fix(core): keep workspace runtime available

tools/tht/internal/modelprojection/projection_test.go

@@ -56,6 +56,50 @@ func TestRenderProducesDeterministicCatalogPiAndComposeProjections(t *testing.T)
 	}
 }
 
+func TestGenerateDoesNotReplaceUnchangedProjection(t *testing.T) {
+	installation := projectionFixture(t)
+	if err := Generate(installation); err != nil {
+		t.Fatalf("Generate() initial error = %v", err)
+	}
+	paths := []string{
+		installation.GeneratedModelCatalogPath(),
+		installation.GeneratedPiModelsPath(),
+		installation.GeneratedPiSettingsPath(),
+		installation.ModelProjectionComposePath(),
+	}
+	before := make(map[string]os.FileInfo, len(paths))
+	for _, path := range paths {
+		info, err := os.Stat(path)
+		if err != nil {
+			t.Fatal(err)
+		}
+		before[path] = info
+	}
+
+	originalRename := renameProjectionDirectory
+	t.Cleanup(func() { renameProjectionDirectory = originalRename })
+	renames := 0
+	renameProjectionDirectory = func(oldPath, newPath string) error {
+		renames++
+		return os.Rename(oldPath, newPath)
+	}
+	if err := Generate(installation); err != nil {
+		t.Fatalf("Generate() repeated error = %v", err)
+	}
+	if renames != 0 {
+		t.Fatalf("Generate() replaced an unchanged generation with %d renames", renames)
+	}
+	for _, path := range paths {
+		after, err := os.Stat(path)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if !os.SameFile(before[path], after) {
+			t.Fatalf("Generate() replaced unchanged artifact %q", path)
+		}
+	}
+}
+
 func TestGenerateRestoresWholePreviousGenerationWhenPublishFails(t *testing.T) {
 	installation := projectionFixture(t)
 	if err := Generate(installation); err != nil {