Merge pull request 'The build modules build a folder module's packages at their paths and take a zero-version requirement from the ask (issue 1966)' (#617) from fix/1966-build-modules-folders into main

Checked by TestTheVaultWholeRotatesANodesLoginWithAStandInEngine: the race it met is what this closes.

Claude-Session: https://claude.ai/code/session_01NcbgfFSnn24M3GcqttoU7i

modules/mesh-build-go/cmd/mesh-build-go/fetch.go

@@ -19,6 +19,7 @@ import (
 
 	"git.novox.be/novox/mesh-catalog/modules/mesh-build-go/buildstep"
 	sdkstep "git.novox.be/novox/mesh-sdk/go/buildstep"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
 	"git.novox.be/novox/mesh-sdk/go/forgekey"
 )
 
@@ -177,7 +178,9 @@ func (m *Module) fetchInto(ctx context.Context, req sdkstep.FetchRequest, id str
 			if taken[i], errs[i] = m.takeVersions(ctx, root, filepath.Join(tree, d), d, req.Packages, &pins); errs[i] != nil {
 				return
 			}
-			errs[i] = m.downloadModules(ctx, root, filepath.Join(tree, d), d, &pins)
+			var more []TakenVersion
+			more, errs[i] = m.downloadModules(ctx, root, filepath.Join(tree, d), d, &pins, req.Packages)
+			taken[i] = append(taken[i], more...)
 		}()
 	}
 	wg.Wait()
@@ -194,21 +197,29 @@ func (m *Module) fetchInto(ctx context.Context, req sdkstep.FetchRequest, id str
 
 // downloadModules downloads and verifies the Go modules of the directory dir (d in the tree). A pin of a forge module
 // that Go cannot fetch is looked for among the forge's pull request heads and handed to Go by a modfile (pins.go); a
-// failure that names no such pin is the first failure.
-func (m *Module) downloadModules(ctx context.Context, root, dir, d string, pins *sync.Mutex) error {
+// failure that names no such pin is the first failure. A requirement at the zero version is taken from the asked
+// versions (pins.go takeZeroPins).
+func (m *Module) downloadModules(ctx context.Context, root, dir, d string, pins *sync.Mutex, asked delivery.PackageVersions) ([]TakenVersion, error) {
+	var taken []TakenVersion
 	for {
 		failure := m.downloadAndVerify(ctx, dir, d)
 		if failure == nil {
-			return nil
+			return taken, nil
+		}
+		// A requirement at the zero version names no commit: it is taken from the asked versions or the trunk's latest.
+		took, err := m.takeZeroPins(ctx, root, dir, d, failure.Error(), asked, pins)
+		taken = append(taken, took...)
+		if err != nil {
+			return taken, err
 		}
 		pins.Lock()
 		progress, err := m.resolvePins(ctx, root, dir, failure.Error())
 		pins.Unlock()
 		if err != nil {
-			return err
+			return taken, err
 		}
-		if !progress {
-			return failure
+		if !progress && len(took) == 0 {
+			return taken, failure
 		}
 	}
 }

modules/mesh-build-go/cmd/mesh-build-go/pins.go

@@ -12,16 +12,23 @@ import (
 	"context"
 	"errors"
 	"fmt"
+	"maps"
 	"os"
 	"path/filepath"
 	"regexp"
+	"slices"
 	"strings"
+	"sync"
 
+	"git.novox.be/novox/mesh-sdk/go/delivery"
 	"git.novox.be/novox/mesh-sdk/go/forgekey"
 )
 
 const forgePrefix = "git.novox.be/novox/"
 
+// zeroShort is the 12 digits a requirement at the zero version v0.0.0-00010101000000-000000000000 ends in: no commit.
+const zeroShort = "000000000000"
+
 var pseudoVersion = regexp.MustCompile(`[-.][0-9]{14}-([0-9a-f]{12})$`)
 
