S2: read a manifest for a merge's named tree as the indexer does

catalogue.ParseManifestForInputs (issue 1751): a manifest falling back to a predefined key was narrowed by the indexer and not by a build module, two computations of one tree (novox/hq ADR 0499 clause 2).

go/buildstep/trees.go

@@ -76,10 +76,10 @@ func ModuleTrees(ctx context.Context, run forgekey.Runner, env []string, dir, co
 
 // narrow sets mt's Paths and its named Tree when the module's manifest names paths on every artifact (novox/hq ADR 0499
 // clause 2): one `git ls-tree -z` gives each named path's object at commit. The merge preview reads the manifest here, as
-// the indexer does, and no other build step reads paths from one (ADR 0495 clause 1). A manifest that does not parse
+// the indexer does, with catalogue.ParseManifestForInputs (issue 1751), and no other build step reads paths from one (ADR 0495 clause 1). A manifest that does not parse
 // is not narrowed: the indexer gives it none. A named path absent at commit fails, naming the module and the path.
 func narrow(ctx context.Context, run forgekey.Runner, env []string, dir, commit, mdir string, raw []byte, mt *ModuleTree) error {
-	m, err := catalogue.ParseManifest(raw)
+	m, err := catalogue.ParseManifestForInputs(raw)
 	if err != nil {
 		return nil
 	}

go/buildstep/trees_named_test.go

@@ -5,6 +5,7 @@ import (
 	"strings"
 	"testing"
 
+	"git.novox.be/novox/mesh-sdk/go/catalogue"
 	"git.novox.be/novox/mesh-sdk/go/delivery"
 	"git.novox.be/novox/mesh-sdk/go/forgekey"
 )
@@ -73,3 +74,40 @@ func TestModuleTreesFailsNamingANamedPathAbsentAtTheCommit(t *testing.T) {
 		t.Fatalf("an absent named path gave %v", err)
 	}
 }
+
+// A manifest whose config value falls back to a predefined key is narrowed here as the indexer narrows it: both read it
+// with catalogue.ParseManifestForInputs (issue 1751), so a build module holding no published list computes the same
+// tree (ADR 0499 clause 2).
+func TestModuleTreesNarrowsAManifestFallingBackToAPredefinedKey(t *testing.T) {
+	was := catalogue.ReplacePublished(nil) // the build modules' case: no published list
+	defer catalogue.ReplacePublished(was)
+	root := t.TempDir()
+	raw := `{"module":"xterm","version":"1","config":{"size":{"type":"number","description":"The text size.","predefined":"font-size","default":12,"runtime":true}},` +
+		`"build":{"artifacts":[{"name":"lib","kind":"package","language":"typescript","paths":["src"]}]}}`
+	if _, err := catalogue.ParseManifest([]byte(raw)); err == nil {
+		t.Fatal("ParseManifest reads the manifest with no list; the test proves nothing")
+	}
+	if _, err := catalogue.ParseManifestForInputs([]byte(raw)); err != nil {
+		t.Fatalf("the indexer's read refuses the manifest: %v", err)
+	}
+	writeTreeFile(t, root, "module.json", raw)
+	run := func(ctx context.Context, env []string, name string, args ...string) forgekey.Ran {
+		switch args[2] {
+		case "ls-files":
+			return forgekey.Ran{Stdout: "module.json\n"}
+		case "rev-parse":
+			return forgekey.Ran{Stdout: "whole\n"}
+		case "ls-tree":
+			return forgekey.Ran{Stdout: "040000 tree " + strings.Repeat("a", 40) + "\tsrc\x00"}
+		}
+		return forgekey.Ran{Status: 1}
+	}
+	got, err := ModuleTrees(context.Background(), run, nil, root, strings.Repeat("c", 40))
+	if err != nil {
+		t.Fatal(err)
+	}
+	want, _ := delivery.NamedTree(hexOf(raw), map[string]string{"src": strings.Repeat("a", 40)})
+	if g := got["."]; g.Tree != want || g.Paths["src"] == "" {
+		t.Fatalf("the module = %+v, want the named tree %s", g, want)
+	}
+}