From 8edd217f1ec90a87e46148769d7651606665b306 Mon Sep 17 00:00:00 2001
From: Theo Parker <theop.parker@gmail.com>
Date: Fri, 13 Nov 2026 00:15:03 -0800
Subject: [PATCH] daq backend: an explicit CONFIG_PATH is the only config it
 touches

getConfigPath() fell back to the checkout's config/config.toml whenever
CONFIG_PATH named a file not yet written. Backend tests point CONFIG_PATH at a
fresh temp dir, so on any machine with a deployed config they read the real
one and created profiles beside it: config/profiles/cold_flow/ and taken/
appeared in the checkout after npm test, and the calibration-profile tests
failed on 'already exists' from the second run on.

With CONFIG_PATH set, it is now the only candidate; the existing self-heal
generates it from the profiles beside it. Unset, the lookup is unchanged.
Production never sets CONFIG_PATH (the deploy scripts say so); the
integration harness and replay_past_db.sh write their file first.

config-path-explicit.test.ts puts a decoy where the fallback looks and fails
on the old code.
---
 .../__tests__/config-path-explicit.test.ts    | 50 +++++++++++++++++++
 .../backend/src/routes/config.ts              | 19 ++++---
 2 files changed, 62 insertions(+), 7 deletions(-)
 create mode 100644 daq-server/diablo_server/backend/src/__tests__/config-path-explicit.test.ts

diff --git a/daq-server/diablo_server/backend/src/__tests__/config-path-explicit.test.ts b/daq-server/diablo_server/backend/src/__tests__/config-path-explicit.test.ts
new file mode 100644
index 00000000..e16c8f52
--- /dev/null
+++ b/daq-server/diablo_server/backend/src/__tests__/config-path-explicit.test.ts
@@ -0,0 +1,50 @@
+/**
+ * An explicit CONFIG_PATH is the only config the backend touches, even before the file exists.
+ *
+ * The backend used to fall back to the checkout's own config/config.toml whenever CONFIG_PATH
+ * named a file not yet written. A test that pointed CONFIG_PATH at a fresh temp directory then
+ * read, and created profiles beside, the developer's real config: `config/profiles/cold_flow/`
+ * and `taken/` appeared in the checkout after `npm test` on any machine with a deployed config.
+ *
+ * Here a decoy config sits where the fallback would look (cwd/../../config/config.toml); the
+ * named one is missing but has a profile to generate from. The backend must generate the named
+ * one and leave the decoy alone.
+ */
+import { describe, it, expect, afterAll } from 'vitest';
+import { mkdtempSync, mkdirSync, writeFileSync, readFileSync, realpathSync, rmSync } from 'fs';
+import { tmpdir } from 'os';
+import { join } from 'path';
+
+// realpath: on macOS the temp dir is a symlink, and cwd comes back resolved.
+const root = realpathSync(mkdtempSync(join(tmpdir(), 'daq-cfgpath-')));
+const decoy = join(root, 'config', 'config.toml');
+const cwd = join(root, 'a', 'b');
+const named = join(root, 'isolated', 'config', 'config.toml');
+
+mkdirSync(join(root, 'config'), { recursive: true });
+writeFileSync(decoy, '# decoy: the checkout config a test must never touch\n');
+mkdirSync(cwd, { recursive: true });
+mkdirSync(join(root, 'isolated', 'config', 'profiles', 'default'), { recursive: true });
+writeFileSync(
+  join(root, 'isolated', 'config', 'profiles', 'default', 'config.toml'),
+  '[network]\nactuator_cmd_port = 5005\n',
+);
+
+const before = process.cwd();
+process.chdir(cwd);
+process.env.CONFIG_PATH = named;
+const { getConfigPath } = await import('../routes/config.js');
+
+afterAll(() => {
+  process.chdir(before);
+  rmSync(root, { recursive: true, force: true });
+});
+
+describe('getConfigPath with CONFIG_PATH set', () => {
+  it('generates the named config and never falls back to the checkout one', () => {
+    const got = getConfigPath();
+    expect(got, 'fell back to the checkout config').not.toBe(decoy);
+    expect(got).toBe(named);
+    expect(readFileSync(named, 'utf-8')).toContain('actuator_cmd_port = 5005');
+  });
+});
diff --git a/daq-server/diablo_server/backend/src/routes/config.ts b/daq-server/diablo_server/backend/src/routes/config.ts
index fca918ce..7374e7c9 100644
--- a/daq-server/diablo_server/backend/src/routes/config.ts
+++ b/daq-server/diablo_server/backend/src/routes/config.ts
@@ -18,13 +18,18 @@ const CONFIG_PATH = process.env.CONFIG_PATH ||
   join(process.cwd(), '..', 'config', 'config.toml');
 
 export function getConfigPath(): string {
-  // Try multiple possible paths
-  const possiblePaths = [
-    CONFIG_PATH,
-    join(process.cwd(), '..', '..', 'config', 'config.toml'),
-    // __dirname resolves relative to the compiled JS — walk up to project root
-    join(__dirname, '..', '..', '..', '..', 'config', 'config.toml'),
-  ];
+  // An explicit CONFIG_PATH is the only candidate, even before its file exists: the self-heal
+  // below generates it from the profiles beside it. Falling back to the checkout's config here is
+  // how tests pointing CONFIG_PATH at a fresh temp dir wrote profiles into a developer's real
+  // config/. Without it, try the usual places.
+  const possiblePaths = process.env.CONFIG_PATH
+    ? [CONFIG_PATH]
+    : [
+        CONFIG_PATH,
+        join(process.cwd(), '..', '..', 'config', 'config.toml'),
+        // __dirname resolves relative to the compiled JS — walk up to project root
+        join(__dirname, '..', '..', '..', '..', 'config', 'config.toml'),
+      ];
 
   for (const path of possiblePaths) {
     try {