 // pin is a requirement of a go.mod on a commit of a repository of the forge, by a pseudo-version.
@@ -107,6 +114,9 @@ func (m *Module) resolvePins(ctx context.Context, root, dir, failure string) (bo
 	}
 	progress := false
 	for _, p := range forgePins(string(raw)) {
+		if p.short == zeroShort {
+			continue // takeZeroPins': a requirement at the zero version names no commit to look for
+		}
 		if !strings.Contains(failure, p.short) || strings.Contains(done, "replace "+p.module+" =>") {
 			continue
 		}
@@ -241,3 +251,66 @@ func absoluteReplaces(body []byte, dir string) []byte {
 	}
 	return []byte(strings.Join(lines, "\n"))
 }
+
+// takeZeroPins takes, for each requirement of dir's go.mod at the zero version that a go failure names, the version it is
+// built against (ADR 0573 §2, §4: whatever go.mod names): the commit the ask names for the package; else the head of
+// the package's repository among the asked versions (the check's or try's members: another package of the same
+// repository names it); else the latest published version, the trunk's head. It never looks for the commit
+// 000000000000 among the pull request heads. It answers what it took; none when no zero requirement is named.
+func (m *Module) takeZeroPins(ctx context.Context, root, dir, d, failure string, asked delivery.PackageVersions, pins *sync.Mutex) ([]TakenVersion, error) {
+	raw, err := os.ReadFile(filepath.Join(dir, "go.mod"))
+	if err != nil || !strings.Contains(failure, zeroShort) {
+		return nil, nil
+	}
+	resolved := map[string]string{}
+	if modfile, ok := m.pinModfile(dir); ok {
+		if b, err := os.ReadFile(modfile); err == nil {
+			resolved, _ = goModRequirements(string(b))
+			for module := range resolved {
+				if strings.Contains(string(b), "replace "+module+" =>") {
+					resolved[module] = "replaced"
+				}
+			}
+		}
+	}
+	var taken []TakenVersion
+	for _, p := range forgePins(string(raw)) {
+		if p.short != zeroShort {
+			continue
+		}
+		if v := resolved[p.module]; v != "" && !strings.HasSuffix(v, zeroShort) {
+			continue // taken before
+		}
+		named := "v0.0.0-00010101000000-" + zeroShort
+		tv := TakenVersion{Dir: d, Package: p.module, Asked: askedFor(asked, p), Named: named}
+		why := "the ask names it"
+		if tv.Asked == "" {
+			tv.Asked, why = "latest", "the ask names no commit of its repository, so the trunk's latest published version"
+		} else if _, ok := asked[p.module]; !ok {
+			why = "the head of its repository among the asked versions"
+		}
+		if err := m.takeVersion(ctx, root, dir, &tv, pins); err != nil {
+			return taken, fmt.Errorf("the requirement of %s at the zero version: %w", p.module, err)
+		}
+		tv.Said = strings.TrimPrefix(tv.Said+"; "+why, "; ")
+		if m.Say != nil {
+			m.Say("%s: %s names no commit; built at %s (%s)", d, p.module, tv.Built, why)
+		}
+		taken = append(taken, tv)
+	}
+	return taken, nil
+}
+
+// askedFor is the commit the ask names for the package p: its own, else that of the first package of the same repository
+// in order (the members' heads are by repository), else none.
+func askedFor(asked delivery.PackageVersions, p pin) string {
+	if c := asked[p.module]; c != "" {
+		return c
+	}
+	for _, pkg := range slices.Sorted(maps.Keys(asked)) {
+		if pkg == forgePrefix+p.repo || strings.HasPrefix(pkg, forgePrefix+p.repo+"/") {
+			return asked[pkg]
+		}
+	}
+	return ""
+}

