Name build-agent's own as the builder's module, build-agent and mesh-tools (ADR 0520 §1, issue 1851)

ADR 0520 narrowed after its review: mesh-tools-go builds from its own
directory on a pinned base and has its key from mesh-build-image, and
mesh-tools-python is no module, so the set is named, not derived from
the toolchain bases.

cmd/mesh-controller/builders_own_test.go

@@ -60,11 +60,12 @@ func TestAWalkAsksBuildAgentForTheBuildersOwnModuleAlone(t *testing.T) {
 	}
 }
 
-// ADR 0520 (issue 1851): until R4g build-agent and the toolchain images its builds stand on are build-agent's own, as the
-// builder's module is: the builder writes no key of them, so a walk asks build-agent for them and reads no key; any other
-// module of the same tier is still taken from its key.
-func TestAWalkAsksBuildAgentForItselfAndItsToolchainsAndReadsNoKeyOfThem(t *testing.T) {
-	own := []string{"build-agent", "mesh-tools", "mesh-tools-go", "mesh-tools-python"}
+// ADR 0520 §1 (issue 1851): until R4g build-agent and mesh-tools, the toolchain image its builds stand on, are build-agent's
+// own, as the builder's module is: the builder writes no key of them, so a walk asks build-agent for them and reads no key;
+// mesh-tools-go (its key from mesh-build-image) and any other module of the same tier are still taken from their keys.
+func TestAWalkAsksBuildAgentForItselfAndMeshToolsAndReadsNoKeyOfThem(t *testing.T) {
+	own := []string{"build-agent", "mesh-tools"}
+	keyed := []string{"mesh-tools-go", "sudo"}
 	wasModule := askedModuleOf
 	askedModuleOf = func(_ context.Context, _ buildSource, path string) (string, error) {
 		return strings.TrimPrefix(path, "modules/"), nil
@@ -75,6 +76,9 @@ func TestAWalkAsksBuildAgentForItselfAndItsToolchainsAndReadsNoKeyOfThem(t *test
 			t.Fatalf("an ask of %s is refused: %v", m, err)
 		}
 	}
+	if err := onlyTheBuildersOwn(t.Context(), buildSource{Repository: "novox/x", Seat: "git"}, "modules/mesh-tools-go"); !errors.Is(err, errNotTheBuildersOwn) {
+		t.Fatalf("an ask of mesh-tools-go went on: %v", err)
+	}
 	var asked []string
 	was := askABuild
 	askABuild = func(_ context.Context, _ buildSource, path, _ string) (string, error) {
@@ -83,8 +87,8 @@ func TestAWalkAsksBuildAgentForItselfAndItsToolchainsAndReadsNoKeyOfThem(t *test
 	}
 	t.Cleanup(func() { askABuild = was })
 	p, byName := aWalkOfOne("sudo")
-	p.Tiers = [][]string{append(append([]string{}, own...), "sudo")}
-	for _, m := range own {
+	p.Tiers = [][]string{append(append([]string{}, own...), keyed...)}
+	for _, m := range append(append([]string{}, own...), keyed...) {
 		e := byName["sudo"]
 		e.Source.Path = "modules/" + m
 		byName[m] = e
@@ -92,7 +96,7 @@ func TestAWalkAsksBuildAgentForItselfAndItsToolchainsAndReadsNoKeyOfThem(t *test
 	for _, m := range p.Tiers[0] {
 		askModule(t.Context(), p, m, byName)
 	}
-	if strings.Join(asked, " ") != "modules/build-agent modules/mesh-tools modules/mesh-tools-go modules/mesh-tools-python" {
+	if strings.Join(asked, " ") != "modules/build-agent modules/mesh-tools" {
 		t.Fatalf("build-agent was asked for %v", asked)
 	}
 	for _, m := range own {
@@ -100,7 +104,9 @@ func TestAWalkAsksBuildAgentForItselfAndItsToolchainsAndReadsNoKeyOfThem(t *test
 			t.Fatalf("%s is not asked of build-agent, or is read from a key: %+v", m, s)
 		}
 	}
-	if s := p.Modules["sudo"]; !s.Key || s.Build != "" {
-		t.Fatalf("the other module is not taken from its key: %+v", s)
+	for _, m := range keyed {
+		if s := p.Modules[m]; !s.Key || s.Build != "" {
+			t.Fatalf("%s is not taken from its key: %+v", m, s)
+		}
 	}
 }

cmd/mesh-controller/plan_keys.go

@@ -25,19 +25,14 @@ import (
 // **No timer**: the builder's and the indexer's writes wake the look (builderkeys.Watch, watchNewModules).
 
 // isBuildersOwn says a module is build-agent's own: asked of build-agent on a merge and taken from its build record, never
-// from the builder's key, until R4g (ADR 0453 §5, ADR 0498 §7, ADR 0520). They are the builder's module, build-agent itself
-// (its image's context is another repository's) and the toolchain images build-agent's builds stand on
-// (builder.Bases): the builder writes no key of any of them, and a walk waiting for one would hold its tier for ever.
+// from the builder's key, until R4g (ADR 0453 §5, ADR 0498 §7, ADR 0520 §1).
 func isBuildersOwn(module string) bool { return buildersOwn(module) }
 
-// buildAgentsOwn are those modules: the builder's, build-agent's and every toolchain's base, read from the toolchains.
-var buildAgentsOwn = func() map[string]bool {
-	own := map[string]bool{sdkdelivery.BuilderModule: true, builder.AgentModule: true}
-	for _, b := range builder.Bases() {
-		own[b] = true
-	}
-	return own
-}()
+// buildAgentsOwn are those modules, named (ADR 0520 §1): the builder's; build-agent itself, whose image's context is another
+// repository's; and mesh-tools, the toolchain image build-agent's builds stand on. The builder writes no key of any of them,
+// and a walk waiting for one would hold its tier for ever. mesh-tools-go is not among them: it builds from a Dockerfile in
+// its own directory on a pinned base, and has its key from mesh-build-image.
+var buildAgentsOwn = map[string]bool{sdkdelivery.BuilderModule: true, builder.AgentModule: true, "mesh-tools": true}
 
 // buildersOwn is isBuildersOwn's rule: a variable only so a test of the asks left (their bus waits, their plan key) may
 // name modules of its own as build-agent's.

internal/builder/toolchain.go

@@ -237,21 +237,6 @@ func spoken() string {
 // AgentModule is build-agent's own module: the machine's builder, whose image is built from another repository's context.
 const AgentModule = "build-agent"
 
-// Bases are the modules whose artifacts provide the toolchains' compilers (Toolchain.Base), each once, sorted: images
-// build-agent's builds stand on.
-func Bases() []string {
-	seen := map[string]bool{}
-	var out []string
-	for _, t := range toolchains {
-		if t.Base != "" && !seen[t.Base] {
-			seen[t.Base] = true
-			out = append(out, t.Base)
-		}
-	}
-	sort.Strings(out)
-	return out
-}
-
 func Languages() []string {
 	names := make([]string, 0, len(toolchains))
 	for _, t := range toolchains {