mesh-controller/internal/builder/reproducible_test.go

package builder

import (
	"bytes"
	"crypto/sha256"
	"encoding/hex"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"testing"
)

// **A Go bundle does not vary with the commit it was built at** (novox/hq ADR 0267 rule 6, issue 363). A
// module built from its repository's root — the controller — is compiled with the clone's `.git` in what
// the toolchain sees, and Go stamps the commit, its time and whether the tree was modified into every
// binary built there unless told not to. Two builds of one program at commits that differ only in a
// README then made two binaries, so an unchanged build source was a new digest.
//
// The toolchain's own compile line is run here, as the build seat runs it inside the toolchain image: in
// two clones at two paths, of two commits that differ outside the program. One digest is wanted.
func TestAGoBundleBuiltTwiceFromOneBuildSourceIsOneDigest(t *testing.T) {
	for _, tool := range []string{"go", "git"} {
		if _, err := exec.LookPath(tool); err != nil {
			t.Skipf("%s is not on this machine: %v", tool, err)
		}
	}
	chain, err := ToolchainFor("go")
	if err != nil {
		t.Fatal(err)
	}
	root := t.TempDir()
	repo := filepath.Join(root, "origin")
	files := map[string]string{
		"go.mod":          "module example.com/ctl\n\ngo 1.22\n",
		"cmd/ctl/main.go": "package main\n\nfunc main() { println(\"ctl\") }\n",
		"README.md":       "one\n",
	}
	for name, body := range files {
		if err := os.MkdirAll(filepath.Dir(filepath.Join(repo, name)), 0o755); err != nil {
			t.Fatal(err)
		}
		if err := os.WriteFile(filepath.Join(repo, name), []byte(body), 0o644); err != nil {
			t.Fatal(err)
		}
	}
	git := func(dir string, args ...string) string {
		t.Helper()
		cmd := exec.Command("git", append([]string{"-c", "user.name=t", "-c", "user.email=t@example.invalid",
			"-c", "commit.gpgsign=false", "-c", "init.defaultBranch=main"}, args...)...)
		cmd.Dir = dir
		out, err := cmd.CombinedOutput()
		if err != nil {
			t.Fatalf("git %s: %v\n%s", strings.Join(args, " "), err, out)
		}
		return strings.TrimSpace(string(out))
	}
	git(repo, "init", "-q")
	git(repo, "add", ".")
	git(repo, "commit", "-q", "-m", "one")
	first := git(repo, "rev-parse", "HEAD")
	if err := os.WriteFile(filepath.Join(repo, "README.md"), []byte("two\n"), 0o644); err != nil {
		t.Fatal(err)
	}
	git(repo, "commit", "-q", "-am", "only the README")
	second := git(repo, "rev-parse", "HEAD")

	build := func(commit, at string) string {
		t.Helper()
		clone := filepath.Join(root, at)
		git(root, "clone", "-q", repo, clone)
		git(clone, "checkout", "-q", commit)
		out := filepath.Join(clone, Out("server"), "ctl")
		line := append([]string(nil), chain.Compile...)
		line = append(line, "-ldflags", strings.Join(chain.LinkerFlags, " "), chain.OutputFlag, out, "./cmd/ctl")
		cmd := exec.Command(line[0], line[1:]...)
		cmd.Dir = clone
		cmd.Env = append(os.Environ(), "GOTOOLCHAIN=local", "GOPROXY=off", "GOWORK=off")
		if b, err := cmd.CombinedOutput(); err != nil {
			t.Fatalf("%s: %v\n%s", strings.Join(line, " "), err, b)
		}
		body, err := os.ReadFile(out)
		if err != nil {
			t.Fatal(err)
		}
		if bytes.Contains(body, []byte(commit)) {
			t.Errorf("the binary built at %s carries the commit it was built at", commit[:12])
		}
		sum := sha256.Sum256(body)
		return hex.EncodeToString(sum[:])
	}
	a, b := build(first, "a"), build(second, "elsewhere/b")
	if a != b {
		t.Fatalf("one build source, two digests: %s at %s, %s at %s (compiled with %q)",
			a[:12], first[:12], b[:12], second[:12], strings.Join(chain.Compile, " "))
	}
}

// The toolchain says so itself, so a reader of the compile line sees it without running a build.
func TestTheGoToolchainStampsNoVersionControl(t *testing.T) {
	chain, err := ToolchainFor("go")
	if err != nil {
		t.Fatal(err)
	}
	if joined := strings.Join(chain.Compile, " "); !strings.Contains(joined, "-buildvcs=false") {
		t.Fatalf("the go toolchain stamps the commit into what it compiles: %q", joined)
	}
}