feat: Expose linked PR information as changeset metadata

Signed-off-by: Yoriyasu Yano <430092+yorinasub17@users.noreply.github.com>

package.json

@@ -42,11 +42,11 @@
     "@babel/core": "^7.23.2",
     "@babel/preset-env": "^7.22.20",
     "@babel/preset-typescript": "^7.23.2",
+    "@fensak-io/front-matter": "^1.0.0",
     "@octokit/rest": "^20.0.2",
     "babel-preset-minify": "^0.5.2"
   },
   "devDependencies": {
-    "JS-Interpreter": "git://github.com/yorinasub17/JS-Interpreter.git#c1e9044f99041dead8c6a49a4f3784486df0fdd9",
     "@jest/globals": "^29.7.0",
     "@parcel/config-default": "2.9.3",
     "@parcel/packager-ts": "2.9.3",
@@ -56,6 +56,7 @@
     "@types/node": "^20.8.2",
     "@typescript-eslint/eslint-plugin": "^6.7.2",
     "@typescript-eslint/parser": "^6.7.2",
+    "JS-Interpreter": "git://github.com/yorinasub17/JS-Interpreter.git#c1e9044f99041dead8c6a49a4f3784486df0fdd9",
     "eslint": "^8.50.0",
     "eslint-config-prettier": "^9.0.0",
     "jest": "^29.7.0",

src/engine/from_github.ts

@@ -4,9 +4,18 @@
 import * as nodecrypto from "crypto";
 
 import { Octokit } from "@octokit/rest";
+import {
+  hasParsableFrontMatter,
+  extract as extractFrontMatter,
+} from "@fensak-io/front-matter";
 
 import { parseUnifiedDiff } from "./patch.ts";
-import { IChangeSetMetadata, IPatch, PatchOp } from "./patch_types.ts";
+import {
+  ILinkedPR,
+  IChangeSetMetadata,
+  IPatch,
+  PatchOp,
+} from "./patch_types.ts";
 import { SourcePlatform } from "./from.ts";
 
 const crypto = nodecrypto.webcrypto;
@@ -71,6 +80,7 @@ export async function patchFromGitHubPullRequest(
     metadata: {
       sourceBranch: pullReq.head.ref,
       targetBranch: pullReq.base.ref,
+      linkedPRs: extractLinkedPRs(pullReq.body),
     },
     patchList: [],
     patchFetchMap: {},
@@ -152,6 +162,20 @@ async function getGitHubPRFileID(salt: string, url: URL): Promise<string> {
   return hexEncode(new Uint8Array(digest));
 }
 
+function extractLinkedPRs(prDescription: string | null): ILinkedPR[] {
+  if (!prDescription || !hasParsableFrontMatter(prDescription)) {
+    return [];
+  }
+
+  interface IExpectedFrontMatter {
+    fensak: {
+      linked: ILinkedPR[];
+    };
+  }
+  const fm = extractFrontMatter<IExpectedFrontMatter>(prDescription);
+  return fm.attrs.fensak.linked;
+}
+
 function hexEncode(hb: Uint8Array): string {
   const hashArray = Array.from(hb);
   const hashHex = hashArray

src/engine/interpreter.test.ts

@@ -10,6 +10,7 @@ import { compileRuleFn, RuleFnSourceLang } from "./compile.ts";
 const nullMeta = {
   sourceBranch: "foo",
   targetBranch: "bar",
+  linkedPRs: [],
 };
 
 test("sanity check", async () => {

src/engine/patch_types.ts

@@ -77,12 +77,36 @@ export interface IPatch {
   diff: IHunk[];
 }
 
+/**
+ * Represents another PR that this PR is linked to. A linked PR can be used to represent a dependency where the upstream PR needs to be merged before this PR should be merged.
+ * @property repo The name of the repository (in the same organization) where the linked PR is located. Blank if the
+ *                same repo.
+ * @property prNum The PR number of the linked PR.
+ * @property isMerged Whether the linked PR has been merged.
+ * @property isClosed Whether the linked PR has been closed. Note that a merged PR is also closed.
+ */
+export interface ILinkedPR {
+  repo: string;
+  prNum: number;
+  isMerged: boolean;
+  isClosed: boolean;
+}
+
 /**
  * Represents metadata about the change set that is under evaluation.
  * @property sourceBranch The branch that the change set originates from.
  * @property targetBranch The branch that the change set is merging into.
+ * @property linkedPRs The list of PRs that this PR is linked to.
  */
 export interface IChangeSetMetadata {
   sourceBranch: string;
   targetBranch: string;
+  linkedPRs: ILinkedPR[];
 }
+
+// A convenient const for test cases to initialize a blank changeset metadata.
+export const emptyChangeSetMetadata: IChangeSetMetadata = {
+  sourceBranch: "",
+  targetBranch: "",
+  linkedPRs: [],
+};