modules/mesh-build-go/cmd/mesh-build-go/pins_test.go

@@ -290,3 +290,71 @@ func TestARelativeReplaceStillResolvesInTheTemporaryModfile(t *testing.T) {
 		t.Fatalf("go mod verify in the pins directory: %v\n%s", err, out)
 	}
 }
+
+// A go.mod requirement at the zero version v0.0.0-00010101000000-000000000000 names no commit (ADR 0573 §2, §4: whatever
+// go.mod names): it is taken from the commit the ask names for the package, else from the head of its repository among
+// the asked versions, else from the trunk's latest published version, and never looked for as the commit 000000000000
+// among the pull request heads.
+func TestARequirementAtTheZeroVersionIsTakenFromTheAskOrTheTrunk(t *testing.T) {
+	const sdk = "git.novox.be/novox/mesh-sdk/go"
+	zeroMod := "module fixture/member\n\ngo 1.26\n\nrequire (\n\t" + sdk + " v0.0.0-00010101000000-" + zeroShort + "\n)\n"
+	trunk := strings.Repeat("a", 40)
+	for _, c := range []struct {
+		name     string
+		packages map[string]any
+		download string // what go mod download -json answers
+		want     string // the version asked of go
+		head     bool   // the asked commit is on no trunk: only a pull request head carries it
+	}{
+		{name: "the ask names the package", packages: map[string]any{sdk: trunk}, want: sdk + "@" + trunk,
+			download: `{"Version":"v0.1.15-0.20261101000000-aaaaaaaaaaaa","Sum":"h1:zip="}`},
+		{name: "the ask names another package of its repository", packages: map[string]any{"git.novox.be/novox/mesh-sdk/other": trunk}, want: sdk + "@" + trunk,
+			download: `{"Version":"v0.1.15-0.20261101000000-aaaaaaaaaaaa","Sum":"h1:zip="}`},
+		{name: "the ask names the head of a pull request", packages: map[string]any{sdk: commitSHA}, want: sdk + "@" + commitSHA, head: true},
+		{name: "the ask names nothing of its repository", packages: map[string]any{"git.novox.be/novox/mesh-tools/go": trunk}, want: sdk + "@latest",
+			download: `{"Version":"v0.1.20-0.20261104000000-bbbbbbbbbbbb","Sum":"h1:zip="}`},
+		{name: "no ask", want: sdk + "@latest", download: `{"Version":"v0.1.20-0.20261104000000-bbbbbbbbbbbb","Sum":"h1:zip="}`},
+	} {
+		t.Run(c.name, func(t *testing.T) {
+			h, states := newPinHarness(t, zeroMod, false, pullList)
+			base := h.m.Run
+			h.m.Run = func(ctx context.Context, env []string, name string, args ...string) forgekey.Ran {
+				line := name + " " + strings.Join(args, " ")
+				switch {
+				case name == "go" && strings.Contains(line, " mod download -json "):
+					h.mu.Lock()
+					h.cmds = append(h.cmds, cmdRecord{env: env, line: line})
+					h.mu.Unlock()
+					if c.head {
+						return forgekey.Ran{Status: 1, Stdout: `{"Error":"invalid version: unknown revision ` + commitSHA[:12] + `"}`}
+					}
+					return forgekey.Ran{Stdout: c.download}
+				case name == "go" && strings.Contains(line, " mod download") && !strings.Contains(strings.Join(env, " "), "-modfile="):
+					return forgekey.Ran{Status: 1, Stderr: "go: " + sdk + "@v0.0.0-00010101000000-" + zeroShort + ": invalid version: unknown revision " + zeroShort + "\n"}
+				}
+				return base(ctx, env, name, args...)
+			}
+			args := map[string]any{"repository": "novox/mesh-delivery", "commit": commitSHA}
+			if c.packages != nil {
+				args["packages"] = c.packages
+			}
+			if _, err := fetchTool(t, h.m)(args); err != nil {
+				t.Fatal(err)
+			}
+			st := states.waitEnd(t)
+			if st.State != delivery.StepPassed {
+				t.Fatalf("the step ended %s: %s", st.State, st.Reason)
+			}
+			if !h.ran(" mod download -json " + c.want) {
+				t.Errorf("go was not asked for %s:\n%s", c.want, strings.Join(h.f.lines(), "\n"))
+			}
+			// The pull request heads are listed only to place an asked head, never to look for the commit of zeros.
+			if listed := h.ran("ls-remote"); listed != c.head {
+				t.Errorf("the pull request heads were listed: %v, want %v", listed, c.head)
+			}
+			if h.ran("pinned/mesh-sdk@" + zeroShort) {
+				t.Error("a repository was placed at the commit of zeros")
+			}
+		})
+	}
+}

