From 9c1e0de3e6d42a7a5d0bb62ac9af1be47f53b6f9 Mon Sep 17 00:00:00 2001
From: Patrik Oldsberg <poldsberg@gmail.com>
Date: Tue, 9 Feb 2021 13:38:33 +0100
Subject: [PATCH 1/3] app-backend: more docs for options

---
 plugins/app-backend/src/service/router.ts | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/plugins/app-backend/src/service/router.ts b/plugins/app-backend/src/service/router.ts
index 65cbddaae6..3a22a7a6b0 100644
--- a/plugins/app-backend/src/service/router.ts
+++ b/plugins/app-backend/src/service/router.ts
@@ -26,7 +26,22 @@ import fs from 'fs-extra';
 export interface RouterOptions {
   config: Config;
   logger: Logger;
+
+  /**
+   * The name of the app package that content should be served from. The same app package should be
+   * added as a dependency to the backend package in order for it to be accessible at runtime.
+   *
+   * In a typical setup with a single app package this would be set to 'app'.
+   */
   appPackageName: string;
+
+  /**
+   * A request handler to handle requests for static content that are not present in the app bundle.
+   *
+   * This can be used to avoid issues with clients on older deployment versions trying to access lazy
+   * loaded content that is no longer present. Typically the requests would fall back to a long-term
+   * object store where all recently deployed versions of the app are present.
+   */
   staticFallbackHandler?: express.Handler;
 }
 

From f807a21dd3d169efde0faa181be218b3e5e3d241 Mon Sep 17 00:00:00 2001
From: Patrik Oldsberg <poldsberg@gmail.com>
Date: Tue, 9 Feb 2021 13:38:58 +0100
Subject: [PATCH 2/3] app-backend: add disableConfigInjection option, which
 disables config injection

---
 plugins/app-backend/src/service/router.ts | 25 +++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/plugins/app-backend/src/service/router.ts b/plugins/app-backend/src/service/router.ts
index 3a22a7a6b0..4379fcccb9 100644
--- a/plugins/app-backend/src/service/router.ts
+++ b/plugins/app-backend/src/service/router.ts
@@ -43,6 +43,17 @@ export interface RouterOptions {
    * object store where all recently deployed versions of the app are present.
    */
   staticFallbackHandler?: express.Handler;
+
+  /**
+   * Disables the configuration injection. This can be useful if you're running in an environment
+   * with a read-only filesystem, or for some other reason don't want configuration to be injected.
+   *
+   * Note that this will cause the configuration used when building the app bundle to be used, unless
+   * a separate configuration loading strategy is set up.
+   *
+   * This also disables configuration injection though `APP_CONFIG_` environment variables.
+   */
+  disableConfigInjection?: boolean;
 }
 
 export async function createRouter(
@@ -63,13 +74,15 @@ export async function createRouter(
 
   logger.info(`Serving static app content from ${appDistDir}`);
 
-  const appConfigs = await readConfigs({
-    config,
-    appDistDir,
-    env: process.env,
-  });
+  if (!options.disableConfigInjection) {
+    const appConfigs = await readConfigs({
+      config,
+      appDistDir,
+      env: process.env,
+    });
 
-  await injectConfig({ appConfigs, logger, staticDir });
+    await injectConfig({ appConfigs, logger, staticDir });
+  }
 
   const router = Router();
 

From 727f0deeca4b18fedb5f4eb1516d9f283921198a Mon Sep 17 00:00:00 2001
From: Patrik Oldsberg <poldsberg@gmail.com>
Date: Tue, 9 Feb 2021 13:39:44 +0100
Subject: [PATCH 3/3] add changeset

---
 .changeset/empty-cooks-laugh.md | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 .changeset/empty-cooks-laugh.md

diff --git a/.changeset/empty-cooks-laugh.md b/.changeset/empty-cooks-laugh.md
new file mode 100644
index 0000000000..8f509f08cd
--- /dev/null
+++ b/.changeset/empty-cooks-laugh.md
@@ -0,0 +1,5 @@
+---
+'@backstage/plugin-app-backend': patch
+---
+
+Added a new `disableConfigInjection` option, which can be used to disable the configuration injection in environments where it can't be used.