fix: derive file ETags from current source content

src/server/routes/file-etag.ts

@@ -1,17 +1,17 @@
 import { createHash } from "crypto";
 
-// Build an ETag that fingerprints the upstream content (?v=<sha>), the file
+// Build an ETag that fingerprints the current upstream content (commit and blob SHA), the file
 // path, and the anonymization config the user has saved. Without the config
 // part the browser kept serving bytes anonymized under an older term list
 // (#439). The path is folded in so two different files inside the same repo
 // can never collide.
 export function fileETag(
-  versionParam: string | undefined,
+  sourceFingerprint: string | undefined,
   filePath: string,
   options: unknown
 ): string {
   const h = createHash("sha1");
-  h.update(versionParam || "");
+  h.update(sourceFingerprint || "");
   h.update("|");
   h.update(filePath || "");
   h.update("|");

src/server/routes/file.ts

@@ -132,7 +132,7 @@ router.get(
         );
       }
       const etag = fileETag(
-        req.query.v as string | undefined,
+        `${repo.model.source.commit || ""}:${await f.sha() || ""}`,
         anonymizedPath,
         repo.model.options
       );

test/production-regressions.test.js

@@ -142,10 +142,15 @@ describe("production regressions", function () {
     await handler(req, response());
     expect(failure.message).to.equal("file_not_supported");
   });
-  it("sandboxes renamed HTML documents", async function () {
-    const { handler, req } = fileRoute("page.html");
+  it("sandboxes renamed HTML and invalidates stale client versions", async function () {
+    const { handler, req, repo } = fileRoute("page.html");
     const first = response(); await handler(req, first);
     expect(first.headers["Content-Security-Policy"]).to.include("sandbox");
+    repo.model.source.commit = "commit-2";
+    req.headers["if-none-match"] = first.headers.ETag;
+    const second = response(); await handler(req, second);
+    expect(second.headers.ETag).not.to.equal(first.headers.ETag);
+    expect(second.statusCode).not.to.equal(304);
   });
   it("omits an upstream length when later text is rewritten", async function () {
     const File = require("../src/core/AnonymizedFile").default;