fix(fri): let startserver run without FLASK_SECRET_KEY set

README.md

@@ -121,7 +121,7 @@ Set a secure secret key for the Flask server before running in production:
 export FLASK_SECRET_KEY=$(python -c "import secrets; print(secrets.token_hex(32))")
 ```
 
-Do **NOT** commit your secret key to version control. If `FLASK_SECRET_KEY` is not set, a temporary random key will be generated automatically (suitable for local development only).
+Do **NOT** commit your secret key to version control. If `FLASK_SECRET_KEY` is not set, `startserver` / `startserver.bat` generate a temporary random key for that run (suitable for local development only); when running `main.py` directly, set `FLASK_ENV=development` instead.
 
 For a detailed and more scientific documentation, please read our extensive [open-access research paper on CONTROL-CORE](https://doi.org/10.1109/ACCESS.2022.3161471). This paper has a complete discussion on the CONTROL-CORE architecture and deployment, together with the commands to execute the studies in different programming languages and programming environments (Ubuntu, Windows, MacOS, Docker, and distributed execution).
 

startserver

@@ -1,5 +1,7 @@
 #!/bin/bash
 cd fri/server
+# main.py refuses to start without a secret key; use a throwaway one for local runs
+export FLASK_SECRET_KEY="${FLASK_SECRET_KEY:-$(head -c 32 /dev/urandom | od -An -tx1 | tr -d ' \n')}"
 if ! command -v python3 >/dev/null 2>&1; then
     python main.py
 else
@@ -8,7 +10,7 @@ fi
 
 if [ $? -ne 0 ]; then
     echo ""
-    echo "Error: Make sure modules are installed from fri/requirements.txt"
+    echo "Error: the server exited with an error (see above). If a module is missing:"
     echo "Run: pip install -r fri/requirements.txt"
     echo ""
 fi

startserver.bat

@@ -1,8 +1,10 @@
 cd fri\server
+rem main.py refuses to start without a secret key; use a throwaway one for local runs
+if not defined FLASK_SECRET_KEY for /f %%k in ('python -c "import secrets; print(secrets.token_hex(32))"') do @set "FLASK_SECRET_KEY=%%k"
 python main.py
 if errorlevel 1 (
     echo.
-    echo Error: Make sure modules are installed from fri/requirements.txt
+    echo Error: the server exited with an error ^(see above^). If a module is missing:
     echo Run: pip install -r fri/requirements.txt
     echo.
 )