Fail fast on missing terrain assets and recover empty renders

renderer/render.mjs

@@ -3,7 +3,8 @@ import { createServer } from "node:http";
 import { readFile, writeFile, mkdir } from "node:fs/promises";
 import { resolve, sep } from "node:path";
 import sharp from "sharp";
-import { assetsRoot } from "../scripts/assets.mjs";
+import { assetsRoot, prepareAssets } from "../scripts/assets.mjs";
+import { assertTerrainImage } from "./image-validation.mjs";
 /** @param {import('../shared/protocol').TerrainSnapshot} snapshot
  * @param {Array<{id:string,x:number,y:number,z:number}>} viewpoints
  * @param {string} output
@@ -15,6 +16,12 @@ export async function renderSnapshot(
   { size = 1024, signal, onProgress } = {},
 ) {
   const start = Date.now();
+  if (signal?.aborted) throw new Error("Rendering cancelled");
+  await onProgress?.({
+    percent: 22,
+    message: "Checking Minecraft models and textures",
+  });
+  await prepareAssets();
   await mkdir(output, { recursive: true });
   const server = createServer(async (req, res) => {
     try {
@@ -126,6 +133,10 @@ export async function renderSnapshot(
       rendererPage.on("pageerror", (err) =>
         console.error("Renderer:", err.message),
       );
+      rendererPage.on("console", (message) => {
+        if (["warning", "error"].includes(message.type()))
+          console.error(`Renderer ${message.type()}: ${message.text()}`);
+      });
       await rendererPage.goto(`http://127.0.0.1:${server.address().port}`);
       await rendererPage.waitForFunction(() => window.rendererReady);
       return rendererPage;
@@ -169,6 +180,8 @@ export async function renderSnapshot(
           { p, face, size },
         );
         const encoded = Buffer.from(data.split(",")[1], "base64");
+        if (face === "ny")
+          await assertTerrainImage(encoded, `Panorama ${p.id}, downward face`);
         // Chromium encodes WebP once; retain a PNG fallback for canvas runtimes
         // without WebP support rather than silently writing the wrong MIME type.
         if (data.startsWith("data:image/webp;"))
@@ -191,6 +204,7 @@ export async function renderSnapshot(
     await report({ percent: 85, message: "Rendering the surface map" });
     const map = await page.evaluate(() => window.renderMap(1024));
     const mapBytes = Buffer.from(map.split(",")[1], "base64");
+    await assertTerrainImage(mapBytes, "Surface map");
     if (map.startsWith("data:image/webp;"))
       await writeFile(`${output}/map.webp`, mapBytes);
     else