modules/mesh-build-go/cmd/mesh-build-go/versions.go

@@ -105,6 +105,10 @@ func (m *Module) takeVersion(ctx context.Context, root, dir string, tv *TakenVer
 		// Not a commit Go can fetch: the head of a group's pull request (ADR 0573 §4), placed from the forge's heads.
 		// Whether it is one is the forge's fact (placePin), whatever go said.
 		failure := strings.TrimSpace(info.Error + "\n" + r.Err + "\n" + r.Stderr)
+		if !commitOK.MatchString(tv.Asked) {
+			// "latest" (the trunk's head) is no commit of a pull request: there is nothing to place.
+			return fmt.Errorf("the %s version of %s could not be taken (a download failure that may be retaken): %s", tv.Asked, tv.Package, causeLine(failure))
+		}
 		repo, sub, _ := strings.Cut(strings.TrimPrefix(tv.Package, forgePrefix), "/")
 		p := pin{module: tv.Package, repo: repo, sub: sub, short: tv.Asked[:12]}
 		pins.Lock()

modules/mesh-build-node/.gitignore

@@ -1 +1,3 @@
-mesh-build-node
+# the binary, built at the module or in its command directory; never the command directory itself
+/mesh-build-node
+/cmd/mesh-build-node/mesh-build-node

modules/mesh-build-node/cmd/mesh-build-node/build.go

@@ -13,6 +13,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"os"
+	"path"
 	"path/filepath"
 	"sort"
 	"strings"
@@ -37,6 +38,27 @@ type artifact struct {
 	Language    string   `json:"language"`
 	Entrypoints []string `json:"entrypoints"`
 	External    []string `json:"external"`
+	// Paths are the directories of a package artifact, relative to the module's: one, holding its package.json and
+	// its package-lock.json (as a Go package's, mesh-build-go gopackage.go); none means the module's directory.
+	Paths []string `json:"paths"`
+}
+
+// packageDir is the directory of a package artifact relative to its module's directory in dir: the one path it names
+// when that is a directory of the module holding a package.json (the contracts folders: ts/seats/<seat>/, each with its
+// own lock, ADR 0634 section 8), else the module's directory itself (a package that names no path, or source paths
+// beside the module's package.json: today's form).
+func (a artifact) packageDir(dir string) string {
+	if len(a.Paths) != 1 {
+		return "."
+	}
+	p := path.Clean(strings.TrimSuffix(a.Paths[0], "/"))
+	if p == "." || path.IsAbs(p) || p == ".." || strings.HasPrefix(p, "../") {
+		return "."
+	}
+	if _, err := os.Stat(filepath.Join(dir, filepath.FromSlash(p), "package.json")); err != nil {
+		return "."
+	}
+	return p
 }
 
 // BuildResult is what a passed build step says.
@@ -88,7 +110,8 @@ func (m *Module) build(ctx context.Context, args map[string]any) (any, error) {
 		return nil, err
 	}
 	if a.Kind == "package" {
-		return m.buildPackage(ctx, workspace, module, root, dir, a, publish)
+		at := a.packageDir(dir)
+		return m.buildPackage(ctx, workspace, module, root, filepath.Join(dir, filepath.FromSlash(at)), at, a, publish)
 	}
 	if why, err := lockProblem(dir, module); err != nil || why != "" {
 		if err == nil {

