Automatically update stale comment links

action/package.json

@@ -3,7 +3,8 @@
   "type": "module",
   "main": "src/index.ts",
   "scripts": {
-    "build": "npx rollup --config rollup.config.ts --configPlugin @rollup/plugin-typescript"
+    "build": "npx rollup --config rollup.config.ts --configPlugin @rollup/plugin-typescript",
+    "test": "node --test \"src/**/*.test.ts\""
   },
   "devDependencies": {
     "@octokit/tsconfig": "^4.0.0",

action/src/comment.test.ts

@@ -0,0 +1,35 @@
+import assert from "node:assert/strict";
+import { describe, it } from "node:test";
+
+import { decideCommentAction } from "./comment.ts";
+
+const successTable =
+  '<table><tbody><tr><td><a href="https://example.test/runs/1">✅success</a></td></tr></tbody></table>';
+const warningTable =
+  '<table><tbody><tr><td><a href="https://example.test/runs/1">⚠️warning</a></td></tr></tbody></table>';
+
+describe("decideCommentAction", () => {
+  it("creates a comment when the bot has not commented yet", () => {
+    assert.deepEqual(decideCommentAction(successTable, undefined), { kind: "create" });
+  });
+
+  it("replaces the previous comment when the new table has a warning", () => {
+    const previous = { id: 7, body: successTable };
+    assert.deepEqual(decideCommentAction(warningTable, previous), { kind: "replace", previous });
+  });
+
+  it("replaces the previous comment when the previous table had a warning", () => {
+    const previous = { id: 7, body: warningTable };
+    assert.deepEqual(decideCommentAction(successTable, previous), { kind: "replace", previous });
+  });
+
+  it("updates the previous comment in place when neither table has a warning", () => {
+    const previous = { id: 7, body: successTable };
+    assert.deepEqual(decideCommentAction(successTable, previous), { kind: "update", previous });
+  });
+
+  it("treats a previous comment without a body as having no warning", () => {
+    const previous: { id: number; body?: string } = { id: 7 };
+    assert.deepEqual(decideCommentAction(successTable, previous), { kind: "update", previous });
+  });
+});

action/src/comment.ts

@@ -0,0 +1,24 @@
+export interface CommentLike {
+  readonly body?: string | undefined;
+}
+
+export type CommentAction<T extends CommentLike> =
+  | { kind: "create" }
+  | { kind: "replace"; previous: T }
+  | { kind: "update"; previous: T };
+
+// Only a warning justifies notifying reviewers with a fresh comment (and
+// marking the old one outdated). Otherwise the previous comment is edited in
+// place so its links point at the latest run without a new notification.
+export function decideCommentAction<T extends CommentLike>(
+  newBody: string,
+  previous: T | undefined,
+): CommentAction<T> {
+  if (previous === undefined) return { kind: "create" };
+  if (hasWarning(newBody) || hasWarning(previous.body ?? "")) return { kind: "replace", previous };
+  return { kind: "update", previous };
+}
+
+function hasWarning(body: string): boolean {
+  return body.includes("warning");
+}

action/src/index.ts

@@ -1,6 +1,8 @@
 import { Octokit } from "@octokit/rest";
 import { graphql } from "@octokit/graphql";
 
+import { decideCommentAction } from "./comment.ts";
+
 if (!process.env.GITHUB_REF?.startsWith("refs/pull/")) {
   console.log("not a pull request, exiting.");
   process.exit(0);
@@ -213,7 +215,7 @@ const body = generateTable(rows);
 console.log("body is", body);
 
 if (body) {
-  console.log("outdates previous comments");
+  console.log("checking previous comments");
   const { data: comments } = await octokit.issues.listComments({
     owner,
     repo,
@@ -234,23 +236,32 @@ if (body) {
     .filter((comment) => comment.user?.login === "cppwarningnotifier[bot]")
     .toSorted((a, b) => new Date(a.created_at).getTime() - new Date(b.created_at).getTime());
 
-  if (sortedComments.length > 0) {
-    const latestComment = sortedComments[sortedComments.length - 1];
+  const action = decideCommentAction(body, sortedComments.at(-1));
 
-    if (body.includes("warning") || latestComment.body?.includes("warning")) {
+  switch (action.kind) {
+    case "create":
+      await postComment();
+      break;
+    case "replace":
       await gql(
         `mutation MinimizeComment($id: ID!) {
           minimizeComment(input: { subjectId: $id, classifier: OUTDATED }) {
             clientMutationId
           }
         }`,
-        { id: latestComment.node_id },
+        { id: action.previous.node_id },
       );
-
       await postComment();
-    }
-  } else {
-    await postComment();
+      break;
+    case "update":
+      console.log("updating links in the previous comment");
+      await octokit.issues.updateComment({
+        owner,
+        repo,
+        comment_id: action.previous.id,
+        body,
+      });
+      break;
   }
 }
 

action/tsconfig.json

@@ -1,6 +1,7 @@
 {
   "extends": "@octokit/tsconfig",
   "compilerOptions": {
-    "outDir": "dist"
+    "outDir": "dist",
+    "rewriteRelativeImportExtensions": true
   }
 }