Let frombus and the composer compose with a given placement and compare a node's compositions with what it runs, so a placement candidate can be answered and checked (issue 1126)

go/composer/composer.go

@@ -17,6 +17,8 @@ import (
 
 	"git.novox.be/novox/mesh-sdk/go/catalogue"
 	"git.novox.be/novox/mesh-sdk/go/compose"
+	"git.novox.be/novox/mesh-sdk/go/compose/frombus"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
 	"git.novox.be/novox/mesh-sdk/go/sdkversion"
 )
 
@@ -64,10 +66,15 @@ type Request struct {
 }
 
 // Case is one catalogue composed: every module's manifest by name, and per node the manifests kept at the build it runs.
+//
+// Placements are, by node, the placement the case composes that node with in place of what Input says of it: a change's
+// own placement files, so a check composes a catalogue pull request's placement (issue 1126, frombus.Placed); a null
+// placement leaves nothing placed on the node. A case without them composes Input's.
 type Case struct {
-	Name      string                         `json:"name"`
-	Manifests map[string]Manifest            `json:"manifests"`
-	Kept      map[string]map[string]Manifest `json:"kept,omitempty"`
+	Name       string                         `json:"name"`
+	Manifests  map[string]Manifest            `json:"manifests"`
+	Kept       map[string]map[string]Manifest `json:"kept,omitempty"`
+	Placements map[string]*delivery.Placement `json:"placements,omitempty"`
 }
 
 // Manifest is a module's manifest as its repository holds it (Raw, the bytes), or the digest the delivery indexer keeps
@@ -251,7 +258,10 @@ func runCase(r Request, c Case, depth string) (CaseVerdict, error) {
 	if err != nil {
 		return CaseVerdict{}, err
 	}
-	in := r.Input
+	in, err := frombus.Placed(r.Input, c.Placements)
+	if err != nil {
+		return CaseVerdict{}, fmt.Errorf("composer: the case %q: %w", c.Name, err)
+	}
 	in.Catalogue = shelf
 	in.Nodes = slices.Clone(in.Nodes)
 	in.Holdings = slices.Clone(in.Holdings)

go/composer/composer_test.go

@@ -10,6 +10,7 @@ import (
 
 	"git.novox.be/novox/mesh-sdk/go/catalogue"
 	"git.novox.be/novox/mesh-sdk/go/compose"
+	"git.novox.be/novox/mesh-sdk/go/delivery"
 )
 
 const demo = `{"module": "demo", "version": "1", "claims": [{"name": "node-files"}]}`
@@ -100,6 +101,19 @@ func TestARequestItCannotRunIsRefused(t *testing.T) {
 	if _, err := Run(Request{V: Version, Depth: "deep"}); err == nil {
 		t.Error("an unknown depth runs")
 	}
+	// A case's own placement (issue 1126) composes over a node the input holds, and is refused for one it does not.
+	placed := Request{V: Version, Input: compose.Input{Nodes: []compose.Node{{Name: "a"}}}, Machines: []string{"a"}, Depth: DepthResolve,
+		Cases: []Case{{Name: "trunk", Manifests: map[string]Manifest{"demo": {Raw: json.RawMessage(demo)}}},
+			{Name: "change", Manifests: map[string]Manifest{"demo": {Raw: json.RawMessage(demo)}},
+				Placements: map[string]*delivery.Placement{"a": {Node: "a", Modules: []delivery.PlacedModule{{Module: "ghost"}}}}}}}
+	if v, err := Run(placed); err != nil || !v.Cases[0].Machines["a"].Composes || v.Cases[1].Machines["a"].Composes ||
+		!strings.Contains(v.Cases[1].Machines["a"].Reason, "ghost") {
+		t.Errorf("a case composes its own placement: %+v, %v", v, err)
+	}
+	placed.Cases[1].Placements = map[string]*delivery.Placement{"z": {Node: "z"}}
+	if _, err := Run(placed); err == nil || !strings.Contains(err.Error(), "holds no node for") {
+		t.Errorf("a case placing a node the input lacks: %v", err)
+	}
 	v, err := Run(Request{V: Version, Cases: []Case{{Name: "only-read", Manifests: map[string]Manifest{"demo": {Raw: json.RawMessage(demo)}}}}})
 	if err != nil || len(v.Cases) != 1 || !v.Cases[0].Manifests["demo"].Accepted || v.Cases[0].Machines != nil || v.SDK == "" {
 		t.Fatalf("a request with no machines: %+v, %v", v, err)