V2: Add function parentTypes() to reflect

packages/protobuf-test/src/reflect/nested-types.test.ts

@@ -0,0 +1,129 @@
+// Copyright 2021-2024 Buf Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import { describe, expect, test } from "@jest/globals";
+import { compileFile, compileMessage, compileMethod } from "../helpers.js";
+import { nestedTypes, parentTypes } from "@bufbuild/protobuf/reflect";
+
+describe("nestedTypes()", () => {
+  test("lists nested types", async () => {
+    const file = await compileFile(`
+      syntax="proto2";
+      message A {
+        extensions 1 to 2;
+        message B {
+          optional int32 f = 1;
+        }
+        enum E {
+          E_UNSPECIFIED = 0;
+        }
+        extend A {
+          optional int32 ext = 2;
+        }
+      }
+      service S {
+        rpc X(A) returns (A);
+      }
+      enum E {
+       E_UNSPECIFIED = 0;
+      }
+      extend A {
+        optional int32 ext = 1;
+      }
+    `);
+    const nested = Array.from(nestedTypes(file));
+    expect(nested.map((d) => d.toString())).toStrictEqual([
+      "message A",
+      "message A.B",
+      "enum A.E",
+      "extension A.ext",
+      "enum E",
+      "service S",
+      "extension ext",
+    ]);
+  });
+});
+
+describe("parentTypes()", () => {
+  test("lists parents of field", async () => {
+    const message = await compileMessage(`
+      syntax="proto3";
+      message A {
+        message B {
+          int32 f = 1;
+        }
+      }
+    `);
+    const field = message.nestedMessages[0].fields[0];
+    const parents = parentTypes(field);
+    expect(parents.map((d) => d.toString())).toStrictEqual([
+      "message A.B",
+      "message A",
+      "file input.proto",
+    ]);
+  });
+  test("lists parents of enum value", async () => {
+    const message = await compileMessage(`
+      syntax="proto3";
+      message A {
+        enum B {
+          B_UNSPECIFIED = 0;
+        }
+      }
+    `);
+    const enumValue = message.nestedEnums[0].values[0];
+    const parents = parentTypes(enumValue);
+    expect(parents.map((d) => d.toString())).toStrictEqual([
+      "enum A.B",
+      "message A",
+      "file input.proto",
+    ]);
+  });
+  test("lists parents of rpc", async () => {
+    const method = await compileMethod(`
+      syntax="proto3";
+      service A {
+        rpc B(M) returns (M);
+      }
+      message M {}
+    `);
+    const parents = parentTypes(method);
+    expect(parents.map((d) => d.toString())).toStrictEqual([
+      "service A",
+      "file input.proto",
+    ]);
+  });
+  test("lists parents of extension", async () => {
+    const message = await compileMessage(`
+      syntax="proto2";
+      message A {
+        message B {
+          extend E {
+            optional int32 e = 1;
+          }
+        }
+      }
+      message E {
+        extensions 1 to 1;
+      }
+    `);
+    const ext = message.nestedMessages[0].nestedExtensions[0];
+    const parents = parentTypes(ext);
+    expect(parents.map((d) => d.toString())).toStrictEqual([
+      "message A.B",
+      "message A",
+      "file input.proto",
+    ]);
+  });
+});

packages/protobuf/src/reflect/nested-types.ts

@@ -13,13 +13,18 @@
 // limitations under the License.
 
 import type {
+  AnyDesc,
   DescEnum,
   DescExtension,
   DescFile,
   DescMessage,
   DescService,
 } from "../desc-types.js";
 
+/**
+ * Iterate over all types - enumerations, extensions, services, messages -
+ * and enumerations, extensions and messages nested in messages.
+ */
 export function* nestedTypes(
   desc: DescFile | DescMessage,
 ): Iterable<DescMessage | DescEnum | DescExtension | DescService> {
@@ -43,3 +48,34 @@ export function* nestedTypes(
       break;
   }
 }
+
+/**
+ * Returns the ancestors of a given Protobuf element, up to the file.
+ */
+export function parentTypes(desc: AnyDesc): Parent[] {
+  const parents: Parent[] = [];
+  while (desc.kind !== "file") {
+    const p = parent(desc);
+    desc = p;
+    parents.push(p);
+  }
+  return parents;
+}
+
+type Parent = DescFile | DescEnum | DescMessage | DescService;
+
+function parent(desc: Exclude<AnyDesc, DescFile>): Parent {
+  switch (desc.kind) {
+    case "enum_value":
+    case "field":
+    case "oneof":
+    case "rpc":
+      return desc.parent;
+    case "service":
+      return desc.file;
+    case "extension":
+    case "enum":
+    case "message":
+      return desc.parent ?? desc.file;
+  }
+}