build: add generating compat.json (#9700)

This is to add the generation of `compat.json` as a release artifact. It
describes the runtime requirements of the release in question. The next
step is to have the upgrade server use this information to filter
releases provided to clients. This is per the discussion in #9656

---------

Co-authored-by: Ross Smith II <ross@smithii.com>

.github/workflows/build-syncthing.yaml

@@ -238,7 +238,9 @@ jobs:
         uses: actions/upload-artifact@v4
         with:
           name: packages-linux
-          path: syncthing-linux-*.tar.gz
+          path: |
+            syncthing-linux-*.tar.gz
+            compat.json
 
   #
   # macOS

.gitignore

@@ -18,3 +18,4 @@ deb
 /repos
 /proto/scripts/protoc-gen-gosyncthing
 /gui/next-gen-gui
+/compat.json

build.go

@@ -4,8 +4,8 @@
 // License, v. 2.0. If a copy of the MPL was not distributed with this file,
 // You can obtain one at https://mozilla.org/MPL/2.0/.
 
-//go:build ignore
+//go:build tools
-// +build ignore
+// +build tools
 
 package main
 
@@ -34,6 +34,8 @@ import (
 	"time"
 
 	buildpkg "github.com/syncthing/syncthing/lib/build"
+	"github.com/syncthing/syncthing/lib/upgrade"
+	"sigs.k8s.io/yaml"
 )
 
 var (
@@ -342,9 +344,11 @@ func runCommand(cmd string, target target) {
 
 	case "tar":
 		buildTar(target, tags)
+		writeCompatJSON()
 
 	case "zip":
 		buildZip(target, tags)
+		writeCompatJSON()
 
 	case "deb":
 		buildDeb(target)
@@ -1557,3 +1561,29 @@ func nextPatchVersion(ver string) string {
 	digits[len(digits)-1] = strconv.Itoa(n + 1)
 	return strings.Join(digits, ".")
 }
+
+func writeCompatJSON() {
+	bs, err := os.ReadFile("compat.yaml")
+	if err != nil {
+		log.Fatal("Reading compat.yaml:", err)
+	}
+
+	var entries []upgrade.ReleaseCompatibility
+	if err := yaml.Unmarshal(bs, &entries); err != nil {
+		log.Fatal("Parsing compat.yaml:", err)
+	}
+
+	rt := runtime.Version()
+	for _, e := range entries {
+		if !strings.HasPrefix(rt, e.Runtime) {
+			continue
+		}
+		bs, _ := json.MarshalIndent(e, "", "  ")
+		if err := os.WriteFile("compat.json", bs, 0o644); err != nil {
+			log.Fatal("Writing compat.json:", err)
+		}
+		return
+	}
+
+	log.Fatalf("runtime %v not found in compat.yaml", rt)
+}

compat.yaml

@@ -0,0 +1,28 @@
+- runtime: go1.21
+  requirements:
+    # See https://en.wikipedia.org/wiki/MacOS_version_history#Releases
+    #
+    # macOS 10.15 (Catalina) per https://go.dev/doc/go1.22#darwin
+    darwin: "19"
+    # Per https://go.dev/doc/go1.23#linux
+    linux: "2.6.32"
+    # Windows 10's initial release was 10.0.10240.16405, per
+    # https://learn.microsoft.com/en-us/windows/release-health/release-information
+    # and Windows 11's initial release was 10.0.22000.194 per
+    # https://learn.microsoft.com/en-us/windows/release-health/windows11-release-information
+    #
+    # Windows 10/Windows Server 2016 per https://go.dev/doc/go1.21#windows
+    windows: "10.0"
+
+- runtime: go1.22
+  requirements:
+    darwin: "19"
+    linux: "2.6.32"
+    windows: "10.0"
+
+- runtime: go1.23
+  requirements:
+    # macOS 11 (Big Sur) per https://tip.golang.org/doc/go1.23#darwin
+    darwin: "20"
+    linux: "2.6.32"
+    windows: "10.0"

go.mod

@@ -46,6 +46,7 @@ require (
 	golang.org/x/time v0.6.0
 	golang.org/x/tools v0.24.0
 	google.golang.org/protobuf v1.34.2
+	sigs.k8s.io/yaml v1.4.0
 )
 
 require (

go.sum

@@ -81,6 +81,7 @@ github.com/google/go-cmp v0.4.0/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/
 github.com/google/go-cmp v0.5.5/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-cmp v0.5.6/go.mod h1:v8dTdLbMG2kIc/vJvl+f65V22dbkXbowE6jgT/gNBxE=
 github.com/google/go-cmp v0.5.7/go.mod h1:n+brtR0CgQNWTVd5ZUFpTBC8YFBDLK/h/bpaJ8/DtOE=
+github.com/google/go-cmp v0.5.9/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/google/go-cmp v0.6.0 h1:ofyhxvXcZhMsU5ulbFiLKl/XBFqE1GSq7atu8tAmTRI=
 github.com/google/go-cmp v0.6.0/go.mod h1:17dUlkBOakJ0+DkrSSNjCkIjxS6bF9zb3elmeNGIjoY=
 github.com/google/pprof v0.0.0-20210407192527-94a9f03dee38/go.mod h1:kpwsk12EmLew5upagYY7GY0pfYCcupk39gWOCRROcvE=
@@ -385,3 +386,5 @@ gopkg.in/yaml.v2 v2.4.0/go.mod h1:RDklbk79AGWmwhnvt/jBztapEOGDOx6ZbXqjP6csGnQ=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+sigs.k8s.io/yaml v1.4.0 h1:Mk1wCc2gy/F0THH0TAp1QYyJNzRm2KCLy3o5ASXVI5E=
+sigs.k8s.io/yaml v1.4.0/go.mod h1:Ejl7/uTz7PSA4eKMyQCUTnhZYNmLIl+5c2lQPGR2BPY=

lib/upgrade/upgrade_common.go

@@ -38,6 +38,13 @@ type Asset struct {
 	BrowserURL string `json:"browser_download_url,omitempty"`
 }
 
+// ReleaseCompatibility defines the structure of compat.json, which is
+// included with each elease.
+type ReleaseCompatibility struct {
+	Runtime      string            `json:"runtime,omitempty"`
+	Requirements map[string]string `json:"requirements,omitempty"`
+}
+
 var (
 	ErrNoReleaseDownload  = errors.New("couldn't find a release to download")
 	ErrNoVersionToSelect  = errors.New("no version to select")