modules/mesh-build-node/cmd/mesh-build-node/check.go

@@ -16,6 +16,7 @@ import (
 	"fmt"
 	"io/fs"
 	"os"
+	"path"
 	"path/filepath"
 	"strings"
 	"time"
@@ -99,78 +100,89 @@ func (m *Module) test(ctx context.Context, args map[string]any) (any, error) {
 	if err != nil {
 		return nil, err
 	}
-	scripts, err := packageScripts(dir)
-	if err != nil {
-		return nil, err
-	}
-	sources, err := typeScriptFiles(dir)
-	if err != nil {
-		return nil, err
-	}
 	res := &TestResult{Workspace: workspace, Module: module, Level: level, By: sdkstep.By("mesh-build-node")}
 	script := "test"
 	if level == "integration" {
 		script = "test:integration"
 	}
-	hasScript := scripts[script] != ""
-	if level == "integration" && !hasScript {
-		res.Passed, res.NoTests, res.Why = true, true, "no tests: the package has no test:integration script"
-		return res, nil
-	}
-	if !hasScript && len(sources) == 0 {
-		res.Passed, res.NoTests, res.Why = true, true, "no tests: the package has no test script and no .ts files"
-		return res, nil
-	}
-	if err := m.provide(root); err != nil {
-		return nil, fmt.Errorf("providing the toolchain's packages to the workspace: %w", err)
-	}
 	where := module
 	if where == "" {
 		where = "."
 	}
+	targets, err := testTargets(dir, where)
+	if err != nil {
+		return nil, err
+	}
 	var check, run time.Duration
 	var failed []Failure
-	// a command that could not start is not a verdict: the step fails. One that ran and said no is.
-	ran := func(name string, r forgekey.Ran, report string) error {
-		if r.Err != "" {
-			return fmt.Errorf("%s could not be run: status %d %s: %s", name, r.Status, r.Err, firstLine(r.Stderr))
-		}
-		if r.Status != 0 {
-			failed = append(failed, testFailures(where, name, dir, r, report)...)
-		}
-		return nil
-	}
-	if len(sources) > 0 {
-		// A package that builds (a build or prepare script, which the fetch's --ignore-scripts never runs) is emitted
-		// by tsc into the workspace, shut off like every run step, so its tests find what they import of its own output
-		// (issue 1869: mesh-sdk's tests import ../dist); any other is type-checked without emitting.
-		name, line := "type-check", m.typeCheck(dir, sources)
-		if emit := m.emitBuild(dir, scripts); emit != nil {
-			name, line = "build", emit
-		}
-		start := m.now()
-		r := m.runIn(ctx, root, false, dir, nil, "node", line...)
-		check = m.now().Sub(start)
-		if err := ran(name, r, ""); err != nil {
+	tested := false
+	for _, tg := range targets {
+		scripts, err := packageScripts(tg.dir)
+		if err != nil {
 			return nil, err
 		}
-		res.Ran = append(res.Ran, name)
-	}
-	if hasScript && len(failed) == 0 {
-		start := m.now()
-		// node --test writes its TAP report to a file of the workspace (issue 1901), whatever the script prints itself
-		report := filepath.Join(root, ".mesh-node-test-"+level+".tap")
-		_ = os.Remove(report)
-		env := []string{"PATH=" + binDir(root) + ":" + pathOrDefault(), "npm_config_cache=" + filepath.Join(m.Toolchain.Paths.Cache, "npm"),
-			"NODE_OPTIONS=" + buildstep.NodeTestOptions(report)}
-		r := m.runIn(ctx, root, false, dir, env, "npm", scriptArgs(script)...)
-		run = m.now().Sub(start)
-		tap, _ := os.ReadFile(report)
-		_ = os.Remove(report)
-		if err := ran(script, r, string(tap)); err != nil {
+		sources, err := typeScriptFiles(tg.dir)
+		if err != nil {
 			return nil, err
 		}
-		res.Ran = append(res.Ran, script)
+		hasScript := scripts[script] != ""
+		if (level == "integration" && !hasScript) || (!hasScript && len(sources) == 0) {
+			continue
+		}
+		tested = true
+		if err := m.provide(root); err != nil {
+			return nil, fmt.Errorf("providing the toolchain's packages to the workspace: %w", err)
+		}
