fix: store base content for deleted PR files

packages/das/src/webhook/github-fetcher.service.spec.ts

@@ -0,0 +1,107 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+import type { ConfigService } from "@nestjs/config";
+import type { Repository } from "typeorm";
+import {
+  Issue,
+  LabelEvent,
+  PrFile,
+  PrFileContent,
+  PullRequest,
+  Repo,
+  Review,
+} from "../entities";
+import { GitHubFetcherService } from "./github-fetcher.service";
+
+type PullFile = {
+  filename: string;
+  previous_filename?: string;
+  status: string;
+};
+
+type FetcherInternals = {
+  fetchContentBatch(
+    repoFullName: string,
+    prNumber: number,
+    batch: PullFile[],
+    owner: string,
+    repo: string,
+    token: string,
+    headSha: string,
+    baseSha: string | null,
+  ): Promise<void>;
+  githubFetch(url: string, init: RequestInit): Promise<Response>;
+};
+
+const emptyRepo = <T extends object>(): Repository<T> => ({}) as Repository<T>;
+
+void test("fetchContentBatch stores only base content for removed files", async () => {
+  let storedContent: Partial<PrFileContent> | null = null;
+  const contentRepo = {
+    upsert: (content: Partial<PrFileContent>): Promise<unknown> => {
+      storedContent = content;
+      return Promise.resolve();
+    },
+  } as unknown as Repository<PrFileContent>;
+
+  const service = new GitHubFetcherService(
+    { getOrThrow: (): string => "123" } as unknown as ConfigService,
+    emptyRepo<PrFile>(),
+    contentRepo,
+    emptyRepo<PullRequest>(),
+    emptyRepo<Issue>(),
+    emptyRepo<Review>(),
+    emptyRepo<LabelEvent>(),
+    emptyRepo<Repo>(),
+  ) as unknown as FetcherInternals;
+
+  service.githubFetch = (
+    _url: string,
+    init: RequestInit,
+  ): Promise<Response> => {
+    const body = init.body;
+    assert.equal(typeof body, "string");
+    if (typeof body !== "string") {
+      throw new Error("Expected GraphQL request body to be a string");
+    }
+    assert.ok(body.includes('base0: object(expression: \\"BASE:src/old.ts\\"'));
+    assert.doesNotMatch(body, /head0:/);
+
+    return Promise.resolve({
+      ok: true,
+      json: () =>
+        Promise.resolve({
+          data: {
+            repository: {
+              base0: {
+                text: "export const removed = true;\n",
+                byteSize: 29,
+                isBinary: false,
+              },
+            },
+          },
+        }),
+    } as Response);
+  };
+
+  await service.fetchContentBatch(
+    "owner/repo",
+    7,
+    [{ filename: "src/old.ts", status: "removed" }],
+    "owner",
+    "repo",
+    "token",
+    "HEAD",
+    "BASE",
+  );
+
+  assert.deepEqual(storedContent, {
+    repoFullName: "owner/repo",
+    prNumber: 7,
+    filename: "src/old.ts",
+    baseContent: "export const removed = true;\n",
+    headContent: null,
+    isBinary: false,
+    byteSize: 29,
+  });
+});

packages/das/src/webhook/github-fetcher.service.ts

@@ -477,8 +477,11 @@ export class GitHubFetcherService implements OnModuleInit {
     headSha: string,
     baseSha: string | null,
   ): Promise<void> {
-    // Only fetch contents for files that have a meaningful version to fetch
-    const scored = files.filter((f) => f.status !== "removed");
+    // Only fetch contents for files that have a meaningful version to fetch.
+    // Removed files still need their base-side blob for scoring.
+    const scored = files.filter(
+      (f) => f.status !== "removed" || baseSha !== null,
+    );
     if (scored.length === 0) return;
 
     let batchSize = GRAPHQL_FILES_BATCH_SIZE;
@@ -537,11 +540,13 @@ export class GitHubFetcherService implements OnModuleInit {
           `base${i}: object(expression: "${baseExpr}") { ... on Blob { text byteSize isBinary } }`,
         );
       }
-      // Head version (already filtered out removed files at caller)
-      const headExpr = this.escapeGraphql(`${headSha}:${file.filename}`);
-      fields.push(
-        `head${i}: object(expression: "${headExpr}") { ... on Blob { text byteSize isBinary } }`,
-      );
+      // Head version: skip for removed files because the path no longer exists.
+      if (file.status !== "removed") {
+        const headExpr = this.escapeGraphql(`${headSha}:${file.filename}`);
+        fields.push(
+          `head${i}: object(expression: "${headExpr}") { ... on Blob { text byteSize isBinary } }`,
+        );
+      }
     }
 
     const query = `