d.%d.%d.",
-			version.Major, version.Minor, version.Patch,
-			appVersion.Major, appVersion.Minor, appVersion.Patch,
-		)
+	got := version.SemVer{Major: int(v.Major), Minor: int(v.Minor), Patch: int(v.Patch)}
+	if got != version.DeployerVersion {
+		return fmt.Errorf("version mismatch: deployer's deployer API version %s is incompatible with app' deployer API version %s.", version.DeployerVersion, got)
 	}
 	return nil
 }

internal/envelope/conn/weavelet_conn.go

@@ -102,9 +102,9 @@ func NewWeaveletConn(r io.ReadCloser, w io.WriteCloser, h WeaveletHandler) (*Wea
 		DialAddr: dialAddr,
 		Pid:      int64(os.Getpid()),
 		Version: &protos.SemVer{
-			Major: version.Major,
-			Minor: version.Minor,
-			Patch: version.Patch,
+			Major: version.DeployerMajor,
+			Minor: version.DeployerMinor,
+			Patch: 0,
 		},
 	}
 	if err := wc.conn.send(&protos.WeaveletMsg{WeaveletInfo: wc.winfo}); err != nil {

internal/tool/generate/generator.go

@@ -37,6 +37,7 @@ import (
 	"github.com/ServiceWeaver/weaver/internal/files"
 	"github.com/ServiceWeaver/weaver/runtime/codegen"
 	"github.com/ServiceWeaver/weaver/runtime/colors"
+	"github.com/ServiceWeaver/weaver/runtime/version"
 	"golang.org/x/exp/maps"
 	"golang.org/x/tools/go/packages"
 	"golang.org/x/tools/go/types/typeutil"
@@ -928,8 +929,8 @@ func (g *generator) generateVersionCheck(p printFn) {
 	//     var _ codegen.LatestVersion = codegen.Version[[0][1]struct{}]("You used ...")
 	p(`var _ %s = %s[[%d][%d]struct{}](%q)`,
 		g.codegen().qualify("LatestVersion"), g.codegen().qualify("Version"),
-		codegen.Major, codegen.Minor,
-		fmt.Sprintf(`You used 'weaver generate' codegen version %d.%d.0, but you built your code with an incompatible weaver module version. Try upgrading 'weaver generate' and re-running it.`, codegen.Major, codegen.Minor),
+		version.CodegenMajor, version.CodegenMinor,
+		fmt.Sprintf(`You used 'weaver generate' codegen version %d.%d.0, but you built your code with an incompatible weaver module version. Try upgrading 'weaver generate' and re-running it.`, version.CodegenMajor, version.CodegenMinor),
 	)
 }
 

internal/tool/multi/multi.go

@@ -21,6 +21,7 @@ import (
 
 	"github.com/ServiceWeaver/weaver/internal/must"
 	"github.com/ServiceWeaver/weaver/internal/status"
+	itool "github.com/ServiceWeaver/weaver/internal/tool"
 	"github.com/ServiceWeaver/weaver/runtime"
 	"github.com/ServiceWeaver/weaver/runtime/logging"
 	"github.com/ServiceWeaver/weaver/runtime/tool"
@@ -66,6 +67,6 @@ var (
 		"metrics":   status.MetricsCommand("weaver multi", defaultRegistry),
 		"profile":   status.ProfileCommand("weaver multi", defaultRegistry),
 		"purge":     tool.PurgeCmd(purgeSpec),
-		"version":   tool.VersionCmd("weaver multi"),
+		"version":   itool.VersionCmd("weaver multi"),
 	}
 )

internal/tool/single/single.go

@@ -21,6 +21,7 @@ import (
 
 	"github.com/ServiceWeaver/weaver/internal/must"
 	"github.com/ServiceWeaver/weaver/internal/status"
+	itool "github.com/ServiceWeaver/weaver/internal/tool"
 	"github.com/ServiceWeaver/weaver/runtime"
 	"github.com/ServiceWeaver/weaver/runtime/tool"
 )
@@ -55,7 +56,7 @@ var (
 		"metrics":   status.MetricsCommand("weaver single", defaultRegistry),
 		"profile":   status.ProfileCommand("weaver single", defaultRegistry),
 		"purge":     tool.PurgeCmd(purgeSpec),
-		"version":   tool.VersionCmd("weaver single"),
+		"version":   itool.VersionCmd("weaver single"),
 	}
 )
 

internal/tool/ssh/ssh.go

@@ -16,6 +16,7 @@ package ssh
 
 import (
 	"github.com/ServiceWeaver/weaver/internal/status"
+	itool "github.com/ServiceWeaver/weaver/internal/tool"
 	"github.com/ServiceWeaver/weaver/runtime/tool"
 )
 