+		// a command that could not start is not a verdict: the step fails. One that ran and said no is.
+		ran := func(name string, r forgekey.Ran, report string) error {
+			if r.Err != "" {
+				return fmt.Errorf("%s could not be run: status %d %s: %s", name, r.Status, r.Err, firstLine(r.Stderr))
+			}
+			if r.Status != 0 {
+				failed = append(failed, testFailures(tg.where, name, tg.dir, r, report)...)
+			}
+			return nil
+		}
+		if len(sources) > 0 {
+			// A package that builds (a build or prepare script, which the fetch's --ignore-scripts never runs) is emitted
+			// by tsc into the workspace, shut off like every run step, so its tests find what they import of its own output
+			// (issue 1869: mesh-sdk's tests import ../dist); any other is type-checked without emitting.
+			name, line := "type-check", m.typeCheck(tg.dir, sources)
+			if emit := m.emitBuild(tg.dir, scripts); emit != nil {
+				name, line = "build", emit
+			}
+			start := m.now()
+			r := m.runIn(ctx, root, false, tg.dir, nil, "node", line...)
+			check += m.now().Sub(start)
+			if err := ran(name, r, ""); err != nil {
+				return nil, err
+			}
+			res.Ran = appendOnce(res.Ran, name)
+		}
+		if hasScript && len(failed) == 0 {
+			start := m.now()
+			// node --test writes its TAP report to a file of the workspace (issue 1901), whatever the script prints itself
+			report := filepath.Join(root, ".mesh-node-test-"+level+".tap")
+			_ = os.Remove(report)
+			env := []string{"PATH=" + binDir(root) + ":" + pathOrDefault(), "npm_config_cache=" + filepath.Join(m.Toolchain.Paths.Cache, "npm"),
+				"NODE_OPTIONS=" + buildstep.NodeTestOptions(report)}
+			r := m.runIn(ctx, root, false, tg.dir, env, "npm", scriptArgs(script)...)
+			run += m.now().Sub(start)
+			tap, _ := os.ReadFile(report)
+			_ = os.Remove(report)
+			if err := ran(script, r, string(tap)); err != nil {
+				return nil, err
+			}
+			res.Ran = appendOnce(res.Ran, script)
+		}
+	}
+	if !tested {
+		res.Passed, res.NoTests = true, true
+		res.Why = "no tests: the package has no test script and no .ts files"
+		if level == "integration" {
+			res.Why = "no tests: the package has no test:integration script"
+		}
+		return res, nil
 	}
 	res.Failed = failed
 	var why []string
@@ -294,3 +306,56 @@ func typeScriptFiles(dir string) ([]string, error) {
 	})
 	return out, err
 }
+
+// testTarget is a directory whose tests a level runs, and the name it is reported under.
+type testTarget struct{ dir, where string }
+
+// testTargets are the directories a module's tests run in: each TypeScript package artifact's own path when every
+// package the module declares names one (ADR 0634 §8: its package.json, its lock, its tests), else the module's
+// directory.
+func testTargets(dir, where string) ([]testTarget, error) {
+	whole := []testTarget{{dir, where}}
+	raw, err := os.ReadFile(filepath.Join(dir, "module.json"))
+	if err != nil {
+		return whole, nil
+	}
+	var mj struct {
+		Build struct {
+			Artifacts []artifact `json:"artifacts"`
+		} `json:"build"`
+	}
+	if json.Unmarshal(raw, &mj) != nil {
+		return whole, nil
+	}
+	var out []testTarget
+	seen := map[string]bool{}
+	for _, a := range mj.Build.Artifacts {
+		if a.Language != "typescript" {
+			continue
+		}
+		if a.Kind != "package" {
+			return whole, nil // a bundle is tested in its module's directory
+		}
+		at := a.packageDir(dir)
+		if at == "." {
+			return whole, nil
+		}
+		if !seen[at] {
+			seen[at] = true
+			out = append(out, testTarget{filepath.Join(dir, filepath.FromSlash(at)), path.Join(where, at)})
+		}
+	}
+	if len(out) == 0 {
+		return whole, nil
+	}
+	return out, nil
+}
+
+func appendOnce(list []string, s string) []string {
+	for _, x := range list {
+		if x == s {
+			return list
+		}
+	}
+	return append(list, s)
+}

