Add semantic paths and safe diagnostics

metadata_test.go

@@ -0,0 +1,58 @@
+package configkit
+
+import "testing"
+
+func TestMetadataQueriesReturnDetachedRecords(t *testing.T) {
+	t.Parallel()
+
+	path := Keys("service", "workers")
+	metadata := Metadata{
+		fields: map[string]FieldInfo{
+			path.String(): {
+				Explicit: true,
+				Origin: Origin{
+					Layer:     LayerBase,
+					Locations: []Location{{SourceID: "source-1", Line: 2, Column: 3}},
+				},
+			},
+		},
+		history: map[string][]Change{
+			path.String(): {{
+				Path:         path,
+				Origin:       Origin{Layer: LayerResolution, Locations: []Location{{SourceID: "source-1"}}},
+				Previous:     []Origin{{Layer: LayerDefault, Locations: []Location{{SourceID: "default"}}}},
+				Reasons:      []string{"bounded worker count"},
+				Dependencies: []Path{Keys("limits")},
+			}},
+		},
+	}
+
+	info, ok := metadata.Lookup(path)
+	if !ok || !info.Explicit || !metadata.IsExplicit(path) {
+		t.Fatalf("Lookup() = %#v, %v", info, ok)
+	}
+	info.Origin.Locations[0].SourceID = "mutated"
+	again, _ := metadata.Lookup(path)
+	if again.Origin.Locations[0].SourceID != "source-1" {
+		t.Fatal("Lookup returned aliased locations")
+	}
+
+	history := metadata.History(path)
+	history[0].Reasons[0] = "mutated"
+	history[0].Previous[0].Locations[0].SourceID = "mutated"
+	history[0].Dependencies[0].segments[0].key = "mutated"
+	againHistory := metadata.History(path)
+	if againHistory[0].Reasons[0] != "bounded worker count" ||
+		againHistory[0].Previous[0].Locations[0].SourceID != "default" ||
+		againHistory[0].Dependencies[0].String() != "/limits" {
+		t.Fatal("History returned aliased nested records")
+	}
+
+	missing := Keys("missing")
+	if _, ok := metadata.Lookup(missing); ok || metadata.IsExplicit(missing) || metadata.History(missing) != nil {
+		t.Fatal("unknown path produced metadata")
+	}
+	if _, ok := metadata.Lookup(Path{}.Index(-1)); ok {
+		t.Fatal("invalid path produced metadata")
+	}
+}