Inline comments

run.ts

@@ -64,12 +64,50 @@ async function postComment(body: string): Promise<void> {
 // picks up narration while a file's first line is written on purpose. That line
 // is the verdict, matched whole; anything unexpected only comments, never
 // approves. The mark in front is added here, so it is never part of the match.
-const REVIEW_PATH = `${await Deno.makeTempDir()}/review.md`;
+const REVIEW_DIR = await Deno.makeTempDir();
+const REVIEW_PATH = `${REVIEW_DIR}/review.md`;
 const VERDICTS: Record<string, [event: string, mark: string]> = {
   Approved: ["APPROVED", "✅"],
   "Changes requested": ["REQUEST_CHANGES", "🛑"],
 };
 
+// A finding about one line is posted on that line of the diff rather than as
+// `file:line` prose in the body. Those anchors come as JSON, so the file and
+// line are structured instead of parsed back out of English; a malformed entry
+// fails the run, because a silently dropped finding is worse than a red run.
+const ANCHORS_PATH = `${REVIEW_DIR}/anchors.json`;
+type Anchor = { path: string; line: number; side: "new" | "old"; body: string };
+
+function parseAnchors(text: string): Anchor[] {
+  const entries: unknown = JSON.parse(text);
+  if (!Array.isArray(entries)) throw new Error(`${ANCHORS_PATH}: not an array`);
+  return entries.map((entry: unknown, index) => {
+    const at = `${ANCHORS_PATH}[${index}]`;
+    if (typeof entry !== "object" || entry === null) {
+      throw new Error(`${at}: not an object`);
+    }
+    const { path, line, side = "new", body } = entry as Record<string, unknown>;
+    if (typeof path !== "string" || path === "") {
+      throw new Error(`${at}.path: expected a repository path`);
+    }
+    if (typeof line !== "number" || !Number.isInteger(line) || line < 1) {
+      throw new Error(`${at}.line: expected a line number`);
+    }
+    if (side !== "new" && side !== "old") {
+      throw new Error(`${at}.side: expected "new" or "old"`);
+    }
+    if (typeof body !== "string" || body.trim() === "") {
+      throw new Error(`${at}.body: expected the finding`);
+    }
+    return { path, line, side, body };
+  });
+}
+
+async function readAnchors(): Promise<Anchor[]> {
+  const written = await Deno.readTextFile(ANCHORS_PATH).catch(() => null);
+  return written === null ? [] : parseAnchors(written);
+}
+
 async function postResult(body: string): Promise<void> {
   const review = await Deno.readTextFile(REVIEW_PATH).catch(() => null);
   if (review === null) {
@@ -80,9 +118,25 @@ async function postResult(body: string): Promise<void> {
   }
   const [verdict, ...rest] = review.split("\n");
   const [event, mark] = VERDICTS[verdict.trim()] ?? ["COMMENT", "💬"];
-  await gitea(REVIEWER_TOKEN, `repos/${REPO}/pulls/${INDEX}/reviews`, {
-    body: stripAnsi([`${mark} ${verdict.trim()}`, ...rest].join("\n")),
-    event,
+  const post = (anchors: Anchor[]) =>
+    gitea(REVIEWER_TOKEN, `repos/${REPO}/pulls/${INDEX}/reviews`, {
+      body: stripAnsi([`${mark} ${verdict.trim()}`, ...rest].join("\n")),
+      event,
+      comments: anchors.map(({ path, line, side, body }) => ({
+        path,
+        body: stripAnsi(body),
+        new_position: side === "new" ? line : 0,
+        old_position: side === "old" ? line : 0,
+      })),
+    });
+  const anchors = await readAnchors();
+  // Gitea rejects the whole review when an anchor names a line outside the
+  // diff, and a verdict that never lands blocks the pull request, so the body
+  // goes up alone rather than not at all.
+  await post(anchors).catch(async (error: Error) => {
+    if (anchors.length === 0) throw error;
+    console.error(`inline comments rejected: ${error.message}`);
+    await post([]);
   });
 }
 
@@ -128,6 +182,7 @@ async function renderPrompt(): Promise<string> {
     GITEA_REPOSITORY: REPO,
     ISSUE_INDEX: INDEX,
     REVIEW_PATH,
+    ANCHORS_PATH,
   };
   const template = await Deno.readTextFile(
     new URL("prompt.md", import.meta.url),