modules/mesh-build-node/cmd/mesh-build-node/fetch.go

@@ -17,6 +17,7 @@ import (
 	"fmt"
 	"io/fs"
 	"os"
+	"path"
 	"path/filepath"
 	"regexp"
 	"sort"
@@ -210,8 +211,8 @@ func (m *Module) fetchInto(ctx context.Context, req sdkstep.FetchRequest, group
 	return res, nil
 }
 
-// typeScriptModules are the directories of the tree whose module.json declares a typescript artifact, relative to
-// it, in order.
+// typeScriptModules are the directories of the tree that a typescript artifact of a module.json is built in, relative to
+// it, in order: the module's directory for a bundle, the artifact's path for a package.
 func (m *Module) typeScriptModules(ctx context.Context, tree string) (dirs []string, packages map[string]bool, err error) {
 	r := m.Run(ctx, m.baseEnv(), "git", "-C", tree, "ls-files", "--", "module.json", "*/module.json")
 	if r.Status != 0 || r.Err != "" {
@@ -237,13 +238,21 @@ func (m *Module) typeScriptModules(ctx context.Context, tree string) (dirs []str
 		if json.Unmarshal(raw, &mj) != nil {
 			continue // a module.json the build step will refuse by name, not a fetch's business
 		}
+		// A bundle is built in its module's directory, a package in its own path (ADR 0634 §8: as at a repository's
+		// root, each package with its own lock); the first artifact to claim a directory decides it.
 		for _, a := range mj.Build.Artifacts {
-			if a.Language == "typescript" {
-				d := filepath.ToSlash(filepath.Dir(l))
-				dirs = append(dirs, d)
-				packages[d] = a.Kind == "package"
-				break
+			if a.Language != "typescript" {
+				continue
 			}
+			d := filepath.ToSlash(filepath.Dir(l))
+			if a.Kind == "package" {
+				d = path.Join(d, a.packageDir(filepath.Join(tree, filepath.FromSlash(d))))
+			}
+			if _, seen := packages[d]; seen {
+				continue
+			}
+			dirs = append(dirs, d)
+			packages[d] = a.Kind == "package"
 		}
 	}
 	sort.Strings(dirs)

modules/mesh-build-node/cmd/mesh-build-node/package.go

@@ -469,11 +469,13 @@ func fetchCommit(ctx context.Context, run forgekey.Runner, dir, remote, commit,
 // (publish) publishes it, from this module's own process with the registry's write credential, which no run step is
 // given: a version the registry lacks is published; the same packed file already there is done without a publish;
 // another packed file under that version fails `version taken:`. The reference is <name>@<version>, answered only when
-// the registry holds this build's file; a candidate answers its digest alone.
-func (m *Module) buildPackage(ctx context.Context, workspace, module, root, dir string, a artifact, publish bool) (any, error) {
-	rel := module
-	if rel == "" {
-		rel = "."
+// the registry holds this build's file; a candidate answers its digest alone. dir is the package's directory, at its
+// place in the module's.
+func (m *Module) buildPackage(ctx context.Context, workspace, module, root, dir, at string, a artifact, publish bool) (any, error) {
+	// rel is the package's directory in the workspace, as the fetch installed it (the shims lie under it).
+	rel := path.Join(module, at)
+	if module == "" {
+		rel = path.Join(".", at)
 	}
 	p, err := m.buildAndPack(ctx, root, dir, rel, publish)
 	if err != nil {

