fix(astro): set the image endpoint entrypoint so /_image works

packages/@apphosting/experimental/adapter-astro/src/index.ts

@@ -11,6 +11,7 @@ import type { Options, UserOptions } from "./types.js";
 import {
   createConfigPlugin,
   getPackageVersion,
+  resolveImageEntrypoint,
   ASTRO_PACKAGE_NAME,
   SUPPORTED_ASTRO_FEATURES,
   usesVirtualConfig,
@@ -59,10 +60,13 @@ export default function createIntegration(userOptions: UserOptions): AstroIntegr
   return {
     name: "@apphosting/astro-adapter",
     hooks: {
-      "astro:config:setup": ({ updateConfig, config }) => {
+      "astro:config:setup": ({ updateConfig, config, command }) => {
         updateConfig({
           image: {
-            endpoint: config.image.endpoint ?? "astro/assets/endpoint/node",
+            endpoint: {
+              route: config.image.endpoint?.route,
+              entrypoint: resolveImageEntrypoint(config.image.endpoint?.entrypoint, command),
+            },
           },
           vite: {
             ssr: {

packages/@apphosting/experimental/adapter-astro/src/utils.spec.ts

@@ -4,6 +4,24 @@ import type { Options } from "./types.js";
 
 const importUtils = import("@apphosting/astro-adapter/dist/utils.js");
 
+describe("resolveImageEntrypoint", () => {
+  it("serves builds from the Node endpoint", async () => {
+    const { resolveImageEntrypoint } = await importUtils;
+    assert.equal(resolveImageEntrypoint(undefined, "build"), "astro/assets/endpoint/node");
+  });
+
+  it("serves `astro dev` from the dev endpoint", async () => {
+    const { resolveImageEntrypoint } = await importUtils;
+    assert.equal(resolveImageEntrypoint(undefined, "dev"), "astro/assets/endpoint/dev");
+  });
+
+  it("keeps a user-configured entrypoint for every command", async () => {
+    const { resolveImageEntrypoint } = await importUtils;
+    assert.equal(resolveImageEntrypoint("my/custom/endpoint", "build"), "my/custom/endpoint");
+    assert.equal(resolveImageEntrypoint("my/custom/endpoint", "dev"), "my/custom/endpoint");
+  });
+});
+
 describe("createConfigPlugin", () => {
   const config = { mode: "standalone", host: true, port: 4321 } as Options;
 

packages/@apphosting/experimental/adapter-astro/src/utils.ts

@@ -22,6 +22,21 @@ export const SUPPORTED_ASTRO_FEATURES: AstroAdapterFeatureMap = {
   i18nDomains: "experimental",
   envGetSecret: "stable",
 } as const;
+const IMAGE_ENDPOINT = {
+  dev: "astro/assets/endpoint/dev",
+  node: "astro/assets/endpoint/node",
+} as const;
+
+/**
+ * Resolves which entrypoint serves the image endpoint. A user-configured entrypoint always wins;
+ * otherwise Astro's dev endpoint serves `astro dev` and its Node endpoint serves builds.
+ * @param entrypoint The entrypoint already set on the Astro config, if any.
+ * @param command The Astro command running this build.
+ * @return The entrypoint to serve the image endpoint from.
+ */
+export function resolveImageEntrypoint(entrypoint: string | undefined, command: string): string {
+  return entrypoint ?? (command === "dev" ? IMAGE_ENDPOINT.dev : IMAGE_ENDPOINT.node);
+}
 
 /**
  * Reads the version of a package as installed in the user's project.