tree: More schema cleanup (microsoft#22322)

## Description

Reduce use of SchemaBuilderInternal.

Fix missing sort when persisting field schema found while editing test
schema: this is not a correctness issue, but should improve consistency
and thus blob reuse in the encoded format.

packages/dds/tree/src/core/schema-stored/schema.ts

@@ -292,7 +292,8 @@ function decodeValueSchema(inMemory: PersistedValueSchema): ValueSchema {
 export function encodeFieldSchema(schema: TreeFieldStoredSchema): FieldSchemaFormat {
 	return {
 		kind: schema.kind,
-		types: [...schema.types],
+		// Types are sorted by identifier to improve stability of persisted data to increase chance of schema blob reuse.
+		types: [...schema.types].sort(),
 	};
 }
 

packages/dds/tree/src/test/feature-libraries/chunked-forest/chunkEncodingEndToEnd.spec.ts

@@ -53,6 +53,7 @@ import {
 	checkoutWithContent,
 	cursorFromInsertableTreeField,
 	flexTreeViewWithContent,
+	forestWithContent,
 	numberSequenceRootSchema,
 	testIdCompressor,
 } from "../../utils.js";
@@ -206,13 +207,13 @@ describe("End to end chunked encoding", () => {
 		const chunk = new UniformChunk(numberShape.withTopLevelLength(4), [1, 2, 3, 4]);
 		assert(!chunk.isShared());
 
-		const flexTree = flexTreeViewWithContent({
+		const forest = forestWithContent({
 			schema: numberSequenceRootSchema,
 			initialTree: chunk.cursor(),
 		});
 
 		const forestSummarizer = new ForestSummarizer(
-			flexTree.context.checkout.forest as IEditableForest,
+			forest,
 			revisionTagCodec,
 			fieldBatchCodec,
 			context,

packages/dds/tree/src/test/feature-libraries/schema-index/schemaSummarizer.spec.ts

@@ -4,13 +4,13 @@
  */
 
 import { storedEmptyFieldSchema } from "../../../core/index.js";
-import { intoStoredSchema } from "../../../feature-libraries/index.js";
 import {
 	encodeTreeSchema,
 	// eslint-disable-next-line import/no-internal-modules
 } from "../../../feature-libraries/schema-index/schemaSummarizer.js";
+import { toStoredSchema } from "../../../simple-tree/index.js";
 import { takeJsonSnapshot, useSnapshotDirectory } from "../../snapshots/index.js";
-import { jsonSequenceRootSchema } from "../../utils.js";
+import { JsonUnion } from "../../utils.js";
 
 describe("schemaSummarizer", () => {
 	describe("encodeTreeSchema", () => {
@@ -24,7 +24,7 @@ describe("schemaSummarizer", () => {
 		});
 
 		it("simple encoded schema", () => {
-			const encoded = encodeTreeSchema(intoStoredSchema(jsonSequenceRootSchema));
+			const encoded = encodeTreeSchema(toStoredSchema(JsonUnion));
 			takeJsonSnapshot(encoded);
 		});
 	});

packages/dds/tree/src/test/sequenceRootUtils.ts

@@ -0,0 +1,71 @@
+/*!
+ * Copyright (c) Microsoft Corporation and contributors. All rights reserved.
+ * Licensed under the MIT License.
+ */
+
+import {
+	type TreeStoredSchema,
+	rootFieldKey,
+	type MapTree,
+	type TreeNodeSchemaIdentifier,
+} from "../core/index.js";
+import { leaf, singleJsonCursor } from "../domains/index.js";
+import { FieldKinds, cursorForMapTreeField } from "../feature-libraries/index.js";
+import type { ITreeCheckout } from "../shared-tree/index.js";
+import { toStoredSchema } from "../simple-tree/index.js";
+import { brand, type JsonCompatible } from "../util/index.js";
+import { checkoutWithContent, JsonUnion } from "./utils.js";
+// eslint-disable-next-line import/no-internal-modules
+import { normalizeAllowedTypes } from "../simple-tree/schemaTypes.js";
+
+// This file provides utilities for testing sequence fields using documents where the root is the sequence being tested.
+// This pattern is not expressible using the public simple-tree API, and is only for testing internal details.
+
+const rootJsonSequenceSchema: TreeStoredSchema = {
+	nodeSchema: toStoredSchema(JsonUnion).nodeSchema,
+	rootFieldSchema: {
+		kind: FieldKinds.sequence.identifier,
+		types: new Set(
+			[...normalizeAllowedTypes(JsonUnion)].map((s) =>
+				brand<TreeNodeSchemaIdentifier>(s.identifier),
+			),
+		),
+	},
+};
+
+/**
+ * Helper function to insert node at a given index.
+ *
+ * @param tree - The tree on which to perform the insert.
+ * @param index - The index in the root field at which to insert.
+ * @param value - The value of the inserted nodes.
+ */
+export function insert(tree: ITreeCheckout, index: number, ...values: string[]): void {
+	const fieldEditor = tree.editor.sequenceField({ field: rootFieldKey, parent: undefined });
+	fieldEditor.insert(
+		index,
+		cursorForMapTreeField(
+			values.map((value): MapTree => ({ fields: new Map(), type: leaf.string.name, value })),
+		),
+	);
+}
+
+/**
+ * Removes `count` items from the root field of `tree`.
+ */
+export function remove(tree: ITreeCheckout, index: number, count: number): void {
+	const field = tree.editor.sequenceField({ parent: undefined, field: rootFieldKey });
+	field.remove(index, count);
+}
+
+/**
+ * Creates a sequence field at the root.
+ */
+export function makeTreeFromJsonSequence(json: JsonCompatible[]): ITreeCheckout {
+	const cursors = json.map(singleJsonCursor);
+	const tree = checkoutWithContent({
+		schema: rootJsonSequenceSchema,
+		initialTree: cursors,
+	});
+	return tree;
+}