@@ -24,7 +25,7 @@ var (
 		"deploy":    &deployCmd,
 		"logs":      tool.LogsCmd(&logsSpec),
 		"dashboard": status.DashboardCommand(dashboardSpec),
-		"version":   tool.VersionCmd("weaver ssh"),
+		"version":   itool.VersionCmd("weaver ssh"),
 
 		// Hidden commands.
 		"babysitter": &babysitterCmd,

internal/tool/version.go

@@ -0,0 +1,39 @@
+// Copyright 2023 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tool
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"runtime"
+
+	"github.com/ServiceWeaver/weaver/runtime/tool"
+	"github.com/ServiceWeaver/weaver/runtime/version"
+)
+
+// VersionCmd returns a command to show a deployer's version.
+func VersionCmd(toolname string) *tool.Command {
+	return &tool.Command{
+		Name:        "version",
+		Flags:       flag.NewFlagSet("version", flag.ContinueOnError),
+		Description: fmt.Sprintf("Show %q version", toolname),
+		Help:        fmt.Sprintf("Usage:\n  %s version", toolname),
+		Fn: func(context.Context, []string) error {
+			fmt.Printf("%s %s %s/%s\n", toolname, version.ModuleVersion, runtime.GOOS, runtime.GOARCH)
+			return nil
+		},
+	}
+}

runtime/bin/bin.go

@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// Package bin contains code to extract data from a Service Weaver binary.
 package bin
 
 import (
@@ -21,12 +22,30 @@ import (
 	"debug/pe"
 	"fmt"
 	"os"
+	"regexp"
+	"strconv"
 
 	"github.com/ServiceWeaver/weaver/runtime/codegen"
+	"github.com/ServiceWeaver/weaver/runtime/version"
 )
 
-// ROData returns the read-only data section of the provided binary.
-func ROData(file string) ([]byte, error) {
+// deployerVersion exists to embed the deployer API version into a Service
+// Weaver binary. We split declaring and assigning version to prevent the
+// compiler from erasing it.
+//
+//nolint:unused
+var deployerVersion string
+
+func init() {
+	// NOTE that deployerVersion must be assigned a string constant that
+	// reflects the values of version.DeployerMajor and version.DeployerMinor.
+	// If the string is not a constant---if we try to use fmt.Sprintf, for
+	// example---it will not be embedded in a Service Weaver binary.
+	deployerVersion = "⟦wEaVeRdEpLoYeRvErSiOn:v0.14.0⟧"
+}
+
+// rodata returns the read-only data section of the provided binary.
+func rodata(file string) ([]byte, error) {
 	f, err := os.Open(file)
 	if err != nil {
 		return nil, err
@@ -76,7 +95,7 @@ func ROData(file string) ([]byte, error) {
 //
 //	github.com/ServiceWeaver/weaver/Main
 func ReadComponentGraph(file string) ([][2]string, error) {
-	data, err := ROData(file)
+	data, err := rodata(file)
 	if err != nil {
 		return nil, err
 	}
@@ -86,9 +105,44 @@ func ReadComponentGraph(file string) ([][2]string, error) {
 // ReadListeners reads the sets of listeners associated with each component
 // in the specified binary.
 func ReadListeners(file string) ([]codegen.ComponentListeners, error) {
-	data, err := ROData(file)
+	data, err := rodata(file)
 	if err != nil {
 		return nil, err
 	}
 	return codegen.ExtractListeners(data), nil
 }
+
+// ReadDeployerVersion reads the deployer API version from the specified binary.
+func ReadDeployerVersion(filename string) (version.SemVer, error) {
+	data, err := rodata(filename)
+	if err != nil {
+		return version.SemVer{}, err
+	}
+	return extractDeployerVersion(data)
+}
+
+// extractDeployerVersion returns the deployer API version embedded in data.
+func extractDeployerVersion(data []byte) (version.SemVer, error) {
+	re := regexp.MustCompile(`⟦wEaVeRdEpLoYeRvErSiOn:v([0-9]*?)\.([0-9]*?)\.([0-9]*?)⟧`)
+	m := re.FindSubmatch(data)
+	if m == nil {
+		return version.SemVer{}, fmt.Errorf("embedded deployer API version not found")
+	}
+	major, minor, patch := string(m[1]), string(m[2]), string(m[3])
+
+	v := version.SemVer{}
+	var err error
+	v.Major, err = strconv.Atoi(major)
+	if err != nil {
+		return version.SemVer{}, fmt.Errorf("invalid embedded deployer API major %q: %w", major, err)
+	}
+	v.Minor, err = strconv.Atoi(minor)
+	if err != nil {
+		return version.SemVer{}, fmt.Errorf("invalid embedded deployer API minor %q: %w", minor, err)
+	}
+	v.Patch, err = strconv.Atoi(patch)
+	if err != nil {
+		return version.SemVer{}, fmt.Errorf("invalid embedded deployer API patch %q: %w", patch, err)
+	}
+	return v, nil
+}