modules/mesh-build-node/cmd/mesh-build-node/package_paths_test.go

@@ -0,0 +1,93 @@
+package main
+
+import (
+	"context"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+// A folder module (mesh-contracts' root, a domain folder) declares several package artifacts, each at its own path
+// with its own package.json and package-lock.json and none at the module's directory (ADR 0634 section 8).
+const folderManifest = `{"module":"c","build":{"artifacts":[` +
+	`{"name":"ts-a","kind":"package","language":"typescript","paths":["ts/seats/a"]},` +
+	`{"name":"ts-b","kind":"package","language":"typescript","paths":["ts/seats/b/"]}]}}`
+
+func folderFiles(prefix string) map[string]string {
+	files := map[string]string{prefix + "module.json": folderManifest}
+	for _, s := range []string{"a", "b"} {
+		files[prefix+"ts/seats/"+s+"/package.json"] = `{"name":"@x/` + s + `","version":"0.1.0","scripts":{"build":"tsc","test":"node --test"}}`
+		files[prefix+"ts/seats/"+s+"/package-lock.json"] = `{"lockfileVersion":3}`
+		files[prefix+"ts/seats/"+s+"/index.ts"] = "export const v = 1;\n"
+	}
+	return files
+}
+
+// The fetch installs each package artifact at its path from the lock there, and finds no lock missing at the module.
+func TestAFolderModulesPackagesAreInstalledEachAtItsPath(t *testing.T) {
+	m, f := fetchMachine(t, folderFiles("modules/c/"), nil)
+	out, err := m.fetch(context.Background(), fetchArgs)
+	if err != nil {
+		t.Fatal(err)
+	}
+	r := out.(FetchResult)
+	if len(r.Modules) != 2 || r.Modules[0] != "modules/c/ts/seats/a" || r.Modules[1] != "modules/c/ts/seats/b" || len(r.Installed) != 2 {
+		t.Errorf("result = %+v, want both package directories found and installed", r)
+	}
+	var prefixes []string
+	for _, c := range npmCalls(f) {
+		for i, a := range c.args {
+			if a == "--prefix" {
+				prefixes = append(prefixes, strings.TrimPrefix(c.args[i+1], filepath.Join(m.Work, r.Workspace, "tree")))
+			}
+		}
+	}
+	if len(prefixes) != 2 || prefixes[0] != "/modules/c/ts/seats/a" || prefixes[1] != "/modules/c/ts/seats/b" {
+		t.Errorf("npm ci ran with --prefix %v, want each package's own directory", prefixes)
+	}
+}
+
+// The build runs the package's script and pack in its own path, and the test level runs in each path.
+func TestAFolderModulesPackageIsBuiltAndTestedInItsPath(t *testing.T) {
+	m, f, work := newMachine(t)
+	workspaceWith(t, work, folderFiles(""))
+	f.effect = func(c call) {
+		if c.name == "npm" && len(c.args) > 0 && c.args[0] == "pack" {
+			for i, a := range c.args {
+				if a == "--pack-destination" {
+					write(t, filepath.Join(c.args[i+1], "x.tgz"), "packed", 0o644)
+				}
+			}
+		}
+	}
+	if _, err := m.build(context.Background(), map[string]any{"workspace": "w1", "module": ".", "artifact": "ts-b"}); err != nil {
+		t.Fatal(err)
+	}
+	want := filepath.Join(work, "w1", "tree", "ts", "seats", "b")
+	built := 0
+	for _, c := range f.calls {
+		if c.name == "npm" {
+			built++
+			if c.dir != want {
+				t.Errorf("%s ran in %s, want %s", joined(c), c.dir, want)
+			}
+		}
+	}
+	if built != 2 {
+		t.Errorf("%d npm commands, want the build and the pack", built)
+	}
+	f.calls = nil
+	res, err := m.test(context.Background(), testArgs("unit"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	tests := map[string]bool{}
+	for _, c := range f.calls {
+		if c.name == "npm" {
+			tests[c.dir] = true
+		}
+	}
+	if r := res.(*TestResult); !r.Passed || len(tests) != 2 || !tests[want] || !tests[filepath.Join(work, "w1", "tree", "ts", "seats", "a")] {
+		t.Errorf("unit level = %+v, ran tests in %v, want both package paths", r, tests)
+	}
+}

modules/mesh-vault/cmd/mesh-vault/main.go

@@ -302,9 +302,20 @@ func readPlanRaw(key string) ([]byte, error) {
 // assignmentKeys is every key of the controller's assignments mirror, read the same way.
 func assignmentKeys() ([]string, error) { return stdio.State(AssignmentsRead).Keys() }
 
+// Checked by TestTheVaultWholeRotatesANodesLoginWithAStandInEngine: the race it met (a pass before Serve, every watch
+// refused, the rotation waiting for the minute's pass) is what this closes.
+// afterServed runs f once served is closed, that is once stdio.Serve holds the runtime's channel: every function of the
+// bus refuses before that ("before Serve"), and a watch refused then waits for the minute's pass.
+func afterServed(served <-chan struct{}, f func()) {
+	go func() {
+		<-served
+		f()
+	}()
+}
+
 func main() {
 	env := build()
-	go func() {
+	afterServed(stdio.Served(), func() {
 		tick := time.NewTicker(time.Minute)
 		defer tick.Stop()
 		// At start, every covered account it holds whose hash is not of its current generation (ADR 0547 clause 9).
@@ -361,7 +372,7 @@ func main() {
 			}
 			<-tick.C
 		}
-	}()
+	})
 	if err := stdio.Serve("", tools(env)); err != nil {
 		say("%v", err)
 		os.Exit(1)